Actual source code: snes.c

  1: #include <petsc/private/snesimpl.h>
  2: #include <petscdmshell.h>
  3: #include <petscdraw.h>
  4: #include <petscds.h>
  5: #include <petscdmadaptor.h>
  6: #include <petscconvest.h>

  8: PetscBool         SNESRegisterAllCalled = PETSC_FALSE;
  9: PetscFunctionList SNESList              = NULL;

 11: /* Logging support */
 12: PetscClassId  SNES_CLASSID, DMSNES_CLASSID;
 13: PetscLogEvent SNES_Solve, SNES_SetUp, SNES_FunctionEval, SNES_JacobianEval, SNES_NGSEval, SNES_NGSFuncEval, SNES_NPCSolve, SNES_ObjectiveEval;

 15: /*@
 16:    SNESSetErrorIfNotConverged - Causes `SNESSolve()` to generate an error immediately if the solver has not converged.

 18:    Logically Collective

 20:    Input Parameters:
 21: +  snes - iterative context obtained from `SNESCreate()`
 22: -  flg - `PETSC_TRUE` indicates you want the error generated

 24:    Options database keys:
 25: .  -snes_error_if_not_converged <true,false> - cause an immediate error condition and stop the program if the solver does not converge

 27:    Level: intermediate

 29:    Note:
 30:    Normally PETSc continues if a solver fails to converge, you can call `SNESGetConvergedReason()` after a `SNESSolve()`
 31:    to determine if it has converged. Otherwise the solution may be inaccurate or wrong

 33: .seealso: [](chapter_snes), `SNES`, `SNESGetErrorIfNotConverged()`, `KSPGetErrorIfNotConverged()`, `KSPSetErrorIfNotConverged()`
 34: @*/
 35: PetscErrorCode SNESSetErrorIfNotConverged(SNES snes, PetscBool flg)
 36: {
 37:   PetscFunctionBegin;
 40:   snes->errorifnotconverged = flg;
 41:   PetscFunctionReturn(PETSC_SUCCESS);
 42: }

 44: /*@
 45:    SNESGetErrorIfNotConverged - Indicates if `SNESSolve()` will generate an error if the solver does not converge?

 47:    Not Collective

 49:    Input Parameter:
 50: .  snes - iterative context obtained from `SNESCreate()`

 52:    Output Parameter:
 53: .  flag - `PETSC_TRUE` if it will generate an error, else `PETSC_FALSE`

 55:    Level: intermediate

 57: .seealso: [](chapter_snes), `SNES`, `SNESSolve()`, `SNESSetErrorIfNotConverged()`, `KSPGetErrorIfNotConverged()`, `KSPSetErrorIfNotConverged()`
 58: @*/
 59: PetscErrorCode SNESGetErrorIfNotConverged(SNES snes, PetscBool *flag)
 60: {
 61:   PetscFunctionBegin;
 64:   *flag = snes->errorifnotconverged;
 65:   PetscFunctionReturn(PETSC_SUCCESS);
 66: }

 68: /*@
 69:     SNESSetAlwaysComputesFinalResidual - tells the `SNES` to always compute the residual (nonlinear function value) at the final solution

 71:    Logically Collective

 73:     Input Parameters:
 74: +   snes - the shell `SNES`
 75: -   flg - `PETSC_TRUE` to always compute the residual

 77:    Level: advanced

 79:    Note:
 80:    Some solvers (such as smoothers in a `SNESFAS`) do not need the residual computed at the final solution so skip computing it
 81:    to save time.

 83: .seealso: [](chapter_snes), `SNES`, `SNESSolve()`, `SNESGetAlwaysComputesFinalResidual()`
 84: @*/
 85: PetscErrorCode SNESSetAlwaysComputesFinalResidual(SNES snes, PetscBool flg)
 86: {
 87:   PetscFunctionBegin;
 89:   snes->alwayscomputesfinalresidual = flg;
 90:   PetscFunctionReturn(PETSC_SUCCESS);
 91: }

 93: /*@
 94:     SNESGetAlwaysComputesFinalResidual - checks if the `SNES` always computes the residual at the final solution

 96:    Logically Collective

 98:     Input Parameter:
 99: .   snes - the `SNES` context

101:     Output Parameter:
102: .   flg - `PETSC_TRUE` if the residual is computed

104:    Level: advanced

106: .seealso: [](chapter_snes), `SNES`, `SNESSolve()`, `SNESSetAlwaysComputesFinalResidual()`
107: @*/
108: PetscErrorCode SNESGetAlwaysComputesFinalResidual(SNES snes, PetscBool *flg)
109: {
110:   PetscFunctionBegin;
112:   *flg = snes->alwayscomputesfinalresidual;
113:   PetscFunctionReturn(PETSC_SUCCESS);
114: }

116: /*@
117:    SNESSetFunctionDomainError - tells `SNES` that the input vector, a proposed new solution, to your function you provided to `SNESSetFunction()` is not
118:      in the functions domain. For example, a step with negative pressure.

120:    Logically Collective

122:    Input Parameters:
123: .  snes - the `SNES` context

125:    Level: advanced

127:    Note:
128:    You can direct `SNES` to avoid certain steps by using `SNESVISetVariableBounds()`, `SNESVISetComputeVariableBounds()` or
129:    `SNESLineSearchSetPreCheck()`, `SNESLineSearchSetPostCheck()`

131: .seealso: [](chapter_snes), `SNESCreate()`, `SNESSetFunction()`, `SNESFunction`, `SNESSetJacobianDomainError()`, `SNESVISetVariableBounds()`,
132:           `SNESVISetComputeVariableBounds()`, `SNESLineSearchSetPreCheck()`, `SNESLineSearchSetPostCheck()`
133: @*/
134: PetscErrorCode SNESSetFunctionDomainError(SNES snes)
135: {
136:   PetscFunctionBegin;
138:   PetscCheck(!snes->errorifnotconverged, PETSC_COMM_SELF, PETSC_ERR_ARG_OUTOFRANGE, "User code indicates input vector is not in the function domain");
139:   snes->domainerror = PETSC_TRUE;
140:   PetscFunctionReturn(PETSC_SUCCESS);
141: }

143: /*@
144:    SNESSetJacobianDomainError - tells `SNES` that the function you provided to `SNESSetJacobian()` at the proposed step. For example there is a negative element transformation.

146:    Logically Collective

148:    Input Parameters:
149: .  snes - the `SNES` context

151:    Level: advanced

153:    Note:
154:    You can direct `SNES` to avoid certain steps by using `SNESVISetVariableBounds()`, `SNESVISetComputeVariableBounds()` or
155:    `SNESLineSearchSetPreCheck()`, `SNESLineSearchSetPostCheck()`

157: .seealso: [](chapter_snes), `SNESCreate()`, `SNESSetFunction()`, `SNESFunction()`, `SNESSetFunctionDomainError()`, `SNESVISetVariableBounds()`,
158:           `SNESVISetComputeVariableBounds()`, `SNESLineSearchSetPreCheck()`, `SNESLineSearchSetPostCheck()`
159: @*/
160: PetscErrorCode SNESSetJacobianDomainError(SNES snes)
161: {
162:   PetscFunctionBegin;
164:   PetscCheck(!snes->errorifnotconverged, PETSC_COMM_SELF, PETSC_ERR_ARG_OUTOFRANGE, "User code indicates computeJacobian does not make sense");
165:   snes->jacobiandomainerror = PETSC_TRUE;
166:   PetscFunctionReturn(PETSC_SUCCESS);
167: }

169: /*@
170:    SNESSetCheckJacobianDomainError - tells `SNESSolve()` whether to check if the user called `SNESSetJacobianDomainError()` Jacobian domain error after
171:    each Jacobian evaluation. By default, we check Jacobian domain error in the debug mode, and do not check it in the optimized mode.

173:    Logically Collective

175:    Input Parameters:
176: +  snes - the SNES context
177: -  flg  - indicates if or not to check Jacobian domain error after each Jacobian evaluation

179:    Level: advanced

181:    Note:
182:    Checks require one extra parallel synchronization for each Jacobian evaluation

184: .seealso: [](chapter_snes), `SNES`, `SNESConvergedReason`, `SNESCreate()`, `SNESSetFunction()`, `SNESFunction()`, `SNESSetFunctionDomainError()`, `SNESGetCheckJacobianDomainError()`
185: @*/
186: PetscErrorCode SNESSetCheckJacobianDomainError(SNES snes, PetscBool flg)
187: {
188:   PetscFunctionBegin;
190:   snes->checkjacdomainerror = flg;
191:   PetscFunctionReturn(PETSC_SUCCESS);
192: }

194: /*@
195:    SNESGetCheckJacobianDomainError - Get an indicator whether or not we are checking Jacobian domain errors after each Jacobian evaluation.

197:    Logically Collective

199:    Input Parameters:
200: .  snes - the `SNES` context

202:    Output Parameters:
203: .  flg  - `PETSC_FALSE` indicates that we don't check Jacobian domain errors after each Jacobian evaluation

205:    Level: advanced

207: .seealso: [](chapter_snes), `SNES`, `SNESCreate()`, `SNESSetFunction()`, `SNESFunction()`, `SNESSetFunctionDomainError()`, `SNESSetCheckJacobianDomainError()`
208: @*/
209: PetscErrorCode SNESGetCheckJacobianDomainError(SNES snes, PetscBool *flg)
210: {
211:   PetscFunctionBegin;
214:   *flg = snes->checkjacdomainerror;
215:   PetscFunctionReturn(PETSC_SUCCESS);
216: }

218: /*@
219:    SNESGetFunctionDomainError - Gets the status of the domain error after a call to `SNESComputeFunction()`;

221:    Logically Collective

223:    Input Parameters:
224: .  snes - the `SNES` context

226:    Output Parameters:
227: .  domainerror - Set to `PETSC_TRUE` if there's a domain error; `PETSC_FALSE` otherwise.

229:    Level: developer

231: .seealso: [](chapter_snes), `SNES`, `SNESSetFunctionDomainError()`, `SNESComputeFunction()`
232: @*/
233: PetscErrorCode SNESGetFunctionDomainError(SNES snes, PetscBool *domainerror)
234: {
235:   PetscFunctionBegin;
238:   *domainerror = snes->domainerror;
239:   PetscFunctionReturn(PETSC_SUCCESS);
240: }

242: /*@
243:    SNESGetJacobianDomainError - Gets the status of the Jacobian domain error after a call to `SNESComputeJacobian()`;

245:    Logically Collective

247:    Input Parameters:
248: .  snes - the `SNES` context

250:    Output Parameters:
251: .  domainerror - Set to `PETSC_TRUE` if there's a Jacobian domain error; `PETSC_FALSE` otherwise.

253:    Level: advanced

255: .seealso: [](chapter_snes), `SNES`, `SNESSetFunctionDomainError()`, `SNESComputeFunction()`, `SNESGetFunctionDomainError()`
256: @*/
257: PetscErrorCode SNESGetJacobianDomainError(SNES snes, PetscBool *domainerror)
258: {
259:   PetscFunctionBegin;
262:   *domainerror = snes->jacobiandomainerror;
263:   PetscFunctionReturn(PETSC_SUCCESS);
264: }

266: /*@C
267:   SNESLoad - Loads a `SNES` that has been stored in `PETSCVIEWERBINARY` with `SNESView()`.

269:   Collective

271:   Input Parameters:
272: + newdm - the newly loaded `SNES`, this needs to have been created with `SNESCreate()` or
273:            some related function before a call to `SNESLoad()`.
274: - viewer - binary file viewer, obtained from `PetscViewerBinaryOpen()`

276:    Level: intermediate

278:   Note:
279:    The type is determined by the data in the file, any type set into the `SNES` before this call is ignored.

281: .seealso: [](chapter_snes), `SNES`, `PetscViewer`, `SNESCreate()`, `SNESType`, `PetscViewerBinaryOpen()`, `SNESView()`, `MatLoad()`, `VecLoad()`
282: @*/
283: PetscErrorCode SNESLoad(SNES snes, PetscViewer viewer)
284: {
285:   PetscBool isbinary;
286:   PetscInt  classid;
287:   char      type[256];
288:   KSP       ksp;
289:   DM        dm;
290:   DMSNES    dmsnes;

292:   PetscFunctionBegin;
295:   PetscCall(PetscObjectTypeCompare((PetscObject)viewer, PETSCVIEWERBINARY, &isbinary));
296:   PetscCheck(isbinary, PETSC_COMM_SELF, PETSC_ERR_ARG_WRONG, "Invalid viewer; open viewer with PetscViewerBinaryOpen()");

298:   PetscCall(PetscViewerBinaryRead(viewer, &classid, 1, NULL, PETSC_INT));
299:   PetscCheck(classid == SNES_FILE_CLASSID, PetscObjectComm((PetscObject)snes), PETSC_ERR_ARG_WRONG, "Not SNES next in file");
300:   PetscCall(PetscViewerBinaryRead(viewer, type, 256, NULL, PETSC_CHAR));
301:   PetscCall(SNESSetType(snes, type));
302:   PetscTryTypeMethod(snes, load, viewer);
303:   PetscCall(SNESGetDM(snes, &dm));
304:   PetscCall(DMGetDMSNES(dm, &dmsnes));
305:   PetscCall(DMSNESLoad(dmsnes, viewer));
306:   PetscCall(SNESGetKSP(snes, &ksp));
307:   PetscCall(KSPLoad(ksp, viewer));
308:   PetscFunctionReturn(PETSC_SUCCESS);
309: }

311: #include <petscdraw.h>
312: #if defined(PETSC_HAVE_SAWS)
313: #include <petscviewersaws.h>
314: #endif

316: /*@C
317:    SNESViewFromOptions - View a `SNES` based on values in the options database

319:    Collective

321:    Input Parameters:
322: +  A - the `SNES` context
323: .  obj - Optional object that provides the options prefix for the checks
324: -  name - command line option

326:    Level: intermediate

328: .seealso: [](chapter_snes), `SNES`, `SNESView`, `PetscObjectViewFromOptions()`, `SNESCreate()`
329: @*/
330: PetscErrorCode SNESViewFromOptions(SNES A, PetscObject obj, const char name[])
331: {
332:   PetscFunctionBegin;
334:   PetscCall(PetscObjectViewFromOptions((PetscObject)A, obj, name));
335:   PetscFunctionReturn(PETSC_SUCCESS);
336: }

338: PETSC_EXTERN PetscErrorCode SNESComputeJacobian_DMDA(SNES, Vec, Mat, Mat, void *);

340: /*@C
341:    SNESView - Prints or visualizes the `SNES` data structure.

343:    Collective

345:    Input Parameters:
346: +  snes - the `SNES` context
347: -  viewer - the `PetscViewer`

349:    Options Database Key:
350: .  -snes_view - Calls `SNESView()` at end of `SNESSolve()`

352:    Level: beginner

354:    Notes:
355:    The available visualization contexts include
356: +     `PETSC_VIEWER_STDOUT_SELF` - standard output (default)
357: -     `PETSC_VIEWER_STDOUT_WORLD` - synchronized standard
358:          output where only the first processor opens
359:          the file.  All other processors send their
360:          data to the first processor to print.

362:    The available formats include
363: +     `PETSC_VIEWER_DEFAULT` - standard output (default)
364: -     `PETSC_VIEWER_ASCII_INFO_DETAIL` - more verbose output for `SNESNASM`

366:    The user can open an alternative visualization context with
367:    `PetscViewerASCIIOpen()` - output to a specified file.

369:   In the debugger you can do "call `SNESView`(snes,0)" to display the `SNES` solver. (The same holds for any PETSc object viewer).

371: .seealso: [](chapter_snes), `SNES`, `SNESLoad()`, `SNESCreate()`, `PetscViewerASCIIOpen()`
372: @*/
373: PetscErrorCode SNESView(SNES snes, PetscViewer viewer)
374: {
375:   SNESKSPEW     *kctx;
376:   KSP            ksp;
377:   SNESLineSearch linesearch;
378:   PetscBool      iascii, isstring, isbinary, isdraw;
379:   DMSNES         dmsnes;
380: #if defined(PETSC_HAVE_SAWS)
381:   PetscBool issaws;
382: #endif

384:   PetscFunctionBegin;
386:   if (!viewer) PetscCall(PetscViewerASCIIGetStdout(PetscObjectComm((PetscObject)snes), &viewer));
388:   PetscCheckSameComm(snes, 1, viewer, 2);

390:   PetscCall(PetscObjectTypeCompare((PetscObject)viewer, PETSCVIEWERASCII, &iascii));
391:   PetscCall(PetscObjectTypeCompare((PetscObject)viewer, PETSCVIEWERSTRING, &isstring));
392:   PetscCall(PetscObjectTypeCompare((PetscObject)viewer, PETSCVIEWERBINARY, &isbinary));
393:   PetscCall(PetscObjectTypeCompare((PetscObject)viewer, PETSCVIEWERDRAW, &isdraw));
394: #if defined(PETSC_HAVE_SAWS)
395:   PetscCall(PetscObjectTypeCompare((PetscObject)viewer, PETSCVIEWERSAWS, &issaws));
396: #endif
397:   if (iascii) {
398:     SNESNormSchedule normschedule;
399:     DM               dm;
400:     PetscErrorCode (*cJ)(SNES, Vec, Mat, Mat, void *);
401:     void       *ctx;
402:     const char *pre = "";

404:     PetscCall(PetscObjectPrintClassNamePrefixType((PetscObject)snes, viewer));
405:     if (!snes->setupcalled) PetscCall(PetscViewerASCIIPrintf(viewer, "  SNES has not been set up so information may be incomplete\n"));
406:     if (snes->ops->view) {
407:       PetscCall(PetscViewerASCIIPushTab(viewer));
408:       PetscUseTypeMethod(snes, view, viewer);
409:       PetscCall(PetscViewerASCIIPopTab(viewer));
410:     }
411:     PetscCall(PetscViewerASCIIPrintf(viewer, "  maximum iterations=%" PetscInt_FMT ", maximum function evaluations=%" PetscInt_FMT "\n", snes->max_its, snes->max_funcs));
412:     PetscCall(PetscViewerASCIIPrintf(viewer, "  tolerances: relative=%g, absolute=%g, solution=%g\n", (double)snes->rtol, (double)snes->abstol, (double)snes->stol));
413:     if (snes->usesksp) PetscCall(PetscViewerASCIIPrintf(viewer, "  total number of linear solver iterations=%" PetscInt_FMT "\n", snes->linear_its));
414:     PetscCall(PetscViewerASCIIPrintf(viewer, "  total number of function evaluations=%" PetscInt_FMT "\n", snes->nfuncs));
415:     PetscCall(SNESGetNormSchedule(snes, &normschedule));
416:     if (normschedule > 0) PetscCall(PetscViewerASCIIPrintf(viewer, "  norm schedule %s\n", SNESNormSchedules[normschedule]));
417:     if (snes->gridsequence) PetscCall(PetscViewerASCIIPrintf(viewer, "  total number of grid sequence refinements=%" PetscInt_FMT "\n", snes->gridsequence));
418:     if (snes->ksp_ewconv) {
419:       kctx = (SNESKSPEW *)snes->kspconvctx;
420:       if (kctx) {
421:         PetscCall(PetscViewerASCIIPrintf(viewer, "  Eisenstat-Walker computation of KSP relative tolerance (version %" PetscInt_FMT ")\n", kctx->version));
422:         PetscCall(PetscViewerASCIIPrintf(viewer, "    rtol_0=%g, rtol_max=%g, threshold=%g\n", (double)kctx->rtol_0, (double)kctx->rtol_max, (double)kctx->threshold));
423:         PetscCall(PetscViewerASCIIPrintf(viewer, "    gamma=%g, alpha=%g, alpha2=%g\n", (double)kctx->gamma, (double)kctx->alpha, (double)kctx->alpha2));
424:       }
425:     }
426:     if (snes->lagpreconditioner == -1) {
427:       PetscCall(PetscViewerASCIIPrintf(viewer, "  Preconditioned is never rebuilt\n"));
428:     } else if (snes->lagpreconditioner > 1) {
429:       PetscCall(PetscViewerASCIIPrintf(viewer, "  Preconditioned is rebuilt every %" PetscInt_FMT " new Jacobians\n", snes->lagpreconditioner));
430:     }
431:     if (snes->lagjacobian == -1) {
432:       PetscCall(PetscViewerASCIIPrintf(viewer, "  Jacobian is never rebuilt\n"));
433:     } else if (snes->lagjacobian > 1) {
434:       PetscCall(PetscViewerASCIIPrintf(viewer, "  Jacobian is rebuilt every %" PetscInt_FMT " SNES iterations\n", snes->lagjacobian));
435:     }
436:     PetscCall(SNESGetDM(snes, &dm));
437:     PetscCall(DMSNESGetJacobian(dm, &cJ, &ctx));
438:     if (snes->mf_operator) {
439:       PetscCall(PetscViewerASCIIPrintf(viewer, "  Jacobian is applied matrix-free with differencing\n"));
440:       pre = "Preconditioning ";
441:     }
442:     if (cJ == SNESComputeJacobianDefault) {
443:       PetscCall(PetscViewerASCIIPrintf(viewer, "  %sJacobian is built using finite differences one column at a time\n", pre));
444:     } else if (cJ == SNESComputeJacobianDefaultColor) {
445:       PetscCall(PetscViewerASCIIPrintf(viewer, "  %sJacobian is built using finite differences with coloring\n", pre));
446:       /* it slightly breaks data encapsulation for access the DMDA information directly */
447:     } else if (cJ == SNESComputeJacobian_DMDA) {
448:       MatFDColoring fdcoloring;
449:       PetscCall(PetscObjectQuery((PetscObject)dm, "DMDASNES_FDCOLORING", (PetscObject *)&fdcoloring));
450:       if (fdcoloring) {
451:         PetscCall(PetscViewerASCIIPrintf(viewer, "  %sJacobian is built using colored finite differences on a DMDA\n", pre));
452:       } else {
453:         PetscCall(PetscViewerASCIIPrintf(viewer, "  %sJacobian is built using a DMDA local Jacobian\n", pre));
454:       }
455:     } else if (snes->mf) {
456:       PetscCall(PetscViewerASCIIPrintf(viewer, "  Jacobian is applied matrix-free with differencing, no explicit Jacobian\n"));
457:     }
458:   } else if (isstring) {
459:     const char *type;
460:     PetscCall(SNESGetType(snes, &type));
461:     PetscCall(PetscViewerStringSPrintf(viewer, " SNESType: %-7.7s", type));
462:     PetscTryTypeMethod(snes, view, viewer);
463:   } else if (isbinary) {
464:     PetscInt    classid = SNES_FILE_CLASSID;
465:     MPI_Comm    comm;
466:     PetscMPIInt rank;
467:     char        type[256];

469:     PetscCall(PetscObjectGetComm((PetscObject)snes, &comm));
470:     PetscCallMPI(MPI_Comm_rank(comm, &rank));
471:     if (rank == 0) {
472:       PetscCall(PetscViewerBinaryWrite(viewer, &classid, 1, PETSC_INT));
473:       PetscCall(PetscStrncpy(type, ((PetscObject)snes)->type_name, sizeof(type)));
474:       PetscCall(PetscViewerBinaryWrite(viewer, type, sizeof(type), PETSC_CHAR));
475:     }
476:     PetscTryTypeMethod(snes, view, viewer);
477:   } else if (isdraw) {
478:     PetscDraw draw;
479:     char      str[36];
480:     PetscReal x, y, bottom, h;

482:     PetscCall(PetscViewerDrawGetDraw(viewer, 0, &draw));
483:     PetscCall(PetscDrawGetCurrentPoint(draw, &x, &y));
484:     PetscCall(PetscStrncpy(str, "SNES: ", sizeof(str)));
485:     PetscCall(PetscStrlcat(str, ((PetscObject)snes)->type_name, sizeof(str)));
486:     PetscCall(PetscDrawStringBoxed(draw, x, y, PETSC_DRAW_BLUE, PETSC_DRAW_BLACK, str, NULL, &h));
487:     bottom = y - h;
488:     PetscCall(PetscDrawPushCurrentPoint(draw, x, bottom));
489:     PetscTryTypeMethod(snes, view, viewer);
490: #if defined(PETSC_HAVE_SAWS)
491:   } else if (issaws) {
492:     PetscMPIInt rank;
493:     const char *name;

495:     PetscCall(PetscObjectGetName((PetscObject)snes, &name));
496:     PetscCallMPI(MPI_Comm_rank(PETSC_COMM_WORLD, &rank));
497:     if (!((PetscObject)snes)->amsmem && rank == 0) {
498:       char dir[1024];

500:       PetscCall(PetscObjectViewSAWs((PetscObject)snes, viewer));
501:       PetscCall(PetscSNPrintf(dir, 1024, "/PETSc/Objects/%s/its", name));
502:       PetscCallSAWs(SAWs_Register, (dir, &snes->iter, 1, SAWs_READ, SAWs_INT));
503:       if (!snes->conv_hist) PetscCall(SNESSetConvergenceHistory(snes, NULL, NULL, PETSC_DECIDE, PETSC_TRUE));
504:       PetscCall(PetscSNPrintf(dir, 1024, "/PETSc/Objects/%s/conv_hist", name));
505:       PetscCallSAWs(SAWs_Register, (dir, snes->conv_hist, 10, SAWs_READ, SAWs_DOUBLE));
506:     }
507: #endif
508:   }
509:   if (snes->linesearch) {
510:     PetscCall(SNESGetLineSearch(snes, &linesearch));
511:     PetscCall(PetscViewerASCIIPushTab(viewer));
512:     PetscCall(SNESLineSearchView(linesearch, viewer));
513:     PetscCall(PetscViewerASCIIPopTab(viewer));
514:   }
515:   if (snes->npc && snes->usesnpc) {
516:     PetscCall(PetscViewerASCIIPushTab(viewer));
517:     PetscCall(SNESView(snes->npc, viewer));
518:     PetscCall(PetscViewerASCIIPopTab(viewer));
519:   }
520:   PetscCall(PetscViewerASCIIPushTab(viewer));
521:   PetscCall(DMGetDMSNES(snes->dm, &dmsnes));
522:   PetscCall(DMSNESView(dmsnes, viewer));
523:   PetscCall(PetscViewerASCIIPopTab(viewer));
524:   if (snes->usesksp) {
525:     PetscCall(SNESGetKSP(snes, &ksp));
526:     PetscCall(PetscViewerASCIIPushTab(viewer));
527:     PetscCall(KSPView(ksp, viewer));
528:     PetscCall(PetscViewerASCIIPopTab(viewer));
529:   }
530:   if (isdraw) {
531:     PetscDraw draw;
532:     PetscCall(PetscViewerDrawGetDraw(viewer, 0, &draw));
533:     PetscCall(PetscDrawPopCurrentPoint(draw));
534:   }
535:   PetscFunctionReturn(PETSC_SUCCESS);
536: }

538: /*
539:   We retain a list of functions that also take SNES command
540:   line options. These are called at the end SNESSetFromOptions()
541: */
542: #define MAXSETFROMOPTIONS 5
543: static PetscInt numberofsetfromoptions;
544: static PetscErrorCode (*othersetfromoptions[MAXSETFROMOPTIONS])(SNES);

546: /*@C
547:   SNESAddOptionsChecker - Adds an additional function to check for `SNES` options.

549:   Not Collective

551:   Input Parameter:
552: . snescheck - function that checks for options

554:   Level: developer

556: .seealso: [](chapter_snes), `SNES`, `SNESSetFromOptions()`
557: @*/
558: PetscErrorCode SNESAddOptionsChecker(PetscErrorCode (*snescheck)(SNES))
559: {
560:   PetscFunctionBegin;
561:   PetscCheck(numberofsetfromoptions < MAXSETFROMOPTIONS, PETSC_COMM_SELF, PETSC_ERR_ARG_OUTOFRANGE, "Too many options checkers, only %d allowed", MAXSETFROMOPTIONS);
562:   othersetfromoptions[numberofsetfromoptions++] = snescheck;
563:   PetscFunctionReturn(PETSC_SUCCESS);
564: }

566: static PetscErrorCode SNESSetUpMatrixFree_Private(SNES snes, PetscBool hasOperator, PetscInt version)
567: {
568:   Mat          J;
569:   MatNullSpace nullsp;

571:   PetscFunctionBegin;

574:   if (!snes->vec_func && (snes->jacobian || snes->jacobian_pre)) {
575:     Mat A = snes->jacobian, B = snes->jacobian_pre;
576:     PetscCall(MatCreateVecs(A ? A : B, NULL, &snes->vec_func));
577:   }

579:   PetscCheck(version == 1 || version == 2, PETSC_COMM_SELF, PETSC_ERR_ARG_OUTOFRANGE, "matrix-free operator routines, only version 1 and 2");
580:   if (version == 1) {
581:     PetscCall(MatCreateSNESMF(snes, &J));
582:     PetscCall(MatMFFDSetOptionsPrefix(J, ((PetscObject)snes)->prefix));
583:     PetscCall(MatSetFromOptions(J));
584:     /* TODO: the version 2 code should be merged into the MatCreateSNESMF() and MatCreateMFFD() infrastructure and then removed */
585:   } else /* if (version == 2) */ {
586:     PetscCheck(snes->vec_func, PETSC_COMM_SELF, PETSC_ERR_ARG_WRONGSTATE, "SNESSetFunction() must be called first");
587: #if !defined(PETSC_USE_COMPLEX) && !defined(PETSC_USE_REAL_SINGLE) && !defined(PETSC_USE_REAL___FLOAT128) && !defined(PETSC_USE_REAL___FP16)
588:     PetscCall(MatCreateSNESMFMore(snes, snes->vec_func, &J));
589: #else
590:     SETERRQ(PETSC_COMM_SELF, PETSC_ERR_SUP, "matrix-free operator routines (version 2)");
591: #endif
592:   }

594:   /* attach any user provided null space that was on Amat to the newly created matrix free matrix */
595:   if (snes->jacobian) {
596:     PetscCall(MatGetNullSpace(snes->jacobian, &nullsp));
597:     if (nullsp) PetscCall(MatSetNullSpace(J, nullsp));
598:   }

600:   PetscCall(PetscInfo(snes, "Setting default matrix-free operator routines (version %" PetscInt_FMT ")\n", version));
601:   if (hasOperator) {
602:     /* This version replaces the user provided Jacobian matrix with a
603:        matrix-free version but still employs the user-provided preconditioner matrix. */
604:     PetscCall(SNESSetJacobian(snes, J, NULL, NULL, NULL));
605:   } else {
606:     /* This version replaces both the user-provided Jacobian and the user-
607:      provided preconditioner Jacobian with the default matrix free version. */
608:     if (snes->npcside == PC_LEFT && snes->npc) {
609:       if (!snes->jacobian) PetscCall(SNESSetJacobian(snes, J, NULL, NULL, NULL));
610:     } else {
611:       KSP       ksp;
612:       PC        pc;
613:       PetscBool match;

615:       PetscCall(SNESSetJacobian(snes, J, J, MatMFFDComputeJacobian, NULL));
616:       /* Force no preconditioner */
617:       PetscCall(SNESGetKSP(snes, &ksp));
618:       PetscCall(KSPGetPC(ksp, &pc));
619:       PetscCall(PetscObjectTypeCompareAny((PetscObject)pc, &match, PCSHELL, PCH2OPUS, ""));
620:       if (!match) {
621:         PetscCall(PetscInfo(snes, "Setting default matrix-free preconditioner routines\nThat is no preconditioner is being used\n"));
622:         PetscCall(PCSetType(pc, PCNONE));
623:       }
624:     }
625:   }
626:   PetscCall(MatDestroy(&J));
627:   PetscFunctionReturn(PETSC_SUCCESS);
628: }

630: static PetscErrorCode DMRestrictHook_SNESVecSol(DM dmfine, Mat Restrict, Vec Rscale, Mat Inject, DM dmcoarse, void *ctx)
631: {
632:   SNES snes = (SNES)ctx;
633:   Vec  Xfine, Xfine_named = NULL, Xcoarse;

635:   PetscFunctionBegin;
636:   if (PetscLogPrintInfo) {
637:     PetscInt finelevel, coarselevel, fineclevel, coarseclevel;
638:     PetscCall(DMGetRefineLevel(dmfine, &finelevel));
639:     PetscCall(DMGetCoarsenLevel(dmfine, &fineclevel));
640:     PetscCall(DMGetRefineLevel(dmcoarse, &coarselevel));
641:     PetscCall(DMGetCoarsenLevel(dmcoarse, &coarseclevel));
642:     PetscCall(PetscInfo(dmfine, "Restricting SNES solution vector from level %" PetscInt_FMT "-%" PetscInt_FMT " to level %" PetscInt_FMT "-%" PetscInt_FMT "\n", finelevel, fineclevel, coarselevel, coarseclevel));
643:   }
644:   if (dmfine == snes->dm) Xfine = snes->vec_sol;
645:   else {
646:     PetscCall(DMGetNamedGlobalVector(dmfine, "SNESVecSol", &Xfine_named));
647:     Xfine = Xfine_named;
648:   }
649:   PetscCall(DMGetNamedGlobalVector(dmcoarse, "SNESVecSol", &Xcoarse));
650:   if (Inject) {
651:     PetscCall(MatRestrict(Inject, Xfine, Xcoarse));
652:   } else {
653:     PetscCall(MatRestrict(Restrict, Xfine, Xcoarse));
654:     PetscCall(VecPointwiseMult(Xcoarse, Xcoarse, Rscale));
655:   }
656:   PetscCall(DMRestoreNamedGlobalVector(dmcoarse, "SNESVecSol", &Xcoarse));
657:   if (Xfine_named) PetscCall(DMRestoreNamedGlobalVector(dmfine, "SNESVecSol", &Xfine_named));
658:   PetscFunctionReturn(PETSC_SUCCESS);
659: }

661: static PetscErrorCode DMCoarsenHook_SNESVecSol(DM dm, DM dmc, void *ctx)
662: {
663:   PetscFunctionBegin;
664:   PetscCall(DMCoarsenHookAdd(dmc, DMCoarsenHook_SNESVecSol, DMRestrictHook_SNESVecSol, ctx));
665:   PetscFunctionReturn(PETSC_SUCCESS);
666: }

668: /* This may be called to rediscretize the operator on levels of linear multigrid. The DM shuffle is so the user can
669:  * safely call SNESGetDM() in their residual evaluation routine. */
670: static PetscErrorCode KSPComputeOperators_SNES(KSP ksp, Mat A, Mat B, void *ctx)
671: {
672:   SNES  snes = (SNES)ctx;
673:   Vec   X, Xnamed = NULL;
674:   DM    dmsave;
675:   void *ctxsave;
676:   PetscErrorCode (*jac)(SNES, Vec, Mat, Mat, void *) = NULL;

678:   PetscFunctionBegin;
679:   dmsave = snes->dm;
680:   PetscCall(KSPGetDM(ksp, &snes->dm));
681:   if (dmsave == snes->dm) X = snes->vec_sol; /* We are on the finest level */
682:   else { /* We are on a coarser level, this vec was initialized using a DM restrict hook */ PetscCall(DMGetNamedGlobalVector(snes->dm, "SNESVecSol", &Xnamed));
683:     X = Xnamed;
684:     PetscCall(SNESGetJacobian(snes, NULL, NULL, &jac, &ctxsave));
685:     /* If the DM's don't match up, the MatFDColoring context needed for the jacobian won't match up either -- fixit. */
686:     if (jac == SNESComputeJacobianDefaultColor) PetscCall(SNESSetJacobian(snes, NULL, NULL, SNESComputeJacobianDefaultColor, NULL));
687:   }
688:   /* Make sure KSP DM has the Jacobian computation routine */
689:   {
690:     DMSNES sdm;

692:     PetscCall(DMGetDMSNES(snes->dm, &sdm));
693:     if (!sdm->ops->computejacobian) PetscCall(DMCopyDMSNES(dmsave, snes->dm));
694:   }
695:   /* Compute the operators */
696:   PetscCall(SNESComputeJacobian(snes, X, A, B));
697:   /* Put the previous context back */
698:   if (snes->dm != dmsave && jac == SNESComputeJacobianDefaultColor) PetscCall(SNESSetJacobian(snes, NULL, NULL, jac, ctxsave));

700:   if (Xnamed) PetscCall(DMRestoreNamedGlobalVector(snes->dm, "SNESVecSol", &Xnamed));
701:   snes->dm = dmsave;
702:   PetscFunctionReturn(PETSC_SUCCESS);
703: }

705: /*@
706:    SNESSetUpMatrices - ensures that matrices are available for `SNES` Newton-like methods, this is called by `SNESSetUp_XXX()`

708:    Collective

710:    Input Parameter:
711: .  snes - snes to configure

713:    Level: developer

715:    Note:
716:    If the matrices do not yet exist it attempts to create them based on options previously set for the `SNES` such as `-snes_mf`

718: .seealso: [](chapter_snes), `SNES`, `SNESSetUp()`
719: @*/
720: PetscErrorCode SNESSetUpMatrices(SNES snes)
721: {
722:   DM     dm;
723:   DMSNES sdm;

725:   PetscFunctionBegin;
726:   PetscCall(SNESGetDM(snes, &dm));
727:   PetscCall(DMGetDMSNES(dm, &sdm));
728:   if (!snes->jacobian && snes->mf) {
729:     Mat   J;
730:     void *functx;
731:     PetscCall(MatCreateSNESMF(snes, &J));
732:     PetscCall(MatMFFDSetOptionsPrefix(J, ((PetscObject)snes)->prefix));
733:     PetscCall(MatSetFromOptions(J));
734:     PetscCall(SNESGetFunction(snes, NULL, NULL, &functx));
735:     PetscCall(SNESSetJacobian(snes, J, J, NULL, NULL));
736:     PetscCall(MatDestroy(&J));
737:   } else if (snes->mf_operator && !snes->jacobian_pre && !snes->jacobian) {
738:     Mat J, B;
739:     PetscCall(MatCreateSNESMF(snes, &J));
740:     PetscCall(MatMFFDSetOptionsPrefix(J, ((PetscObject)snes)->prefix));
741:     PetscCall(MatSetFromOptions(J));
742:     PetscCall(DMCreateMatrix(snes->dm, &B));
743:     /* sdm->computejacobian was already set to reach here */
744:     PetscCall(SNESSetJacobian(snes, J, B, NULL, NULL));
745:     PetscCall(MatDestroy(&J));
746:     PetscCall(MatDestroy(&B));
747:   } else if (!snes->jacobian_pre) {
748:     PetscDS   prob;
749:     Mat       J, B;
750:     PetscBool hasPrec = PETSC_FALSE;

752:     J = snes->jacobian;
753:     PetscCall(DMGetDS(dm, &prob));
754:     if (prob) PetscCall(PetscDSHasJacobianPreconditioner(prob, &hasPrec));
755:     if (J) PetscCall(PetscObjectReference((PetscObject)J));
756:     else if (hasPrec) PetscCall(DMCreateMatrix(snes->dm, &J));
757:     PetscCall(DMCreateMatrix(snes->dm, &B));
758:     PetscCall(SNESSetJacobian(snes, J ? J : B, B, NULL, NULL));
759:     PetscCall(MatDestroy(&J));
760:     PetscCall(MatDestroy(&B));
761:   }
762:   {
763:     KSP ksp;
764:     PetscCall(SNESGetKSP(snes, &ksp));
765:     PetscCall(KSPSetComputeOperators(ksp, KSPComputeOperators_SNES, snes));
766:     PetscCall(DMCoarsenHookAdd(snes->dm, DMCoarsenHook_SNESVecSol, DMRestrictHook_SNESVecSol, snes));
767:   }
768:   PetscFunctionReturn(PETSC_SUCCESS);
769: }

771: static PetscErrorCode SNESMonitorPauseFinal_Internal(SNES snes)
772: {
773:   PetscInt i;

775:   PetscFunctionBegin;
776:   if (!snes->pauseFinal) PetscFunctionReturn(PETSC_SUCCESS);
777:   for (i = 0; i < snes->numbermonitors; ++i) {
778:     PetscViewerAndFormat *vf = (PetscViewerAndFormat *)snes->monitorcontext[i];
779:     PetscDraw             draw;
780:     PetscReal             lpause;

782:     if (!vf) continue;
783:     if (vf->lg) {
784:       if (!PetscCheckPointer(vf->lg, PETSC_OBJECT)) continue;
785:       if (((PetscObject)vf->lg)->classid != PETSC_DRAWLG_CLASSID) continue;
786:       PetscCall(PetscDrawLGGetDraw(vf->lg, &draw));
787:       PetscCall(PetscDrawGetPause(draw, &lpause));
788:       PetscCall(PetscDrawSetPause(draw, -1.0));
789:       PetscCall(PetscDrawPause(draw));
790:       PetscCall(PetscDrawSetPause(draw, lpause));
791:     } else {
792:       PetscBool isdraw;

794:       if (!PetscCheckPointer(vf->viewer, PETSC_OBJECT)) continue;
795:       if (((PetscObject)vf->viewer)->classid != PETSC_VIEWER_CLASSID) continue;
796:       PetscCall(PetscObjectTypeCompare((PetscObject)vf->viewer, PETSCVIEWERDRAW, &isdraw));
797:       if (!isdraw) continue;
798:       PetscCall(PetscViewerDrawGetDraw(vf->viewer, 0, &draw));
799:       PetscCall(PetscDrawGetPause(draw, &lpause));
800:       PetscCall(PetscDrawSetPause(draw, -1.0));
801:       PetscCall(PetscDrawPause(draw));
802:       PetscCall(PetscDrawSetPause(draw, lpause));
803:     }
804:   }
805:   PetscFunctionReturn(PETSC_SUCCESS);
806: }

808: /*@C
809:    SNESMonitorSetFromOptions - Sets a monitor function and viewer appropriate for the type indicated by the user

811:    Collective

813:    Input Parameters:
814: +  snes - `SNES` object you wish to monitor
815: .  name - the monitor type one is seeking
816: .  help - message indicating what monitoring is done
817: .  manual - manual page for the monitor
818: .  monitor - the monitor function
819: -  monitorsetup - a function that is called once ONLY if the user selected this monitor that may set additional features of the `SNES` or `PetscViewer` objects

821:    Options Database Key:
822: .  -name - trigger the use of this monitor in `SNESSetFromOptions()`

824:    Level: advanced

826: .seealso: [](chapter_snes), `PetscOptionsGetViewer()`, `PetscOptionsGetReal()`, `PetscOptionsHasName()`, `PetscOptionsGetString()`,
827:           `PetscOptionsGetIntArray()`, `PetscOptionsGetRealArray()`, `PetscOptionsBool()`
828:           `PetscOptionsInt()`, `PetscOptionsString()`, `PetscOptionsReal()`, `PetscOptionsBool()`,
829:           `PetscOptionsName()`, `PetscOptionsBegin()`, `PetscOptionsEnd()`, `PetscOptionsHeadBegin()`,
830:           `PetscOptionsStringArray()`, `PetscOptionsRealArray()`, `PetscOptionsScalar()`,
831:           `PetscOptionsBoolGroupBegin()`, `PetscOptionsBoolGroup()`, `PetscOptionsBoolGroupEnd()`,
832:           `PetscOptionsFList()`, `PetscOptionsEList()`
833: @*/
834: PetscErrorCode SNESMonitorSetFromOptions(SNES snes, const char name[], const char help[], const char manual[], PetscErrorCode (*monitor)(SNES, PetscInt, PetscReal, PetscViewerAndFormat *), PetscErrorCode (*monitorsetup)(SNES, PetscViewerAndFormat *))
835: {
836:   PetscViewer       viewer;
837:   PetscViewerFormat format;
838:   PetscBool         flg;

840:   PetscFunctionBegin;
841:   PetscCall(PetscOptionsGetViewer(PetscObjectComm((PetscObject)snes), ((PetscObject)snes)->options, ((PetscObject)snes)->prefix, name, &viewer, &format, &flg));
842:   if (flg) {
843:     PetscViewerAndFormat *vf;
844:     PetscCall(PetscViewerAndFormatCreate(viewer, format, &vf));
845:     PetscCall(PetscObjectDereference((PetscObject)viewer));
846:     if (monitorsetup) PetscCall((*monitorsetup)(snes, vf));
847:     PetscCall(SNESMonitorSet(snes, (PetscErrorCode(*)(SNES, PetscInt, PetscReal, void *))monitor, vf, (PetscErrorCode(*)(void **))PetscViewerAndFormatDestroy));
848:   }
849:   PetscFunctionReturn(PETSC_SUCCESS);
850: }

852: PetscErrorCode SNESEWSetFromOptions_Private(SNESKSPEW *kctx, MPI_Comm comm, const char *prefix)
853: {
854:   PetscFunctionBegin;
855:   PetscOptionsBegin(comm, prefix, "Eisenstat and Walker type forcing options", "KSP");
856:   PetscCall(PetscOptionsInt("-ksp_ew_version", "Version 1, 2 or 3", NULL, kctx->version, &kctx->version, NULL));
857:   PetscCall(PetscOptionsReal("-ksp_ew_rtol0", "0 <= rtol0 < 1", NULL, kctx->rtol_0, &kctx->rtol_0, NULL));
858:   PetscCall(PetscOptionsReal("-ksp_ew_rtolmax", "0 <= rtolmax < 1", NULL, kctx->rtol_max, &kctx->rtol_max, NULL));
859:   PetscCall(PetscOptionsReal("-ksp_ew_gamma", "0 <= gamma <= 1", NULL, kctx->gamma, &kctx->gamma, NULL));
860:   PetscCall(PetscOptionsReal("-ksp_ew_alpha", "1 < alpha <= 2", NULL, kctx->alpha, &kctx->alpha, NULL));
861:   PetscCall(PetscOptionsReal("-ksp_ew_alpha2", "alpha2", NULL, kctx->alpha2, &kctx->alpha2, NULL));
862:   PetscCall(PetscOptionsReal("-ksp_ew_threshold", "0 < threshold < 1", NULL, kctx->threshold, &kctx->threshold, NULL));
863:   PetscCall(PetscOptionsReal("-ksp_ew_v4_p1", "p1", NULL, kctx->v4_p1, &kctx->v4_p1, NULL));
864:   PetscCall(PetscOptionsReal("-ksp_ew_v4_p2", "p2", NULL, kctx->v4_p2, &kctx->v4_p2, NULL));
865:   PetscCall(PetscOptionsReal("-ksp_ew_v4_p3", "p3", NULL, kctx->v4_p3, &kctx->v4_p3, NULL));
866:   PetscCall(PetscOptionsReal("-ksp_ew_v4_m1", "Scaling when rk-1 in [p2,p3)", NULL, kctx->v4_m1, &kctx->v4_m1, NULL));
867:   PetscCall(PetscOptionsReal("-ksp_ew_v4_m2", "Scaling when rk-1 in [p3,+infty)", NULL, kctx->v4_m2, &kctx->v4_m2, NULL));
868:   PetscCall(PetscOptionsReal("-ksp_ew_v4_m3", "Threshold for successive rtol (0.1 in Eq.7)", NULL, kctx->v4_m3, &kctx->v4_m3, NULL));
869:   PetscCall(PetscOptionsReal("-ksp_ew_v4_m4", "Adaptation scaling (0.5 in Eq.7)", NULL, kctx->v4_m4, &kctx->v4_m4, NULL));
870:   PetscOptionsEnd();
871:   PetscFunctionReturn(PETSC_SUCCESS);
872: }

874: /*@
875:    SNESSetFromOptions - Sets various `SNES` and `KSP` parameters from user options.

877:    Collective

879:    Input Parameter:
880: .  snes - the `SNES` context

882:    Options Database Keys:
883: +  -snes_type <type> - newtonls, newtontr, ngmres, ncg, nrichardson, qn, vi, fas, `SNESType` for complete list
884: .  -snes_stol - convergence tolerance in terms of the norm
885:                 of the change in the solution between steps
886: .  -snes_atol <abstol> - absolute tolerance of residual norm
887: .  -snes_rtol <rtol> - relative decrease in tolerance norm from initial
888: .  -snes_divergence_tolerance <divtol> - if the residual goes above divtol*rnorm0, exit with divergence
889: .  -snes_force_iteration <force> - force SNESSolve() to take at least one iteration
890: .  -snes_max_it <max_it> - maximum number of iterations
891: .  -snes_max_funcs <max_funcs> - maximum number of function evaluations
892: .  -snes_max_fail <max_fail> - maximum number of line search failures allowed before stopping, default is none
893: .  -snes_max_linear_solve_fail - number of linear solver failures before SNESSolve() stops
894: .  -snes_lag_preconditioner <lag> - how often preconditioner is rebuilt (use -1 to never rebuild)
895: .  -snes_lag_preconditioner_persists <true,false> - retains the -snes_lag_preconditioner information across multiple SNESSolve()
896: .  -snes_lag_jacobian <lag> - how often Jacobian is rebuilt (use -1 to never rebuild)
897: .  -snes_lag_jacobian_persists <true,false> - retains the -snes_lag_jacobian information across multiple SNESSolve()
898: .  -snes_trtol <trtol> - trust region tolerance
899: .  -snes_convergence_test - <default,skip,correct_pressure> convergence test in nonlinear solver.
900:                                default `SNESConvergedDefault()`. skip `SNESConvergedSkip()` means continue iterating until max_it or some other criterion is reached, saving expense
901:                                of convergence test. correct_pressure S`NESConvergedCorrectPressure()` has special handling of a pressure null space.
902: .  -snes_monitor [ascii][:filename][:viewer format] - prints residual norm at each iteration. if no filename given prints to stdout
903: .  -snes_monitor_solution [ascii binary draw][:filename][:viewer format] - plots solution at each iteration
904: .  -snes_monitor_residual [ascii binary draw][:filename][:viewer format] - plots residual (not its norm) at each iteration
905: .  -snes_monitor_solution_update [ascii binary draw][:filename][:viewer format] - plots update to solution at each iteration
906: .  -snes_monitor_lg_residualnorm - plots residual norm at each iteration
907: .  -snes_monitor_lg_range - plots residual norm at each iteration
908: .  -snes_monitor_pause_final - Pauses all monitor drawing after the solver ends
909: .  -snes_fd - use finite differences to compute Jacobian; very slow, only for testing
910: .  -snes_fd_color - use finite differences with coloring to compute Jacobian
911: .  -snes_mf_ksp_monitor - if using matrix-free multiply then print h at each KSP iteration
912: .  -snes_converged_reason - print the reason for convergence/divergence after each solve
913: .  -npc_snes_type <type> - the SNES type to use as a nonlinear preconditioner
914: .   -snes_test_jacobian <optional threshold> - compare the user provided Jacobian with one computed via finite differences to check for errors.  If a threshold is given, display only those entries whose difference is greater than the threshold.
915: -   -snes_test_jacobian_view - display the user provided Jacobian, the finite difference Jacobian and the difference between them to help users detect the location of errors in the user provided Jacobian.

917:     Options Database Keys for Eisenstat-Walker method:
918: +  -snes_ksp_ew - use Eisenstat-Walker method for determining linear system convergence
919: .  -snes_ksp_ew_version ver - version of  Eisenstat-Walker method
920: .  -snes_ksp_ew_rtol0 <rtol0> - Sets rtol0
921: .  -snes_ksp_ew_rtolmax <rtolmax> - Sets rtolmax
922: .  -snes_ksp_ew_gamma <gamma> - Sets gamma
923: .  -snes_ksp_ew_alpha <alpha> - Sets alpha
924: .  -snes_ksp_ew_alpha2 <alpha2> - Sets alpha2
925: -  -snes_ksp_ew_threshold <threshold> - Sets threshold

927:    Level: beginner

929:    Notes:
930:    To see all options, run your program with the -help option or consult the users manual

932:    `SNES` supports three approaches for computing (approximate) Jacobians: user provided via `SNESSetJacobian()`, matrix free, and computing explicitly with
933:    finite differences and coloring using `MatFDColoring`. It is also possible to use automatic differentiation and the `MatFDColoring` object.

935: .seealso: [](chapter_snes), `SNESType`, `SNESSetOptionsPrefix()`, `SNESResetFromOptions()`, `SNES`, `SNESCreate()`
936: @*/
937: PetscErrorCode SNESSetFromOptions(SNES snes)
938: {
939:   PetscBool   flg, pcset, persist, set;
940:   PetscInt    i, indx, lag, grids;
941:   const char *deft        = SNESNEWTONLS;
942:   const char *convtests[] = {"default", "skip", "correct_pressure"};
943:   SNESKSPEW  *kctx        = NULL;
944:   char        type[256], monfilename[PETSC_MAX_PATH_LEN], ewprefix[256];
945:   PCSide      pcside;
946:   const char *optionsprefix;

948:   PetscFunctionBegin;
950:   PetscCall(SNESRegisterAll());
951:   PetscObjectOptionsBegin((PetscObject)snes);
952:   if (((PetscObject)snes)->type_name) deft = ((PetscObject)snes)->type_name;
953:   PetscCall(PetscOptionsFList("-snes_type", "Nonlinear solver method", "SNESSetType", SNESList, deft, type, 256, &flg));
954:   if (flg) {
955:     PetscCall(SNESSetType(snes, type));
956:   } else if (!((PetscObject)snes)->type_name) {
957:     PetscCall(SNESSetType(snes, deft));
958:   }
959:   PetscCall(PetscOptionsReal("-snes_stol", "Stop if step length less than", "SNESSetTolerances", snes->stol, &snes->stol, NULL));
960:   PetscCall(PetscOptionsReal("-snes_atol", "Stop if function norm less than", "SNESSetTolerances", snes->abstol, &snes->abstol, NULL));

962:   PetscCall(PetscOptionsReal("-snes_rtol", "Stop if decrease in function norm less than", "SNESSetTolerances", snes->rtol, &snes->rtol, NULL));
963:   PetscCall(PetscOptionsReal("-snes_divergence_tolerance", "Stop if residual norm increases by this factor", "SNESSetDivergenceTolerance", snes->divtol, &snes->divtol, NULL));
964:   PetscCall(PetscOptionsInt("-snes_max_it", "Maximum iterations", "SNESSetTolerances", snes->max_its, &snes->max_its, NULL));
965:   PetscCall(PetscOptionsInt("-snes_max_funcs", "Maximum function evaluations", "SNESSetTolerances", snes->max_funcs, &snes->max_funcs, NULL));
966:   PetscCall(PetscOptionsInt("-snes_max_fail", "Maximum nonlinear step failures", "SNESSetMaxNonlinearStepFailures", snes->maxFailures, &snes->maxFailures, NULL));
967:   PetscCall(PetscOptionsInt("-snes_max_linear_solve_fail", "Maximum failures in linear solves allowed", "SNESSetMaxLinearSolveFailures", snes->maxLinearSolveFailures, &snes->maxLinearSolveFailures, NULL));
968:   PetscCall(PetscOptionsBool("-snes_error_if_not_converged", "Generate error if solver does not converge", "SNESSetErrorIfNotConverged", snes->errorifnotconverged, &snes->errorifnotconverged, NULL));
969:   PetscCall(PetscOptionsBool("-snes_force_iteration", "Force SNESSolve() to take at least one iteration", "SNESSetForceIteration", snes->forceiteration, &snes->forceiteration, NULL));
970:   PetscCall(PetscOptionsBool("-snes_check_jacobian_domain_error", "Check Jacobian domain error after Jacobian evaluation", "SNESCheckJacobianDomainError", snes->checkjacdomainerror, &snes->checkjacdomainerror, NULL));

972:   PetscCall(PetscOptionsInt("-snes_lag_preconditioner", "How often to rebuild preconditioner", "SNESSetLagPreconditioner", snes->lagpreconditioner, &lag, &flg));
973:   if (flg) {
974:     PetscCheck(lag != -1, PetscObjectComm((PetscObject)snes), PETSC_ERR_USER, "Cannot set the lag to -1 from the command line since the preconditioner must be built as least once, perhaps you mean -2");
975:     PetscCall(SNESSetLagPreconditioner(snes, lag));
976:   }
977:   PetscCall(PetscOptionsBool("-snes_lag_preconditioner_persists", "Preconditioner lagging through multiple SNES solves", "SNESSetLagPreconditionerPersists", snes->lagjac_persist, &persist, &flg));
978:   if (flg) PetscCall(SNESSetLagPreconditionerPersists(snes, persist));
979:   PetscCall(PetscOptionsInt("-snes_lag_jacobian", "How often to rebuild Jacobian", "SNESSetLagJacobian", snes->lagjacobian, &lag, &flg));
980:   if (flg) {
981:     PetscCheck(lag != -1, PetscObjectComm((PetscObject)snes), PETSC_ERR_USER, "Cannot set the lag to -1 from the command line since the Jacobian must be built as least once, perhaps you mean -2");
982:     PetscCall(SNESSetLagJacobian(snes, lag));
983:   }
984:   PetscCall(PetscOptionsBool("-snes_lag_jacobian_persists", "Jacobian lagging through multiple SNES solves", "SNESSetLagJacobianPersists", snes->lagjac_persist, &persist, &flg));
985:   if (flg) PetscCall(SNESSetLagJacobianPersists(snes, persist));

987:   PetscCall(PetscOptionsInt("-snes_grid_sequence", "Use grid sequencing to generate initial guess", "SNESSetGridSequence", snes->gridsequence, &grids, &flg));
988:   if (flg) PetscCall(SNESSetGridSequence(snes, grids));

990:   PetscCall(PetscOptionsEList("-snes_convergence_test", "Convergence test", "SNESSetConvergenceTest", convtests, sizeof(convtests) / sizeof(char *), "default", &indx, &flg));
991:   if (flg) {
992:     switch (indx) {
993:     case 0:
994:       PetscCall(SNESSetConvergenceTest(snes, SNESConvergedDefault, NULL, NULL));
995:       break;
996:     case 1:
997:       PetscCall(SNESSetConvergenceTest(snes, SNESConvergedSkip, NULL, NULL));
998:       break;
999:     case 2:
1000:       PetscCall(SNESSetConvergenceTest(snes, SNESConvergedCorrectPressure, NULL, NULL));
1001:       break;
1002:     }
1003:   }

1005:   PetscCall(PetscOptionsEList("-snes_norm_schedule", "SNES Norm schedule", "SNESSetNormSchedule", SNESNormSchedules, 5, "function", &indx, &flg));
1006:   if (flg) PetscCall(SNESSetNormSchedule(snes, (SNESNormSchedule)indx));

1008:   PetscCall(PetscOptionsEList("-snes_function_type", "SNES Norm schedule", "SNESSetFunctionType", SNESFunctionTypes, 2, "unpreconditioned", &indx, &flg));
1009:   if (flg) PetscCall(SNESSetFunctionType(snes, (SNESFunctionType)indx));

1011:   kctx = (SNESKSPEW *)snes->kspconvctx;

1013:   PetscCall(PetscOptionsBool("-snes_ksp_ew", "Use Eisentat-Walker linear system convergence test", "SNESKSPSetUseEW", snes->ksp_ewconv, &snes->ksp_ewconv, NULL));

1015:   PetscCall(SNESGetOptionsPrefix(snes, &optionsprefix));
1016:   PetscCall(PetscSNPrintf(ewprefix, sizeof(ewprefix), "%s%s", optionsprefix ? optionsprefix : "", "snes_"));
1017:   PetscCall(SNESEWSetFromOptions_Private(kctx, PetscObjectComm((PetscObject)snes), ewprefix));

1019:   PetscCall(PetscOptionsInt("-snes_ksp_ew_version", "Version 1, 2 or 3", "SNESKSPSetParametersEW", kctx->version, &kctx->version, NULL));
1020:   PetscCall(PetscOptionsReal("-snes_ksp_ew_rtol0", "0 <= rtol0 < 1", "SNESKSPSetParametersEW", kctx->rtol_0, &kctx->rtol_0, NULL));
1021:   PetscCall(PetscOptionsReal("-snes_ksp_ew_rtolmax", "0 <= rtolmax < 1", "SNESKSPSetParametersEW", kctx->rtol_max, &kctx->rtol_max, NULL));
1022:   PetscCall(PetscOptionsReal("-snes_ksp_ew_gamma", "0 <= gamma <= 1", "SNESKSPSetParametersEW", kctx->gamma, &kctx->gamma, NULL));
1023:   PetscCall(PetscOptionsReal("-snes_ksp_ew_alpha", "1 < alpha <= 2", "SNESKSPSetParametersEW", kctx->alpha, &kctx->alpha, NULL));
1024:   PetscCall(PetscOptionsReal("-snes_ksp_ew_alpha2", "alpha2", "SNESKSPSetParametersEW", kctx->alpha2, &kctx->alpha2, NULL));
1025:   PetscCall(PetscOptionsReal("-snes_ksp_ew_threshold", "0 < threshold < 1", "SNESKSPSetParametersEW", kctx->threshold, &kctx->threshold, NULL));

1027:   flg = PETSC_FALSE;
1028:   PetscCall(PetscOptionsBool("-snes_monitor_cancel", "Remove all monitors", "SNESMonitorCancel", flg, &flg, &set));
1029:   if (set && flg) PetscCall(SNESMonitorCancel(snes));

1031:   PetscCall(SNESMonitorSetFromOptions(snes, "-snes_monitor", "Monitor norm of function", "SNESMonitorDefault", SNESMonitorDefault, SNESMonitorDefaultSetUp));
1032:   PetscCall(SNESMonitorSetFromOptions(snes, "-snes_monitor_short", "Monitor norm of function with fewer digits", "SNESMonitorDefaultShort", SNESMonitorDefaultShort, NULL));
1033:   PetscCall(SNESMonitorSetFromOptions(snes, "-snes_monitor_range", "Monitor range of elements of function", "SNESMonitorRange", SNESMonitorRange, NULL));

1035:   PetscCall(SNESMonitorSetFromOptions(snes, "-snes_monitor_ratio", "Monitor ratios of the norm of function for consecutive steps", "SNESMonitorRatio", SNESMonitorRatio, SNESMonitorRatioSetUp));
1036:   PetscCall(SNESMonitorSetFromOptions(snes, "-snes_monitor_field", "Monitor norm of function (split into fields)", "SNESMonitorDefaultField", SNESMonitorDefaultField, NULL));
1037:   PetscCall(SNESMonitorSetFromOptions(snes, "-snes_monitor_solution", "View solution at each iteration", "SNESMonitorSolution", SNESMonitorSolution, NULL));
1038:   PetscCall(SNESMonitorSetFromOptions(snes, "-snes_monitor_solution_update", "View correction at each iteration", "SNESMonitorSolutionUpdate", SNESMonitorSolutionUpdate, NULL));
1039:   PetscCall(SNESMonitorSetFromOptions(snes, "-snes_monitor_residual", "View residual at each iteration", "SNESMonitorResidual", SNESMonitorResidual, NULL));
1040:   PetscCall(SNESMonitorSetFromOptions(snes, "-snes_monitor_jacupdate_spectrum", "Print the change in the spectrum of the Jacobian", "SNESMonitorJacUpdateSpectrum", SNESMonitorJacUpdateSpectrum, NULL));
1041:   PetscCall(SNESMonitorSetFromOptions(snes, "-snes_monitor_fields", "Monitor norm of function per field", "SNESMonitorSet", SNESMonitorFields, NULL));
1042:   PetscCall(PetscOptionsBool("-snes_monitor_pause_final", "Pauses all draw monitors at the final iterate", "SNESMonitorPauseFinal_Internal", PETSC_FALSE, &snes->pauseFinal, NULL));

1044:   PetscCall(PetscOptionsString("-snes_monitor_python", "Use Python function", "SNESMonitorSet", NULL, monfilename, sizeof(monfilename), &flg));
1045:   if (flg) PetscCall(PetscPythonMonitorSet((PetscObject)snes, monfilename));

1047:   flg = PETSC_FALSE;
1048:   PetscCall(PetscOptionsBool("-snes_monitor_lg_range", "Plot function range at each iteration", "SNESMonitorLGRange", flg, &flg, NULL));
1049:   if (flg) {
1050:     PetscViewer ctx;

1052:     PetscCall(PetscViewerDrawOpen(PetscObjectComm((PetscObject)snes), NULL, NULL, PETSC_DECIDE, PETSC_DECIDE, 400, 300, &ctx));
1053:     PetscCall(SNESMonitorSet(snes, SNESMonitorLGRange, ctx, (PetscErrorCode(*)(void **))PetscViewerDestroy));
1054:   }

1056:   flg = PETSC_FALSE;
1057:   PetscCall(PetscOptionsBool("-snes_converged_reason_view_cancel", "Remove all converged reason viewers", "SNESConvergedReasonViewCancel", flg, &flg, &set));
1058:   if (set && flg) PetscCall(SNESConvergedReasonViewCancel(snes));

1060:   flg = PETSC_FALSE;
1061:   PetscCall(PetscOptionsBool("-snes_fd", "Use finite differences (slow) to compute Jacobian", "SNESComputeJacobianDefault", flg, &flg, NULL));
1062:   if (flg) {
1063:     void *functx;
1064:     DM    dm;
1065:     PetscCall(SNESGetDM(snes, &dm));
1066:     PetscCall(DMSNESUnsetJacobianContext_Internal(dm));
1067:     PetscCall(SNESGetFunction(snes, NULL, NULL, &functx));
1068:     PetscCall(SNESSetJacobian(snes, snes->jacobian, snes->jacobian_pre, SNESComputeJacobianDefault, functx));
1069:     PetscCall(PetscInfo(snes, "Setting default finite difference Jacobian matrix\n"));
1070:   }

1072:   flg = PETSC_FALSE;
1073:   PetscCall(PetscOptionsBool("-snes_fd_function", "Use finite differences (slow) to compute function from user objective", "SNESObjectiveComputeFunctionDefaultFD", flg, &flg, NULL));
1074:   if (flg) PetscCall(SNESSetFunction(snes, NULL, SNESObjectiveComputeFunctionDefaultFD, NULL));

1076:   flg = PETSC_FALSE;
1077:   PetscCall(PetscOptionsBool("-snes_fd_color", "Use finite differences with coloring to compute Jacobian", "SNESComputeJacobianDefaultColor", flg, &flg, NULL));
1078:   if (flg) {
1079:     DM dm;
1080:     PetscCall(SNESGetDM(snes, &dm));
1081:     PetscCall(DMSNESUnsetJacobianContext_Internal(dm));
1082:     PetscCall(SNESSetJacobian(snes, snes->jacobian, snes->jacobian_pre, SNESComputeJacobianDefaultColor, NULL));
1083:     PetscCall(PetscInfo(snes, "Setting default finite difference coloring Jacobian matrix\n"));
1084:   }

1086:   flg = PETSC_FALSE;
1087:   PetscCall(PetscOptionsBool("-snes_mf_operator", "Use a Matrix-Free Jacobian with user-provided preconditioner matrix", "SNESSetUseMatrixFree", PETSC_FALSE, &snes->mf_operator, &flg));
1088:   if (flg && snes->mf_operator) {
1089:     snes->mf_operator = PETSC_TRUE;
1090:     snes->mf          = PETSC_TRUE;
1091:   }
1092:   flg = PETSC_FALSE;
1093:   PetscCall(PetscOptionsBool("-snes_mf", "Use a Matrix-Free Jacobian with no preconditioner matrix", "SNESSetUseMatrixFree", PETSC_FALSE, &snes->mf, &flg));
1094:   if (!flg && snes->mf_operator) snes->mf = PETSC_TRUE;
1095:   PetscCall(PetscOptionsInt("-snes_mf_version", "Matrix-Free routines version 1 or 2", "None", snes->mf_version, &snes->mf_version, NULL));

1097:   flg = PETSC_FALSE;
1098:   PetscCall(SNESGetNPCSide(snes, &pcside));
1099:   PetscCall(PetscOptionsEnum("-snes_npc_side", "SNES nonlinear preconditioner side", "SNESSetNPCSide", PCSides, (PetscEnum)pcside, (PetscEnum *)&pcside, &flg));
1100:   if (flg) PetscCall(SNESSetNPCSide(snes, pcside));

1102: #if defined(PETSC_HAVE_SAWS)
1103:   /*
1104:     Publish convergence information using SAWs
1105:   */
1106:   flg = PETSC_FALSE;
1107:   PetscCall(PetscOptionsBool("-snes_monitor_saws", "Publish SNES progress using SAWs", "SNESMonitorSet", flg, &flg, NULL));
1108:   if (flg) {
1109:     void *ctx;
1110:     PetscCall(SNESMonitorSAWsCreate(snes, &ctx));
1111:     PetscCall(SNESMonitorSet(snes, SNESMonitorSAWs, ctx, SNESMonitorSAWsDestroy));
1112:   }
1113: #endif
1114: #if defined(PETSC_HAVE_SAWS)
1115:   {
1116:     PetscBool set;
1117:     flg = PETSC_FALSE;
1118:     PetscCall(PetscOptionsBool("-snes_saws_block", "Block for SAWs at end of SNESSolve", "PetscObjectSAWsBlock", ((PetscObject)snes)->amspublishblock, &flg, &set));
1119:     if (set) PetscCall(PetscObjectSAWsSetBlock((PetscObject)snes, flg));
1120:   }
1121: #endif

1123:   for (i = 0; i < numberofsetfromoptions; i++) PetscCall((*othersetfromoptions[i])(snes));

1125:   PetscTryTypeMethod(snes, setfromoptions, PetscOptionsObject);

1127:   /* process any options handlers added with PetscObjectAddOptionsHandler() */
1128:   PetscCall(PetscObjectProcessOptionsHandlers((PetscObject)snes, PetscOptionsObject));
1129:   PetscOptionsEnd();

1131:   if (snes->linesearch) {
1132:     PetscCall(SNESGetLineSearch(snes, &snes->linesearch));
1133:     PetscCall(SNESLineSearchSetFromOptions(snes->linesearch));
1134:   }

1136:   if (snes->usesksp) {
1137:     if (!snes->ksp) PetscCall(SNESGetKSP(snes, &snes->ksp));
1138:     PetscCall(KSPSetOperators(snes->ksp, snes->jacobian, snes->jacobian_pre));
1139:     PetscCall(KSPSetFromOptions(snes->ksp));
1140:   }

1142:   /* if user has set the SNES NPC type via options database, create it. */
1143:   PetscCall(SNESGetOptionsPrefix(snes, &optionsprefix));
1144:   PetscCall(PetscOptionsHasName(((PetscObject)snes)->options, optionsprefix, "-npc_snes_type", &pcset));
1145:   if (pcset && (!snes->npc)) PetscCall(SNESGetNPC(snes, &snes->npc));
1146:   if (snes->npc) PetscCall(SNESSetFromOptions(snes->npc));
1147:   snes->setfromoptionscalled++;
1148:   PetscFunctionReturn(PETSC_SUCCESS);
1149: }

1151: /*@
1152:    SNESResetFromOptions - Sets various `SNES` and `KSP` parameters from user options ONLY if the `SNESSetFromOptions()` was previously set from options

1154:    Collective

1156:    Input Parameter:
1157: .  snes - the `SNES` context

1159:    Level: beginner

1161: .seealso: [](chapter_snes), `SNES`, `SNESSetFromOptions()`, `SNESSetOptionsPrefix()`
1162: @*/
1163: PetscErrorCode SNESResetFromOptions(SNES snes)
1164: {
1165:   PetscFunctionBegin;
1166:   if (snes->setfromoptionscalled) PetscCall(SNESSetFromOptions(snes));
1167:   PetscFunctionReturn(PETSC_SUCCESS);
1168: }

1170: /*@C
1171:    SNESSetComputeApplicationContext - Sets an optional function to compute a user-defined context for
1172:    the nonlinear solvers.

1174:    Logically Collective; No Fortran Support

1176:    Input Parameters:
1177: +  snes - the `SNES` context
1178: .  compute - function to compute the context
1179: -  destroy - function to destroy the context

1181:    Level: intermediate

1183:    Note:
1184:    This routine is useful if you are performing grid sequencing or using `SNESFAS` and need the appropriate context generated for each level.

1186:    Use `SNESSetApplicationContext()` to see the context immediately

1188: .seealso: [](chapter_snes), `SNESGetApplicationContext()`, `SNESSetComputeApplicationContext()`, `SNESSetApplicationContext()`
1189: @*/
1190: PetscErrorCode SNESSetComputeApplicationContext(SNES snes, PetscErrorCode (*compute)(SNES, void **), PetscErrorCode (*destroy)(void **))
1191: {
1192:   PetscFunctionBegin;
1194:   snes->ops->usercompute = compute;
1195:   snes->ops->userdestroy = destroy;
1196:   PetscFunctionReturn(PETSC_SUCCESS);
1197: }

1199: /*@
1200:    SNESSetApplicationContext - Sets the optional user-defined context for the nonlinear solvers.

1202:    Logically Collective

1204:    Input Parameters:
1205: +  snes - the `SNES` context
1206: -  usrP - optional user context

1208:    Level: intermediate

1210:    Notes:
1211:    Users can provide a context when constructing the `SNES` options and then access it inside their function, Jacobian, or other evaluation function
1212:    with `SNESGetApplicationContext()`

1214:    To provide a function that computes the context for you use `SNESSetComputeApplicationContext()`

1216:    Fortran Note:
1217:     You must write a Fortran interface definition for this
1218:     function that tells Fortran the Fortran derived data type that you are passing in as the ctx argument.

1220: .seealso: [](chapter_snes), `SNES`, `SNESSetComputeApplicationContext()`, `SNESGetApplicationContext()`
1221: @*/
1222: PetscErrorCode SNESSetApplicationContext(SNES snes, void *usrP)
1223: {
1224:   KSP ksp;

1226:   PetscFunctionBegin;
1228:   PetscCall(SNESGetKSP(snes, &ksp));
1229:   PetscCall(KSPSetApplicationContext(ksp, usrP));
1230:   snes->user = usrP;
1231:   PetscFunctionReturn(PETSC_SUCCESS);
1232: }

1234: /*@
1235:    SNESGetApplicationContext - Gets the user-defined context for the
1236:    nonlinear solvers set with `SNESGetApplicationContext()` or with `SNESSetComputeApplicationContext()`

1238:    Not Collective

1240:    Input Parameter:
1241: .  snes - `SNES` context

1243:    Output Parameter:
1244: .  usrP - user context

1246:    Level: intermediate

1248:    Fortran Note:
1249:    You must write a Fortran interface definition for this
1250:    function that tells Fortran the Fortran derived data type that you are passing in as the ctx argument.

1252: .seealso: [](chapter_snes), `SNESSetApplicationContext()`
1253: @*/
1254: PetscErrorCode SNESGetApplicationContext(SNES snes, void *usrP)
1255: {
1256:   PetscFunctionBegin;
1258:   *(void **)usrP = snes->user;
1259:   PetscFunctionReturn(PETSC_SUCCESS);
1260: }

1262: /*@
1263:    SNESSetUseMatrixFree - indicates that `SNES` should use matrix free finite difference matrix vector products to apply the Jacobian.

1265:    Logically Collective

1267:    Input Parameters:
1268: +  snes - `SNES` context
1269: .  mf_operator - use matrix-free only for the Amat used by `SNESSetJacobian()`, this means the user provided Pmat will continue to be used
1270: -  mf - use matrix-free for both the Amat and Pmat used by `SNESSetJacobian()`, both the Amat and Pmat set in `SNESSetJacobian()` will be ignored. With
1271:    this option no matrix element based preconditioners can be used in the linear solve since the matrix won't be explicitly available

1273:    Options Database Keys:
1274: + -snes_mf_operator - use matrix free only for the mat operator
1275: . -snes_mf - use matrix-free for both the mat and pmat operator
1276: . -snes_fd_color - compute the Jacobian via coloring and finite differences.
1277: - -snes_fd - compute the Jacobian via finite differences (slow)

1279:    Level: intermediate

1281:    Note:
1282:    `SNES` supports three approaches for computing (approximate) Jacobians: user provided via `SNESSetJacobian()`, matrix-free, and computing explicitly with
1283:    finite differences and coloring using `MatFDColoring`. It is also possible to use automatic differentiation and the `MatFDColoring` object.

1285: .seealso: [](chapter_snes), `SNES`, `SNESGetUseMatrixFree()`, `MatCreateSNESMF()`, `SNESComputeJacobianDefaultColor()`
1286: @*/
1287: PetscErrorCode SNESSetUseMatrixFree(SNES snes, PetscBool mf_operator, PetscBool mf)
1288: {
1289:   PetscFunctionBegin;
1293:   snes->mf          = mf_operator ? PETSC_TRUE : mf;
1294:   snes->mf_operator = mf_operator;
1295:   PetscFunctionReturn(PETSC_SUCCESS);
1296: }

1298: /*@
1299:    SNESGetUseMatrixFree - indicates if the `SNES` uses matrix-free finite difference matrix vector products to apply the Jacobian.

1301:    Not Collective, but the resulting flags will be the same on all MPI ranks

1303:    Input Parameter:
1304: .  snes - `SNES` context

1306:    Output Parameters:
1307: +  mf_operator - use matrix-free only for the Amat used by `SNESSetJacobian()`, this means the user provided Pmat will continue to be used
1308: -  mf - use matrix-free for both the Amat and Pmat used by `SNESSetJacobian()`, both the Amat and Pmat set in `SNESSetJacobian()` will be ignored

1310:    Level: intermediate

1312: .seealso: [](chapter_snes), `SNES`, `SNESSetUseMatrixFree()`, `MatCreateSNESMF()`
1313: @*/
1314: PetscErrorCode SNESGetUseMatrixFree(SNES snes, PetscBool *mf_operator, PetscBool *mf)
1315: {
1316:   PetscFunctionBegin;
1318:   if (mf) *mf = snes->mf;
1319:   if (mf_operator) *mf_operator = snes->mf_operator;
1320:   PetscFunctionReturn(PETSC_SUCCESS);
1321: }

1323: /*@
1324:    SNESGetIterationNumber - Gets the number of nonlinear iterations completed
1325:    at this time.

1327:    Not Collective

1329:    Input Parameter:
1330: .  snes - `SNES` context

1332:    Output Parameter:
1333: .  iter - iteration number

1335:    Level: intermediate

1337:    Notes:
1338:    For example, during the computation of iteration 2 this would return 1.

1340:    This is useful for using lagged Jacobians (where one does not recompute the
1341:    Jacobian at each `SNES` iteration). For example, the code
1342: .vb
1343:       ierr = SNESGetIterationNumber(snes,&it);
1344:       if (!(it % 2)) {
1345:         [compute Jacobian here]
1346:       }
1347: .ve
1348:    can be used in your function that computes the Jacobian to cause the Jacobian to be
1349:    recomputed every second `SNES` iteration. See also `SNESSetLagJacobian()`

1351:    After the `SNES` solve is complete this will return the number of nonlinear iterations used.

1353: .seealso: [](chapter_snes), `SNES`, `SNESSolve()`, `SNESSetLagJacobian()`, `SNESGetLinearSolveIterations()`
1354: @*/
1355: PetscErrorCode SNESGetIterationNumber(SNES snes, PetscInt *iter)
1356: {
1357:   PetscFunctionBegin;
1360:   *iter = snes->iter;
1361:   PetscFunctionReturn(PETSC_SUCCESS);
1362: }

1364: /*@
1365:    SNESSetIterationNumber - Sets the current iteration number.

1367:    Not Collective

1369:    Input Parameters:
1370: +  snes - `SNES` context
1371: -  iter - iteration number

1373:    Level: developer

1375: .seealso: [](chapter_snes), `SNESGetLinearSolveIterations()`
1376: @*/
1377: PetscErrorCode SNESSetIterationNumber(SNES snes, PetscInt iter)
1378: {
1379:   PetscFunctionBegin;
1381:   PetscCall(PetscObjectSAWsTakeAccess((PetscObject)snes));
1382:   snes->iter = iter;
1383:   PetscCall(PetscObjectSAWsGrantAccess((PetscObject)snes));
1384:   PetscFunctionReturn(PETSC_SUCCESS);
1385: }

1387: /*@
1388:    SNESGetNonlinearStepFailures - Gets the number of unsuccessful steps
1389:    attempted by the nonlinear solver.

1391:    Not Collective

1393:    Input Parameter:
1394: .  snes - `SNES` context

1396:    Output Parameter:
1397: .  nfails - number of unsuccessful steps attempted

1399:    Level: intermediate

1401:    Note:
1402:    This counter is reset to zero for each successive call to `SNESSolve()`.

1404: .seealso: [](chapter_snes), `SNES`, `SNESGetMaxLinearSolveFailures()`, `SNESGetLinearSolveIterations()`, `SNESSetMaxLinearSolveFailures()`, `SNESGetLinearSolveFailures()`,
1405:           `SNESSetMaxNonlinearStepFailures()`, `SNESGetMaxNonlinearStepFailures()`
1406: @*/
1407: PetscErrorCode SNESGetNonlinearStepFailures(SNES snes, PetscInt *nfails)
1408: {
1409:   PetscFunctionBegin;
1412:   *nfails = snes->numFailures;
1413:   PetscFunctionReturn(PETSC_SUCCESS);
1414: }

1416: /*@
1417:    SNESSetMaxNonlinearStepFailures - Sets the maximum number of unsuccessful steps
1418:    attempted by the nonlinear solver before it gives up and generates an error

1420:    Not Collective

1422:    Input Parameters:
1423: +  snes     - `SNES` context
1424: -  maxFails - maximum of unsuccessful steps

1426:    Level: intermediate

1428: .seealso: [](chapter_snes), `SNESSetErrorIfNotConverged()`, `SNESGetMaxLinearSolveFailures()`, `SNESGetLinearSolveIterations()`, `SNESSetMaxLinearSolveFailures()`, `SNESGetLinearSolveFailures()`,
1429:           `SNESGetMaxNonlinearStepFailures()`, `SNESGetNonlinearStepFailures()`
1430: @*/
1431: PetscErrorCode SNESSetMaxNonlinearStepFailures(SNES snes, PetscInt maxFails)
1432: {
1433:   PetscFunctionBegin;
1435:   snes->maxFailures = maxFails;
1436:   PetscFunctionReturn(PETSC_SUCCESS);
1437: }

1439: /*@
1440:    SNESGetMaxNonlinearStepFailures - Gets the maximum number of unsuccessful steps
1441:    attempted by the nonlinear solver before it gives up and generates an error

1443:    Not Collective

1445:    Input Parameter:
1446: .  snes     - SNES context

1448:    Output Parameter:
1449: .  maxFails - maximum of unsuccessful steps

1451:    Level: intermediate

1453: .seealso: [](chapter_snes), `SNESSetErrorIfNotConverged()`, `SNESGetMaxLinearSolveFailures()`, `SNESGetLinearSolveIterations()`, `SNESSetMaxLinearSolveFailures()`, `SNESGetLinearSolveFailures()`,
1454:           `SNESSetMaxNonlinearStepFailures()`, `SNESGetNonlinearStepFailures()`
1455: @*/
1456: PetscErrorCode SNESGetMaxNonlinearStepFailures(SNES snes, PetscInt *maxFails)
1457: {
1458:   PetscFunctionBegin;
1461:   *maxFails = snes->maxFailures;
1462:   PetscFunctionReturn(PETSC_SUCCESS);
1463: }

1465: /*@
1466:    SNESGetNumberFunctionEvals - Gets the number of user provided function evaluations
1467:      done by the `SNES` object

1469:    Not Collective

1471:    Input Parameter:
1472: .  snes     - `SNES` context

1474:    Output Parameter:
1475: .  nfuncs - number of evaluations

1477:    Level: intermediate

1479:    Note:
1480:     Reset every time `SNESSolve()` is called unless `SNESSetCountersReset()` is used.

1482: .seealso: [](chapter_snes), `SNES`, `SNESGetMaxLinearSolveFailures()`, `SNESGetLinearSolveIterations()`, `SNESSetMaxLinearSolveFailures()`, `SNESGetLinearSolveFailures()`, `SNESSetCountersReset()`
1483: @*/
1484: PetscErrorCode SNESGetNumberFunctionEvals(SNES snes, PetscInt *nfuncs)
1485: {
1486:   PetscFunctionBegin;
1489:   *nfuncs = snes->nfuncs;
1490:   PetscFunctionReturn(PETSC_SUCCESS);
1491: }

1493: /*@
1494:    SNESGetLinearSolveFailures - Gets the number of failed (non-converged)
1495:    linear solvers.

1497:    Not Collective

1499:    Input Parameter:
1500: .  snes - `SNES` context

1502:    Output Parameter:
1503: .  nfails - number of failed solves

1505:    Options Database Key:
1506: . -snes_max_linear_solve_fail <num> - The number of failures before the solve is terminated

1508:    Level: intermediate

1510:    Note:
1511:    This counter is reset to zero for each successive call to `SNESSolve()`.

1513: .seealso: [](chapter_snes), `SNESGetMaxLinearSolveFailures()`, `SNESGetLinearSolveIterations()`, `SNESSetMaxLinearSolveFailures()`
1514: @*/
1515: PetscErrorCode SNESGetLinearSolveFailures(SNES snes, PetscInt *nfails)
1516: {
1517:   PetscFunctionBegin;
1520:   *nfails = snes->numLinearSolveFailures;
1521:   PetscFunctionReturn(PETSC_SUCCESS);
1522: }

1524: /*@
1525:    SNESSetMaxLinearSolveFailures - the number of failed linear solve attempts
1526:    allowed before `SNES` returns with a diverged reason of `SNES_DIVERGED_LINEAR_SOLVE`

1528:    Logically Collective

1530:    Input Parameters:
1531: +  snes     - `SNES` context
1532: -  maxFails - maximum allowed linear solve failures

1534:    Options Database Key:
1535: . -snes_max_linear_solve_fail <num> - The number of failures before the solve is terminated

1537:    Level: intermediate

1539:    Note:
1540:     By default this is 0; that is `SNES` returns on the first failed linear solve

1542: .seealso: [](chapter_snes), `SNESSetErrorIfNotConverged()`, `SNESGetLinearSolveFailures()`, `SNESGetMaxLinearSolveFailures()`, `SNESGetLinearSolveIterations()`
1543: @*/
1544: PetscErrorCode SNESSetMaxLinearSolveFailures(SNES snes, PetscInt maxFails)
1545: {
1546:   PetscFunctionBegin;
1549:   snes->maxLinearSolveFailures = maxFails;
1550:   PetscFunctionReturn(PETSC_SUCCESS);
1551: }

1553: /*@
1554:    SNESGetMaxLinearSolveFailures - gets the maximum number of linear solve failures that
1555:      are allowed before `SNES` returns as unsuccessful

1557:    Not Collective

1559:    Input Parameter:
1560: .  snes     - `SNES` context

1562:    Output Parameter:
1563: .  maxFails - maximum of unsuccessful solves allowed

1565:    Level: intermediate

1567:    Note:
1568:     By default this is 1; that is `SNES` returns on the first failed linear solve

1570: .seealso: [](chapter_snes), `SNESSetErrorIfNotConverged()`, `SNESGetLinearSolveFailures()`, `SNESGetLinearSolveIterations()`, `SNESSetMaxLinearSolveFailures()`,
1571: @*/
1572: PetscErrorCode SNESGetMaxLinearSolveFailures(SNES snes, PetscInt *maxFails)
1573: {
1574:   PetscFunctionBegin;
1577:   *maxFails = snes->maxLinearSolveFailures;
1578:   PetscFunctionReturn(PETSC_SUCCESS);
1579: }

1581: /*@
1582:    SNESGetLinearSolveIterations - Gets the total number of linear iterations
1583:    used by the nonlinear solver.

1585:    Not Collective

1587:    Input Parameter:
1588: .  snes - `SNES` context

1590:    Output Parameter:
1591: .  lits - number of linear iterations

1593:    Level: intermediate

1595:    Notes:
1596:    This counter is reset to zero for each successive call to `SNESSolve()` unless `SNESSetCountersReset()` is used.

1598:    If the linear solver fails inside the `SNESSolve()` the iterations for that call to the linear solver are not included. If you wish to count them
1599:    then call `KSPGetIterationNumber()` after the failed solve.

1601: .seealso: [](chapter_snes), `SNES`, `SNESGetIterationNumber()`, `SNESGetLinearSolveFailures()`, `SNESGetMaxLinearSolveFailures()`, `SNESSetCountersReset()`
1602: @*/
1603: PetscErrorCode SNESGetLinearSolveIterations(SNES snes, PetscInt *lits)
1604: {
1605:   PetscFunctionBegin;
1608:   *lits = snes->linear_its;
1609:   PetscFunctionReturn(PETSC_SUCCESS);
1610: }

1612: /*@
1613:    SNESSetCountersReset - Sets whether or not the counters for linear iterations and function evaluations
1614:    are reset every time `SNESSolve()` is called.

1616:    Logically Collective

1618:    Input Parameters:
1619: +  snes - `SNES` context
1620: -  reset - whether to reset the counters or not, defaults to `PETSC_TRUE`

1622:    Level: developer

1624: .seealso: [](chapter_snes), `SNESGetNumberFunctionEvals()`, `SNESGetLinearSolveIterations()`, `SNESGetNPC()`
1625: @*/
1626: PetscErrorCode SNESSetCountersReset(SNES snes, PetscBool reset)
1627: {
1628:   PetscFunctionBegin;
1631:   snes->counters_reset = reset;
1632:   PetscFunctionReturn(PETSC_SUCCESS);
1633: }

1635: /*@
1636:    SNESSetKSP - Sets a `KSP` context for the `SNES` object to use

1638:    Not Collective, but the `SNES` and `KSP` objects must live on the same MPI_Comm

1640:    Input Parameters:
1641: +  snes - the `SNES` context
1642: -  ksp - the `KSP` context

1644:    Level: developer

1646:    Notes:
1647:    The `SNES` object already has its `KSP` object, you can obtain with `SNESGetKSP()`
1648:    so this routine is rarely needed.

1650:    The `KSP` object that is already in the `SNES` object has its reference count
1651:    decreased by one.

1653: .seealso: [](chapter_snes), `SNES`, `KSP`, `KSPGetPC()`, `SNESCreate()`, `KSPCreate()`, `SNESSetKSP()`
1654: @*/
1655: PetscErrorCode SNESSetKSP(SNES snes, KSP ksp)
1656: {
1657:   PetscFunctionBegin;
1660:   PetscCheckSameComm(snes, 1, ksp, 2);
1661:   PetscCall(PetscObjectReference((PetscObject)ksp));
1662:   if (snes->ksp) PetscCall(PetscObjectDereference((PetscObject)snes->ksp));
1663:   snes->ksp = ksp;
1664:   PetscFunctionReturn(PETSC_SUCCESS);
1665: }

1667: /*@
1668:    SNESCreate - Creates a nonlinear solver context used to manage a set of nonlinear solves

1670:    Collective

1672:    Input Parameter:
1673: .  comm - MPI communicator

1675:    Output Parameter:
1676: .  outsnes - the new SNES context

1678:    Options Database Keys:
1679: +   -snes_mf - Activates default matrix-free Jacobian-vector products, and no preconditioning matrix
1680: .   -snes_mf_operator - Activates default matrix-free Jacobian-vector products, and a user-provided preconditioning matrix
1681:                as set by `SNESSetJacobian()`
1682: .   -snes_fd_coloring - uses a relative fast computation of the Jacobian using finite differences and a graph coloring
1683: -   -snes_fd - Uses (slow!) finite differences to compute Jacobian

1685:    Level: beginner

1687:    Developer Notes:
1688:    `SNES` always creates a `KSP` object even though many `SNES` methods do not use it. This is
1689:    unfortunate and should be fixed at some point. The flag snes->usesksp indicates if the
1690:    particular method does use `KSP` and regulates if the information about the `KSP` is printed
1691:    in `SNESView()`.

1693:    `TSSetFromOptions()` does call `SNESSetFromOptions()` which can lead to users being confused
1694:    by help messages about meaningless `SNES` options.

1696:    `SNES` always creates the snes->kspconvctx even though it is used by only one type. This should be fixed.

1698: .seealso: [](chapter_snes), `SNES`, `SNESSolve()`, `SNESDestroy()`, `SNES`, `SNESSetLagPreconditioner()`, `SNESSetLagJacobian()`
1699: @*/
1700: PetscErrorCode SNESCreate(MPI_Comm comm, SNES *outsnes)
1701: {
1702:   SNES       snes;
1703:   SNESKSPEW *kctx;

1705:   PetscFunctionBegin;
1707:   *outsnes = NULL;
1708:   PetscCall(SNESInitializePackage());

1710:   PetscCall(PetscHeaderCreate(snes, SNES_CLASSID, "SNES", "Nonlinear solver", "SNES", comm, SNESDestroy, SNESView));

1712:   snes->ops->converged = SNESConvergedDefault;
1713:   snes->usesksp        = PETSC_TRUE;
1714:   snes->tolerancesset  = PETSC_FALSE;
1715:   snes->max_its        = 50;
1716:   snes->max_funcs      = 10000;
1717:   snes->norm           = 0.0;
1718:   snes->xnorm          = 0.0;
1719:   snes->ynorm          = 0.0;
1720:   snes->normschedule   = SNES_NORM_ALWAYS;
1721:   snes->functype       = SNES_FUNCTION_DEFAULT;
1722: #if defined(PETSC_USE_REAL_SINGLE)
1723:   snes->rtol = 1.e-5;
1724: #else
1725:   snes->rtol = 1.e-8;
1726: #endif
1727:   snes->ttol = 0.0;
1728: #if defined(PETSC_USE_REAL_SINGLE)
1729:   snes->abstol = 1.e-25;
1730: #else
1731:   snes->abstol = 1.e-50;
1732: #endif
1733: #if defined(PETSC_USE_REAL_SINGLE)
1734:   snes->stol = 1.e-5;
1735: #else
1736:   snes->stol = 1.e-8;
1737: #endif
1738: #if defined(PETSC_USE_REAL_SINGLE)
1739:   snes->deltatol = 1.e-6;
1740: #else
1741:   snes->deltatol = 1.e-12;
1742: #endif
1743:   snes->divtol               = 1.e4;
1744:   snes->rnorm0               = 0;
1745:   snes->nfuncs               = 0;
1746:   snes->numFailures          = 0;
1747:   snes->maxFailures          = 1;
1748:   snes->linear_its           = 0;
1749:   snes->lagjacobian          = 1;
1750:   snes->jac_iter             = 0;
1751:   snes->lagjac_persist       = PETSC_FALSE;
1752:   snes->lagpreconditioner    = 1;
1753:   snes->pre_iter             = 0;
1754:   snes->lagpre_persist       = PETSC_FALSE;
1755:   snes->numbermonitors       = 0;
1756:   snes->numberreasonviews    = 0;
1757:   snes->data                 = NULL;
1758:   snes->setupcalled          = PETSC_FALSE;
1759:   snes->ksp_ewconv           = PETSC_FALSE;
1760:   snes->nwork                = 0;
1761:   snes->work                 = NULL;
1762:   snes->nvwork               = 0;
1763:   snes->vwork                = NULL;
1764:   snes->conv_hist_len        = 0;
1765:   snes->conv_hist_max        = 0;
1766:   snes->conv_hist            = NULL;
1767:   snes->conv_hist_its        = NULL;
1768:   snes->conv_hist_reset      = PETSC_TRUE;
1769:   snes->counters_reset       = PETSC_TRUE;
1770:   snes->vec_func_init_set    = PETSC_FALSE;
1771:   snes->reason               = SNES_CONVERGED_ITERATING;
1772:   snes->npcside              = PC_RIGHT;
1773:   snes->setfromoptionscalled = 0;

1775:   snes->mf          = PETSC_FALSE;
1776:   snes->mf_operator = PETSC_FALSE;
1777:   snes->mf_version  = 1;

1779:   snes->numLinearSolveFailures = 0;
1780:   snes->maxLinearSolveFailures = 1;

1782:   snes->vizerotolerance     = 1.e-8;
1783:   snes->checkjacdomainerror = PetscDefined(USE_DEBUG) ? PETSC_TRUE : PETSC_FALSE;

1785:   /* Set this to true if the implementation of SNESSolve_XXX does compute the residual at the final solution. */
1786:   snes->alwayscomputesfinalresidual = PETSC_FALSE;

1788:   /* Create context to compute Eisenstat-Walker relative tolerance for KSP */
1789:   PetscCall(PetscNew(&kctx));

1791:   snes->kspconvctx  = (void *)kctx;
1792:   kctx->version     = 2;
1793:   kctx->rtol_0      = 0.3; /* Eisenstat and Walker suggest rtol_0=.5, but
1794:                              this was too large for some test cases */
1795:   kctx->rtol_last   = 0.0;
1796:   kctx->rtol_max    = 0.9;
1797:   kctx->gamma       = 1.0;
1798:   kctx->alpha       = 0.5 * (1.0 + PetscSqrtReal(5.0));
1799:   kctx->alpha2      = kctx->alpha;
1800:   kctx->threshold   = 0.1;
1801:   kctx->lresid_last = 0.0;
1802:   kctx->norm_last   = 0.0;

1804:   kctx->rk_last     = 0.0;
1805:   kctx->rk_last_2   = 0.0;
1806:   kctx->rtol_last_2 = 0.0;
1807:   kctx->v4_p1       = 0.1;
1808:   kctx->v4_p2       = 0.4;
1809:   kctx->v4_p3       = 0.7;
1810:   kctx->v4_m1       = 0.8;
1811:   kctx->v4_m2       = 0.5;
1812:   kctx->v4_m3       = 0.1;
1813:   kctx->v4_m4       = 0.5;

1815:   *outsnes = snes;
1816:   PetscFunctionReturn(PETSC_SUCCESS);
1817: }

1819: /*MC
1820:     SNESFunction - Functional form used to convey the nonlinear function to `SNES` in `SNESSetFunction()`

1822:      Synopsis:
1823:      #include "petscsnes.h"
1824:      PetscErrorCode SNESFunction(SNES snes,Vec x,Vec f,void *ctx);

1826:      Collective

1828:      Input Parameters:
1829: +     snes - the `SNES` context
1830: .     x    - state at which to evaluate residual
1831: -     ctx     - optional user-defined function context, passed in with `SNESSetFunction()`

1833:      Output Parameter:
1834: .     f  - vector to put residual (function value)

1836:    Level: intermediate

1838: .seealso: [](chapter_snes), `SNESSetFunction()`, `SNESGetFunction()`
1839: M*/

1841: /*@C
1842:    SNESSetFunction - Sets the function evaluation routine and function
1843:    vector for use by the `SNES` routines in solving systems of nonlinear
1844:    equations.

1846:    Logically Collective

1848:    Input Parameters:
1849: +  snes - the `SNES` context
1850: .  r - vector to store function values, may be `NULL`
1851: .  f - function evaluation routine; see `SNESFunction` for calling sequence details
1852: -  ctx - [optional] user-defined context for private data for the
1853:          function evaluation routine (may be `NULL`)

1855:    Level: beginner

1857: .seealso: [](chapter_snes), `SNES`, `SNESGetFunction()`, `SNESComputeFunction()`, `SNESSetJacobian()`, `SNESSetPicard()`, `SNESFunction`
1858: @*/
1859: PetscErrorCode SNESSetFunction(SNES snes, Vec r, PetscErrorCode (*f)(SNES, Vec, Vec, void *), void *ctx)
1860: {
1861:   DM dm;

1863:   PetscFunctionBegin;
1865:   if (r) {
1867:     PetscCheckSameComm(snes, 1, r, 2);
1868:     PetscCall(PetscObjectReference((PetscObject)r));
1869:     PetscCall(VecDestroy(&snes->vec_func));
1870:     snes->vec_func = r;
1871:   }
1872:   PetscCall(SNESGetDM(snes, &dm));
1873:   PetscCall(DMSNESSetFunction(dm, f, ctx));
1874:   if (f == SNESPicardComputeFunction) PetscCall(DMSNESSetMFFunction(dm, SNESPicardComputeMFFunction, ctx));
1875:   PetscFunctionReturn(PETSC_SUCCESS);
1876: }

1878: /*@C
1879:    SNESSetInitialFunction - Sets the function vector to be used as the
1880:    initial function value at the initialization of the method.  In some
1881:    instances, the user has precomputed the function before calling
1882:    `SNESSolve()`.  This function allows one to avoid a redundant call
1883:    to `SNESComputeFunction()` in that case.

1885:    Logically Collective

1887:    Input Parameters:
1888: +  snes - the `SNES` context
1889: -  f - vector to store function value

1891:    Level: developer

1893:    Notes:
1894:    This should not be modified during the solution procedure.

1896:    This is used extensively in the `SNESFAS` hierarchy and in nonlinear preconditioning.

1898: .seealso: [](chapter_snes), `SNES`, `SNESFAS`, `SNESSetFunction()`, `SNESComputeFunction()`, `SNESSetInitialFunctionNorm()`
1899: @*/
1900: PetscErrorCode SNESSetInitialFunction(SNES snes, Vec f)
1901: {
1902:   Vec vec_func;

1904:   PetscFunctionBegin;
1907:   PetscCheckSameComm(snes, 1, f, 2);
1908:   if (snes->npcside == PC_LEFT && snes->functype == SNES_FUNCTION_PRECONDITIONED) {
1909:     snes->vec_func_init_set = PETSC_FALSE;
1910:     PetscFunctionReturn(PETSC_SUCCESS);
1911:   }
1912:   PetscCall(SNESGetFunction(snes, &vec_func, NULL, NULL));
1913:   PetscCall(VecCopy(f, vec_func));

1915:   snes->vec_func_init_set = PETSC_TRUE;
1916:   PetscFunctionReturn(PETSC_SUCCESS);
1917: }

1919: /*@
1920:    SNESSetNormSchedule - Sets the `SNESNormSchedule` used in convergence and monitoring
1921:    of the `SNES` method, when norms are computed in the solving process

1923:    Logically Collective

1925:    Input Parameters:
1926: +  snes - the `SNES` context
1927: -  normschedule - the frequency of norm computation

1929:    Options Database Key:
1930: .  -snes_norm_schedule <none, always, initialonly, finalonly, initialfinalonly> - set the schedule

1932:    Level: advanced

1934:    Notes:
1935:    Only certain `SNES` methods support certain `SNESNormSchedules`.  Most require evaluation
1936:    of the nonlinear function and the taking of its norm at every iteration to
1937:    even ensure convergence at all.  However, methods such as custom Gauss-Seidel methods
1938:    `SNESNGS` and the like do not require the norm of the function to be computed, and therefore
1939:    may either be monitored for convergence or not.  As these are often used as nonlinear
1940:    preconditioners, monitoring the norm of their error is not a useful enterprise within
1941:    their solution.

1943: .seealso: [](chapter_snes), `SNESNormSchedule`, `SNESGetNormSchedule()`, `SNESComputeFunction()`, `VecNorm()`, `SNESSetFunction()`, `SNESSetInitialFunction()`, `SNESNormSchedule`
1944: @*/
1945: PetscErrorCode SNESSetNormSchedule(SNES snes, SNESNormSchedule normschedule)
1946: {
1947:   PetscFunctionBegin;
1949:   snes->normschedule = normschedule;
1950:   PetscFunctionReturn(PETSC_SUCCESS);
1951: }

1953: /*@
1954:    SNESGetNormSchedule - Gets the `SNESNormSchedule` used in convergence and monitoring
1955:    of the `SNES` method.

1957:    Logically Collective

1959:    Input Parameters:
1960: +  snes - the `SNES` context
1961: -  normschedule - the type of the norm used

1963:    Level: advanced

1965: .seealso: [](chapter_snes), `SNES`, `SNESSetNormSchedule()`, `SNESComputeFunction()`, `VecNorm()`, `SNESSetFunction()`, `SNESSetInitialFunction()`, `SNESNormSchedule`
1966: @*/
1967: PetscErrorCode SNESGetNormSchedule(SNES snes, SNESNormSchedule *normschedule)
1968: {
1969:   PetscFunctionBegin;
1971:   *normschedule = snes->normschedule;
1972:   PetscFunctionReturn(PETSC_SUCCESS);
1973: }

1975: /*@
1976:   SNESSetFunctionNorm - Sets the last computed residual norm.

1978:   Logically Collective

1980:   Input Parameters:
1981: +  snes - the `SNES` context
1982: -  norm - the value of the norm

1984:   Level: developer

1986: .seealso: [](chapter_snes), `SNES`, `SNESGetNormSchedule()`, `SNESComputeFunction()`, `VecNorm()`, `SNESSetFunction()`, `SNESSetInitialFunction()`, `SNESNormSchedule`
1987: @*/
1988: PetscErrorCode SNESSetFunctionNorm(SNES snes, PetscReal norm)
1989: {
1990:   PetscFunctionBegin;
1992:   snes->norm = norm;
1993:   PetscFunctionReturn(PETSC_SUCCESS);
1994: }

1996: /*@
1997:   SNESGetFunctionNorm - Gets the last computed norm of the residual

1999:   Not Collective

2001:   Input Parameter:
2002: . snes - the `SNES` context

2004:   Output Parameter:
2005: . norm - the last computed residual norm

2007:   Level: developer

2009: .seealso: [](chapter_snes), `SNES`, `SNESSetNormSchedule()`, `SNESComputeFunction()`, `VecNorm()`, `SNESSetFunction()`, `SNESSetInitialFunction()`, `SNESNormSchedule`
2010: @*/
2011: PetscErrorCode SNESGetFunctionNorm(SNES snes, PetscReal *norm)
2012: {
2013:   PetscFunctionBegin;
2016:   *norm = snes->norm;
2017:   PetscFunctionReturn(PETSC_SUCCESS);
2018: }

2020: /*@
2021:   SNESGetUpdateNorm - Gets the last computed norm of the solution update

2023:   Not Collective

2025:   Input Parameter:
2026: . snes - the `SNES` context

2028:   Output Parameter:
2029: . ynorm - the last computed update norm

2031:   Level: developer

2033:   Note:
2034:   The new solution is the current solution plus the update, so this norm is an indication of the size of the update

2036: .seealso: [](chapter_snes), `SNES`, `SNESSetNormSchedule()`, `SNESComputeFunction()`, `SNESGetFunctionNorm()`
2037: @*/
2038: PetscErrorCode SNESGetUpdateNorm(SNES snes, PetscReal *ynorm)
2039: {
2040:   PetscFunctionBegin;
2043:   *ynorm = snes->ynorm;
2044:   PetscFunctionReturn(PETSC_SUCCESS);
2045: }

2047: /*@
2048:   SNESGetSolutionNorm - Gets the last computed norm of the solution

2050:   Not Collective

2052:   Input Parameter:
2053: . snes - the `SNES` context

2055:   Output Parameter:
2056: . xnorm - the last computed solution norm

2058:   Level: developer

2060: .seealso: [](chapter_snes), `SNES`, `SNESSetNormSchedule()`, `SNESComputeFunction()`, `SNESGetFunctionNorm()`, `SNESGetUpdateNorm()`
2061: @*/
2062: PetscErrorCode SNESGetSolutionNorm(SNES snes, PetscReal *xnorm)
2063: {
2064:   PetscFunctionBegin;
2067:   *xnorm = snes->xnorm;
2068:   PetscFunctionReturn(PETSC_SUCCESS);
2069: }

2071: /*@C
2072:    SNESSetFunctionType - Sets the `SNESFunctionType`
2073:    of the `SNES` method.

2075:    Logically Collective

2077:    Input Parameters:
2078: +  snes - the `SNES` context
2079: -  type - the function type

2081:    Level: developer

2083:    Notes:
2084:    Possible values of the function type
2085: +  `SNES_FUNCTION_DEFAULT` - the default for the given `SNESType`
2086: .  `SNES_FUNCTION_UNPRECONDITIONED` - an unpreconditioned function evaluation (this is the function provided with `SNESSetFunction()`
2087: -  `SNES_FUNCTION_PRECONDITIONED` - a transformation of the function provided with `SNESSetFunction()`

2089:    Different `SNESType`s use this value in different ways

2091: .seealso: [](chapter_snes), `SNES`, `SNESFunctionType`, `SNESGetNormSchedule()`, `SNESComputeFunction()`, `VecNorm()`, `SNESSetFunction()`, `SNESSetInitialFunction()`, `SNESNormSchedule`
2092: @*/
2093: PetscErrorCode SNESSetFunctionType(SNES snes, SNESFunctionType type)
2094: {
2095:   PetscFunctionBegin;
2097:   snes->functype = type;
2098:   PetscFunctionReturn(PETSC_SUCCESS);
2099: }

2101: /*@C
2102:    SNESGetFunctionType - Gets the `SNESFunctionType` used in convergence and monitoring set with `SNESSetFunctionType()`
2103:    of the SNES method.

2105:    Logically Collective

2107:    Input Parameters:
2108: +  snes - the `SNES` context
2109: -  type - the type of the function evaluation, see `SNESSetFunctionType()`

2111:    Level: advanced

2113: .seealso: [](chapter_snes), `SNESSetFunctionType()`, `SNESFunctionType`, `SNESSetNormSchedule()`, `SNESComputeFunction()`, `VecNorm()`, `SNESSetFunction()`, `SNESSetInitialFunction()`, `SNESNormSchedule`
2114: @*/
2115: PetscErrorCode SNESGetFunctionType(SNES snes, SNESFunctionType *type)
2116: {
2117:   PetscFunctionBegin;
2119:   *type = snes->functype;
2120:   PetscFunctionReturn(PETSC_SUCCESS);
2121: }

2123: /*MC
2124:     SNESNGSFunction - function used to apply a Gauss-Seidel sweep on the nonlinear function

2126:      Synopsis:
2127: #include <petscsnes.h>
2128: $    SNESNGSFunction(SNES snes,Vec x,Vec b,void *ctx);

2130:      Collective

2132:      Input Parameters:
2133: +  X   - solution vector
2134: .  B   - RHS vector
2135: -  ctx - optional user-defined Gauss-Seidel context

2137:      Output Parameter:
2138: .  X   - solution vector

2140:    Level: intermediate

2142: .seealso: [](chapter_snes), `SNESNGS`, `SNESSetNGS()`, `SNESGetNGS()`
2143: M*/

2145: /*@C
2146:    SNESSetNGS - Sets the user nonlinear Gauss-Seidel routine for
2147:    use with composed nonlinear solvers.

2149:    Input Parameters:
2150: +  snes   - the `SNES` context
2151: .  f - function evaluation routine to apply Gauss-Seidel see `SNESNGSFunction`
2152: -  ctx    - [optional] user-defined context for private data for the
2153:             smoother evaluation routine (may be `NULL`)

2155:    Calling sequence of f:
2156: $  PetscErrorCode f(SNES snes,Vec X,Vec B,void *ctx);

2158:    Arguments of f:
2159: +  snes - the `SNES` context
2160: .  X - the current solution
2161: .  B - the right hand side vector (which may be `NULL`)
2162: -  ctx - a user provided context

2164:    Level: intermediate

2166:    Note:
2167:    The `SNESNGS` routines are used by the composed nonlinear solver to generate
2168:     a problem appropriate update to the solution, particularly `SNESFAS`.

2170: .seealso: [](chapter_snes), `SNESGetNGS()`, `SNESNGSFunction`, `SNESNCG`, `SNESGetFunction()`, `SNESComputeNGS()`
2171: @*/
2172: PetscErrorCode SNESSetNGS(SNES snes, PetscErrorCode (*f)(SNES, Vec, Vec, void *), void *ctx)
2173: {
2174:   DM dm;

2176:   PetscFunctionBegin;
2178:   PetscCall(SNESGetDM(snes, &dm));
2179:   PetscCall(DMSNESSetNGS(dm, f, ctx));
2180:   PetscFunctionReturn(PETSC_SUCCESS);
2181: }

2183: /*
2184:      This is used for -snes_mf_operator; it uses a duplicate of snes->jacobian_pre because snes->jacobian_pre cannot be
2185:    changed during the KSPSolve()
2186: */
2187: PetscErrorCode SNESPicardComputeMFFunction(SNES snes, Vec x, Vec f, void *ctx)
2188: {
2189:   DM     dm;
2190:   DMSNES sdm;

2192:   PetscFunctionBegin;
2193:   PetscCall(SNESGetDM(snes, &dm));
2194:   PetscCall(DMGetDMSNES(dm, &sdm));
2195:   /*  A(x)*x - b(x) */
2196:   if (sdm->ops->computepfunction) {
2197:     PetscCallBack("SNES Picard callback function", (*sdm->ops->computepfunction)(snes, x, f, sdm->pctx));
2198:     PetscCall(VecScale(f, -1.0));
2199:     /* Cannot share nonzero pattern because of the possible use of SNESComputeJacobianDefault() */
2200:     if (!snes->picard) PetscCall(MatDuplicate(snes->jacobian_pre, MAT_DO_NOT_COPY_VALUES, &snes->picard));
2201:     PetscCallBack("SNES Picard callback Jacobian", (*sdm->ops->computepjacobian)(snes, x, snes->picard, snes->picard, sdm->pctx));
2202:     PetscCall(MatMultAdd(snes->picard, x, f, f));
2203:   } else {
2204:     PetscCallBack("SNES Picard callback Jacobian", (*sdm->ops->computepjacobian)(snes, x, snes->picard, snes->picard, sdm->pctx));
2205:     PetscCall(MatMult(snes->picard, x, f));
2206:   }
2207:   PetscFunctionReturn(PETSC_SUCCESS);
2208: }

2210: PetscErrorCode SNESPicardComputeFunction(SNES snes, Vec x, Vec f, void *ctx)
2211: {
2212:   DM     dm;
2213:   DMSNES sdm;

2215:   PetscFunctionBegin;
2216:   PetscCall(SNESGetDM(snes, &dm));
2217:   PetscCall(DMGetDMSNES(dm, &sdm));
2218:   /*  A(x)*x - b(x) */
2219:   if (sdm->ops->computepfunction) {
2220:     PetscCallBack("SNES Picard callback function", (*sdm->ops->computepfunction)(snes, x, f, sdm->pctx));
2221:     PetscCall(VecScale(f, -1.0));
2222:     PetscCallBack("SNES Picard callback Jacobian", (*sdm->ops->computepjacobian)(snes, x, snes->jacobian, snes->jacobian_pre, sdm->pctx));
2223:     PetscCall(MatMultAdd(snes->jacobian_pre, x, f, f));
2224:   } else {
2225:     PetscCallBack("SNES Picard callback Jacobian", (*sdm->ops->computepjacobian)(snes, x, snes->jacobian, snes->jacobian_pre, sdm->pctx));
2226:     PetscCall(MatMult(snes->jacobian_pre, x, f));
2227:   }
2228:   PetscFunctionReturn(PETSC_SUCCESS);
2229: }

2231: PetscErrorCode SNESPicardComputeJacobian(SNES snes, Vec x1, Mat J, Mat B, void *ctx)
2232: {
2233:   PetscFunctionBegin;
2234:   /* the jacobian matrix should be pre-filled in SNESPicardComputeFunction */
2235:   /* must assembly if matrix-free to get the last SNES solution */
2236:   PetscCall(MatAssemblyBegin(J, MAT_FINAL_ASSEMBLY));
2237:   PetscCall(MatAssemblyEnd(J, MAT_FINAL_ASSEMBLY));
2238:   PetscFunctionReturn(PETSC_SUCCESS);
2239: }

2241: /*@C
2242:    SNESSetPicard - Use `SNES` to solve the system A(x) x = bp(x) + b via a Picard type iteration (Picard linearization)

2244:    Logically Collective

2246:    Input Parameters:
2247: +  snes - the `SNES` context
2248: .  r - vector to store function values, may be `NULL`
2249: .  bp - function evaluation routine, may be `NULL`
2250: .  Amat - matrix with which A(x) x - bp(x) - b is to be computed
2251: .  Pmat - matrix from which preconditioner is computed (usually the same as `Amat`)
2252: .  J  - function to compute matrix values, see `SNESJacobianFunction()` for details on its calling sequence
2253: -  ctx - [optional] user-defined context for private data for the function evaluation routine (may be `NULL`)

2255:    Level: intermediate

2257:    Notes:
2258:     It is often better to provide the nonlinear function F() and some approximation to its Jacobian directly and use
2259:     an approximate Newton solver. This interface is provided to allow porting/testing a previous Picard based code in PETSc before converting it to approximate Newton.

2261:     One can call `SNESSetPicard()` or `SNESSetFunction()` (and possibly `SNESSetJacobian()`) but cannot call both

2263:      Solves the equation A(x) x = bp(x) - b via the defect correction algorithm A(x^{n}) (x^{n+1} - x^{n}) = bp(x^{n}) + b - A(x^{n})x^{n}.
2264:      When an exact solver is used this corresponds to the "classic" Picard A(x^{n}) x^{n+1} = bp(x^{n}) + b iteration.

2266:      Run with `-snes_mf_operator` to solve the system with Newton's method using A(x^{n}) to construct the preconditioner.

2268:    We implement the defect correction form of the Picard iteration because it converges much more generally when inexact linear solvers are used then
2269:    the direct Picard iteration A(x^n) x^{n+1} = bp(x^n) + b

2271:    There is some controversity over the definition of a Picard iteration for nonlinear systems but almost everyone agrees that it involves a linear solve and some
2272:    believe it is the iteration  A(x^{n}) x^{n+1} = b(x^{n}) hence we use the name Picard. If anyone has an authoritative  reference that defines the Picard iteration
2273:    different please contact us at petsc-dev@mcs.anl.gov and we'll have an entirely new argument :-).

2275:    When used with `-snes_mf_operator` this will run matrix-free Newton's method where the matrix-vector product is of the true Jacobian of A(x)x - bp(x) -b and
2276:     A(x^{n}) is used to build the preconditioner

2278:    When used with `-snes_fd` this will compute the true Jacobian (very slowly one column at at time) and thus represent Newton's method.

2280:    When used with `-snes_fd_coloring` this will compute the Jacobian via coloring and thus represent a faster implementation of Newton's method. But the
2281:    the nonzero structure of the Jacobian is, in general larger than that of the Picard matrix A so you must provide in A the needed nonzero structure for the correct
2282:    coloring. When using `DMDA` this may mean creating the matrix A with `DMCreateMatrix()` using a wider stencil than strictly needed for A or with a `DMDA_STENCIL_BOX`.
2283:    See the commment in src/snes/tutorials/ex15.c.

2285: .seealso: [](chapter_snes), `SNES`, `SNESGetFunction()`, `SNESSetFunction()`, `SNESComputeFunction()`, `SNESSetJacobian()`, `SNESGetPicard()`, `SNESLineSearchPreCheckPicard()`, `SNESJacobianFunction`
2286: @*/
2287: PetscErrorCode SNESSetPicard(SNES snes, Vec r, PetscErrorCode (*bp)(SNES, Vec, Vec, void *), Mat Amat, Mat Pmat, PetscErrorCode (*J)(SNES, Vec, Mat, Mat, void *), void *ctx)
2288: {
2289:   DM dm;

2291:   PetscFunctionBegin;
2293:   PetscCall(SNESGetDM(snes, &dm));
2294:   PetscCall(DMSNESSetPicard(dm, bp, J, ctx));
2295:   PetscCall(DMSNESSetMFFunction(dm, SNESPicardComputeMFFunction, ctx));
2296:   PetscCall(SNESSetFunction(snes, r, SNESPicardComputeFunction, ctx));
2297:   PetscCall(SNESSetJacobian(snes, Amat, Pmat, SNESPicardComputeJacobian, ctx));
2298:   PetscFunctionReturn(PETSC_SUCCESS);
2299: }

2301: /*@C
2302:    SNESGetPicard - Returns the context for the Picard iteration

2304:    Not Collective, but `Vec` is parallel if `SNES` is parallel. Collective if `Vec` is requested, but has not been created yet.

2306:    Input Parameter:
2307: .  snes - the `SNES` context

2309:    Output Parameters:
2310: +  r - the function (or `NULL`)
2311: .  f - the function (or `NULL`); see `SNESFunction` for calling sequence details
2312: .  Amat - the matrix used to defined the operation A(x) x - b(x) (or `NULL`)
2313: .  Pmat  - the matrix from which the preconditioner will be constructed (or `NULL`)
2314: .  J - the function for matrix evaluation (or `NULL`); see `SNESJacobianFunction` for calling sequence details
2315: -  ctx - the function context (or `NULL`)

2317:    Level: advanced

2319: .seealso: [](chapter_snes), `SNESSetFunction()`, `SNESSetPicard()`, `SNESGetFunction()`, `SNESGetJacobian()`, `SNESGetDM()`, `SNESFunction`, `SNESJacobianFunction`
2320: @*/
2321: PetscErrorCode SNESGetPicard(SNES snes, Vec *r, PetscErrorCode (**f)(SNES, Vec, Vec, void *), Mat *Amat, Mat *Pmat, PetscErrorCode (**J)(SNES, Vec, Mat, Mat, void *), void **ctx)
2322: {
2323:   DM dm;

2325:   PetscFunctionBegin;
2327:   PetscCall(SNESGetFunction(snes, r, NULL, NULL));
2328:   PetscCall(SNESGetJacobian(snes, Amat, Pmat, NULL, NULL));
2329:   PetscCall(SNESGetDM(snes, &dm));
2330:   PetscCall(DMSNESGetPicard(dm, f, J, ctx));
2331:   PetscFunctionReturn(PETSC_SUCCESS);
2332: }

2334: /*@C
2335:    SNESSetComputeInitialGuess - Sets a routine used to compute an initial guess for the nonlinear problem

2337:    Logically Collective

2339:    Input Parameters:
2340: +  snes - the `SNES` context
2341: .  func - function evaluation routine
2342: -  ctx - [optional] user-defined context for private data for the
2343:          function evaluation routine (may be `NULL`)

2345:    Calling sequence of func:
2346: $    func (SNES snes,Vec x,void *ctx);

2348: .  f - function vector
2349: -  ctx - optional user-defined function context

2351:    Level: intermediate

2353: .seealso: [](chapter_snes), `SNES`, `SNESSolve()`, `SNESGetFunction()`, `SNESComputeFunction()`, `SNESSetJacobian()`
2354: @*/
2355: PetscErrorCode SNESSetComputeInitialGuess(SNES snes, PetscErrorCode (*func)(SNES, Vec, void *), void *ctx)
2356: {
2357:   PetscFunctionBegin;
2359:   if (func) snes->ops->computeinitialguess = func;
2360:   if (ctx) snes->initialguessP = ctx;
2361:   PetscFunctionReturn(PETSC_SUCCESS);
2362: }

2364: /*@C
2365:    SNESGetRhs - Gets the vector for solving F(x) = `rhs`. If `rhs` is not set
2366:    it assumes a zero right hand side.

2368:    Logically Collective

2370:    Input Parameter:
2371: .  snes - the `SNES` context

2373:    Output Parameter:
2374: .  rhs - the right hand side vector or `NULL` if the right hand side vector is null

2376:    Level: intermediate

2378: .seealso: [](chapter_snes), `SNES`, `SNESGetSolution()`, `SNESGetFunction()`, `SNESComputeFunction()`, `SNESSetJacobian()`, `SNESSetFunction()`
2379: @*/
2380: PetscErrorCode SNESGetRhs(SNES snes, Vec *rhs)
2381: {
2382:   PetscFunctionBegin;
2385:   *rhs = snes->vec_rhs;
2386:   PetscFunctionReturn(PETSC_SUCCESS);
2387: }

2389: /*@
2390:    SNESComputeFunction - Calls the function that has been set with `SNESSetFunction()`.

2392:    Collective

2394:    Input Parameters:
2395: +  snes - the `SNES` context
2396: -  x - input vector

2398:    Output Parameter:
2399: .  y - function vector, as set by `SNESSetFunction()`

2401:    Level: developer

2403:    Note:
2404:    `SNESComputeFunction()` is typically used within nonlinear solvers
2405:    implementations, so users would not generally call this routine themselves.

2407: .seealso: [](chapter_snes), `SNES`, `SNESSetFunction()`, `SNESGetFunction()`, `SNESComputeMFFunction()`
2408: @*/
2409: PetscErrorCode SNESComputeFunction(SNES snes, Vec x, Vec y)
2410: {
2411:   DM     dm;
2412:   DMSNES sdm;

2414:   PetscFunctionBegin;
2418:   PetscCheckSameComm(snes, 1, x, 2);
2419:   PetscCheckSameComm(snes, 1, y, 3);
2420:   PetscCall(VecValidValues_Internal(x, 2, PETSC_TRUE));

2422:   PetscCall(SNESGetDM(snes, &dm));
2423:   PetscCall(DMGetDMSNES(dm, &sdm));
2424:   PetscCheck(sdm->ops->computefunction || snes->vec_rhs, PETSC_COMM_SELF, PETSC_ERR_ARG_WRONGSTATE, "Must call SNESSetFunction() or SNESSetDM() before SNESComputeFunction(), likely called from SNESSolve().");
2425:   if (sdm->ops->computefunction) {
2426:     if (sdm->ops->computefunction != SNESObjectiveComputeFunctionDefaultFD) PetscCall(PetscLogEventBegin(SNES_FunctionEval, snes, x, y, 0));
2427:     PetscCall(VecLockReadPush(x));
2428:     /* ensure domainerror is false prior to computefunction evaluation (may not have been reset) */
2429:     snes->domainerror = PETSC_FALSE;
2430:     {
2431:       void *ctx;
2432:       PetscErrorCode (*computefunction)(SNES, Vec, Vec, void *);
2433:       PetscCall(DMSNESGetFunction(dm, &computefunction, &ctx));
2434:       PetscCallBack("SNES callback function", (*computefunction)(snes, x, y, ctx));
2435:     }
2436:     PetscCall(VecLockReadPop(x));
2437:     if (sdm->ops->computefunction != SNESObjectiveComputeFunctionDefaultFD) PetscCall(PetscLogEventEnd(SNES_FunctionEval, snes, x, y, 0));
2438:   } else /* if (snes->vec_rhs) */ {
2439:     PetscCall(MatMult(snes->jacobian, x, y));
2440:   }
2441:   if (snes->vec_rhs) PetscCall(VecAXPY(y, -1.0, snes->vec_rhs));
2442:   snes->nfuncs++;
2443:   /*
2444:      domainerror might not be set on all processes; so we tag vector locally with Inf and the next inner product or norm will
2445:      propagate the value to all processes
2446:   */
2447:   if (snes->domainerror) PetscCall(VecSetInf(y));
2448:   PetscFunctionReturn(PETSC_SUCCESS);
2449: }

2451: /*@
2452:    SNESComputeMFFunction - Calls the function that has been set with `SNESSetMFFunction()`.

2454:    Collective

2456:    Input Parameters:
2457: +  snes - the `SNES` context
2458: -  x - input vector

2460:    Output Parameter:
2461: .  y - function vector, as set by `SNESSetMFFunction()`

2463:    Level: developer

2465:    Notes:
2466:    `SNESComputeMFFunction()` is used within the matrix vector products called by the matrix created with `MatCreateSNESMF()`
2467:    so users would not generally call this routine themselves.

2469:     Since this function is intended for use with finite differencing it does not subtract the right hand side vector provided with `SNESSolve()`
2470:     while `SNESComputeFunction()` does. As such, this routine cannot be used with  `MatMFFDSetBase()` with a provided F function value even if it applies the
2471:     same function as `SNESComputeFunction()` if a `SNESSolve()` right hand side vector is use because the two functions difference would include this right hand side function.

2473: .seealso: [](chapter_snes), `SNES`, `SNESSetFunction()`, `SNESGetFunction()`, `SNESComputeFunction()`, `MatCreateSNESMF`
2474: @*/
2475: PetscErrorCode SNESComputeMFFunction(SNES snes, Vec x, Vec y)
2476: {
2477:   DM     dm;
2478:   DMSNES sdm;

2480:   PetscFunctionBegin;
2484:   PetscCheckSameComm(snes, 1, x, 2);
2485:   PetscCheckSameComm(snes, 1, y, 3);
2486:   PetscCall(VecValidValues_Internal(x, 2, PETSC_TRUE));

2488:   PetscCall(SNESGetDM(snes, &dm));
2489:   PetscCall(DMGetDMSNES(dm, &sdm));
2490:   PetscCall(PetscLogEventBegin(SNES_FunctionEval, snes, x, y, 0));
2491:   PetscCall(VecLockReadPush(x));
2492:   /* ensure domainerror is false prior to computefunction evaluation (may not have been reset) */
2493:   snes->domainerror = PETSC_FALSE;
2494:   PetscCallBack("SNES callback function", (*sdm->ops->computemffunction)(snes, x, y, sdm->mffunctionctx));
2495:   PetscCall(VecLockReadPop(x));
2496:   PetscCall(PetscLogEventEnd(SNES_FunctionEval, snes, x, y, 0));
2497:   snes->nfuncs++;
2498:   /*
2499:      domainerror might not be set on all processes; so we tag vector locally with Inf and the next inner product or norm will
2500:      propagate the value to all processes
2501:   */
2502:   if (snes->domainerror) PetscCall(VecSetInf(y));
2503:   PetscFunctionReturn(PETSC_SUCCESS);
2504: }

2506: /*@
2507:    SNESComputeNGS - Calls the Gauss-Seidel function that has been set with  `SNESSetNGS()`.

2509:    Collective

2511:    Input Parameters:
2512: +  snes - the `SNES` context
2513: .  x - input vector
2514: -  b - rhs vector

2516:    Output Parameter:
2517: .  x - new solution vector

2519:    Level: developer

2521:    Note:
2522:    `SNESComputeNGS()` is typically used within composed nonlinear solver
2523:    implementations, so most users would not generally call this routine
2524:    themselves.

2526: .seealso: [](chapter_snes), `SNESNGS`, `SNESSetNGS()`, `SNESComputeFunction()`
2527: @*/
2528: PetscErrorCode SNESComputeNGS(SNES snes, Vec b, Vec x)
2529: {
2530:   DM     dm;
2531:   DMSNES sdm;

2533:   PetscFunctionBegin;
2537:   PetscCheckSameComm(snes, 1, x, 3);
2538:   if (b) PetscCheckSameComm(snes, 1, b, 2);
2539:   if (b) PetscCall(VecValidValues_Internal(b, 2, PETSC_TRUE));
2540:   PetscCall(PetscLogEventBegin(SNES_NGSEval, snes, x, b, 0));
2541:   PetscCall(SNESGetDM(snes, &dm));
2542:   PetscCall(DMGetDMSNES(dm, &sdm));
2543:   PetscCheck(sdm->ops->computegs, PETSC_COMM_SELF, PETSC_ERR_ARG_WRONGSTATE, "Must call SNESSetNGS() before SNESComputeNGS(), likely called from SNESSolve().");
2544:   if (b) PetscCall(VecLockReadPush(b));
2545:   PetscCallBack("SNES callback NGS", (*sdm->ops->computegs)(snes, x, b, sdm->gsctx));
2546:   if (b) PetscCall(VecLockReadPop(b));
2547:   PetscCall(PetscLogEventEnd(SNES_NGSEval, snes, x, b, 0));
2548:   PetscFunctionReturn(PETSC_SUCCESS);
2549: }

2551: PetscErrorCode SNESTestJacobian(SNES snes)
2552: {
2553:   Mat               A, B, C, D, jacobian;
2554:   Vec               x = snes->vec_sol, f = snes->vec_func;
2555:   PetscReal         nrm, gnorm;
2556:   PetscReal         threshold = 1.e-5;
2557:   MatType           mattype;
2558:   PetscInt          m, n, M, N;
2559:   void             *functx;
2560:   PetscBool         complete_print = PETSC_FALSE, threshold_print = PETSC_FALSE, test = PETSC_FALSE, flg, istranspose;
2561:   PetscViewer       viewer, mviewer;
2562:   MPI_Comm          comm;
2563:   PetscInt          tabs;
2564:   static PetscBool  directionsprinted = PETSC_FALSE;
2565:   PetscViewerFormat format;

2567:   PetscFunctionBegin;
2568:   PetscObjectOptionsBegin((PetscObject)snes);
2569:   PetscCall(PetscOptionsName("-snes_test_jacobian", "Compare hand-coded and finite difference Jacobians", "None", &test));
2570:   PetscCall(PetscOptionsReal("-snes_test_jacobian", "Threshold for element difference between hand-coded and finite difference being meaningful", "None", threshold, &threshold, NULL));
2571:   PetscCall(PetscOptionsViewer("-snes_test_jacobian_view", "View difference between hand-coded and finite difference Jacobians element entries", "None", &mviewer, &format, &complete_print));
2572:   if (!complete_print) {
2573:     PetscCall(PetscOptionsDeprecated("-snes_test_jacobian_display", "-snes_test_jacobian_view", "3.13", NULL));
2574:     PetscCall(PetscOptionsViewer("-snes_test_jacobian_display", "Display difference between hand-coded and finite difference Jacobians", "None", &mviewer, &format, &complete_print));
2575:   }
2576:   /* for compatibility with PETSc 3.9 and older. */
2577:   PetscCall(PetscOptionsDeprecated("-snes_test_jacobian_display_threshold", "-snes_test_jacobian", "3.13", "-snes_test_jacobian accepts an optional threshold (since v3.10)"));
2578:   PetscCall(PetscOptionsReal("-snes_test_jacobian_display_threshold", "Display difference between hand-coded and finite difference Jacobians which exceed input threshold", "None", threshold, &threshold, &threshold_print));
2579:   PetscOptionsEnd();
2580:   if (!test) PetscFunctionReturn(PETSC_SUCCESS);

2582:   PetscCall(PetscObjectGetComm((PetscObject)snes, &comm));
2583:   PetscCall(PetscViewerASCIIGetStdout(comm, &viewer));
2584:   PetscCall(PetscViewerASCIIGetTab(viewer, &tabs));
2585:   PetscCall(PetscViewerASCIISetTab(viewer, ((PetscObject)snes)->tablevel));
2586:   PetscCall(PetscViewerASCIIPrintf(viewer, "  ---------- Testing Jacobian -------------\n"));
2587:   if (!complete_print && !directionsprinted) {
2588:     PetscCall(PetscViewerASCIIPrintf(viewer, "  Run with -snes_test_jacobian_view and optionally -snes_test_jacobian <threshold> to show difference\n"));
2589:     PetscCall(PetscViewerASCIIPrintf(viewer, "    of hand-coded and finite difference Jacobian entries greater than <threshold>.\n"));
2590:   }
2591:   if (!directionsprinted) {
2592:     PetscCall(PetscViewerASCIIPrintf(viewer, "  Testing hand-coded Jacobian, if (for double precision runs) ||J - Jfd||_F/||J||_F is\n"));
2593:     PetscCall(PetscViewerASCIIPrintf(viewer, "    O(1.e-8), the hand-coded Jacobian is probably correct.\n"));
2594:     directionsprinted = PETSC_TRUE;
2595:   }
2596:   if (complete_print) PetscCall(PetscViewerPushFormat(mviewer, format));

2598:   PetscCall(PetscObjectTypeCompare((PetscObject)snes->jacobian, MATMFFD, &flg));
2599:   if (!flg) jacobian = snes->jacobian;
2600:   else jacobian = snes->jacobian_pre;

2602:   if (!x) {
2603:     PetscCall(MatCreateVecs(jacobian, &x, NULL));
2604:   } else {
2605:     PetscCall(PetscObjectReference((PetscObject)x));
2606:   }
2607:   if (!f) {
2608:     PetscCall(VecDuplicate(x, &f));
2609:   } else {
2610:     PetscCall(PetscObjectReference((PetscObject)f));
2611:   }
2612:   /* evaluate the function at this point because SNESComputeJacobianDefault() assumes that the function has been evaluated and put into snes->vec_func */
2613:   PetscCall(SNESComputeFunction(snes, x, f));
2614:   PetscCall(VecDestroy(&f));
2615:   PetscCall(PetscObjectTypeCompare((PetscObject)snes, SNESKSPTRANSPOSEONLY, &istranspose));
2616:   while (jacobian) {
2617:     Mat JT = NULL, Jsave = NULL;

2619:     if (istranspose) {
2620:       PetscCall(MatCreateTranspose(jacobian, &JT));
2621:       Jsave    = jacobian;
2622:       jacobian = JT;
2623:     }
2624:     PetscCall(PetscObjectBaseTypeCompareAny((PetscObject)jacobian, &flg, MATSEQAIJ, MATMPIAIJ, MATSEQDENSE, MATMPIDENSE, MATSEQBAIJ, MATMPIBAIJ, MATSEQSBAIJ, MATMPISBAIJ, ""));
2625:     if (flg) {
2626:       A = jacobian;
2627:       PetscCall(PetscObjectReference((PetscObject)A));
2628:     } else {
2629:       PetscCall(MatComputeOperator(jacobian, MATAIJ, &A));
2630:     }

2632:     PetscCall(MatGetType(A, &mattype));
2633:     PetscCall(MatGetSize(A, &M, &N));
2634:     PetscCall(MatGetLocalSize(A, &m, &n));
2635:     PetscCall(MatCreate(PetscObjectComm((PetscObject)A), &B));
2636:     PetscCall(MatSetType(B, mattype));
2637:     PetscCall(MatSetSizes(B, m, n, M, N));
2638:     PetscCall(MatSetBlockSizesFromMats(B, A, A));
2639:     PetscCall(MatSetUp(B));
2640:     PetscCall(MatSetOption(B, MAT_NEW_NONZERO_ALLOCATION_ERR, PETSC_FALSE));

2642:     PetscCall(SNESGetFunction(snes, NULL, NULL, &functx));
2643:     PetscCall(SNESComputeJacobianDefault(snes, x, B, B, functx));

2645:     PetscCall(MatDuplicate(B, MAT_COPY_VALUES, &D));
2646:     PetscCall(MatAYPX(D, -1.0, A, DIFFERENT_NONZERO_PATTERN));
2647:     PetscCall(MatNorm(D, NORM_FROBENIUS, &nrm));
2648:     PetscCall(MatNorm(A, NORM_FROBENIUS, &gnorm));
2649:     PetscCall(MatDestroy(&D));
2650:     if (!gnorm) gnorm = 1; /* just in case */
2651:     PetscCall(PetscViewerASCIIPrintf(viewer, "  ||J - Jfd||_F/||J||_F = %g, ||J - Jfd||_F = %g\n", (double)(nrm / gnorm), (double)nrm));

2653:     if (complete_print) {
2654:       PetscCall(PetscViewerASCIIPrintf(viewer, "  Hand-coded Jacobian ----------\n"));
2655:       PetscCall(MatView(A, mviewer));
2656:       PetscCall(PetscViewerASCIIPrintf(viewer, "  Finite difference Jacobian ----------\n"));
2657:       PetscCall(MatView(B, mviewer));
2658:     }

2660:     if (threshold_print || complete_print) {
2661:       PetscInt           Istart, Iend, *ccols, bncols, cncols, j, row;
2662:       PetscScalar       *cvals;
2663:       const PetscInt    *bcols;
2664:       const PetscScalar *bvals;

2666:       PetscCall(MatCreate(PetscObjectComm((PetscObject)A), &C));
2667:       PetscCall(MatSetType(C, mattype));
2668:       PetscCall(MatSetSizes(C, m, n, M, N));
2669:       PetscCall(MatSetBlockSizesFromMats(C, A, A));
2670:       PetscCall(MatSetUp(C));
2671:       PetscCall(MatSetOption(C, MAT_NEW_NONZERO_ALLOCATION_ERR, PETSC_FALSE));

2673:       PetscCall(MatAYPX(B, -1.0, A, DIFFERENT_NONZERO_PATTERN));
2674:       PetscCall(MatGetOwnershipRange(B, &Istart, &Iend));

2676:       for (row = Istart; row < Iend; row++) {
2677:         PetscCall(MatGetRow(B, row, &bncols, &bcols, &bvals));
2678:         PetscCall(PetscMalloc2(bncols, &ccols, bncols, &cvals));
2679:         for (j = 0, cncols = 0; j < bncols; j++) {
2680:           if (PetscAbsScalar(bvals[j]) > threshold) {
2681:             ccols[cncols] = bcols[j];
2682:             cvals[cncols] = bvals[j];
2683:             cncols += 1;
2684:           }
2685:         }
2686:         if (cncols) PetscCall(MatSetValues(C, 1, &row, cncols, ccols, cvals, INSERT_VALUES));
2687:         PetscCall(MatRestoreRow(B, row, &bncols, &bcols, &bvals));
2688:         PetscCall(PetscFree2(ccols, cvals));
2689:       }
2690:       PetscCall(MatAssemblyBegin(C, MAT_FINAL_ASSEMBLY));
2691:       PetscCall(MatAssemblyEnd(C, MAT_FINAL_ASSEMBLY));
2692:       PetscCall(PetscViewerASCIIPrintf(viewer, "  Hand-coded minus finite-difference Jacobian with tolerance %g ----------\n", (double)threshold));
2693:       PetscCall(MatView(C, complete_print ? mviewer : viewer));
2694:       PetscCall(MatDestroy(&C));
2695:     }
2696:     PetscCall(MatDestroy(&A));
2697:     PetscCall(MatDestroy(&B));
2698:     PetscCall(MatDestroy(&JT));
2699:     if (Jsave) jacobian = Jsave;
2700:     if (jacobian != snes->jacobian_pre) {
2701:       jacobian = snes->jacobian_pre;
2702:       PetscCall(PetscViewerASCIIPrintf(viewer, "  ---------- Testing Jacobian for preconditioner -------------\n"));
2703:     } else jacobian = NULL;
2704:   }
2705:   PetscCall(VecDestroy(&x));
2706:   if (complete_print) PetscCall(PetscViewerPopFormat(mviewer));
2707:   if (mviewer) PetscCall(PetscViewerDestroy(&mviewer));
2708:   PetscCall(PetscViewerASCIISetTab(viewer, tabs));
2709:   PetscFunctionReturn(PETSC_SUCCESS);
2710: }

2712: /*@
2713:    SNESComputeJacobian - Computes the Jacobian matrix that has been set with `SNESSetJacobian()`.

2715:    Collective

2717:    Input Parameters:
2718: +  snes - the `SNES` context
2719: -  x - input vector

2721:    Output Parameters:
2722: +  A - Jacobian matrix
2723: -  B - optional matrix for building the preconditioner

2725:   Options Database Keys:
2726: +    -snes_lag_preconditioner <lag> - how often to rebuild preconditioner
2727: .    -snes_lag_jacobian <lag> - how often to rebuild Jacobian
2728: .    -snes_test_jacobian <optional threshold> - compare the user provided Jacobian with one compute via finite differences to check for errors.  If a threshold is given, display only those entries whose difference is greater than the threshold.
2729: .    -snes_test_jacobian_view - display the user provided Jacobian, the finite difference Jacobian and the difference between them to help users detect the location of errors in the user provided Jacobian
2730: .    -snes_compare_explicit - Compare the computed Jacobian to the finite difference Jacobian and output the differences
2731: .    -snes_compare_explicit_draw  - Compare the computed Jacobian to the finite difference Jacobian and draw the result
2732: .    -snes_compare_explicit_contour  - Compare the computed Jacobian to the finite difference Jacobian and draw a contour plot with the result
2733: .    -snes_compare_operator  - Make the comparison options above use the operator instead of the preconditioning matrix
2734: .    -snes_compare_coloring - Compute the finite difference Jacobian using coloring and display norms of difference
2735: .    -snes_compare_coloring_display - Compute the finite difference Jacobian using coloring and display verbose differences
2736: .    -snes_compare_coloring_threshold - Display only those matrix entries that differ by more than a given threshold
2737: .    -snes_compare_coloring_threshold_atol - Absolute tolerance for difference in matrix entries to be displayed by `-snes_compare_coloring_threshold`
2738: .    -snes_compare_coloring_threshold_rtol - Relative tolerance for difference in matrix entries to be displayed by `-snes_compare_coloring_threshold`
2739: .    -snes_compare_coloring_draw - Compute the finite difference Jacobian using coloring and draw differences
2740: -    -snes_compare_coloring_draw_contour - Compute the finite difference Jacobian using coloring and show contours of matrices and differences

2742:    Level: developer

2744:    Note:
2745:    Most users should not need to explicitly call this routine, as it
2746:    is used internally within the nonlinear solvers.

2748:    Developer Note:
2749:     This has duplicative ways of checking the accuracy of the user provided Jacobian (see the options above). This is for historical reasons, the routine `SNESTestJacobian()` use to used
2750:       for with the `SNESType` of test that has been removed.

2752: .seealso: [](chapter_snes), `SNESSetJacobian()`, `KSPSetOperators()`, `MatStructure`, `SNESSetLagPreconditioner()`, `SNESSetLagJacobian()`
2753: @*/
2754: PetscErrorCode SNESComputeJacobian(SNES snes, Vec X, Mat A, Mat B)
2755: {
2756:   PetscBool flag;
2757:   DM        dm;
2758:   DMSNES    sdm;
2759:   KSP       ksp;

2761:   PetscFunctionBegin;
2764:   PetscCheckSameComm(snes, 1, X, 2);
2765:   PetscCall(VecValidValues_Internal(X, 2, PETSC_TRUE));
2766:   PetscCall(SNESGetDM(snes, &dm));
2767:   PetscCall(DMGetDMSNES(dm, &sdm));

2769:   /* make sure that MatAssemblyBegin/End() is called on A matrix if it is matrix free */
2770:   if (snes->lagjacobian == -2) {
2771:     snes->lagjacobian = -1;

2773:     PetscCall(PetscInfo(snes, "Recomputing Jacobian/preconditioner because lag is -2 (means compute Jacobian, but then never again) \n"));
2774:   } else if (snes->lagjacobian == -1) {
2775:     PetscCall(PetscInfo(snes, "Reusing Jacobian/preconditioner because lag is -1\n"));
2776:     PetscCall(PetscObjectTypeCompare((PetscObject)A, MATMFFD, &flag));
2777:     if (flag) {
2778:       PetscCall(MatAssemblyBegin(A, MAT_FINAL_ASSEMBLY));
2779:       PetscCall(MatAssemblyEnd(A, MAT_FINAL_ASSEMBLY));
2780:     }
2781:     PetscFunctionReturn(PETSC_SUCCESS);
2782:   } else if (snes->lagjacobian > 1 && (snes->iter + snes->jac_iter) % snes->lagjacobian) {
2783:     PetscCall(PetscInfo(snes, "Reusing Jacobian/preconditioner because lag is %" PetscInt_FMT " and SNES iteration is %" PetscInt_FMT "\n", snes->lagjacobian, snes->iter));
2784:     PetscCall(PetscObjectTypeCompare((PetscObject)A, MATMFFD, &flag));
2785:     if (flag) {
2786:       PetscCall(MatAssemblyBegin(A, MAT_FINAL_ASSEMBLY));
2787:       PetscCall(MatAssemblyEnd(A, MAT_FINAL_ASSEMBLY));
2788:     }
2789:     PetscFunctionReturn(PETSC_SUCCESS);
2790:   }
2791:   if (snes->npc && snes->npcside == PC_LEFT) {
2792:     PetscCall(MatAssemblyBegin(A, MAT_FINAL_ASSEMBLY));
2793:     PetscCall(MatAssemblyEnd(A, MAT_FINAL_ASSEMBLY));
2794:     PetscFunctionReturn(PETSC_SUCCESS);
2795:   }

2797:   PetscCall(PetscLogEventBegin(SNES_JacobianEval, snes, X, A, B));
2798:   PetscCall(VecLockReadPush(X));
2799:   {
2800:     void *ctx;
2801:     PetscErrorCode (*J)(SNES, Vec, Mat, Mat, void *);
2802:     PetscCall(DMSNESGetJacobian(dm, &J, &ctx));
2803:     PetscCallBack("SNES callback Jacobian", (*J)(snes, X, A, B, ctx));
2804:   }
2805:   PetscCall(VecLockReadPop(X));
2806:   PetscCall(PetscLogEventEnd(SNES_JacobianEval, snes, X, A, B));

2808:   /* attach latest linearization point to the preconditioning matrix */
2809:   PetscCall(PetscObjectCompose((PetscObject)B, "__SNES_latest_X", (PetscObject)X));

2811:   /* the next line ensures that snes->ksp exists */
2812:   PetscCall(SNESGetKSP(snes, &ksp));
2813:   if (snes->lagpreconditioner == -2) {
2814:     PetscCall(PetscInfo(snes, "Rebuilding preconditioner exactly once since lag is -2\n"));
2815:     PetscCall(KSPSetReusePreconditioner(snes->ksp, PETSC_FALSE));
2816:     snes->lagpreconditioner = -1;
2817:   } else if (snes->lagpreconditioner == -1) {
2818:     PetscCall(PetscInfo(snes, "Reusing preconditioner because lag is -1\n"));
2819:     PetscCall(KSPSetReusePreconditioner(snes->ksp, PETSC_TRUE));
2820:   } else if (snes->lagpreconditioner > 1 && (snes->iter + snes->pre_iter) % snes->lagpreconditioner) {
2821:     PetscCall(PetscInfo(snes, "Reusing preconditioner because lag is %" PetscInt_FMT " and SNES iteration is %" PetscInt_FMT "\n", snes->lagpreconditioner, snes->iter));
2822:     PetscCall(KSPSetReusePreconditioner(snes->ksp, PETSC_TRUE));
2823:   } else {
2824:     PetscCall(PetscInfo(snes, "Rebuilding preconditioner\n"));
2825:     PetscCall(KSPSetReusePreconditioner(snes->ksp, PETSC_FALSE));
2826:   }

2828:   PetscCall(SNESTestJacobian(snes));
2829:   /* make sure user returned a correct Jacobian and preconditioner */
2832:   {
2833:     PetscBool flag = PETSC_FALSE, flag_draw = PETSC_FALSE, flag_contour = PETSC_FALSE, flag_operator = PETSC_FALSE;
2834:     PetscCall(PetscOptionsGetViewer(PetscObjectComm((PetscObject)snes), ((PetscObject)snes)->options, ((PetscObject)snes)->prefix, "-snes_compare_explicit", NULL, NULL, &flag));
2835:     PetscCall(PetscOptionsGetViewer(PetscObjectComm((PetscObject)snes), ((PetscObject)snes)->options, ((PetscObject)snes)->prefix, "-snes_compare_explicit_draw", NULL, NULL, &flag_draw));
2836:     PetscCall(PetscOptionsGetViewer(PetscObjectComm((PetscObject)snes), ((PetscObject)snes)->options, ((PetscObject)snes)->prefix, "-snes_compare_explicit_draw_contour", NULL, NULL, &flag_contour));
2837:     PetscCall(PetscOptionsGetViewer(PetscObjectComm((PetscObject)snes), ((PetscObject)snes)->options, ((PetscObject)snes)->prefix, "-snes_compare_operator", NULL, NULL, &flag_operator));
2838:     if (flag || flag_draw || flag_contour) {
2839:       Mat         Bexp_mine = NULL, Bexp, FDexp;
2840:       PetscViewer vdraw, vstdout;
2841:       PetscBool   flg;
2842:       if (flag_operator) {
2843:         PetscCall(MatComputeOperator(A, MATAIJ, &Bexp_mine));
2844:         Bexp = Bexp_mine;
2845:       } else {
2846:         /* See if the preconditioning matrix can be viewed and added directly */
2847:         PetscCall(PetscObjectBaseTypeCompareAny((PetscObject)B, &flg, MATSEQAIJ, MATMPIAIJ, MATSEQDENSE, MATMPIDENSE, MATSEQBAIJ, MATMPIBAIJ, MATSEQSBAIJ, MATMPIBAIJ, ""));
2848:         if (flg) Bexp = B;
2849:         else {
2850:           /* If the "preconditioning" matrix is itself MATSHELL or some other type without direct support */
2851:           PetscCall(MatComputeOperator(B, MATAIJ, &Bexp_mine));
2852:           Bexp = Bexp_mine;
2853:         }
2854:       }
2855:       PetscCall(MatConvert(Bexp, MATSAME, MAT_INITIAL_MATRIX, &FDexp));
2856:       PetscCall(SNESComputeJacobianDefault(snes, X, FDexp, FDexp, NULL));
2857:       PetscCall(PetscViewerASCIIGetStdout(PetscObjectComm((PetscObject)snes), &vstdout));
2858:       if (flag_draw || flag_contour) {
2859:         PetscCall(PetscViewerDrawOpen(PetscObjectComm((PetscObject)snes), NULL, "Explicit Jacobians", PETSC_DECIDE, PETSC_DECIDE, 300, 300, &vdraw));
2860:         if (flag_contour) PetscCall(PetscViewerPushFormat(vdraw, PETSC_VIEWER_DRAW_CONTOUR));
2861:       } else vdraw = NULL;
2862:       PetscCall(PetscViewerASCIIPrintf(vstdout, "Explicit %s\n", flag_operator ? "Jacobian" : "preconditioning Jacobian"));
2863:       if (flag) PetscCall(MatView(Bexp, vstdout));
2864:       if (vdraw) PetscCall(MatView(Bexp, vdraw));
2865:       PetscCall(PetscViewerASCIIPrintf(vstdout, "Finite difference Jacobian\n"));
2866:       if (flag) PetscCall(MatView(FDexp, vstdout));
2867:       if (vdraw) PetscCall(MatView(FDexp, vdraw));
2868:       PetscCall(MatAYPX(FDexp, -1.0, Bexp, SAME_NONZERO_PATTERN));
2869:       PetscCall(PetscViewerASCIIPrintf(vstdout, "User-provided matrix minus finite difference Jacobian\n"));
2870:       if (flag) PetscCall(MatView(FDexp, vstdout));
2871:       if (vdraw) { /* Always use contour for the difference */
2872:         PetscCall(PetscViewerPushFormat(vdraw, PETSC_VIEWER_DRAW_CONTOUR));
2873:         PetscCall(MatView(FDexp, vdraw));
2874:         PetscCall(PetscViewerPopFormat(vdraw));
2875:       }
2876:       if (flag_contour) PetscCall(PetscViewerPopFormat(vdraw));
2877:       PetscCall(PetscViewerDestroy(&vdraw));
2878:       PetscCall(MatDestroy(&Bexp_mine));
2879:       PetscCall(MatDestroy(&FDexp));
2880:     }
2881:   }
2882:   {
2883:     PetscBool flag = PETSC_FALSE, flag_display = PETSC_FALSE, flag_draw = PETSC_FALSE, flag_contour = PETSC_FALSE, flag_threshold = PETSC_FALSE;
2884:     PetscReal threshold_atol = PETSC_SQRT_MACHINE_EPSILON, threshold_rtol = 10 * PETSC_SQRT_MACHINE_EPSILON;
2885:     PetscCall(PetscOptionsGetViewer(PetscObjectComm((PetscObject)snes), ((PetscObject)snes)->options, ((PetscObject)snes)->prefix, "-snes_compare_coloring", NULL, NULL, &flag));
2886:     PetscCall(PetscOptionsGetViewer(PetscObjectComm((PetscObject)snes), ((PetscObject)snes)->options, ((PetscObject)snes)->prefix, "-snes_compare_coloring_display", NULL, NULL, &flag_display));
2887:     PetscCall(PetscOptionsGetViewer(PetscObjectComm((PetscObject)snes), ((PetscObject)snes)->options, ((PetscObject)snes)->prefix, "-snes_compare_coloring_draw", NULL, NULL, &flag_draw));
2888:     PetscCall(PetscOptionsGetViewer(PetscObjectComm((PetscObject)snes), ((PetscObject)snes)->options, ((PetscObject)snes)->prefix, "-snes_compare_coloring_draw_contour", NULL, NULL, &flag_contour));
2889:     PetscCall(PetscOptionsGetViewer(PetscObjectComm((PetscObject)snes), ((PetscObject)snes)->options, ((PetscObject)snes)->prefix, "-snes_compare_coloring_threshold", NULL, NULL, &flag_threshold));
2890:     if (flag_threshold) {
2891:       PetscCall(PetscOptionsGetReal(((PetscObject)snes)->options, ((PetscObject)snes)->prefix, "-snes_compare_coloring_threshold_rtol", &threshold_rtol, NULL));
2892:       PetscCall(PetscOptionsGetReal(((PetscObject)snes)->options, ((PetscObject)snes)->prefix, "-snes_compare_coloring_threshold_atol", &threshold_atol, NULL));
2893:     }
2894:     if (flag || flag_display || flag_draw || flag_contour || flag_threshold) {
2895:       Mat           Bfd;
2896:       PetscViewer   vdraw, vstdout;
2897:       MatColoring   coloring;
2898:       ISColoring    iscoloring;
2899:       MatFDColoring matfdcoloring;
2900:       PetscErrorCode (*func)(SNES, Vec, Vec, void *);
2901:       void     *funcctx;
2902:       PetscReal norm1, norm2, normmax;

2904:       PetscCall(MatDuplicate(B, MAT_DO_NOT_COPY_VALUES, &Bfd));
2905:       PetscCall(MatColoringCreate(Bfd, &coloring));
2906:       PetscCall(MatColoringSetType(coloring, MATCOLORINGSL));
2907:       PetscCall(MatColoringSetFromOptions(coloring));
2908:       PetscCall(MatColoringApply(coloring, &iscoloring));
2909:       PetscCall(MatColoringDestroy(&coloring));
2910:       PetscCall(MatFDColoringCreate(Bfd, iscoloring, &matfdcoloring));
2911:       PetscCall(MatFDColoringSetFromOptions(matfdcoloring));
2912:       PetscCall(MatFDColoringSetUp(Bfd, iscoloring, matfdcoloring));
2913:       PetscCall(ISColoringDestroy(&iscoloring));

2915:       /* This method of getting the function is currently unreliable since it doesn't work for DM local functions. */
2916:       PetscCall(SNESGetFunction(snes, NULL, &func, &funcctx));
2917:       PetscCall(MatFDColoringSetFunction(matfdcoloring, (PetscErrorCode(*)(void))func, funcctx));
2918:       PetscCall(PetscObjectSetOptionsPrefix((PetscObject)matfdcoloring, ((PetscObject)snes)->prefix));
2919:       PetscCall(PetscObjectAppendOptionsPrefix((PetscObject)matfdcoloring, "coloring_"));
2920:       PetscCall(MatFDColoringSetFromOptions(matfdcoloring));
2921:       PetscCall(MatFDColoringApply(Bfd, matfdcoloring, X, snes));
2922:       PetscCall(MatFDColoringDestroy(&matfdcoloring));

2924:       PetscCall(PetscViewerASCIIGetStdout(PetscObjectComm((PetscObject)snes), &vstdout));
2925:       if (flag_draw || flag_contour) {
2926:         PetscCall(PetscViewerDrawOpen(PetscObjectComm((PetscObject)snes), NULL, "Colored Jacobians", PETSC_DECIDE, PETSC_DECIDE, 300, 300, &vdraw));
2927:         if (flag_contour) PetscCall(PetscViewerPushFormat(vdraw, PETSC_VIEWER_DRAW_CONTOUR));
2928:       } else vdraw = NULL;
2929:       PetscCall(PetscViewerASCIIPrintf(vstdout, "Explicit preconditioning Jacobian\n"));
2930:       if (flag_display) PetscCall(MatView(B, vstdout));
2931:       if (vdraw) PetscCall(MatView(B, vdraw));
2932:       PetscCall(PetscViewerASCIIPrintf(vstdout, "Colored Finite difference Jacobian\n"));
2933:       if (flag_display) PetscCall(MatView(Bfd, vstdout));
2934:       if (vdraw) PetscCall(MatView(Bfd, vdraw));
2935:       PetscCall(MatAYPX(Bfd, -1.0, B, SAME_NONZERO_PATTERN));
2936:       PetscCall(MatNorm(Bfd, NORM_1, &norm1));
2937:       PetscCall(MatNorm(Bfd, NORM_FROBENIUS, &norm2));
2938:       PetscCall(MatNorm(Bfd, NORM_MAX, &normmax));
2939:       PetscCall(PetscViewerASCIIPrintf(vstdout, "User-provided matrix minus finite difference Jacobian, norm1=%g normFrob=%g normmax=%g\n", (double)norm1, (double)norm2, (double)normmax));
2940:       if (flag_display) PetscCall(MatView(Bfd, vstdout));
2941:       if (vdraw) { /* Always use contour for the difference */
2942:         PetscCall(PetscViewerPushFormat(vdraw, PETSC_VIEWER_DRAW_CONTOUR));
2943:         PetscCall(MatView(Bfd, vdraw));
2944:         PetscCall(PetscViewerPopFormat(vdraw));
2945:       }
2946:       if (flag_contour) PetscCall(PetscViewerPopFormat(vdraw));

2948:       if (flag_threshold) {
2949:         PetscInt bs, rstart, rend, i;
2950:         PetscCall(MatGetBlockSize(B, &bs));
2951:         PetscCall(MatGetOwnershipRange(B, &rstart, &rend));
2952:         for (i = rstart; i < rend; i++) {
2953:           const PetscScalar *ba, *ca;
2954:           const PetscInt    *bj, *cj;
2955:           PetscInt           bn, cn, j, maxentrycol = -1, maxdiffcol = -1, maxrdiffcol = -1;
2956:           PetscReal          maxentry = 0, maxdiff = 0, maxrdiff = 0;
2957:           PetscCall(MatGetRow(B, i, &bn, &bj, &ba));
2958:           PetscCall(MatGetRow(Bfd, i, &cn, &cj, &ca));
2959:           PetscCheck(bn == cn, ((PetscObject)A)->comm, PETSC_ERR_PLIB, "Unexpected different nonzero pattern in -snes_compare_coloring_threshold");
2960:           for (j = 0; j < bn; j++) {
2961:             PetscReal rdiff = PetscAbsScalar(ca[j]) / (threshold_atol + threshold_rtol * PetscAbsScalar(ba[j]));
2962:             if (PetscAbsScalar(ba[j]) > PetscAbs(maxentry)) {
2963:               maxentrycol = bj[j];
2964:               maxentry    = PetscRealPart(ba[j]);
2965:             }
2966:             if (PetscAbsScalar(ca[j]) > PetscAbs(maxdiff)) {
2967:               maxdiffcol = bj[j];
2968:               maxdiff    = PetscRealPart(ca[j]);
2969:             }
2970:             if (rdiff > maxrdiff) {
2971:               maxrdiffcol = bj[j];
2972:               maxrdiff    = rdiff;
2973:             }
2974:           }
2975:           if (maxrdiff > 1) {
2976:             PetscCall(PetscViewerASCIIPrintf(vstdout, "row %" PetscInt_FMT " (maxentry=%g at %" PetscInt_FMT ", maxdiff=%g at %" PetscInt_FMT ", maxrdiff=%g at %" PetscInt_FMT "):", i, (double)maxentry, maxentrycol, (double)maxdiff, maxdiffcol, (double)maxrdiff, maxrdiffcol));
2977:             for (j = 0; j < bn; j++) {
2978:               PetscReal rdiff;
2979:               rdiff = PetscAbsScalar(ca[j]) / (threshold_atol + threshold_rtol * PetscAbsScalar(ba[j]));
2980:               if (rdiff > 1) PetscCall(PetscViewerASCIIPrintf(vstdout, " (%" PetscInt_FMT ",%g:%g)", bj[j], (double)PetscRealPart(ba[j]), (double)PetscRealPart(ca[j])));
2981:             }
2982:             PetscCall(PetscViewerASCIIPrintf(vstdout, "\n"));
2983:           }
2984:           PetscCall(MatRestoreRow(B, i, &bn, &bj, &ba));
2985:           PetscCall(MatRestoreRow(Bfd, i, &cn, &cj, &ca));
2986:         }
2987:       }
2988:       PetscCall(PetscViewerDestroy(&vdraw));
2989:       PetscCall(MatDestroy(&Bfd));
2990:     }
2991:   }
2992:   PetscFunctionReturn(PETSC_SUCCESS);
2993: }

2995: /*MC
2996:     SNESJacobianFunction - Function used by `SNES` to compute the nonlinear Jacobian of the function to be solved by `SNES`

2998:      Synopsis:
2999:      #include "petscsnes.h"
3000:      PetscErrorCode SNESJacobianFunction(SNES snes,Vec x,Mat Amat,Mat Pmat,void *ctx);

3002:      Collective

3004:     Input Parameters:
3005: +  x - input vector, the Jacobian is to be computed at this value
3006: -  ctx - [optional] user-defined Jacobian context

3008:     Output Parameters:
3009: +  Amat - the matrix that defines the (approximate) Jacobian
3010: -  Pmat - the matrix to be used in constructing the preconditioner, usually the same as `Amat`.

3012:    Level: intermediate

3014: .seealso: [](chapter_snes), `SNES`, `SNESSetFunction()`, `SNESGetFunction()`, `SNESSetJacobian()`, `SNESGetJacobian()`
3015: M*/

3017: /*@C
3018:    SNESSetJacobian - Sets the function to compute Jacobian as well as the
3019:    location to store the matrix.

3021:    Logically Collective

3023:    Input Parameters:
3024: +  snes - the `SNES` context
3025: .  Amat - the matrix that defines the (approximate) Jacobian
3026: .  Pmat - the matrix to be used in constructing the preconditioner, usually the same as `Amat`.
3027: .  J - Jacobian evaluation routine (if `NULL` then `SNES` retains any previously set value), see `SNESJacobianFunction` for details
3028: -  ctx - [optional] user-defined context for private data for the
3029:          Jacobian evaluation routine (may be `NULL`) (if `NULL` then `SNES` retains any previously set value)

3031:    Level: beginner

3033:    Notes:
3034:    If the `Amat` matrix and `Pmat` matrix are different you must call `MatAssemblyBegin()`/`MatAssemblyEnd()` on
3035:    each matrix.

3037:    If you know the operator `Amat` has a null space you can use `MatSetNullSpace()` and `MatSetTransposeNullSpace()` to supply the null
3038:    space to `Amat` and the `KSP` solvers will automatically use that null space as needed during the solution process.

3040:    If using `SNESComputeJacobianDefaultColor()` to assemble a Jacobian, the `ctx` argument
3041:    must be a `MatFDColoring`.

3043:    Other defect-correction schemes can be used by computing a different matrix in place of the Jacobian.  One common
3044:    example is to use the "Picard linearization" which only differentiates through the highest order parts of each term using `SNESSetPicard()`

3046: .seealso: [](chapter_snes), `SNES`, `KSPSetOperators()`, `SNESSetFunction()`, `MatMFFDComputeJacobian()`, `SNESComputeJacobianDefaultColor()`, `MatStructure`,
3047:           `SNESSetPicard()`, `SNESJacobianFunction`
3048: @*/
3049: PetscErrorCode SNESSetJacobian(SNES snes, Mat Amat, Mat Pmat, PetscErrorCode (*J)(SNES, Vec, Mat, Mat, void *), void *ctx)
3050: {
3051:   DM dm;

3053:   PetscFunctionBegin;
3057:   if (Amat) PetscCheckSameComm(snes, 1, Amat, 2);
3058:   if (Pmat) PetscCheckSameComm(snes, 1, Pmat, 3);
3059:   PetscCall(SNESGetDM(snes, &dm));
3060:   PetscCall(DMSNESSetJacobian(dm, J, ctx));
3061:   if (Amat) {
3062:     PetscCall(PetscObjectReference((PetscObject)Amat));
3063:     PetscCall(MatDestroy(&snes->jacobian));

3065:     snes->jacobian = Amat;
3066:   }
3067:   if (Pmat) {
3068:     PetscCall(PetscObjectReference((PetscObject)Pmat));
3069:     PetscCall(MatDestroy(&snes->jacobian_pre));

3071:     snes->jacobian_pre = Pmat;
3072:   }
3073:   PetscFunctionReturn(PETSC_SUCCESS);
3074: }

3076: /*@C
3077:    SNESGetJacobian - Returns the Jacobian matrix and optionally the user
3078:    provided context for evaluating the Jacobian.

3080:    Not Collective, but `Mat` object will be parallel if `SNES` object is

3082:    Input Parameter:
3083: .  snes - the nonlinear solver context

3085:    Output Parameters:
3086: +  Amat - location to stash (approximate) Jacobian matrix (or `NULL`)
3087: .  Pmat - location to stash matrix used to compute the preconditioner (or `NULL`)
3088: .  J - location to put Jacobian function (or `NULL`), see `SNESJacobianFunction` for details on its calling sequence
3089: -  ctx - location to stash Jacobian ctx (or `NULL`)

3091:    Level: advanced

3093: .seealso: [](chapter_snes), `SNES`, `Mat`, `SNESSetJacobian()`, `SNESComputeJacobian()`, `SNESJacobianFunction`, `SNESGetFunction()`
3094: @*/
3095: PetscErrorCode SNESGetJacobian(SNES snes, Mat *Amat, Mat *Pmat, PetscErrorCode (**J)(SNES, Vec, Mat, Mat, void *), void **ctx)
3096: {
3097:   DM dm;

3099:   PetscFunctionBegin;
3101:   if (Amat) *Amat = snes->jacobian;
3102:   if (Pmat) *Pmat = snes->jacobian_pre;
3103:   PetscCall(SNESGetDM(snes, &dm));
3104:   PetscCall(DMSNESGetJacobian(dm, J, ctx));
3105:   PetscFunctionReturn(PETSC_SUCCESS);
3106: }

3108: static PetscErrorCode SNESSetDefaultComputeJacobian(SNES snes)
3109: {
3110:   DM     dm;
3111:   DMSNES sdm;

3113:   PetscFunctionBegin;
3114:   PetscCall(SNESGetDM(snes, &dm));
3115:   PetscCall(DMGetDMSNES(dm, &sdm));
3116:   if (!sdm->ops->computejacobian && snes->jacobian_pre) {
3117:     DM        dm;
3118:     PetscBool isdense, ismf;

3120:     PetscCall(SNESGetDM(snes, &dm));
3121:     PetscCall(PetscObjectTypeCompareAny((PetscObject)snes->jacobian_pre, &isdense, MATSEQDENSE, MATMPIDENSE, MATDENSE, NULL));
3122:     PetscCall(PetscObjectTypeCompareAny((PetscObject)snes->jacobian_pre, &ismf, MATMFFD, MATSHELL, NULL));
3123:     if (isdense) {
3124:       PetscCall(DMSNESSetJacobian(dm, SNESComputeJacobianDefault, NULL));
3125:     } else if (!ismf) {
3126:       PetscCall(DMSNESSetJacobian(dm, SNESComputeJacobianDefaultColor, NULL));
3127:     }
3128:   }
3129:   PetscFunctionReturn(PETSC_SUCCESS);
3130: }

3132: /*@
3133:    SNESSetUp - Sets up the internal data structures for the later use
3134:    of a nonlinear solver.

3136:    Collective

3138:    Input Parameters:
3139: .  snes - the `SNES` context

3141:    Level: advanced

3143:    Note:
3144:    For basic use of the `SNES` solvers the user need not explicitly call
3145:    `SNESSetUp()`, since these actions will automatically occur during
3146:    the call to `SNESSolve()`.  However, if one wishes to control this
3147:    phase separately, `SNESSetUp()` should be called after `SNESCreate()`
3148:    and optional routines of the form SNESSetXXX(), but before `SNESSolve()`.

3150: .seealso: [](chapter_snes), `SNES`, `SNESCreate()`, `SNESSolve()`, `SNESDestroy()`
3151: @*/
3152: PetscErrorCode SNESSetUp(SNES snes)
3153: {
3154:   DM             dm;
3155:   DMSNES         sdm;
3156:   SNESLineSearch linesearch, pclinesearch;
3157:   void          *lsprectx, *lspostctx;
3158:   PetscBool      mf_operator, mf;
3159:   Vec            f, fpc;
3160:   void          *funcctx;
3161:   void          *jacctx, *appctx;
3162:   Mat            j, jpre;
3163:   PetscErrorCode (*precheck)(SNESLineSearch, Vec, Vec, PetscBool *, void *);
3164:   PetscErrorCode (*postcheck)(SNESLineSearch, Vec, Vec, Vec, PetscBool *, PetscBool *, void *);
3165:   PetscErrorCode (*func)(SNES, Vec, Vec, void *);
3166:   PetscErrorCode (*jac)(SNES, Vec, Mat, Mat, void *);

3168:   PetscFunctionBegin;
3170:   if (snes->setupcalled) PetscFunctionReturn(PETSC_SUCCESS);
3171:   PetscCall(PetscLogEventBegin(SNES_SetUp, snes, 0, 0, 0));

3173:   if (!((PetscObject)snes)->type_name) PetscCall(SNESSetType(snes, SNESNEWTONLS));

3175:   PetscCall(SNESGetFunction(snes, &snes->vec_func, NULL, NULL));

3177:   PetscCall(SNESGetDM(snes, &dm));
3178:   PetscCall(DMGetDMSNES(dm, &sdm));
3179:   PetscCall(SNESSetDefaultComputeJacobian(snes));

3181:   if (!snes->vec_func) PetscCall(DMCreateGlobalVector(dm, &snes->vec_func));

3183:   if (!snes->ksp) PetscCall(SNESGetKSP(snes, &snes->ksp));

3185:   if (snes->linesearch) {
3186:     PetscCall(SNESGetLineSearch(snes, &snes->linesearch));
3187:     PetscCall(SNESLineSearchSetFunction(snes->linesearch, SNESComputeFunction));
3188:   }

3190:   PetscCall(SNESGetUseMatrixFree(snes, &mf_operator, &mf));
3191:   if (snes->npc && snes->npcside == PC_LEFT) {
3192:     snes->mf          = PETSC_TRUE;
3193:     snes->mf_operator = PETSC_FALSE;
3194:   }

3196:   if (snes->npc) {
3197:     /* copy the DM over */
3198:     PetscCall(SNESGetDM(snes, &dm));
3199:     PetscCall(SNESSetDM(snes->npc, dm));

3201:     PetscCall(SNESGetFunction(snes, &f, &func, &funcctx));
3202:     PetscCall(VecDuplicate(f, &fpc));
3203:     PetscCall(SNESSetFunction(snes->npc, fpc, func, funcctx));
3204:     PetscCall(SNESGetJacobian(snes, &j, &jpre, &jac, &jacctx));
3205:     PetscCall(SNESSetJacobian(snes->npc, j, jpre, jac, jacctx));
3206:     PetscCall(SNESGetApplicationContext(snes, &appctx));
3207:     PetscCall(SNESSetApplicationContext(snes->npc, appctx));
3208:     PetscCall(SNESSetUseMatrixFree(snes->npc, mf_operator, mf));
3209:     PetscCall(VecDestroy(&fpc));

3211:     /* copy the function pointers over */
3212:     PetscCall(PetscObjectCopyFortranFunctionPointers((PetscObject)snes, (PetscObject)snes->npc));

3214:     /* default to 1 iteration */
3215:     PetscCall(SNESSetTolerances(snes->npc, 0.0, 0.0, 0.0, 1, snes->npc->max_funcs));
3216:     if (snes->npcside == PC_RIGHT) {
3217:       PetscCall(SNESSetNormSchedule(snes->npc, SNES_NORM_FINAL_ONLY));
3218:     } else {
3219:       PetscCall(SNESSetNormSchedule(snes->npc, SNES_NORM_NONE));
3220:     }
3221:     PetscCall(SNESSetFromOptions(snes->npc));

3223:     /* copy the line search context over */
3224:     if (snes->linesearch && snes->npc->linesearch) {
3225:       PetscCall(SNESGetLineSearch(snes, &linesearch));
3226:       PetscCall(SNESGetLineSearch(snes->npc, &pclinesearch));
3227:       PetscCall(SNESLineSearchGetPreCheck(linesearch, &precheck, &lsprectx));
3228:       PetscCall(SNESLineSearchGetPostCheck(linesearch, &postcheck, &lspostctx));
3229:       PetscCall(SNESLineSearchSetPreCheck(pclinesearch, precheck, lsprectx));
3230:       PetscCall(SNESLineSearchSetPostCheck(pclinesearch, postcheck, lspostctx));
3231:       PetscCall(PetscObjectCopyFortranFunctionPointers((PetscObject)linesearch, (PetscObject)pclinesearch));
3232:     }
3233:   }
3234:   if (snes->mf) PetscCall(SNESSetUpMatrixFree_Private(snes, snes->mf_operator, snes->mf_version));
3235:   if (snes->ops->usercompute && !snes->user) PetscCall((*snes->ops->usercompute)(snes, (void **)&snes->user));

3237:   snes->jac_iter = 0;
3238:   snes->pre_iter = 0;

3240:   PetscTryTypeMethod(snes, setup);

3242:   PetscCall(SNESSetDefaultComputeJacobian(snes));

3244:   if (snes->npc && snes->npcside == PC_LEFT) {
3245:     if (snes->functype == SNES_FUNCTION_PRECONDITIONED) {
3246:       if (snes->linesearch) {
3247:         PetscCall(SNESGetLineSearch(snes, &linesearch));
3248:         PetscCall(SNESLineSearchSetFunction(linesearch, SNESComputeFunctionDefaultNPC));
3249:       }
3250:     }
3251:   }
3252:   PetscCall(PetscLogEventEnd(SNES_SetUp, snes, 0, 0, 0));
3253:   snes->setupcalled = PETSC_TRUE;
3254:   PetscFunctionReturn(PETSC_SUCCESS);
3255: }

3257: /*@
3258:    SNESReset - Resets a `SNES` context to the snessetupcalled = 0 state and removes any allocated `Vec`s and `Mat`s

3260:    Collective

3262:    Input Parameter:
3263: .  snes - iterative context obtained from `SNESCreate()`

3265:    Level: intermediate

3267:    Notes:
3268:    Call this if you wish to reuse a `SNES` but with different size vectors

3270:    Also calls the application context destroy routine set with `SNESSetComputeApplicationContext()`

3272: .seealso: [](chapter_snes), `SNES`, `SNESDestroy()`, `SNESCreate()`, `SNESSetUp()`, `SNESSolve()`
3273: @*/
3274: PetscErrorCode SNESReset(SNES snes)
3275: {
3276:   PetscFunctionBegin;
3278:   if (snes->ops->userdestroy && snes->user) {
3279:     PetscCall((*snes->ops->userdestroy)((void **)&snes->user));
3280:     snes->user = NULL;
3281:   }
3282:   if (snes->npc) PetscCall(SNESReset(snes->npc));

3284:   PetscTryTypeMethod(snes, reset);
3285:   if (snes->ksp) PetscCall(KSPReset(snes->ksp));

3287:   if (snes->linesearch) PetscCall(SNESLineSearchReset(snes->linesearch));

3289:   PetscCall(VecDestroy(&snes->vec_rhs));
3290:   PetscCall(VecDestroy(&snes->vec_sol));
3291:   PetscCall(VecDestroy(&snes->vec_sol_update));
3292:   PetscCall(VecDestroy(&snes->vec_func));
3293:   PetscCall(MatDestroy(&snes->jacobian));
3294:   PetscCall(MatDestroy(&snes->jacobian_pre));
3295:   PetscCall(MatDestroy(&snes->picard));
3296:   PetscCall(VecDestroyVecs(snes->nwork, &snes->work));
3297:   PetscCall(VecDestroyVecs(snes->nvwork, &snes->vwork));

3299:   snes->alwayscomputesfinalresidual = PETSC_FALSE;

3301:   snes->nwork = snes->nvwork = 0;
3302:   snes->setupcalled          = PETSC_FALSE;
3303:   PetscFunctionReturn(PETSC_SUCCESS);
3304: }

3306: /*@
3307:    SNESConvergedReasonViewCancel - Clears all the reason view functions for a `SNES` object.

3309:    Collective

3311:    Input Parameter:
3312: .  snes - iterative context obtained from `SNESCreate()`

3314:    Level: intermediate

3316: .seealso: [](chapter_snes), `SNES`, `SNESCreate()`, `SNESDestroy()`, `SNESReset()`
3317: @*/
3318: PetscErrorCode SNESConvergedReasonViewCancel(SNES snes)
3319: {
3320:   PetscInt i;

3322:   PetscFunctionBegin;
3324:   for (i = 0; i < snes->numberreasonviews; i++) {
3325:     if (snes->reasonviewdestroy[i]) PetscCall((*snes->reasonviewdestroy[i])(&snes->reasonviewcontext[i]));
3326:   }
3327:   snes->numberreasonviews = 0;
3328:   PetscFunctionReturn(PETSC_SUCCESS);
3329: }

3331: /*@C
3332:    SNESDestroy - Destroys the nonlinear solver context that was created
3333:    with `SNESCreate()`.

3335:    Collective

3337:    Input Parameter:
3338: .  snes - the `SNES` context

3340:    Level: beginner

3342: .seealso: [](chapter_snes), `SNES`, `SNESCreate()`, `SNESSolve()`
3343: @*/
3344: PetscErrorCode SNESDestroy(SNES *snes)
3345: {
3346:   PetscFunctionBegin;
3347:   if (!*snes) PetscFunctionReturn(PETSC_SUCCESS);
3349:   if (--((PetscObject)(*snes))->refct > 0) {
3350:     *snes = NULL;
3351:     PetscFunctionReturn(PETSC_SUCCESS);
3352:   }

3354:   PetscCall(SNESReset((*snes)));
3355:   PetscCall(SNESDestroy(&(*snes)->npc));

3357:   /* if memory was published with SAWs then destroy it */
3358:   PetscCall(PetscObjectSAWsViewOff((PetscObject)*snes));
3359:   PetscTryTypeMethod((*snes), destroy);

3361:   if ((*snes)->dm) PetscCall(DMCoarsenHookRemove((*snes)->dm, DMCoarsenHook_SNESVecSol, DMRestrictHook_SNESVecSol, *snes));
3362:   PetscCall(DMDestroy(&(*snes)->dm));
3363:   PetscCall(KSPDestroy(&(*snes)->ksp));
3364:   PetscCall(SNESLineSearchDestroy(&(*snes)->linesearch));

3366:   PetscCall(PetscFree((*snes)->kspconvctx));
3367:   if ((*snes)->ops->convergeddestroy) PetscCall((*(*snes)->ops->convergeddestroy)((*snes)->cnvP));
3368:   if ((*snes)->conv_hist_alloc) PetscCall(PetscFree2((*snes)->conv_hist, (*snes)->conv_hist_its));
3369:   PetscCall(SNESMonitorCancel((*snes)));
3370:   PetscCall(SNESConvergedReasonViewCancel((*snes)));
3371:   PetscCall(PetscHeaderDestroy(snes));
3372:   PetscFunctionReturn(PETSC_SUCCESS);
3373: }

3375: /* ----------- Routines to set solver parameters ---------- */

3377: /*@
3378:    SNESSetLagPreconditioner - Determines when the preconditioner is rebuilt in the nonlinear solve.

3380:    Logically Collective

3382:    Input Parameters:
3383: +  snes - the `SNES` context
3384: -  lag - 1 means rebuild every time the Jacobian is computed within a single nonlinear solve, 2 means every second time
3385:          the Jacobian is built etc. -2 indicates rebuild preconditioner at next chance but then never rebuild after that

3387:    Options Database Keys:
3388: +    -snes_lag_jacobian_persists <true,false> - sets the persistence
3389: .    -snes_lag_jacobian <-2,1,2,...> - sets the lag
3390: .    -snes_lag_preconditioner_persists <true,false> - sets the persistence
3391: -    -snes_lag_preconditioner <-2,1,2,...> - sets the lag

3393:    Notes:
3394:    Level: intermediate

3396:    The default is 1
3397:    The preconditioner is ALWAYS built in the first iteration of a nonlinear solve unless lag is -1 or `SNESSetLagPreconditionerPersists()` was called

3399:    `SNESSetLagPreconditionerPersists()` allows using the same uniform lagging (for example every second linear solve) across multiple nonlinear solves.

3401: .seealso: [](chapter_snes), `SNESSetTrustRegionTolerance()`, `SNESGetLagPreconditioner()`, `SNESSetLagJacobian()`, `SNESGetLagJacobian()`, `SNESSetLagPreconditionerPersists()`,
3402:           `SNESSetLagJacobianPersists()`, `SNES`, `SNESSolve()`
3403: @*/
3404: PetscErrorCode SNESSetLagPreconditioner(SNES snes, PetscInt lag)
3405: {
3406:   PetscFunctionBegin;
3408:   PetscCheck(lag >= -2, PETSC_COMM_SELF, PETSC_ERR_ARG_OUTOFRANGE, "Lag must be -2, -1, 1 or greater");
3409:   PetscCheck(lag, PETSC_COMM_SELF, PETSC_ERR_ARG_OUTOFRANGE, "Lag cannot be 0");
3411:   snes->lagpreconditioner = lag;
3412:   PetscFunctionReturn(PETSC_SUCCESS);
3413: }

3415: /*@
3416:    SNESSetGridSequence - sets the number of steps of grid sequencing that `SNES` will do

3418:    Logically Collective

3420:    Input Parameters:
3421: +  snes - the `SNES` context
3422: -  steps - the number of refinements to do, defaults to 0

3424:    Options Database Key:
3425: .    -snes_grid_sequence <steps> - Use grid sequencing to generate initial guess

3427:    Level: intermediate

3429:    Note:
3430:    Use `SNESGetSolution()` to extract the fine grid solution after grid sequencing.

3432: .seealso: [](chapter_snes), `SNES`, `SNESSetTrustRegionTolerance()`, `SNESGetLagPreconditioner()`, `SNESSetLagJacobian()`, `SNESGetLagJacobian()`, `SNESGetGridSequence()`
3433: @*/
3434: PetscErrorCode SNESSetGridSequence(SNES snes, PetscInt steps)
3435: {
3436:   PetscFunctionBegin;
3439:   snes->gridsequence = steps;
3440:   PetscFunctionReturn(PETSC_SUCCESS);
3441: }

3443: /*@
3444:    SNESGetGridSequence - gets the number of steps of grid sequencing that `SNES` will do

3446:    Logically Collective

3448:    Input Parameter:
3449: .  snes - the `SNES` context

3451:    Output Parameter:
3452: .  steps - the number of refinements to do, defaults to 0

3454:    Options Database Key:
3455: .    -snes_grid_sequence <steps> - set number of refinements

3457:    Level: intermediate

3459:    Note:
3460:    Use `SNESGetSolution()` to extract the fine grid solution after grid sequencing.

3462: .seealso: [](chapter_snes), `SNESSetTrustRegionTolerance()`, `SNESGetLagPreconditioner()`, `SNESSetLagJacobian()`, `SNESGetLagJacobian()`, `SNESSetGridSequence()`
3463: @*/
3464: PetscErrorCode SNESGetGridSequence(SNES snes, PetscInt *steps)
3465: {
3466:   PetscFunctionBegin;
3468:   *steps = snes->gridsequence;
3469:   PetscFunctionReturn(PETSC_SUCCESS);
3470: }

3472: /*@
3473:    SNESGetLagPreconditioner - Return how often the preconditioner is rebuilt

3475:    Not Collective

3477:    Input Parameter:
3478: .  snes - the `SNES` context

3480:    Output Parameter:
3481: .   lag - -1 indicates NEVER rebuild, 1 means rebuild every time the Jacobian is computed within a single nonlinear solve, 2 means every second time
3482:          the Jacobian is built etc. -2 indicates rebuild preconditioner at next chance but then never rebuild after that

3484:    Options Database Keys:
3485: +    -snes_lag_jacobian_persists <true,false> - sets the persistence
3486: .    -snes_lag_jacobian <-2,1,2,...> - sets the lag
3487: .    -snes_lag_preconditioner_persists <true,false> - sets the persistence
3488: -    -snes_lag_preconditioner <-2,1,2,...> - sets the lag

3490:    Level: intermediate

3492:    Notes:
3493:    The default is 1

3495:    The preconditioner is ALWAYS built in the first iteration of a nonlinear solve unless lag is -1

3497: .seealso: [](chapter_snes), `SNES`, `SNESSetTrustRegionTolerance()`, `SNESSetLagPreconditioner()`, `SNESSetLagJacobianPersists()`, `SNESSetLagPreconditionerPersists()`
3498: @*/
3499: PetscErrorCode SNESGetLagPreconditioner(SNES snes, PetscInt *lag)
3500: {
3501:   PetscFunctionBegin;
3503:   *lag = snes->lagpreconditioner;
3504:   PetscFunctionReturn(PETSC_SUCCESS);
3505: }

3507: /*@
3508:    SNESSetLagJacobian - Set when the Jacobian is rebuilt in the nonlinear solve. See `SNESSetLagPreconditioner()` for determining how
3509:      often the preconditioner is rebuilt.

3511:    Logically Collective

3513:    Input Parameters:
3514: +  snes - the `SNES` context
3515: -  lag - -1 indicates NEVER rebuild, 1 means rebuild every time the Jacobian is computed within a single nonlinear solve, 2 means every second time
3516:          the Jacobian is built etc. -2 means rebuild at next chance but then never again

3518:    Options Database Keys:
3519: +    -snes_lag_jacobian_persists <true,false> - sets the persistence
3520: .    -snes_lag_jacobian <-2,1,2,...> - sets the lag
3521: .    -snes_lag_preconditioner_persists <true,false> - sets the persistence
3522: -    -snes_lag_preconditioner <-2,1,2,...> - sets the lag.

3524:    Level: intermediate

3526:    Notes:
3527:    The default is 1

3529:    The Jacobian is ALWAYS built in the first iteration of a nonlinear solve unless lag is -1

3531:    If  -1 is used before the very first nonlinear solve the CODE WILL FAIL! because no Jacobian is used, use -2 to indicate you want it recomputed
3532:    at the next Newton step but never again (unless it is reset to another value)

3534: .seealso: [](chapter_snes), `SNES`, `SNESSetTrustRegionTolerance()`, `SNESGetLagPreconditioner()`, `SNESSetLagPreconditioner()`, `SNESGetLagJacobianPersists()`, `SNESSetLagPreconditionerPersists()`
3535: @*/
3536: PetscErrorCode SNESSetLagJacobian(SNES snes, PetscInt lag)
3537: {
3538:   PetscFunctionBegin;
3540:   PetscCheck(lag >= -2, PETSC_COMM_SELF, PETSC_ERR_ARG_OUTOFRANGE, "Lag must be -2, -1, 1 or greater");
3541:   PetscCheck(lag, PETSC_COMM_SELF, PETSC_ERR_ARG_OUTOFRANGE, "Lag cannot be 0");
3543:   snes->lagjacobian = lag;
3544:   PetscFunctionReturn(PETSC_SUCCESS);
3545: }

3547: /*@
3548:    SNESGetLagJacobian - Get how often the Jacobian is rebuilt. See `SNESGetLagPreconditioner()` to determine when the preconditioner is rebuilt

3550:    Not Collective

3552:    Input Parameter:
3553: .  snes - the `SNES` context

3555:    Output Parameter:
3556: .   lag - -1 indicates NEVER rebuild, 1 means rebuild every time the Jacobian is computed within a single nonlinear solve, 2 means every second time
3557:          the Jacobian is built etc.

3559:    Level: intermediate

3561:    Notes:
3562:    The default is 1

3564:    The jacobian is ALWAYS built in the first iteration of a nonlinear solve unless lag is -1 or `SNESSetLagJacobianPersists()` was called.

3566: .seealso: [](chapter_snes), `SNES`, `SNESSetTrustRegionTolerance()`, `SNESSetLagJacobian()`, `SNESSetLagPreconditioner()`, `SNESGetLagPreconditioner()`, `SNESSetLagJacobianPersists()`, `SNESSetLagPreconditionerPersists()`

3568: @*/
3569: PetscErrorCode SNESGetLagJacobian(SNES snes, PetscInt *lag)
3570: {
3571:   PetscFunctionBegin;
3573:   *lag = snes->lagjacobian;
3574:   PetscFunctionReturn(PETSC_SUCCESS);
3575: }

3577: /*@
3578:    SNESSetLagJacobianPersists - Set whether or not the Jacobian lagging persists through multiple nonlinear solves

3580:    Logically collective

3582:    Input Parameters:
3583: +  snes - the `SNES` context
3584: -   flg - jacobian lagging persists if true

3586:    Options Database Keys:
3587: +    -snes_lag_jacobian_persists <true,false> - sets the persistence
3588: .    -snes_lag_jacobian <-2,1,2,...> - sets the lag
3589: .    -snes_lag_preconditioner_persists <true,false> - sets the persistence
3590: -    -snes_lag_preconditioner <-2,1,2,...> - sets the lag

3592:    Level: advanced

3594:    Notes:
3595:     Normally when `SNESSetLagJacobian()` is used, the Jacobian is always rebuilt at the beginning of each new nonlinear solve, this removes that.

3597:     This is useful both for nonlinear preconditioning, where it's appropriate to have the Jacobian be stale by
3598:    several solves, and for implicit time-stepping, where Jacobian lagging in the inner nonlinear solve over several
3599:    timesteps may present huge efficiency gains.

3601: .seealso: [](chapter_snes), `SNES, `SNESSetLagPreconditionerPersists()`, `SNESSetLagJacobian()`, `SNESGetLagJacobian()`, `SNESGetNPC()`, `SNESSetLagJacobianPersists()`
3602: @*/
3603: PetscErrorCode SNESSetLagJacobianPersists(SNES snes, PetscBool flg)
3604: {
3605:   PetscFunctionBegin;
3608:   snes->lagjac_persist = flg;
3609:   PetscFunctionReturn(PETSC_SUCCESS);
3610: }

3612: /*@
3613:    SNESSetLagPreconditionerPersists - Set whether or not the preconditioner lagging persists through multiple nonlinear solves

3615:    Logically Collective

3617:    Input Parameters:
3618: +  snes - the `SNES` context
3619: -   flg - preconditioner lagging persists if true

3621:    Options Database Keys:
3622: +    -snes_lag_jacobian_persists <true,false> - sets the persistence
3623: .    -snes_lag_jacobian <-2,1,2,...> - sets the lag
3624: .    -snes_lag_preconditioner_persists <true,false> - sets the persistence
3625: -    -snes_lag_preconditioner <-2,1,2,...> - sets the lag

3627:    Level: developer

3629:    Notes:
3630:     Normally when `SNESSetLagPreconditioner()` is used, the preconditioner is always rebuilt at the beginning of each new nonlinear solve, this removes that.

3632:    This is useful both for nonlinear preconditioning, where it's appropriate to have the preconditioner be stale
3633:    by several solves, and for implicit time-stepping, where preconditioner lagging in the inner nonlinear solve over
3634:    several timesteps may present huge efficiency gains.

3636: .seealso: [](chapter_snes), `SNES`, `SNESSetLagJacobianPersists()`, `SNESSetLagJacobian()`, `SNESGetLagJacobian()`, `SNESGetNPC()`, `SNESSetLagPreconditioner()`
3637: @*/
3638: PetscErrorCode SNESSetLagPreconditionerPersists(SNES snes, PetscBool flg)
3639: {
3640:   PetscFunctionBegin;
3643:   snes->lagpre_persist = flg;
3644:   PetscFunctionReturn(PETSC_SUCCESS);
3645: }

3647: /*@
3648:    SNESSetForceIteration - force `SNESSolve()` to take at least one iteration regardless of the initial residual norm

3650:    Logically Collective

3652:    Input Parameters:
3653: +  snes - the `SNES` context
3654: -  force - `PETSC_TRUE` require at least one iteration

3656:    Options Database Key:
3657: .    -snes_force_iteration <force> - Sets forcing an iteration

3659:    Level: intermediate

3661:    Note:
3662:    This is used sometimes with `TS` to prevent `TS` from detecting a false steady state solution

3664: .seealso: [](chapter_snes), `SNES`, `TS`, `SNESSetTrustRegionTolerance()`, `SNESSetDivergenceTolerance()`
3665: @*/
3666: PetscErrorCode SNESSetForceIteration(SNES snes, PetscBool force)
3667: {
3668:   PetscFunctionBegin;
3670:   snes->forceiteration = force;
3671:   PetscFunctionReturn(PETSC_SUCCESS);
3672: }

3674: /*@
3675:    SNESGetForceIteration - Check whether or not `SNESSolve()` take at least one iteration regardless of the initial residual norm

3677:    Logically Collective

3679:    Input Parameters:
3680: .  snes - the `SNES` context

3682:    Output Parameter:
3683: .  force - `PETSC_TRUE` requires at least one iteration.

3685:    Level: intermediate

3687: .seealso: [](chapter_snes), `SNES`, `SNESSetForceIteration()`, `SNESSetTrustRegionTolerance()`, `SNESSetDivergenceTolerance()`
3688: @*/
3689: PetscErrorCode SNESGetForceIteration(SNES snes, PetscBool *force)
3690: {
3691:   PetscFunctionBegin;
3693:   *force = snes->forceiteration;
3694:   PetscFunctionReturn(PETSC_SUCCESS);
3695: }

3697: /*@
3698:    SNESSetTolerances - Sets `SNES` various parameters used in convergence tests.

3700:    Logically Collective

3702:    Input Parameters:
3703: +  snes - the `SNES` context
3704: .  abstol - absolute convergence tolerance
3705: .  rtol - relative convergence tolerance
3706: .  stol -  convergence tolerance in terms of the norm of the change in the solution between steps,  || delta x || < stol*|| x ||
3707: .  maxit - maximum number of iterations, default 50.
3708: -  maxf - maximum number of function evaluations (-1 indicates no limit), default 1000

3710:    Options Database Keys:
3711: +    -snes_atol <abstol> - Sets abstol
3712: .    -snes_rtol <rtol> - Sets rtol
3713: .    -snes_stol <stol> - Sets stol
3714: .    -snes_max_it <maxit> - Sets maxit
3715: -    -snes_max_funcs <maxf> - Sets maxf

3717:    Level: intermediate

3719: .seealso: [](chapter_snes), `SNESolve()`, `SNES`, `SNESSetTrustRegionTolerance()`, `SNESSetDivergenceTolerance()`, `SNESSetForceIteration()`
3720: @*/
3721: PetscErrorCode SNESSetTolerances(SNES snes, PetscReal abstol, PetscReal rtol, PetscReal stol, PetscInt maxit, PetscInt maxf)
3722: {
3723:   PetscFunctionBegin;

3731:   if (abstol != PETSC_DEFAULT) {
3732:     PetscCheck(abstol >= 0.0, PetscObjectComm((PetscObject)snes), PETSC_ERR_ARG_OUTOFRANGE, "Absolute tolerance %g must be non-negative", (double)abstol);
3733:     snes->abstol = abstol;
3734:   }
3735:   if (rtol != PETSC_DEFAULT) {
3736:     PetscCheck(rtol >= 0.0 && 1.0 > rtol, PetscObjectComm((PetscObject)snes), PETSC_ERR_ARG_OUTOFRANGE, "Relative tolerance %g must be non-negative and less than 1.0", (double)rtol);
3737:     snes->rtol = rtol;
3738:   }
3739:   if (stol != PETSC_DEFAULT) {
3740:     PetscCheck(stol >= 0.0, PetscObjectComm((PetscObject)snes), PETSC_ERR_ARG_OUTOFRANGE, "Step tolerance %g must be non-negative", (double)stol);
3741:     snes->stol = stol;
3742:   }
3743:   if (maxit != PETSC_DEFAULT) {
3744:     PetscCheck(maxit >= 0, PetscObjectComm((PetscObject)snes), PETSC_ERR_ARG_OUTOFRANGE, "Maximum number of iterations %" PetscInt_FMT " must be non-negative", maxit);
3745:     snes->max_its = maxit;
3746:   }
3747:   if (maxf != PETSC_DEFAULT) {
3748:     PetscCheck(maxf >= -1, PetscObjectComm((PetscObject)snes), PETSC_ERR_ARG_OUTOFRANGE, "Maximum number of function evaluations %" PetscInt_FMT " must be -1 or nonnegative", maxf);
3749:     snes->max_funcs = maxf;
3750:   }
3751:   snes->tolerancesset = PETSC_TRUE;
3752:   PetscFunctionReturn(PETSC_SUCCESS);
3753: }

3755: /*@
3756:    SNESSetDivergenceTolerance - Sets the divergence tolerance used for the `SNES` divergence test.

3758:    Logically Collective

3760:    Input Parameters:
3761: +  snes - the `SNES` context
3762: -  divtol - the divergence tolerance. Use -1 to deactivate the test, default is 1e4

3764:    Options Database Key:
3765: .    -snes_divergence_tolerance <divtol> - Sets `divtol`

3767:    Level: intermediate

3769: .seealso: [](chapter_snes), `SNES`, `SNESSolve()`, `SNESSetTolerances()`, `SNESGetDivergenceTolerance`
3770: @*/
3771: PetscErrorCode SNESSetDivergenceTolerance(SNES snes, PetscReal divtol)
3772: {
3773:   PetscFunctionBegin;

3777:   if (divtol != PETSC_DEFAULT) {
3778:     snes->divtol = divtol;
3779:   } else {
3780:     snes->divtol = 1.0e4;
3781:   }
3782:   PetscFunctionReturn(PETSC_SUCCESS);
3783: }

3785: /*@
3786:    SNESGetTolerances - Gets various parameters used in convergence tests.

3788:    Not Collective

3790:    Input Parameters:
3791: +  snes - the `SNES` context
3792: .  atol - absolute convergence tolerance
3793: .  rtol - relative convergence tolerance
3794: .  stol -  convergence tolerance in terms of the norm
3795:            of the change in the solution between steps
3796: .  maxit - maximum number of iterations
3797: -  maxf - maximum number of function evaluations

3799:    Level: intermediate

3801:    Note:
3802:    The user can specify `NULL` for any parameter that is not needed.

3804: .seealso: [](chapter_snes), `SNES`, `SNESSetTolerances()`
3805: @*/
3806: PetscErrorCode SNESGetTolerances(SNES snes, PetscReal *atol, PetscReal *rtol, PetscReal *stol, PetscInt *maxit, PetscInt *maxf)
3807: {
3808:   PetscFunctionBegin;
3810:   if (atol) *atol = snes->abstol;
3811:   if (rtol) *rtol = snes->rtol;
3812:   if (stol) *stol = snes->stol;
3813:   if (maxit) *maxit = snes->max_its;
3814:   if (maxf) *maxf = snes->max_funcs;
3815:   PetscFunctionReturn(PETSC_SUCCESS);
3816: }

3818: /*@
3819:    SNESGetDivergenceTolerance - Gets divergence tolerance used in divergence test.

3821:    Not Collective

3823:    Input Parameters:
3824: +  snes - the `SNES` context
3825: -  divtol - divergence tolerance

3827:    Level: intermediate

3829: .seealso: [](chapter_snes), `SNES`, `SNESSetDivergenceTolerance()`
3830: @*/
3831: PetscErrorCode SNESGetDivergenceTolerance(SNES snes, PetscReal *divtol)
3832: {
3833:   PetscFunctionBegin;
3835:   if (divtol) *divtol = snes->divtol;
3836:   PetscFunctionReturn(PETSC_SUCCESS);
3837: }

3839: /*@
3840:    SNESSetTrustRegionTolerance - Sets the trust region parameter tolerance.

3842:    Logically Collective

3844:    Input Parameters:
3845: +  snes - the `SNES` context
3846: -  tol - tolerance

3848:    Options Database Key:
3849: .  -snes_trtol <tol> - Sets tol

3851:    Level: intermediate

3853: .seealso: [](chapter_snes), `SNES`, `SNESNEWTONTRDC`, `SNESSetTolerances()`
3854: @*/
3855: PetscErrorCode SNESSetTrustRegionTolerance(SNES snes, PetscReal tol)
3856: {
3857:   PetscFunctionBegin;
3860:   snes->deltatol = tol;
3861:   PetscFunctionReturn(PETSC_SUCCESS);
3862: }

3864: PETSC_INTERN PetscErrorCode SNESMonitorRange_Private(SNES, PetscInt, PetscReal *);

3866: PetscErrorCode SNESMonitorLGRange(SNES snes, PetscInt n, PetscReal rnorm, void *monctx)
3867: {
3868:   PetscDrawLG      lg;
3869:   PetscReal        x, y, per;
3870:   PetscViewer      v = (PetscViewer)monctx;
3871:   static PetscReal prev; /* should be in the context */
3872:   PetscDraw        draw;

3874:   PetscFunctionBegin;
3876:   PetscCall(PetscViewerDrawGetDrawLG(v, 0, &lg));
3877:   if (!n) PetscCall(PetscDrawLGReset(lg));
3878:   PetscCall(PetscDrawLGGetDraw(lg, &draw));
3879:   PetscCall(PetscDrawSetTitle(draw, "Residual norm"));
3880:   x = (PetscReal)n;
3881:   if (rnorm > 0.0) y = PetscLog10Real(rnorm);
3882:   else y = -15.0;
3883:   PetscCall(PetscDrawLGAddPoint(lg, &x, &y));
3884:   if (n < 20 || !(n % 5) || snes->reason) {
3885:     PetscCall(PetscDrawLGDraw(lg));
3886:     PetscCall(PetscDrawLGSave(lg));
3887:   }

3889:   PetscCall(PetscViewerDrawGetDrawLG(v, 1, &lg));
3890:   if (!n) PetscCall(PetscDrawLGReset(lg));
3891:   PetscCall(PetscDrawLGGetDraw(lg, &draw));
3892:   PetscCall(PetscDrawSetTitle(draw, "% elemts > .2*max elemt"));
3893:   PetscCall(SNESMonitorRange_Private(snes, n, &per));
3894:   x = (PetscReal)n;
3895:   y = 100.0 * per;
3896:   PetscCall(PetscDrawLGAddPoint(lg, &x, &y));
3897:   if (n < 20 || !(n % 5) || snes->reason) {
3898:     PetscCall(PetscDrawLGDraw(lg));
3899:     PetscCall(PetscDrawLGSave(lg));
3900:   }

3902:   PetscCall(PetscViewerDrawGetDrawLG(v, 2, &lg));
3903:   if (!n) {
3904:     prev = rnorm;
3905:     PetscCall(PetscDrawLGReset(lg));
3906:   }
3907:   PetscCall(PetscDrawLGGetDraw(lg, &draw));
3908:   PetscCall(PetscDrawSetTitle(draw, "(norm -oldnorm)/oldnorm"));
3909:   x = (PetscReal)n;
3910:   y = (prev - rnorm) / prev;
3911:   PetscCall(PetscDrawLGAddPoint(lg, &x, &y));
3912:   if (n < 20 || !(n % 5) || snes->reason) {
3913:     PetscCall(PetscDrawLGDraw(lg));
3914:     PetscCall(PetscDrawLGSave(lg));
3915:   }

3917:   PetscCall(PetscViewerDrawGetDrawLG(v, 3, &lg));
3918:   if (!n) PetscCall(PetscDrawLGReset(lg));
3919:   PetscCall(PetscDrawLGGetDraw(lg, &draw));
3920:   PetscCall(PetscDrawSetTitle(draw, "(norm -oldnorm)/oldnorm*(% > .2 max)"));
3921:   x = (PetscReal)n;
3922:   y = (prev - rnorm) / (prev * per);
3923:   if (n > 2) { /*skip initial crazy value */
3924:     PetscCall(PetscDrawLGAddPoint(lg, &x, &y));
3925:   }
3926:   if (n < 20 || !(n % 5) || snes->reason) {
3927:     PetscCall(PetscDrawLGDraw(lg));
3928:     PetscCall(PetscDrawLGSave(lg));
3929:   }
3930:   prev = rnorm;
3931:   PetscFunctionReturn(PETSC_SUCCESS);
3932: }

3934: /*@
3935:    SNESMonitor - runs the user provided monitor routines, if they exist

3937:    Collective

3939:    Input Parameters:
3940: +  snes - nonlinear solver context obtained from `SNESCreate()`
3941: .  iter - iteration number
3942: -  rnorm - relative norm of the residual

3944:    Level: developer

3946:    Note:
3947:    This routine is called by the `SNES` implementations.
3948:    It does not typically need to be called by the user.

3950: .seealso: [](chapter_snes), `SNES`, `SNESMonitorSet()`
3951: @*/
3952: PetscErrorCode SNESMonitor(SNES snes, PetscInt iter, PetscReal rnorm)
3953: {
3954:   PetscInt i, n = snes->numbermonitors;

3956:   PetscFunctionBegin;
3957:   PetscCall(VecLockReadPush(snes->vec_sol));
3958:   for (i = 0; i < n; i++) PetscCall((*snes->monitor[i])(snes, iter, rnorm, snes->monitorcontext[i]));
3959:   PetscCall(VecLockReadPop(snes->vec_sol));
3960:   PetscFunctionReturn(PETSC_SUCCESS);
3961: }

3963: /* ------------ Routines to set performance monitoring options ----------- */

3965: /*MC
3966:     SNESMonitorFunction - functional form passed to `SNESMonitorSet()` to monitor convergence of nonlinear solver

3968:      Synopsis:
3969: #include <petscsnes.h>
3970: $    PetscErrorCode SNESMonitorFunction(SNES snes,PetscInt its, PetscReal norm,void *mctx)

3972:      Collective

3974:     Input Parameters:
3975: +    snes - the `SNES` context
3976: .    its - iteration number
3977: .    norm - 2-norm function value (may be estimated)
3978: -    mctx - [optional] monitoring context

3980:    Level: advanced

3982: .seealso: [](chapter_snes), `SNESMonitorSet()`, `SNESMonitorSet()`, `SNESMonitorGet()`
3983: M*/

3985: /*@C
3986:    SNESMonitorSet - Sets an ADDITIONAL function that is to be used at every
3987:    iteration of the nonlinear solver to display the iteration's
3988:    progress.

3990:    Logically Collective

3992:    Input Parameters:
3993: +  snes - the `SNES` context
3994: .  f - the monitor function, see `SNESMonitorFunction` for the calling sequence
3995: .  mctx - [optional] user-defined context for private data for the
3996:           monitor routine (use `NULL` if no context is desired)
3997: -  monitordestroy - [optional] routine that frees monitor context (may be `NULL`)

3999:    Options Database Keys:
4000: +    -snes_monitor        - sets `SNESMonitorDefault()`
4001: .    -snes_monitor draw::draw_lg - sets line graph monitor,
4002: -    -snes_monitor_cancel - cancels all monitors that have been hardwired into a code by calls to `SNESMonitorSet()`, but does not cancel those set via
4003:                             the options database.

4005:    Level: intermediate

4007:    Note:
4008:    Several different monitoring routines may be set by calling
4009:    `SNESMonitorSet()` multiple times; all will be called in the
4010:    order in which they were set.

4012:    Fortran Note:
4013:    Only a single monitor function can be set for each `SNES` object

4015: .seealso: [](chapter_snes), `SNES`, `SNESSolve()`, `SNESMonitorDefault()`, `SNESMonitorCancel()`, `SNESMonitorFunction`
4016: @*/
4017: PetscErrorCode SNESMonitorSet(SNES snes, PetscErrorCode (*f)(SNES, PetscInt, PetscReal, void *), void *mctx, PetscErrorCode (*monitordestroy)(void **))
4018: {
4019:   PetscInt  i;
4020:   PetscBool identical;

4022:   PetscFunctionBegin;
4024:   for (i = 0; i < snes->numbermonitors; i++) {
4025:     PetscCall(PetscMonitorCompare((PetscErrorCode(*)(void))f, mctx, monitordestroy, (PetscErrorCode(*)(void))snes->monitor[i], snes->monitorcontext[i], snes->monitordestroy[i], &identical));
4026:     if (identical) PetscFunctionReturn(PETSC_SUCCESS);
4027:   }
4028:   PetscCheck(snes->numbermonitors < MAXSNESMONITORS, PETSC_COMM_SELF, PETSC_ERR_ARG_OUTOFRANGE, "Too many monitors set");
4029:   snes->monitor[snes->numbermonitors]          = f;
4030:   snes->monitordestroy[snes->numbermonitors]   = monitordestroy;
4031:   snes->monitorcontext[snes->numbermonitors++] = (void *)mctx;
4032:   PetscFunctionReturn(PETSC_SUCCESS);
4033: }

4035: /*@
4036:    SNESMonitorCancel - Clears all the monitor functions for a `SNES` object.

4038:    Logically Collective

4040:    Input Parameters:
4041: .  snes - the `SNES` context

4043:    Options Database Key:
4044: .  -snes_monitor_cancel - cancels all monitors that have been hardwired
4045:     into a code by calls to `SNESMonitorSet()`, but does not cancel those
4046:     set via the options database

4048:    Level: intermediate

4050:    Note:
4051:    There is no way to clear one specific monitor from a `SNES` object.

4053: .seealso: [](chapter_snes), `SNES`, `SNESMonitorGet()`, `SNESMonitorDefault()`, `SNESMonitorSet()`
4054: @*/
4055: PetscErrorCode SNESMonitorCancel(SNES snes)
4056: {
4057:   PetscInt i;

4059:   PetscFunctionBegin;
4061:   for (i = 0; i < snes->numbermonitors; i++) {
4062:     if (snes->monitordestroy[i]) PetscCall((*snes->monitordestroy[i])(&snes->monitorcontext[i]));
4063:   }
4064:   snes->numbermonitors = 0;
4065:   PetscFunctionReturn(PETSC_SUCCESS);
4066: }

4068: /*MC
4069:     SNESConvergenceTestFunction - functional form used for testing of convergence of nonlinear solver

4071:      Synopsis:
4072: #include <petscsnes.h>
4073: $     PetscErrorCode SNESConvergenceTest(SNES snes,PetscInt it,PetscReal xnorm,PetscReal gnorm,PetscReal f,SNESConvergedReason *reason,void *cctx)

4075:      Collective

4077:     Input Parameters:
4078: +    snes - the `SNES` context
4079: .    it - current iteration (0 is the first and is before any Newton step)
4080: .    xnorm - 2-norm of current iterate
4081: .    gnorm - 2-norm of current step
4082: .    f - 2-norm of function
4083: -    cctx - [optional] convergence context

4085:     Output Parameter:
4086: .    reason - reason for convergence/divergence, only needs to be set when convergence or divergence is detected

4088:    Level: intermediate

4090: .seealso: [](chapter_snes), `SNES`, `SNESSolve`, `SNESSetConvergenceTest()`, `SNESGetConvergenceTest()`
4091: M*/

4093: /*@C
4094:    SNESSetConvergenceTest - Sets the function that is to be used
4095:    to test for convergence of the nonlinear iterative solution.

4097:    Logically Collective

4099:    Input Parameters:
4100: +  snes - the `SNES` context
4101: .  `SNESConvergenceTestFunction` - routine to test for convergence
4102: .  cctx - [optional] context for private data for the convergence routine  (may be `NULL`)
4103: -  destroy - [optional] destructor for the context (may be `NULL`; `PETSC_NULL_FUNCTION` in Fortran)

4105:    Level: advanced

4107: .seealso: [](chapter_snes), `SNES`, `SNESConvergedDefault()`, `SNESConvergedSkip()`, `SNESConvergenceTestFunction`
4108: @*/
4109: PetscErrorCode SNESSetConvergenceTest(SNES snes, PetscErrorCode (*SNESConvergenceTestFunction)(SNES, PetscInt, PetscReal, PetscReal, PetscReal, SNESConvergedReason *, void *), void *cctx, PetscErrorCode (*destroy)(void *))
4110: {
4111:   PetscFunctionBegin;
4113:   if (!SNESConvergenceTestFunction) SNESConvergenceTestFunction = SNESConvergedSkip;
4114:   if (snes->ops->convergeddestroy) PetscCall((*snes->ops->convergeddestroy)(snes->cnvP));
4115:   snes->ops->converged        = SNESConvergenceTestFunction;
4116:   snes->ops->convergeddestroy = destroy;
4117:   snes->cnvP                  = cctx;
4118:   PetscFunctionReturn(PETSC_SUCCESS);
4119: }

4121: /*@
4122:    SNESGetConvergedReason - Gets the reason the `SNES` iteration was stopped.

4124:    Not Collective

4126:    Input Parameter:
4127: .  snes - the `SNES` context

4129:    Output Parameter:
4130: .  reason - negative value indicates diverged, positive value converged, see `SNESConvergedReason` for the individual convergence tests for complete lists

4132:    Options Database Key:
4133: .   -snes_converged_reason - prints the reason to standard out

4135:    Level: intermediate

4137:    Note:
4138:     Should only be called after the call the `SNESSolve()` is complete, if it is called earlier it returns the value `SNES__CONVERGED_ITERATING`.

4140: .seealso: [](chapter_snes), `SNESSolve()`, `SNESSetConvergenceTest()`, `SNESSetConvergedReason()`, `SNESConvergedReason`, `SNESGetConvergedReasonString()`
4141: @*/
4142: PetscErrorCode SNESGetConvergedReason(SNES snes, SNESConvergedReason *reason)
4143: {
4144:   PetscFunctionBegin;
4147:   *reason = snes->reason;
4148:   PetscFunctionReturn(PETSC_SUCCESS);
4149: }

4151: /*@C
4152:    SNESGetConvergedReasonString - Return a human readable string for `SNESConvergedReason`

4154:    Not Collective

4156:    Input Parameter:
4157: .  snes - the `SNES` context

4159:    Output Parameter:
4160: .  strreason - a human readable string that describes `SNES` converged reason

4162:    Level: beginner

4164: .seealso: [](chapter_snes), `SNES`, `SNESGetConvergedReason()`
4165: @*/
4166: PetscErrorCode SNESGetConvergedReasonString(SNES snes, const char **strreason)
4167: {
4168:   PetscFunctionBegin;
4171:   *strreason = SNESConvergedReasons[snes->reason];
4172:   PetscFunctionReturn(PETSC_SUCCESS);
4173: }

4175: /*@
4176:    SNESSetConvergedReason - Sets the reason the `SNES` iteration was stopped.

4178:    Not Collective

4180:    Input Parameters:
4181: +  snes - the `SNES` context
4182: -  reason - negative value indicates diverged, positive value converged, see `SNESConvergedReason` or the
4183:             manual pages for the individual convergence tests for complete lists

4185:    Level: developer

4187:    Developer Note:
4188:    Called inside the various `SNESSolve()` implementations

4190: .seealso: [](chapter_snes), `SNESGetConvergedReason()`, `SNESSetConvergenceTest()`, `SNESConvergedReason`
4191: @*/
4192: PetscErrorCode SNESSetConvergedReason(SNES snes, SNESConvergedReason reason)
4193: {
4194:   PetscFunctionBegin;
4196:   snes->reason = reason;
4197:   PetscFunctionReturn(PETSC_SUCCESS);
4198: }

4200: /*@
4201:    SNESSetConvergenceHistory - Sets the array used to hold the convergence history.

4203:    Logically Collective

4205:    Input Parameters:
4206: +  snes - iterative context obtained from `SNESCreate()`
4207: .  a   - array to hold history, this array will contain the function norms computed at each step
4208: .  its - integer array holds the number of linear iterations for each solve.
4209: .  na  - size of a and its
4210: -  reset - `PETSC_TRUE` indicates each new nonlinear solve resets the history counter to zero,
4211:            else it continues storing new values for new nonlinear solves after the old ones

4213:    Level: intermediate

4215:    Notes:
4216:    If 'a' and 'its' are `NULL` then space is allocated for the history. If 'na' `PETSC_DECIDE` or `PETSC_DEFAULT` then a
4217:    default array of length 10000 is allocated.

4219:    This routine is useful, e.g., when running a code for purposes
4220:    of accurate performance monitoring, when no I/O should be done
4221:    during the section of code that is being timed.

4223: .seealso: [](chapter_snes), `SNES`, `SNESSolve()`, `SNESGetConvergenceHistory()`
4224: @*/
4225: PetscErrorCode SNESSetConvergenceHistory(SNES snes, PetscReal a[], PetscInt its[], PetscInt na, PetscBool reset)
4226: {
4227:   PetscFunctionBegin;
4231:   if (!a) {
4232:     if (na == PETSC_DECIDE || na == PETSC_DEFAULT) na = 1000;
4233:     PetscCall(PetscCalloc2(na, &a, na, &its));
4234:     snes->conv_hist_alloc = PETSC_TRUE;
4235:   }
4236:   snes->conv_hist       = a;
4237:   snes->conv_hist_its   = its;
4238:   snes->conv_hist_max   = (size_t)na;
4239:   snes->conv_hist_len   = 0;
4240:   snes->conv_hist_reset = reset;
4241:   PetscFunctionReturn(PETSC_SUCCESS);
4242: }

4244: #if defined(PETSC_HAVE_MATLAB)
4245:   #include <engine.h> /* MATLAB include file */
4246:   #include <mex.h>    /* MATLAB include file */

4248: PETSC_EXTERN mxArray *SNESGetConvergenceHistoryMatlab(SNES snes)
4249: {
4250:   mxArray   *mat;
4251:   PetscInt   i;
4252:   PetscReal *ar;

4254:   mat = mxCreateDoubleMatrix(snes->conv_hist_len, 1, mxREAL);
4255:   ar  = (PetscReal *)mxGetData(mat);
4256:   for (i = 0; i < snes->conv_hist_len; i++) ar[i] = snes->conv_hist[i];
4257:   return mat;
4258: }
4259: #endif

4261: /*@C
4262:    SNESGetConvergenceHistory - Gets the array used to hold the convergence history.

4264:    Not Collective

4266:    Input Parameter:
4267: .  snes - iterative context obtained from `SNESCreate()`

4269:    Output Parameters:
4270: +  a   - array to hold history, usually was set with `SNESSetConvergenceHistory()`
4271: .  its - integer array holds the number of linear iterations (or
4272:          negative if not converged) for each solve.
4273: -  na  - size of a and its

4275:    Level: intermediate

4277:    Notes:
4278:     The calling sequence for this routine in Fortran is
4279: .vb
4280:     call SNESGetConvergenceHistory(SNES snes, integer na, integer ierr)
4281: .ve

4283:    This routine is useful, e.g., when running a code for purposes
4284:    of accurate performance monitoring, when no I/O should be done
4285:    during the section of code that is being timed.

4287: .seealso: [](chapter_snes), `SNES`, `SNESSolve()`, `SNESSetConvergenceHistory()`
4288: @*/
4289: PetscErrorCode SNESGetConvergenceHistory(SNES snes, PetscReal *a[], PetscInt *its[], PetscInt *na)
4290: {
4291:   PetscFunctionBegin;
4293:   if (a) *a = snes->conv_hist;
4294:   if (its) *its = snes->conv_hist_its;
4295:   if (na) *na = (PetscInt)snes->conv_hist_len;
4296:   PetscFunctionReturn(PETSC_SUCCESS);
4297: }

4299: /*@C
4300:   SNESSetUpdate - Sets the general-purpose update function called
4301:   at the beginning of every iteration of the nonlinear solve. Specifically
4302:   it is called just before the Jacobian is "evaluated".

4304:   Logically Collective

4306:   Input Parameters:
4307: + snes - The nonlinear solver context
4308: - func - The function

4310:   Calling sequence of func:
4311: $ func (SNES snes, PetscInt step);

4313: . step - The current step of the iteration

4315:   Level: advanced

4317:   Note:
4318:      This is NOT what one uses to update the ghost points before a function evaluation, that should be done at the beginning of your function provided
4319:      to `SNESSetFunction()`, or `SNESSetPicard()`
4320:      This is not used by most users.

4322:      There are a varity of function hooks one many set that are called at different stages of the nonlinear solution process, see the functions listed below.

4324: .seealso: [](chapter_snes), `SNES`, `SNESSolve()`, `SNESSetJacobian()`, `SNESSolve()`, `SNESLineSearchSetPreCheck()`, `SNESLineSearchSetPostCheck()`, `SNESNewtonTRSetPreCheck()`, `SNESNewtonTRSetPostCheck()`,
4325:          `SNESMonitorSet()`, `SNESSetDivergenceTest()`
4326: @*/
4327: PetscErrorCode SNESSetUpdate(SNES snes, PetscErrorCode (*func)(SNES, PetscInt))
4328: {
4329:   PetscFunctionBegin;
4331:   snes->ops->update = func;
4332:   PetscFunctionReturn(PETSC_SUCCESS);
4333: }

4335: /*
4336:    SNESScaleStep_Private - Scales a step so that its length is less than the
4337:    positive parameter delta.

4339:     Input Parameters:
4340: +   snes - the `SNES` context
4341: .   y - approximate solution of linear system
4342: .   fnorm - 2-norm of current function
4343: -   delta - trust region size

4345:     Output Parameters:
4346: +   gpnorm - predicted function norm at the new point, assuming local
4347:     linearization.  The value is zero if the step lies within the trust
4348:     region, and exceeds zero otherwise.
4349: -   ynorm - 2-norm of the step

4351:     Level: developer

4353:     Note:
4354:     For non-trust region methods such as `SNESNEWTONLS`, the parameter delta
4355:     is set to be the maximum allowable step size.
4356: */
4357: PetscErrorCode SNESScaleStep_Private(SNES snes, Vec y, PetscReal *fnorm, PetscReal *delta, PetscReal *gpnorm, PetscReal *ynorm)
4358: {
4359:   PetscReal   nrm;
4360:   PetscScalar cnorm;

4362:   PetscFunctionBegin;
4365:   PetscCheckSameComm(snes, 1, y, 2);

4367:   PetscCall(VecNorm(y, NORM_2, &nrm));
4368:   if (nrm > *delta) {
4369:     nrm     = *delta / nrm;
4370:     *gpnorm = (1.0 - nrm) * (*fnorm);
4371:     cnorm   = nrm;
4372:     PetscCall(VecScale(y, cnorm));
4373:     *ynorm = *delta;
4374:   } else {
4375:     *gpnorm = 0.0;
4376:     *ynorm  = nrm;
4377:   }
4378:   PetscFunctionReturn(PETSC_SUCCESS);
4379: }

4381: /*@C
4382:    SNESConvergedReasonView - Displays the reason a `SNES` solve converged or diverged to a viewer

4384:    Collective

4386:    Parameter:
4387: +  snes - iterative context obtained from `SNESCreate()`
4388: -  viewer - the viewer to display the reason

4390:    Options Database Keys:
4391: +  -snes_converged_reason - print reason for converged or diverged, also prints number of iterations
4392: -  -snes_converged_reason ::failed - only print reason and number of iterations when diverged

4394:   Note:
4395:      To change the format of the output call `PetscViewerPushFormat`(viewer,format) before this call. Use `PETSC_VIEWER_DEFAULT` for the default,
4396:      use `PETSC_VIEWER_FAILED` to only display a reason if it fails.

4398:    Level: beginner

4400: .seealso: [](chapter_snes), `SNESConvergedReason`, `PetscViewer`, `SNES`,
4401:           `SNESCreate()`, `SNESSetUp()`, `SNESDestroy()`, `SNESSetTolerances()`, `SNESConvergedDefault()`, `SNESGetConvergedReason()`,
4402:           `SNESConvergedReasonViewFromOptions()`,
4403:           `PetscViewerPushFormat()`, `PetscViewerPopFormat()`
4404: @*/
4405: PetscErrorCode SNESConvergedReasonView(SNES snes, PetscViewer viewer)
4406: {
4407:   PetscViewerFormat format;
4408:   PetscBool         isAscii;

4410:   PetscFunctionBegin;
4411:   if (!viewer) viewer = PETSC_VIEWER_STDOUT_(PetscObjectComm((PetscObject)snes));
4412:   PetscCall(PetscObjectTypeCompare((PetscObject)viewer, PETSCVIEWERASCII, &isAscii));
4413:   if (isAscii) {
4414:     PetscCall(PetscViewerGetFormat(viewer, &format));
4415:     PetscCall(PetscViewerASCIIAddTab(viewer, ((PetscObject)snes)->tablevel));
4416:     if (format == PETSC_VIEWER_ASCII_INFO_DETAIL) {
4417:       DM       dm;
4418:       Vec      u;
4419:       PetscDS  prob;
4420:       PetscInt Nf, f;
4421:       PetscErrorCode (**exactSol)(PetscInt, PetscReal, const PetscReal[], PetscInt, PetscScalar[], void *);
4422:       void    **exactCtx;
4423:       PetscReal error;

4425:       PetscCall(SNESGetDM(snes, &dm));
4426:       PetscCall(SNESGetSolution(snes, &u));
4427:       PetscCall(DMGetDS(dm, &prob));
4428:       PetscCall(PetscDSGetNumFields(prob, &Nf));
4429:       PetscCall(PetscMalloc2(Nf, &exactSol, Nf, &exactCtx));
4430:       for (f = 0; f < Nf; ++f) PetscCall(PetscDSGetExactSolution(prob, f, &exactSol[f], &exactCtx[f]));
4431:       PetscCall(DMComputeL2Diff(dm, 0.0, exactSol, exactCtx, u, &error));
4432:       PetscCall(PetscFree2(exactSol, exactCtx));
4433:       if (error < 1.0e-11) PetscCall(PetscViewerASCIIPrintf(viewer, "L_2 Error: < 1.0e-11\n"));
4434:       else PetscCall(PetscViewerASCIIPrintf(viewer, "L_2 Error: %g\n", (double)error));
4435:     }
4436:     if (snes->reason > 0 && format != PETSC_VIEWER_FAILED) {
4437:       if (((PetscObject)snes)->prefix) {
4438:         PetscCall(PetscViewerASCIIPrintf(viewer, "Nonlinear %s solve converged due to %s iterations %" PetscInt_FMT "\n", ((PetscObject)snes)->prefix, SNESConvergedReasons[snes->reason], snes->iter));
4439:       } else {
4440:         PetscCall(PetscViewerASCIIPrintf(viewer, "Nonlinear solve converged due to %s iterations %" PetscInt_FMT "\n", SNESConvergedReasons[snes->reason], snes->iter));
4441:       }
4442:     } else if (snes->reason <= 0) {
4443:       if (((PetscObject)snes)->prefix) {
4444:         PetscCall(PetscViewerASCIIPrintf(viewer, "Nonlinear %s solve did not converge due to %s iterations %" PetscInt_FMT "\n", ((PetscObject)snes)->prefix, SNESConvergedReasons[snes->reason], snes->iter));
4445:       } else {
4446:         PetscCall(PetscViewerASCIIPrintf(viewer, "Nonlinear solve did not converge due to %s iterations %" PetscInt_FMT "\n", SNESConvergedReasons[snes->reason], snes->iter));
4447:       }
4448:     }
4449:     PetscCall(PetscViewerASCIISubtractTab(viewer, ((PetscObject)snes)->tablevel));
4450:   }
4451:   PetscFunctionReturn(PETSC_SUCCESS);
4452: }

4454: /*@C
4455:    SNESConvergedReasonViewSet - Sets an ADDITIONAL function that is to be used at the
4456:     end of the nonlinear solver to display the conver reason of the nonlinear solver.

4458:    Logically Collective

4460:    Input Parameters:
4461: +  snes - the `SNES` context
4462: .  f - the snes converged reason view function
4463: .  vctx - [optional] user-defined context for private data for the
4464:           snes converged reason view routine (use `NULL` if no context is desired)
4465: -  reasonviewdestroy - [optional] routine that frees reasonview context (may be `NULL`)

4467:    Options Database Keys:
4468: +    -snes_converged_reason        - sets a default `SNESConvergedReasonView()`
4469: -    -snes_converged_reason_view_cancel - cancels all converged reason viewers that have
4470:                             been hardwired into a code by
4471:                             calls to `SNESConvergedReasonViewSet()`, but
4472:                             does not cancel those set via
4473:                             the options database.

4475:    Level: intermediate

4477:    Note:
4478:    Several different converged reason view routines may be set by calling
4479:    `SNESConvergedReasonViewSet()` multiple times; all will be called in the
4480:    order in which they were set.

4482: .seealso: [](chapter_snes), `SNES`, `SNESSolve()`, `SNESConvergedReason`, `SNESGetConvergedReason()`, `SNESConvergedReasonView()`, `SNESConvergedReasonViewCancel()`
4483: @*/
4484: PetscErrorCode SNESConvergedReasonViewSet(SNES snes, PetscErrorCode (*f)(SNES, void *), void *vctx, PetscErrorCode (*reasonviewdestroy)(void **))
4485: {
4486:   PetscInt  i;
4487:   PetscBool identical;

4489:   PetscFunctionBegin;
4491:   for (i = 0; i < snes->numberreasonviews; i++) {
4492:     PetscCall(PetscMonitorCompare((PetscErrorCode(*)(void))f, vctx, reasonviewdestroy, (PetscErrorCode(*)(void))snes->reasonview[i], snes->reasonviewcontext[i], snes->reasonviewdestroy[i], &identical));
4493:     if (identical) PetscFunctionReturn(PETSC_SUCCESS);
4494:   }
4495:   PetscCheck(snes->numberreasonviews < MAXSNESREASONVIEWS, PETSC_COMM_SELF, PETSC_ERR_ARG_OUTOFRANGE, "Too many SNES reasonview set");
4496:   snes->reasonview[snes->numberreasonviews]          = f;
4497:   snes->reasonviewdestroy[snes->numberreasonviews]   = reasonviewdestroy;
4498:   snes->reasonviewcontext[snes->numberreasonviews++] = (void *)vctx;
4499:   PetscFunctionReturn(PETSC_SUCCESS);
4500: }

4502: /*@
4503:   SNESConvergedReasonViewFromOptions - Processes command line options to determine if/how a `SNESConvergedReason` is to be viewed.
4504:                                        All the user-provided convergedReasonView routines will be involved as well, if they exist.

4506:   Collective

4508:   Input Parameters:
4509: . snes   - the `SNES` object

4511:   Level: advanced

4513: .seealso: [](chapter_snes), `SNES`, `SNESConvergedReason`, `SNESConvergedReasonViewSet()`, `SNESCreate()`, `SNESSetUp()`, `SNESDestroy()`,
4514:           `SNESSetTolerances()`, `SNESConvergedDefault()`, `SNESGetConvergedReason()`, `SNESConvergedReasonView()`
4515: @*/
4516: PetscErrorCode SNESConvergedReasonViewFromOptions(SNES snes)
4517: {
4518:   PetscViewer       viewer;
4519:   PetscBool         flg;
4520:   static PetscBool  incall = PETSC_FALSE;
4521:   PetscViewerFormat format;
4522:   PetscInt          i;

4524:   PetscFunctionBegin;
4525:   if (incall) PetscFunctionReturn(PETSC_SUCCESS);
4526:   incall = PETSC_TRUE;

4528:   /* All user-provided viewers are called first, if they exist. */
4529:   for (i = 0; i < snes->numberreasonviews; i++) PetscCall((*snes->reasonview[i])(snes, snes->reasonviewcontext[i]));

4531:   /* Call PETSc default routine if users ask for it */
4532:   PetscCall(PetscOptionsGetViewer(PetscObjectComm((PetscObject)snes), ((PetscObject)snes)->options, ((PetscObject)snes)->prefix, "-snes_converged_reason", &viewer, &format, &flg));
4533:   if (flg) {
4534:     PetscCall(PetscViewerPushFormat(viewer, format));
4535:     PetscCall(SNESConvergedReasonView(snes, viewer));
4536:     PetscCall(PetscViewerPopFormat(viewer));
4537:     PetscCall(PetscViewerDestroy(&viewer));
4538:   }
4539:   incall = PETSC_FALSE;
4540:   PetscFunctionReturn(PETSC_SUCCESS);
4541: }

4543: /*@
4544:    SNESSolve - Solves a nonlinear system F(x) = b.
4545:    Call `SNESSolve()` after calling `SNESCreate()` and optional routines of the form `SNESSetXXX()`.

4547:    Collective

4549:    Input Parameters:
4550: +  snes - the `SNES` context
4551: .  b - the constant part of the equation F(x) = b, or `NULL` to use zero.
4552: -  x - the solution vector.

4554:    Level: beginner

4556:    Note:
4557:    The user should initialize the vector,x, with the initial guess
4558:    for the nonlinear solve prior to calling `SNESSolve()`.  In particular,
4559:    to employ an initial guess of zero, the user should explicitly set
4560:    this vector to zero by calling `VecSet()`.

4562: .seealso: [](chapter_snes), `SNES`, `SNESCreate()`, `SNESDestroy()`, `SNESSetFunction()`, `SNESSetJacobian()`, `SNESSetGridSequence()`, `SNESGetSolution()`,
4563:           `SNESNewtonTRSetPreCheck()`, `SNESNewtonTRGetPreCheck()`, `SNESNewtonTRSetPostCheck()`, `SNESNewtonTRGetPostCheck()`,
4564:           `SNESLineSearchSetPostCheck()`, `SNESLineSearchGetPostCheck()`, `SNESLineSearchSetPreCheck()`, `SNESLineSearchGetPreCheck()`
4565: @*/
4566: PetscErrorCode SNESSolve(SNES snes, Vec b, Vec x)
4567: {
4568:   PetscBool flg;
4569:   PetscInt  grid;
4570:   Vec       xcreated = NULL;
4571:   DM        dm;

4573:   PetscFunctionBegin;
4576:   if (x) PetscCheckSameComm(snes, 1, x, 3);
4578:   if (b) PetscCheckSameComm(snes, 1, b, 2);

4580:   /* High level operations using the nonlinear solver */
4581:   {
4582:     PetscViewer       viewer;
4583:     PetscViewerFormat format;
4584:     PetscInt          num;
4585:     PetscBool         flg;
4586:     static PetscBool  incall = PETSC_FALSE;

4588:     if (!incall) {
4589:       /* Estimate the convergence rate of the discretization */
4590:       PetscCall(PetscOptionsGetViewer(PetscObjectComm((PetscObject)snes), ((PetscObject)snes)->options, ((PetscObject)snes)->prefix, "-snes_convergence_estimate", &viewer, &format, &flg));
4591:       if (flg) {
4592:         PetscConvEst conv;
4593:         DM           dm;
4594:         PetscReal   *alpha; /* Convergence rate of the solution error for each field in the L_2 norm */
4595:         PetscInt     Nf;

4597:         incall = PETSC_TRUE;
4598:         PetscCall(SNESGetDM(snes, &dm));
4599:         PetscCall(DMGetNumFields(dm, &Nf));
4600:         PetscCall(PetscCalloc1(Nf, &alpha));
4601:         PetscCall(PetscConvEstCreate(PetscObjectComm((PetscObject)snes), &conv));
4602:         PetscCall(PetscConvEstSetSolver(conv, (PetscObject)snes));
4603:         PetscCall(PetscConvEstSetFromOptions(conv));
4604:         PetscCall(PetscConvEstSetUp(conv));
4605:         PetscCall(PetscConvEstGetConvRate(conv, alpha));
4606:         PetscCall(PetscViewerPushFormat(viewer, format));
4607:         PetscCall(PetscConvEstRateView(conv, alpha, viewer));
4608:         PetscCall(PetscViewerPopFormat(viewer));
4609:         PetscCall(PetscViewerDestroy(&viewer));
4610:         PetscCall(PetscConvEstDestroy(&conv));
4611:         PetscCall(PetscFree(alpha));
4612:         incall = PETSC_FALSE;
4613:       }
4614:       /* Adaptively refine the initial grid */
4615:       num = 1;
4616:       PetscCall(PetscOptionsGetInt(NULL, ((PetscObject)snes)->prefix, "-snes_adapt_initial", &num, &flg));
4617:       if (flg) {
4618:         DMAdaptor adaptor;

4620:         incall = PETSC_TRUE;
4621:         PetscCall(DMAdaptorCreate(PetscObjectComm((PetscObject)snes), &adaptor));
4622:         PetscCall(DMAdaptorSetSolver(adaptor, snes));
4623:         PetscCall(DMAdaptorSetSequenceLength(adaptor, num));
4624:         PetscCall(DMAdaptorSetFromOptions(adaptor));
4625:         PetscCall(DMAdaptorSetUp(adaptor));
4626:         PetscCall(DMAdaptorAdapt(adaptor, x, DM_ADAPTATION_INITIAL, &dm, &x));
4627:         PetscCall(DMAdaptorDestroy(&adaptor));
4628:         incall = PETSC_FALSE;
4629:       }
4630:       /* Use grid sequencing to adapt */
4631:       num = 0;
4632:       PetscCall(PetscOptionsGetInt(NULL, ((PetscObject)snes)->prefix, "-snes_adapt_sequence", &num, NULL));
4633:       if (num) {
4634:         DMAdaptor adaptor;

4636:         incall = PETSC_TRUE;
4637:         PetscCall(DMAdaptorCreate(PetscObjectComm((PetscObject)snes), &adaptor));
4638:         PetscCall(DMAdaptorSetSolver(adaptor, snes));
4639:         PetscCall(DMAdaptorSetSequenceLength(adaptor, num));
4640:         PetscCall(DMAdaptorSetFromOptions(adaptor));
4641:         PetscCall(DMAdaptorSetUp(adaptor));
4642:         PetscCall(DMAdaptorAdapt(adaptor, x, DM_ADAPTATION_SEQUENTIAL, &dm, &x));
4643:         PetscCall(DMAdaptorDestroy(&adaptor));
4644:         incall = PETSC_FALSE;
4645:       }
4646:     }
4647:   }
4648:   if (!x) x = snes->vec_sol;
4649:   if (!x) {
4650:     PetscCall(SNESGetDM(snes, &dm));
4651:     PetscCall(DMCreateGlobalVector(dm, &xcreated));
4652:     x = xcreated;
4653:   }
4654:   PetscCall(SNESViewFromOptions(snes, NULL, "-snes_view_pre"));

4656:   for (grid = 0; grid < snes->gridsequence; grid++) PetscCall(PetscViewerASCIIPushTab(PETSC_VIEWER_STDOUT_(PetscObjectComm((PetscObject)snes))));
4657:   for (grid = 0; grid < snes->gridsequence + 1; grid++) {
4658:     /* set solution vector */
4659:     if (!grid) PetscCall(PetscObjectReference((PetscObject)x));
4660:     PetscCall(VecDestroy(&snes->vec_sol));
4661:     snes->vec_sol = x;
4662:     PetscCall(SNESGetDM(snes, &dm));

4664:     /* set affine vector if provided */
4665:     if (b) PetscCall(PetscObjectReference((PetscObject)b));
4666:     PetscCall(VecDestroy(&snes->vec_rhs));
4667:     snes->vec_rhs = b;

4669:     if (snes->vec_rhs) PetscCheck(snes->vec_func != snes->vec_rhs, PETSC_COMM_SELF, PETSC_ERR_ARG_IDN, "Right hand side vector cannot be function vector");
4670:     PetscCheck(snes->vec_func != snes->vec_sol, PETSC_COMM_SELF, PETSC_ERR_ARG_IDN, "Solution vector cannot be function vector");
4671:     PetscCheck(snes->vec_rhs != snes->vec_sol, PETSC_COMM_SELF, PETSC_ERR_ARG_IDN, "Solution vector cannot be right hand side vector");
4672:     if (!snes->vec_sol_update /* && snes->vec_sol */) PetscCall(VecDuplicate(snes->vec_sol, &snes->vec_sol_update));
4673:     PetscCall(DMShellSetGlobalVector(dm, snes->vec_sol));
4674:     PetscCall(SNESSetUp(snes));

4676:     if (!grid) {
4677:       if (snes->ops->computeinitialguess) PetscCallBack("SNES callback initial guess", (*snes->ops->computeinitialguess)(snes, snes->vec_sol, snes->initialguessP));
4678:     }

4680:     if (snes->conv_hist_reset) snes->conv_hist_len = 0;
4681:     if (snes->counters_reset) {
4682:       snes->nfuncs      = 0;
4683:       snes->linear_its  = 0;
4684:       snes->numFailures = 0;
4685:     }

4687:     PetscCall(PetscLogEventBegin(SNES_Solve, snes, 0, 0, 0));
4688:     PetscUseTypeMethod(snes, solve);
4689:     PetscCall(PetscLogEventEnd(SNES_Solve, snes, 0, 0, 0));
4690:     PetscCheck(snes->reason, PETSC_COMM_SELF, PETSC_ERR_PLIB, "Internal error, solver returned without setting converged reason");
4691:     snes->domainerror = PETSC_FALSE; /* clear the flag if it has been set */

4693:     if (snes->lagjac_persist) snes->jac_iter += snes->iter;
4694:     if (snes->lagpre_persist) snes->pre_iter += snes->iter;

4696:     PetscCall(PetscOptionsGetViewer(PetscObjectComm((PetscObject)snes), ((PetscObject)snes)->options, ((PetscObject)snes)->prefix, "-snes_test_local_min", NULL, NULL, &flg));
4697:     if (flg && !PetscPreLoadingOn) PetscCall(SNESTestLocalMin(snes));
4698:     /* Call converged reason views. This may involve user-provided viewers as well */
4699:     PetscCall(SNESConvergedReasonViewFromOptions(snes));

4701:     if (snes->errorifnotconverged) PetscCheck(snes->reason >= 0, PetscObjectComm((PetscObject)snes), PETSC_ERR_NOT_CONVERGED, "SNESSolve has not converged");
4702:     if (snes->reason < 0) break;
4703:     if (grid < snes->gridsequence) {
4704:       DM  fine;
4705:       Vec xnew;
4706:       Mat interp;

4708:       PetscCall(DMRefine(snes->dm, PetscObjectComm((PetscObject)snes), &fine));
4709:       PetscCheck(fine, PetscObjectComm((PetscObject)snes), PETSC_ERR_ARG_INCOMP, "DMRefine() did not perform any refinement, cannot continue grid sequencing");
4710:       PetscCall(DMCreateInterpolation(snes->dm, fine, &interp, NULL));
4711:       PetscCall(DMCreateGlobalVector(fine, &xnew));
4712:       PetscCall(MatInterpolate(interp, x, xnew));
4713:       PetscCall(DMInterpolate(snes->dm, interp, fine));
4714:       PetscCall(MatDestroy(&interp));
4715:       x = xnew;

4717:       PetscCall(SNESReset(snes));
4718:       PetscCall(SNESSetDM(snes, fine));
4719:       PetscCall(SNESResetFromOptions(snes));
4720:       PetscCall(DMDestroy(&fine));
4721:       PetscCall(PetscViewerASCIIPopTab(PETSC_VIEWER_STDOUT_(PetscObjectComm((PetscObject)snes))));
4722:     }
4723:   }
4724:   PetscCall(SNESViewFromOptions(snes, NULL, "-snes_view"));
4725:   PetscCall(VecViewFromOptions(snes->vec_sol, (PetscObject)snes, "-snes_view_solution"));
4726:   PetscCall(DMMonitor(snes->dm));
4727:   PetscCall(SNESMonitorPauseFinal_Internal(snes));

4729:   PetscCall(VecDestroy(&xcreated));
4730:   PetscCall(PetscObjectSAWsBlock((PetscObject)snes));
4731:   PetscFunctionReturn(PETSC_SUCCESS);
4732: }

4734: /* --------- Internal routines for SNES Package --------- */

4736: /*@C
4737:    SNESSetType - Sets the method for the nonlinear solver.

4739:    Collective

4741:    Input Parameters:
4742: +  snes - the `SNES` context
4743: -  type - a known method

4745:    Options Database Key:
4746: .  -snes_type <type> - Sets the method; use -help for a list
4747:    of available methods (for instance, newtonls or newtontr)

4749:   Level: intermediate

4751:    Notes:
4752:    See "petsc/include/petscsnes.h" for available methods (for instance)
4753: +    `SNESNEWTONLS` - Newton's method with line search
4754:      (systems of nonlinear equations)
4755: -    `SNESNEWTONTRDC` - Newton's method with trust region
4756:      (systems of nonlinear equations)

4758:   Normally, it is best to use the `SNESSetFromOptions()` command and then
4759:   set the `SNES` solver type from the options database rather than by using
4760:   this routine.  Using the options database provides the user with
4761:   maximum flexibility in evaluating the many nonlinear solvers.
4762:   The `SNESSetType()` routine is provided for those situations where it
4763:   is necessary to set the nonlinear solver independently of the command
4764:   line or options database.  This might be the case, for example, when
4765:   the choice of solver changes during the execution of the program,
4766:   and the user's application is taking responsibility for choosing the
4767:   appropriate method.

4769:     Developer Note:
4770:     `SNESRegister()` adds a constructor for a new `SNESType` to `SNESList`, `SNESSetType()` locates
4771:     the constructor in that list and calls it to create the specific object.

4773: .seealso: [](chapter_snes), `SNES`, `SNESSolve()`, `SNESType`, `SNESCreate()`, `SNESDestroy()`, `SNESGetType()`, `SNESSetFromOptions()`
4774: @*/
4775: PetscErrorCode SNESSetType(SNES snes, SNESType type)
4776: {
4777:   PetscBool match;
4778:   PetscErrorCode (*r)(SNES);

4780:   PetscFunctionBegin;

4784:   PetscCall(PetscObjectTypeCompare((PetscObject)snes, type, &match));
4785:   if (match) PetscFunctionReturn(PETSC_SUCCESS);

4787:   PetscCall(PetscFunctionListFind(SNESList, type, &r));
4788:   PetscCheck(r, PETSC_COMM_SELF, PETSC_ERR_ARG_UNKNOWN_TYPE, "Unable to find requested SNES type %s", type);
4789:   /* Destroy the previous private SNES context */
4790:   PetscTryTypeMethod(snes, destroy);
4791:   /* Reinitialize function pointers in SNESOps structure */
4792:   snes->ops->setup          = NULL;
4793:   snes->ops->solve          = NULL;
4794:   snes->ops->view           = NULL;
4795:   snes->ops->setfromoptions = NULL;
4796:   snes->ops->destroy        = NULL;

4798:   /* It may happen the user has customized the line search before calling SNESSetType */
4799:   if (((PetscObject)snes)->type_name) PetscCall(SNESLineSearchDestroy(&snes->linesearch));

4801:   /* Call the SNESCreate_XXX routine for this particular Nonlinear solver */
4802:   snes->setupcalled = PETSC_FALSE;

4804:   PetscCall(PetscObjectChangeTypeName((PetscObject)snes, type));
4805:   PetscCall((*r)(snes));
4806:   PetscFunctionReturn(PETSC_SUCCESS);
4807: }

4809: /*@C
4810:    SNESGetType - Gets the `SNES` method type and name (as a string).

4812:    Not Collective

4814:    Input Parameter:
4815: .  snes - nonlinear solver context

4817:    Output Parameter:
4818: .  type - `SNES` method (a character string)

4820:    Level: intermediate

4822: .seealso: [](chapter_snes), `SNESSetType()`, `SNESType`, `SNESSetFromOptions()`, `SNES`
4823: @*/
4824: PetscErrorCode SNESGetType(SNES snes, SNESType *type)
4825: {
4826:   PetscFunctionBegin;
4829:   *type = ((PetscObject)snes)->type_name;
4830:   PetscFunctionReturn(PETSC_SUCCESS);
4831: }

4833: /*@
4834:   SNESSetSolution - Sets the solution vector for use by the `SNES` routines.

4836:   Logically Collective

4838:   Input Parameters:
4839: + snes - the `SNES` context obtained from `SNESCreate()`
4840: - u    - the solution vector

4842:   Level: beginner

4844: .seealso: [](chapter_snes), `SNES`, `SNESSolve()`, `SNESGetSolution()`, `Vec`
4845: @*/
4846: PetscErrorCode SNESSetSolution(SNES snes, Vec u)
4847: {
4848:   DM dm;

4850:   PetscFunctionBegin;
4853:   PetscCall(PetscObjectReference((PetscObject)u));
4854:   PetscCall(VecDestroy(&snes->vec_sol));

4856:   snes->vec_sol = u;

4858:   PetscCall(SNESGetDM(snes, &dm));
4859:   PetscCall(DMShellSetGlobalVector(dm, u));
4860:   PetscFunctionReturn(PETSC_SUCCESS);
4861: }

4863: /*@
4864:    SNESGetSolution - Returns the vector where the approximate solution is
4865:    stored. This is the fine grid solution when using `SNESSetGridSequence()`.

4867:    Not Collective, but x is parallel if snes is parallel

4869:    Input Parameter:
4870: .  snes - the `SNES` context

4872:    Output Parameter:
4873: .  x - the solution

4875:    Level: intermediate

4877: .seealso: [](chapter_snes), `SNESSetSolution()`, `SNESSolve()`, `SNES`, `SNESGetSolutionUpdate()`, `SNESGetFunction()`
4878: @*/
4879: PetscErrorCode SNESGetSolution(SNES snes, Vec *x)
4880: {
4881:   PetscFunctionBegin;
4884:   *x = snes->vec_sol;
4885:   PetscFunctionReturn(PETSC_SUCCESS);
4886: }

4888: /*@
4889:    SNESGetSolutionUpdate - Returns the vector where the solution update is
4890:    stored.

4892:    Not Collective, but x is parallel if snes is parallel

4894:    Input Parameter:
4895: .  snes - the `SNES` context

4897:    Output Parameter:
4898: .  x - the solution update

4900:    Level: advanced

4902: .seealso: [](chapter_snes), `SNES`, `SNESGetSolution()`, `SNESGetFunction()`
4903: @*/
4904: PetscErrorCode SNESGetSolutionUpdate(SNES snes, Vec *x)
4905: {
4906:   PetscFunctionBegin;
4909:   *x = snes->vec_sol_update;
4910:   PetscFunctionReturn(PETSC_SUCCESS);
4911: }

4913: /*@C
4914:    SNESGetFunction - Returns the function that defines the nonlinear system set with `SNESSetFunction()`

4916:    Not Collective, but r is parallel if snes is parallel. Collective if r is requested, but has not been created yet.

4918:    Input Parameter:
4919: .  snes - the `SNES` context

4921:    Output Parameters:
4922: +  r - the vector that is used to store residuals (or `NULL` if you don't want it)
4923: .  f - the function (or `NULL` if you don't want it); see `SNESFunction` for calling sequence details
4924: -  ctx - the function context (or `NULL` if you don't want it)

4926:    Level: advanced

4928:     Note:
4929:    The vector `r` DOES NOT, in general, contain the current value of the `SNES` nonlinear function

4931: .seealso: [](chapter_snes), `SNES, `SNESSolve()`, `SNESSetFunction()`, `SNESGetSolution()`, `SNESFunction`
4932: @*/
4933: PetscErrorCode SNESGetFunction(SNES snes, Vec *r, PetscErrorCode (**f)(SNES, Vec, Vec, void *), void **ctx)
4934: {
4935:   DM dm;

4937:   PetscFunctionBegin;
4939:   if (r) {
4940:     if (!snes->vec_func) {
4941:       if (snes->vec_rhs) {
4942:         PetscCall(VecDuplicate(snes->vec_rhs, &snes->vec_func));
4943:       } else if (snes->vec_sol) {
4944:         PetscCall(VecDuplicate(snes->vec_sol, &snes->vec_func));
4945:       } else if (snes->dm) {
4946:         PetscCall(DMCreateGlobalVector(snes->dm, &snes->vec_func));
4947:       }
4948:     }
4949:     *r = snes->vec_func;
4950:   }
4951:   PetscCall(SNESGetDM(snes, &dm));
4952:   PetscCall(DMSNESGetFunction(dm, f, ctx));
4953:   PetscFunctionReturn(PETSC_SUCCESS);
4954: }

4956: /*@C
4957:    SNESGetNGS - Returns the `SNESNGS` function and context set with `SNESSetNGS()`

4959:    Input Parameter:
4960: .  snes - the `SNES` context

4962:    Output Parameters:
4963: +  f - the function (or `NULL`) see `SNESNGSFunction` for details
4964: -  ctx    - the function context (or `NULL`)

4966:    Level: advanced

4968: .seealso: [](chapter_snes), `SNESSetNGS()`, `SNESGetFunction()`
4969: @*/

4971: PetscErrorCode SNESGetNGS(SNES snes, PetscErrorCode (**f)(SNES, Vec, Vec, void *), void **ctx)
4972: {
4973:   DM dm;

4975:   PetscFunctionBegin;
4977:   PetscCall(SNESGetDM(snes, &dm));
4978:   PetscCall(DMSNESGetNGS(dm, f, ctx));
4979:   PetscFunctionReturn(PETSC_SUCCESS);
4980: }

4982: /*@C
4983:    SNESSetOptionsPrefix - Sets the prefix used for searching for all
4984:    `SNES` options in the database.

4986:    Logically Collective

4988:    Input Parameters:
4989: +  snes - the `SNES` context
4990: -  prefix - the prefix to prepend to all option names

4992:    Level: advanced

4994:    Note:
4995:    A hyphen (-) must NOT be given at the beginning of the prefix name.
4996:    The first character of all runtime options is AUTOMATICALLY the hyphen.

4998: .seealso: [](chapter_snes), `SNES`, `SNESSetFromOptions()`, `SNESAppendOptionsPrefix()`
4999: @*/
5000: PetscErrorCode SNESSetOptionsPrefix(SNES snes, const char prefix[])
5001: {
5002:   PetscFunctionBegin;
5004:   PetscCall(PetscObjectSetOptionsPrefix((PetscObject)snes, prefix));
5005:   if (!snes->ksp) PetscCall(SNESGetKSP(snes, &snes->ksp));
5006:   if (snes->linesearch) {
5007:     PetscCall(SNESGetLineSearch(snes, &snes->linesearch));
5008:     PetscCall(PetscObjectSetOptionsPrefix((PetscObject)snes->linesearch, prefix));
5009:   }
5010:   PetscCall(KSPSetOptionsPrefix(snes->ksp, prefix));
5011:   PetscFunctionReturn(PETSC_SUCCESS);
5012: }

5014: /*@C
5015:    SNESAppendOptionsPrefix - Appends to the prefix used for searching for all
5016:    `SNES` options in the database.

5018:    Logically Collective

5020:    Input Parameters:
5021: +  snes - the `SNES` context
5022: -  prefix - the prefix to prepend to all option names

5024:    Level: advanced

5026:    Note:
5027:    A hyphen (-) must NOT be given at the beginning of the prefix name.
5028:    The first character of all runtime options is AUTOMATICALLY the hyphen.

5030: .seealso: [](chapter_snes), `SNESGetOptionsPrefix()`, `SNESSetOptionsPrefix()`
5031: @*/
5032: PetscErrorCode SNESAppendOptionsPrefix(SNES snes, const char prefix[])
5033: {
5034:   PetscFunctionBegin;
5036:   PetscCall(PetscObjectAppendOptionsPrefix((PetscObject)snes, prefix));
5037:   if (!snes->ksp) PetscCall(SNESGetKSP(snes, &snes->ksp));
5038:   if (snes->linesearch) {
5039:     PetscCall(SNESGetLineSearch(snes, &snes->linesearch));
5040:     PetscCall(PetscObjectAppendOptionsPrefix((PetscObject)snes->linesearch, prefix));
5041:   }
5042:   PetscCall(KSPAppendOptionsPrefix(snes->ksp, prefix));
5043:   PetscFunctionReturn(PETSC_SUCCESS);
5044: }

5046: /*@C
5047:    SNESGetOptionsPrefix - Gets the prefix used for searching for all
5048:    `SNES` options in the database.

5050:    Not Collective

5052:    Input Parameter:
5053: .  snes - the `SNES` context

5055:    Output Parameter:
5056: .  prefix - pointer to the prefix string used

5058:    Level: advanced

5060:    Fortran Note:
5061:     The user should pass in a string 'prefix' of
5062:    sufficient length to hold the prefix.

5064: .seealso: [](chapter_snes), `SNES`, `SNESSetOptionsPrefix()`, `SNESAppendOptionsPrefix()`
5065: @*/
5066: PetscErrorCode SNESGetOptionsPrefix(SNES snes, const char *prefix[])
5067: {
5068:   PetscFunctionBegin;
5070:   PetscCall(PetscObjectGetOptionsPrefix((PetscObject)snes, prefix));
5071:   PetscFunctionReturn(PETSC_SUCCESS);
5072: }

5074: /*@C
5075:   SNESRegister - Adds a method to the nonlinear solver package.

5077:    Not collective

5079:    Input Parameters:
5080: +  name_solver - name of a new user-defined solver
5081: -  routine_create - routine to create method context

5083:    Level: advanced

5085:    Note:
5086:    `SNESRegister()` may be called multiple times to add several user-defined solvers.

5088:    Sample usage:
5089: .vb
5090:    SNESRegister("my_solver",MySolverCreate);
5091: .ve

5093:    Then, your solver can be chosen with the procedural interface via
5094: $     SNESSetType(snes,"my_solver")
5095:    or at runtime via the option
5096: $     -snes_type my_solver

5098: .seealso: [](chapter_snes), `SNESRegisterAll()`, `SNESRegisterDestroy()`
5099: @*/
5100: PetscErrorCode SNESRegister(const char sname[], PetscErrorCode (*function)(SNES))
5101: {
5102:   PetscFunctionBegin;
5103:   PetscCall(SNESInitializePackage());
5104:   PetscCall(PetscFunctionListAdd(&SNESList, sname, function));
5105:   PetscFunctionReturn(PETSC_SUCCESS);
5106: }

5108: PetscErrorCode SNESTestLocalMin(SNES snes)
5109: {
5110:   PetscInt    N, i, j;
5111:   Vec         u, uh, fh;
5112:   PetscScalar value;
5113:   PetscReal   norm;

5115:   PetscFunctionBegin;
5116:   PetscCall(SNESGetSolution(snes, &u));
5117:   PetscCall(VecDuplicate(u, &uh));
5118:   PetscCall(VecDuplicate(u, &fh));

5120:   /* currently only works for sequential */
5121:   PetscCall(PetscPrintf(PetscObjectComm((PetscObject)snes), "Testing FormFunction() for local min\n"));
5122:   PetscCall(VecGetSize(u, &N));
5123:   for (i = 0; i < N; i++) {
5124:     PetscCall(VecCopy(u, uh));
5125:     PetscCall(PetscPrintf(PetscObjectComm((PetscObject)snes), "i = %" PetscInt_FMT "\n", i));
5126:     for (j = -10; j < 11; j++) {
5127:       value = PetscSign(j) * PetscExpReal(PetscAbs(j) - 10.0);
5128:       PetscCall(VecSetValue(uh, i, value, ADD_VALUES));
5129:       PetscCall(SNESComputeFunction(snes, uh, fh));
5130:       PetscCall(VecNorm(fh, NORM_2, &norm));
5131:       PetscCall(PetscPrintf(PetscObjectComm((PetscObject)snes), "       j norm %" PetscInt_FMT " %18.16e\n", j, (double)norm));
5132:       value = -value;
5133:       PetscCall(VecSetValue(uh, i, value, ADD_VALUES));
5134:     }
5135:   }
5136:   PetscCall(VecDestroy(&uh));
5137:   PetscCall(VecDestroy(&fh));
5138:   PetscFunctionReturn(PETSC_SUCCESS);
5139: }

5141: /*@
5142:    SNESKSPSetUseEW - Sets `SNES` to the use Eisenstat-Walker method for
5143:    computing relative tolerance for linear solvers within an inexact
5144:    Newton method.

5146:    Logically Collective

5148:    Input Parameters:
5149: +  snes - `SNES` context
5150: -  flag - `PETSC_TRUE` or `PETSC_FALSE`

5152:     Options Database Keys:
5153: +  -snes_ksp_ew - use Eisenstat-Walker method for determining linear system convergence
5154: .  -snes_ksp_ew_version ver - version of  Eisenstat-Walker method
5155: .  -snes_ksp_ew_rtol0 <rtol0> - Sets rtol0
5156: .  -snes_ksp_ew_rtolmax <rtolmax> - Sets rtolmax
5157: .  -snes_ksp_ew_gamma <gamma> - Sets gamma
5158: .  -snes_ksp_ew_alpha <alpha> - Sets alpha
5159: .  -snes_ksp_ew_alpha2 <alpha2> - Sets alpha2
5160: -  -snes_ksp_ew_threshold <threshold> - Sets threshold

5162:    Level: advanced

5164:    Note:
5165:    The default is to use a constant relative tolerance for
5166:    the inner linear solvers.  Alternatively, one can use the
5167:    Eisenstat-Walker method, where the relative convergence tolerance
5168:    is reset at each Newton iteration according progress of the nonlinear
5169:    solver.

5171:    Reference:
5172: .  - * S. C. Eisenstat and H. F. Walker, "Choosing the forcing terms in an inexact Newton method", SISC 17 (1), pp.16-32, 1996.

5174: .seealso: [](chapter_snes), `KSP`, `SNES`, `SNESKSPGetUseEW()`, `SNESKSPGetParametersEW()`, `SNESKSPSetParametersEW()`
5175: @*/
5176: PetscErrorCode SNESKSPSetUseEW(SNES snes, PetscBool flag)
5177: {
5178:   PetscFunctionBegin;
5181:   snes->ksp_ewconv = flag;
5182:   PetscFunctionReturn(PETSC_SUCCESS);
5183: }

5185: /*@
5186:    SNESKSPGetUseEW - Gets if `SNES` is using Eisenstat-Walker method
5187:    for computing relative tolerance for linear solvers within an
5188:    inexact Newton method.

5190:    Not Collective

5192:    Input Parameter:
5193: .  snes - `SNES` context

5195:    Output Parameter:
5196: .  flag - `PETSC_TRUE` or `PETSC_FALSE`

5198:    Level: advanced

5200: .seealso: [](chapter_snes), `SNESKSPSetUseEW()`, `SNESKSPGetParametersEW()`, `SNESKSPSetParametersEW()`
5201: @*/
5202: PetscErrorCode SNESKSPGetUseEW(SNES snes, PetscBool *flag)
5203: {
5204:   PetscFunctionBegin;
5207:   *flag = snes->ksp_ewconv;
5208:   PetscFunctionReturn(PETSC_SUCCESS);
5209: }

5211: /*@
5212:    SNESKSPSetParametersEW - Sets parameters for Eisenstat-Walker
5213:    convergence criteria for the linear solvers within an inexact
5214:    Newton method.

5216:    Logically Collective

5218:    Input Parameters:
5219: +    snes - `SNES` context
5220: .    version - version 1, 2 (default is 2), 3 or 4
5221: .    rtol_0 - initial relative tolerance (0 <= rtol_0 < 1)
5222: .    rtol_max - maximum relative tolerance (0 <= rtol_max < 1)
5223: .    gamma - multiplicative factor for version 2 rtol computation
5224:              (0 <= gamma2 <= 1)
5225: .    alpha - power for version 2 rtol computation (1 < alpha <= 2)
5226: .    alpha2 - power for safeguard
5227: -    threshold - threshold for imposing safeguard (0 < threshold < 1)

5229:    Level: advanced

5231:    Notes:
5232:    Version 3 was contributed by Luis Chacon, June 2006.

5234:    Use `PETSC_DEFAULT` to retain the default for any of the parameters.

5236: .seealso: [](chapter_snes), `SNES`, `SNESKSPSetUseEW()`, `SNESKSPGetUseEW()`, `SNESKSPGetParametersEW()`
5237: @*/
5238: PetscErrorCode SNESKSPSetParametersEW(SNES snes, PetscInt version, PetscReal rtol_0, PetscReal rtol_max, PetscReal gamma, PetscReal alpha, PetscReal alpha2, PetscReal threshold)
5239: {
5240:   SNESKSPEW *kctx;

5242:   PetscFunctionBegin;
5244:   kctx = (SNESKSPEW *)snes->kspconvctx;
5245:   PetscCheck(kctx, PETSC_COMM_SELF, PETSC_ERR_ARG_WRONGSTATE, "No Eisenstat-Walker context existing");

5254:   if (version != PETSC_DEFAULT) kctx->version = version;
5255:   if (rtol_0 != PETSC_DEFAULT) kctx->rtol_0 = rtol_0;
5256:   if (rtol_max != PETSC_DEFAULT) kctx->rtol_max = rtol_max;
5257:   if (gamma != PETSC_DEFAULT) kctx->gamma = gamma;
5258:   if (alpha != PETSC_DEFAULT) kctx->alpha = alpha;
5259:   if (alpha2 != PETSC_DEFAULT) kctx->alpha2 = alpha2;
5260:   if (threshold != PETSC_DEFAULT) kctx->threshold = threshold;

5262:   PetscCheck(kctx->version >= 1 && kctx->version <= 4, PETSC_COMM_SELF, PETSC_ERR_ARG_OUTOFRANGE, "Only versions 1 to 4 are supported: %" PetscInt_FMT, kctx->version);
5263:   PetscCheck(kctx->rtol_0 >= 0.0 && kctx->rtol_0 < 1.0, PETSC_COMM_SELF, PETSC_ERR_ARG_OUTOFRANGE, "0.0 <= rtol_0 < 1.0: %g", (double)kctx->rtol_0);
5264:   PetscCheck(kctx->rtol_max >= 0.0 && kctx->rtol_max < 1.0, PETSC_COMM_SELF, PETSC_ERR_ARG_OUTOFRANGE, "0.0 <= rtol_max (%g) < 1.0", (double)kctx->rtol_max);
5265:   PetscCheck(kctx->gamma >= 0.0 && kctx->gamma <= 1.0, PETSC_COMM_SELF, PETSC_ERR_ARG_OUTOFRANGE, "0.0 <= gamma (%g) <= 1.0", (double)kctx->gamma);
5266:   PetscCheck(kctx->alpha > 1.0 && kctx->alpha <= 2.0, PETSC_COMM_SELF, PETSC_ERR_ARG_OUTOFRANGE, "1.0 < alpha (%g) <= 2.0", (double)kctx->alpha);
5267:   PetscCheck(kctx->threshold > 0.0 && kctx->threshold < 1.0, PETSC_COMM_SELF, PETSC_ERR_ARG_OUTOFRANGE, "0.0 < threshold (%g) < 1.0", (double)kctx->threshold);
5268:   PetscFunctionReturn(PETSC_SUCCESS);
5269: }

5271: /*@
5272:    SNESKSPGetParametersEW - Gets parameters for Eisenstat-Walker
5273:    convergence criteria for the linear solvers within an inexact
5274:    Newton method.

5276:    Not Collective

5278:    Input Parameter:
5279: .    snes - `SNES` context

5281:    Output Parameters:
5282: +    version - version 1, 2 (default is 2), 3 or 4
5283: .    rtol_0 - initial relative tolerance (0 <= rtol_0 < 1)
5284: .    rtol_max - maximum relative tolerance (0 <= rtol_max < 1)
5285: .    gamma - multiplicative factor for version 2 rtol computation (0 <= gamma2 <= 1)
5286: .    alpha - power for version 2 rtol computation (1 < alpha <= 2)
5287: .    alpha2 - power for safeguard
5288: -    threshold - threshold for imposing safeguard (0 < threshold < 1)

5290:    Level: advanced

5292: .seealso: [](chapter_snes), `SNES`, `SNESKSPSetUseEW()`, `SNESKSPGetUseEW()`, `SNESKSPSetParametersEW()`
5293: @*/
5294: PetscErrorCode SNESKSPGetParametersEW(SNES snes, PetscInt *version, PetscReal *rtol_0, PetscReal *rtol_max, PetscReal *gamma, PetscReal *alpha, PetscReal *alpha2, PetscReal *threshold)
5295: {
5296:   SNESKSPEW *kctx;

5298:   PetscFunctionBegin;
5300:   kctx = (SNESKSPEW *)snes->kspconvctx;
5301:   PetscCheck(kctx, PETSC_COMM_SELF, PETSC_ERR_ARG_WRONGSTATE, "No Eisenstat-Walker context existing");
5302:   if (version) *version = kctx->version;
5303:   if (rtol_0) *rtol_0 = kctx->rtol_0;
5304:   if (rtol_max) *rtol_max = kctx->rtol_max;
5305:   if (gamma) *gamma = kctx->gamma;
5306:   if (alpha) *alpha = kctx->alpha;
5307:   if (alpha2) *alpha2 = kctx->alpha2;
5308:   if (threshold) *threshold = kctx->threshold;
5309:   PetscFunctionReturn(PETSC_SUCCESS);
5310: }

5312: PetscErrorCode KSPPreSolve_SNESEW(KSP ksp, Vec b, Vec x, SNES snes)
5313: {
5314:   SNESKSPEW *kctx = (SNESKSPEW *)snes->kspconvctx;
5315:   PetscReal  rtol = PETSC_DEFAULT, stol;

5317:   PetscFunctionBegin;
5318:   if (!snes->ksp_ewconv) PetscFunctionReturn(PETSC_SUCCESS);
5319:   if (!snes->iter) {
5320:     rtol = kctx->rtol_0; /* first time in, so use the original user rtol */
5321:     PetscCall(VecNorm(snes->vec_func, NORM_2, &kctx->norm_first));
5322:   } else {
5323:     PetscCheck(kctx->version >= 1 && kctx->version <= 4, PETSC_COMM_SELF, PETSC_ERR_ARG_OUTOFRANGE, "Only versions 1-4 are supported: %" PetscInt_FMT, kctx->version);
5324:     if (kctx->version == 1) {
5325:       rtol = PetscAbsReal(snes->norm - kctx->lresid_last) / kctx->norm_last;
5326:       stol = PetscPowReal(kctx->rtol_last, kctx->alpha2);
5327:       if (stol > kctx->threshold) rtol = PetscMax(rtol, stol);
5328:     } else if (kctx->version == 2) {
5329:       rtol = kctx->gamma * PetscPowReal(snes->norm / kctx->norm_last, kctx->alpha);
5330:       stol = kctx->gamma * PetscPowReal(kctx->rtol_last, kctx->alpha);
5331:       if (stol > kctx->threshold) rtol = PetscMax(rtol, stol);
5332:     } else if (kctx->version == 3) { /* contributed by Luis Chacon, June 2006. */
5333:       rtol = kctx->gamma * PetscPowReal(snes->norm / kctx->norm_last, kctx->alpha);
5334:       /* safeguard: avoid sharp decrease of rtol */
5335:       stol = kctx->gamma * PetscPowReal(kctx->rtol_last, kctx->alpha);
5336:       stol = PetscMax(rtol, stol);
5337:       rtol = PetscMin(kctx->rtol_0, stol);
5338:       /* safeguard: avoid oversolving */
5339:       stol = kctx->gamma * (kctx->norm_first * snes->rtol) / snes->norm;
5340:       stol = PetscMax(rtol, stol);
5341:       rtol = PetscMin(kctx->rtol_0, stol);
5342:     } else /* if (kctx->version == 4) */ {
5343:       /* H.-B. An et al. Journal of Computational and Applied Mathematics 200 (2007) 47-60 */
5344:       PetscReal ared = PetscAbsReal(kctx->norm_last - snes->norm);
5345:       PetscReal pred = PetscAbsReal(kctx->norm_last - kctx->lresid_last);
5346:       PetscReal rk   = ared / pred;
5347:       if (rk < kctx->v4_p1) rtol = 1. - 2. * kctx->v4_p1;
5348:       else if (rk < kctx->v4_p2) rtol = kctx->rtol_last;
5349:       else if (rk < kctx->v4_p3) rtol = kctx->v4_m1 * kctx->rtol_last;
5350:       else rtol = kctx->v4_m2 * kctx->rtol_last;

5352:       if (kctx->rtol_last_2 > kctx->v4_m3 && kctx->rtol_last > kctx->v4_m3 && kctx->rk_last_2 < kctx->v4_p1 && kctx->rk_last < kctx->v4_p1) {
5353:         rtol = kctx->v4_m4 * kctx->rtol_last;
5354:         //printf("iter %" PetscInt_FMT ", Eisenstat-Walker (version %" PetscInt_FMT ") KSP rtol=%g (rk %g ps %g %g %g) (AD)\n",snes->iter,kctx->version,(double)rtol,rk,kctx->v4_p1,kctx->v4_p2,kctx->v4_p3);
5355:       } else {
5356:         //printf("iter %" PetscInt_FMT ", Eisenstat-Walker (version %" PetscInt_FMT ") KSP rtol=%g (rk %g ps %g %g %g)\n",snes->iter,kctx->version,(double)rtol,rk,kctx->v4_p1,kctx->v4_p2,kctx->v4_p3);
5357:       }
5358:       kctx->rtol_last_2 = kctx->rtol_last;
5359:       kctx->rk_last_2   = kctx->rk_last;
5360:       kctx->rk_last     = rk;
5361:     }
5362:   }
5363:   /* safeguard: avoid rtol greater than rtol_max */
5364:   rtol = PetscMin(rtol, kctx->rtol_max);
5365:   PetscCall(KSPSetTolerances(ksp, rtol, PETSC_DEFAULT, PETSC_DEFAULT, PETSC_DEFAULT));
5366:   PetscCall(PetscInfo(snes, "iter %" PetscInt_FMT ", Eisenstat-Walker (version %" PetscInt_FMT ") KSP rtol=%g\n", snes->iter, kctx->version, (double)rtol));
5367:   PetscFunctionReturn(PETSC_SUCCESS);
5368: }

5370: PetscErrorCode KSPPostSolve_SNESEW(KSP ksp, Vec b, Vec x, SNES snes)
5371: {
5372:   SNESKSPEW *kctx = (SNESKSPEW *)snes->kspconvctx;
5373:   PCSide     pcside;
5374:   Vec        lres;

5376:   PetscFunctionBegin;
5377:   if (!snes->ksp_ewconv) PetscFunctionReturn(PETSC_SUCCESS);
5378:   PetscCall(KSPGetTolerances(ksp, &kctx->rtol_last, NULL, NULL, NULL));
5379:   kctx->norm_last = snes->norm;
5380:   if (kctx->version == 1 || kctx->version == 4) {
5381:     PC        pc;
5382:     PetscBool getRes;

5384:     PetscCall(KSPGetPC(ksp, &pc));
5385:     PetscCall(PetscObjectTypeCompare((PetscObject)pc, PCNONE, &getRes));
5386:     if (!getRes) {
5387:       KSPNormType normtype;

5389:       PetscCall(KSPGetNormType(ksp, &normtype));
5390:       getRes = (PetscBool)(normtype == KSP_NORM_UNPRECONDITIONED);
5391:     }
5392:     PetscCall(KSPGetPCSide(ksp, &pcside));
5393:     if (pcside == PC_RIGHT || getRes) { /* KSP residual is true linear residual */
5394:       PetscCall(KSPGetResidualNorm(ksp, &kctx->lresid_last));
5395:     } else {
5396:       /* KSP residual is preconditioned residual */
5397:       /* compute true linear residual norm */
5398:       Mat J;
5399:       PetscCall(KSPGetOperators(ksp, &J, NULL));
5400:       PetscCall(VecDuplicate(b, &lres));
5401:       PetscCall(MatMult(J, x, lres));
5402:       PetscCall(VecAYPX(lres, -1.0, b));
5403:       PetscCall(VecNorm(lres, NORM_2, &kctx->lresid_last));
5404:       PetscCall(VecDestroy(&lres));
5405:     }
5406:   }
5407:   PetscFunctionReturn(PETSC_SUCCESS);
5408: }

5410: /*@
5411:    SNESGetKSP - Returns the `KSP` context for a `SNES` solver.

5413:    Not Collective, but if snes is parallel, then ksp is parallel

5415:    Input Parameter:
5416: .  snes - the `SNES` context

5418:    Output Parameter:
5419: .  ksp - the `KSP` context

5421:    Level: beginner

5423:    Notes:
5424:    The user can then directly manipulate the `KSP` context to set various
5425:    options, etc.  Likewise, the user can then extract and manipulate the
5426:    `PC` contexts as well.

5428:    Some `SNESType`s do not use a `KSP` but a `KSP` is still returned by this function

5430: .seealso: [](chapter_snes), `SNES`, `KSP`, `PC`, `KSPGetPC()`, `SNESCreate()`, `KSPCreate()`, `SNESSetKSP()`
5431: @*/
5432: PetscErrorCode SNESGetKSP(SNES snes, KSP *ksp)
5433: {
5434:   PetscFunctionBegin;

5438:   if (!snes->ksp) {
5439:     PetscCall(KSPCreate(PetscObjectComm((PetscObject)snes), &snes->ksp));
5440:     PetscCall(PetscObjectIncrementTabLevel((PetscObject)snes->ksp, (PetscObject)snes, 1));

5442:     PetscCall(KSPSetPreSolve(snes->ksp, (PetscErrorCode(*)(KSP, Vec, Vec, void *))KSPPreSolve_SNESEW, snes));
5443:     PetscCall(KSPSetPostSolve(snes->ksp, (PetscErrorCode(*)(KSP, Vec, Vec, void *))KSPPostSolve_SNESEW, snes));

5445:     PetscCall(KSPMonitorSetFromOptions(snes->ksp, "-snes_monitor_ksp", "snes_preconditioned_residual", snes));
5446:     PetscCall(PetscObjectSetOptions((PetscObject)snes->ksp, ((PetscObject)snes)->options));
5447:   }
5448:   *ksp = snes->ksp;
5449:   PetscFunctionReturn(PETSC_SUCCESS);
5450: }

5452: #include <petsc/private/dmimpl.h>
5453: /*@
5454:    SNESSetDM - Sets the `DM` that may be used by some nonlinear solvers or their underlying preconditioners

5456:    Logically Collective

5458:    Input Parameters:
5459: +  snes - the nonlinear solver context
5460: -  dm - the dm, cannot be `NULL`

5462:    Level: intermediate

5464:    Note:
5465:    A `DM` can only be used for solving one problem at a time because information about the problem is stored on the `DM`,
5466:    even when not using interfaces like `DMSNESSetFunction()`.  Use `DMClone()` to get a distinct `DM` when solving different
5467:    problems using the same function space.

5469: .seealso: [](chapter_snes), `DM`, `SNESGetDM()`, `KSPSetDM()`, `KSPGetDM()`
5470: @*/
5471: PetscErrorCode SNESSetDM(SNES snes, DM dm)
5472: {
5473:   KSP    ksp;
5474:   DMSNES sdm;

5476:   PetscFunctionBegin;
5479:   PetscCall(PetscObjectReference((PetscObject)dm));
5480:   if (snes->dm) { /* Move the DMSNES context over to the new DM unless the new DM already has one */
5481:     if (snes->dm->dmsnes && !dm->dmsnes) {
5482:       PetscCall(DMCopyDMSNES(snes->dm, dm));
5483:       PetscCall(DMGetDMSNES(snes->dm, &sdm));
5484:       if (sdm->originaldm == snes->dm) sdm->originaldm = dm; /* Grant write privileges to the replacement DM */
5485:     }
5486:     PetscCall(DMCoarsenHookRemove(snes->dm, DMCoarsenHook_SNESVecSol, DMRestrictHook_SNESVecSol, snes));
5487:     PetscCall(DMDestroy(&snes->dm));
5488:   }
5489:   snes->dm     = dm;
5490:   snes->dmAuto = PETSC_FALSE;

5492:   PetscCall(SNESGetKSP(snes, &ksp));
5493:   PetscCall(KSPSetDM(ksp, dm));
5494:   PetscCall(KSPSetDMActive(ksp, PETSC_FALSE));
5495:   if (snes->npc) {
5496:     PetscCall(SNESSetDM(snes->npc, snes->dm));
5497:     PetscCall(SNESSetNPCSide(snes, snes->npcside));
5498:   }
5499:   PetscFunctionReturn(PETSC_SUCCESS);
5500: }

5502: /*@
5503:    SNESGetDM - Gets the `DM` that may be used by some preconditioners

5505:    Not Collective but dm obtained is parallel on snes

5507:    Input Parameter:
5508: . snes - the preconditioner context

5510:    Output Parameter:
5511: .  dm - the dm

5513:    Level: intermediate

5515: .seealso: [](chapter_snes), `DM`, `SNESSetDM()`, `KSPSetDM()`, `KSPGetDM()`
5516: @*/
5517: PetscErrorCode SNESGetDM(SNES snes, DM *dm)
5518: {
5519:   PetscFunctionBegin;
5521:   if (!snes->dm) {
5522:     PetscCall(DMShellCreate(PetscObjectComm((PetscObject)snes), &snes->dm));
5523:     snes->dmAuto = PETSC_TRUE;
5524:   }
5525:   *dm = snes->dm;
5526:   PetscFunctionReturn(PETSC_SUCCESS);
5527: }

5529: /*@
5530:   SNESSetNPC - Sets the nonlinear preconditioner to be used.

5532:   Collective

5534:   Input Parameters:
5535: + snes - iterative context obtained from `SNESCreate()`
5536: - npc   - the preconditioner object

5538:   Level: developer

5540:   Notes:
5541:   Use `SNESGetNPC()` to retrieve the preconditioner context (for example,
5542:   to configure it using the API).

5544:   Only some `SNESType` can use a nonlinear preconditioner

5546: .seealso: [](chapter_snes), `SNESNGS`, `SNESFAS`, `SNESGetNPC()`, `SNESHasNPC()`
5547: @*/
5548: PetscErrorCode SNESSetNPC(SNES snes, SNES npc)
5549: {
5550:   PetscFunctionBegin;
5553:   PetscCheckSameComm(snes, 1, npc, 2);
5554:   PetscCall(PetscObjectReference((PetscObject)npc));
5555:   PetscCall(SNESDestroy(&snes->npc));
5556:   snes->npc = npc;
5557:   PetscFunctionReturn(PETSC_SUCCESS);
5558: }

5560: /*@
5561:   SNESGetNPC - Gets a nonlinear preconditioning solver SNES` to be used to precondition the original nonlinear solver.

5563:   Not Collective; but any changes to the obtained the npc object must be applied collectively

5565:   Input Parameter:
5566: . snes - iterative context obtained from `SNESCreate()`

5568:   Output Parameter:
5569: . npc - preconditioner context

5571:   Options Database Key:
5572: . -npc_snes_type <type> - set the type of the `SNES` to use as the nonlinear preconditioner

5574:   Level: developer

5576:   Notes:
5577:     If a `SNES` was previously set with `SNESSetNPC()` then that value is returned, otherwise a new `SNES` object is created.

5579:     The (preconditioner) `SNES` returned automatically inherits the same nonlinear function and Jacobian supplied to the original
5580:     `SNES`

5582: .seealso: [](chapter_snes), `SNESSetNPC()`, `SNESHasNPC()`, `SNES`, `SNESCreate()`
5583: @*/
5584: PetscErrorCode SNESGetNPC(SNES snes, SNES *pc)
5585: {
5586:   const char *optionsprefix;

5588:   PetscFunctionBegin;
5591:   if (!snes->npc) {
5592:     PetscCall(SNESCreate(PetscObjectComm((PetscObject)snes), &snes->npc));
5593:     PetscCall(PetscObjectIncrementTabLevel((PetscObject)snes->npc, (PetscObject)snes, 1));
5594:     PetscCall(SNESGetOptionsPrefix(snes, &optionsprefix));
5595:     PetscCall(SNESSetOptionsPrefix(snes->npc, optionsprefix));
5596:     PetscCall(SNESAppendOptionsPrefix(snes->npc, "npc_"));
5597:     PetscCall(SNESSetCountersReset(snes->npc, PETSC_FALSE));
5598:   }
5599:   *pc = snes->npc;
5600:   PetscFunctionReturn(PETSC_SUCCESS);
5601: }

5603: /*@
5604:   SNESHasNPC - Returns whether a nonlinear preconditioner exists

5606:   Not Collective

5608:   Input Parameter:
5609: . snes - iterative context obtained from `SNESCreate()`

5611:   Output Parameter:
5612: . has_npc - whether the `SNES` has an NPC or not

5614:   Level: developer

5616: .seealso: [](chapter_snes), `SNESSetNPC()`, `SNESGetNPC()`
5617: @*/
5618: PetscErrorCode SNESHasNPC(SNES snes, PetscBool *has_npc)
5619: {
5620:   PetscFunctionBegin;
5622:   *has_npc = (PetscBool)(snes->npc ? PETSC_TRUE : PETSC_FALSE);
5623:   PetscFunctionReturn(PETSC_SUCCESS);
5624: }

5626: /*@
5627:     SNESSetNPCSide - Sets the preconditioning side.

5629:     Logically Collective

5631:     Input Parameter:
5632: .   snes - iterative context obtained from `SNESCreate()`

5634:     Output Parameter:
5635: .   side - the preconditioning side, where side is one of
5636: .vb
5637:       PC_LEFT - left preconditioning
5638:       PC_RIGHT - right preconditioning (default for most nonlinear solvers)
5639: .ve

5641:     Options Database Key:
5642: .   -snes_npc_side <right,left> - nonlinear preconditioner side

5644:     Level: intermediate

5646:     Note:
5647:     `SNESNRICHARDSON` and `SNESNCG` only support left preconditioning.

5649: .seealso: [](chapter_snes), `SNESType`, `SNESGetNPCSide()`, `KSPSetPCSide()`
5650: @*/
5651: PetscErrorCode SNESSetNPCSide(SNES snes, PCSide side)
5652: {
5653:   PetscFunctionBegin;
5656:   if (side == PC_SIDE_DEFAULT) side = PC_RIGHT;
5657:   PetscCheck((side == PC_LEFT) || (side == PC_RIGHT), PetscObjectComm((PetscObject)snes), PETSC_ERR_ARG_WRONG, "Only PC_LEFT and PC_RIGHT are supported");
5658:   snes->npcside = side;
5659:   PetscFunctionReturn(PETSC_SUCCESS);
5660: }

5662: /*@
5663:     SNESGetNPCSide - Gets the preconditioning side.

5665:     Not Collective

5667:     Input Parameter:
5668: .   snes - iterative context obtained from `SNESCreate()`

5670:     Output Parameter:
5671: .   side - the preconditioning side, where side is one of
5672: .vb
5673:       `PC_LEFT` - left preconditioning
5674:       `PC_RIGHT` - right preconditioning (default for most nonlinear solvers)
5675: .ve

5677:     Level: intermediate

5679: .seealso: [](chapter_snes), `SNES`, `SNESSetNPCSide()`, `KSPGetPCSide()`
5680: @*/
5681: PetscErrorCode SNESGetNPCSide(SNES snes, PCSide *side)
5682: {
5683:   PetscFunctionBegin;
5686:   *side = snes->npcside;
5687:   PetscFunctionReturn(PETSC_SUCCESS);
5688: }

5690: /*@
5691:   SNESSetLineSearch - Sets the linesearch on the `SNES` instance.

5693:   Collective

5695:   Input Parameters:
5696: + snes - iterative context obtained from `SNESCreate()`
5697: - linesearch   - the linesearch object

5699:   Level: developer

5701:   Note:
5702:   Use `SNESGetLineSearch()` to retrieve the preconditioner context (for example,
5703:   to configure it using the API).

5705: .seealso: [](chapter_snes), `SNESGetLineSearch()`
5706: @*/
5707: PetscErrorCode SNESSetLineSearch(SNES snes, SNESLineSearch linesearch)
5708: {
5709:   PetscFunctionBegin;
5712:   PetscCheckSameComm(snes, 1, linesearch, 2);
5713:   PetscCall(PetscObjectReference((PetscObject)linesearch));
5714:   PetscCall(SNESLineSearchDestroy(&snes->linesearch));

5716:   snes->linesearch = linesearch;

5718:   PetscFunctionReturn(PETSC_SUCCESS);
5719: }

5721: /*@
5722:   SNESGetLineSearch - Returns the line search context set with `SNESSetLineSearch()`
5723:   or creates a default line search instance associated with the `SNES` and returns it.

5725:   Not Collective

5727:   Input Parameter:
5728: . snes - iterative context obtained from `SNESCreate()`

5730:   Output Parameter:
5731: . linesearch - linesearch context

5733:   Level: beginner

5735: .seealso: [](chapter_snes), `SNESLineSearch`, `SNESSetLineSearch()`, `SNESLineSearchCreate()`
5736: @*/
5737: PetscErrorCode SNESGetLineSearch(SNES snes, SNESLineSearch *linesearch)
5738: {
5739:   const char *optionsprefix;

5741:   PetscFunctionBegin;
5744:   if (!snes->linesearch) {
5745:     PetscCall(SNESGetOptionsPrefix(snes, &optionsprefix));
5746:     PetscCall(SNESLineSearchCreate(PetscObjectComm((PetscObject)snes), &snes->linesearch));
5747:     PetscCall(SNESLineSearchSetSNES(snes->linesearch, snes));
5748:     PetscCall(SNESLineSearchAppendOptionsPrefix(snes->linesearch, optionsprefix));
5749:     PetscCall(PetscObjectIncrementTabLevel((PetscObject)snes->linesearch, (PetscObject)snes, 1));
5750:   }
5751:   *linesearch = snes->linesearch;
5752:   PetscFunctionReturn(PETSC_SUCCESS);
5753: }