Actual source code: dmi.c

  1: #include <petsc/private/dmimpl.h>
  2: #include <petscds.h>

  4: // Greatest common divisor of two nonnegative integers
  5: PetscInt PetscGCD(PetscInt a, PetscInt b)
  6: {
  7:   while (b != 0) {
  8:     PetscInt tmp = b;
  9:     b            = a % b;
 10:     a            = tmp;
 11:   }
 12:   return a;
 13: }

 15: PetscErrorCode DMCreateGlobalVector_Section_Private(DM dm, Vec *vec)
 16: {
 17:   PetscSection gSection;
 18:   PetscInt     localSize, bs, blockSize = -1, pStart, pEnd, p;
 19:   PetscInt     in[2], out[2];

 21:   PetscFunctionBegin;
 22:   PetscCall(DMGetGlobalSection(dm, &gSection));
 23:   PetscCall(PetscSectionGetChart(gSection, &pStart, &pEnd));
 24:   for (p = pStart; p < pEnd; ++p) {
 25:     PetscInt dof, cdof;

 27:     PetscCall(PetscSectionGetDof(gSection, p, &dof));
 28:     PetscCall(PetscSectionGetConstraintDof(gSection, p, &cdof));

 30:     if (dof - cdof > 0) {
 31:       if (blockSize < 0) {
 32:         /* set blockSize */
 33:         blockSize = dof - cdof;
 34:       } else {
 35:         blockSize = PetscGCD(dof - cdof, blockSize);
 36:       }
 37:     }
 38:   }

 40:   in[0] = blockSize < 0 ? PETSC_MIN_INT : -blockSize;
 41:   in[1] = blockSize;
 42:   PetscCall(MPIU_Allreduce(in, out, 2, MPIU_INT, MPI_MAX, PetscObjectComm((PetscObject)dm)));
 43:   /* -out[0] = min(blockSize), out[1] = max(blockSize) */
 44:   if (-out[0] == out[1]) {
 45:     bs = out[1];
 46:   } else bs = 1;

 48:   if (bs < 0) { /* Everyone was empty */
 49:     blockSize = 1;
 50:     bs        = 1;
 51:   }

 53:   PetscCall(PetscSectionGetConstrainedStorageSize(gSection, &localSize));
 54:   PetscCheck(localSize % blockSize == 0, PetscObjectComm((PetscObject)dm), PETSC_ERR_ARG_WRONG, "Mismatch between blocksize %" PetscInt_FMT " and local storage size %" PetscInt_FMT, blockSize, localSize);
 55:   PetscCall(VecCreate(PetscObjectComm((PetscObject)dm), vec));
 56:   PetscCall(VecSetSizes(*vec, localSize, PETSC_DETERMINE));
 57:   PetscCall(VecSetBlockSize(*vec, bs));
 58:   PetscCall(VecSetType(*vec, dm->vectype));
 59:   PetscCall(VecSetDM(*vec, dm));
 60:   /* PetscCall(VecSetLocalToGlobalMapping(*vec, dm->ltogmap)); */
 61:   PetscFunctionReturn(PETSC_SUCCESS);
 62: }

 64: PetscErrorCode DMCreateLocalVector_Section_Private(DM dm, Vec *vec)
 65: {
 66:   PetscSection section;
 67:   PetscInt     localSize, blockSize = -1, pStart, pEnd, p;

 69:   PetscFunctionBegin;
 70:   PetscCall(DMGetLocalSection(dm, &section));
 71:   PetscCall(PetscSectionGetChart(section, &pStart, &pEnd));
 72:   for (p = pStart; p < pEnd; ++p) {
 73:     PetscInt dof;

 75:     PetscCall(PetscSectionGetDof(section, p, &dof));
 76:     if ((blockSize < 0) && (dof > 0)) blockSize = dof;
 77:     if (dof > 0) blockSize = PetscGCD(dof, blockSize);
 78:   }
 79:   PetscCall(PetscSectionGetStorageSize(section, &localSize));
 80:   PetscCall(VecCreate(PETSC_COMM_SELF, vec));
 81:   PetscCall(VecSetSizes(*vec, localSize, localSize));
 82:   PetscCall(VecSetBlockSize(*vec, blockSize));
 83:   PetscCall(VecSetType(*vec, dm->vectype));
 84:   PetscCall(VecSetDM(*vec, dm));
 85:   PetscFunctionReturn(PETSC_SUCCESS);
 86: }

 88: /*@C
 89:   DMCreateSectionSubDM - Returns an IS and subDM+subSection encapsulating a subproblem defined by the fields in a PetscSection in the DM.

 91:   Not collective

 93:   Input Parameters:
 94: + dm        - The DM object
 95: . numFields - The number of fields in this subproblem
 96: - fields    - The field numbers of the selected fields

 98:   Output Parameters:
 99: + is - The global indices for the subproblem
100: - subdm - The DM for the subproblem, which must already have be cloned from dm

102:   Note: This handles all information in the DM class and the PetscSection. This is used as the basis for creating subDMs in specialized classes,
103:   such as Plex and Forest.

105:   Level: intermediate

107: .seealso `DMCreateSubDM()`, `DMGetLocalSection()`, `DMPlexSetMigrationSF()`, `DMView()`
108: @*/
109: PetscErrorCode DMCreateSectionSubDM(DM dm, PetscInt numFields, const PetscInt fields[], IS *is, DM *subdm)
110: {
111:   PetscSection section, sectionGlobal;
112:   PetscInt    *subIndices;
113:   PetscInt     subSize = 0, subOff = 0, Nf, f, pStart, pEnd, p;

115:   PetscFunctionBegin;
116:   if (!numFields) PetscFunctionReturn(PETSC_SUCCESS);
117:   PetscCall(DMGetLocalSection(dm, &section));
118:   PetscCall(DMGetGlobalSection(dm, &sectionGlobal));
119:   PetscCheck(section, PetscObjectComm((PetscObject)dm), PETSC_ERR_ARG_WRONG, "Must set default section for DM before splitting fields");
120:   PetscCheck(sectionGlobal, PetscObjectComm((PetscObject)dm), PETSC_ERR_ARG_WRONG, "Must set default global section for DM before splitting fields");
121:   PetscCall(PetscSectionGetNumFields(section, &Nf));
122:   PetscCheck(numFields <= Nf, PetscObjectComm((PetscObject)dm), PETSC_ERR_ARG_WRONG, "Number of requested fields %" PetscInt_FMT " greater than number of DM fields %" PetscInt_FMT, numFields, Nf);
123:   if (is) {
124:     PetscInt bs, bsLocal[2], bsMinMax[2];

126:     for (f = 0, bs = 0; f < numFields; ++f) {
127:       PetscInt Nc;

129:       PetscCall(PetscSectionGetFieldComponents(section, fields[f], &Nc));
130:       bs += Nc;
131:     }
132:     PetscCall(PetscSectionGetChart(sectionGlobal, &pStart, &pEnd));
133:     for (p = pStart; p < pEnd; ++p) {
134:       PetscInt gdof, pSubSize = 0;

136:       PetscCall(PetscSectionGetDof(sectionGlobal, p, &gdof));
137:       if (gdof > 0) {
138:         for (f = 0; f < numFields; ++f) {
139:           PetscInt fdof, fcdof;

141:           PetscCall(PetscSectionGetFieldDof(section, p, fields[f], &fdof));
142:           PetscCall(PetscSectionGetFieldConstraintDof(section, p, fields[f], &fcdof));
143:           pSubSize += fdof - fcdof;
144:         }
145:         subSize += pSubSize;
146:         if (pSubSize && bs != pSubSize) {
147:           /* Layout does not admit a pointwise block size */
148:           bs = 1;
149:         }
150:       }
151:     }
152:     /* Must have same blocksize on all procs (some might have no points) */
153:     bsLocal[0] = bs < 0 ? PETSC_MAX_INT : bs;
154:     bsLocal[1] = bs;
155:     PetscCall(PetscGlobalMinMaxInt(PetscObjectComm((PetscObject)dm), bsLocal, bsMinMax));
156:     if (bsMinMax[0] != bsMinMax[1]) {
157:       bs = 1;
158:     } else {
159:       bs = bsMinMax[0];
160:     }
161:     PetscCall(PetscMalloc1(subSize, &subIndices));
162:     for (p = pStart; p < pEnd; ++p) {
163:       PetscInt gdof, goff;

165:       PetscCall(PetscSectionGetDof(sectionGlobal, p, &gdof));
166:       if (gdof > 0) {
167:         PetscCall(PetscSectionGetOffset(sectionGlobal, p, &goff));
168:         for (f = 0; f < numFields; ++f) {
169:           PetscInt fdof, fcdof, fc, f2, poff = 0;

171:           /* Can get rid of this loop by storing field information in the global section */
172:           for (f2 = 0; f2 < fields[f]; ++f2) {
173:             PetscCall(PetscSectionGetFieldDof(section, p, f2, &fdof));
174:             PetscCall(PetscSectionGetFieldConstraintDof(section, p, f2, &fcdof));
175:             poff += fdof - fcdof;
176:           }
177:           PetscCall(PetscSectionGetFieldDof(section, p, fields[f], &fdof));
178:           PetscCall(PetscSectionGetFieldConstraintDof(section, p, fields[f], &fcdof));
179:           for (fc = 0; fc < fdof - fcdof; ++fc, ++subOff) subIndices[subOff] = goff + poff + fc;
180:         }
181:       }
182:     }
183:     PetscCall(ISCreateGeneral(PetscObjectComm((PetscObject)dm), subSize, subIndices, PETSC_OWN_POINTER, is));
184:     if (bs > 1) {
185:       /* We need to check that the block size does not come from non-contiguous fields */
186:       PetscInt i, j, set = 1, rset = 1;
187:       for (i = 0; i < subSize; i += bs) {
188:         for (j = 0; j < bs; ++j) {
189:           if (subIndices[i + j] != subIndices[i] + j) {
190:             set = 0;
191:             break;
192:           }
193:         }
194:       }
195:       PetscCallMPI(MPI_Allreduce(&set, &rset, 1, MPIU_INT, MPI_PROD, PetscObjectComm((PetscObject)dm)));
196:       if (rset) PetscCall(ISSetBlockSize(*is, bs));
197:     }
198:   }
199:   if (subdm) {
200:     PetscSection subsection;
201:     PetscBool    haveNull = PETSC_FALSE;
202:     PetscInt     f, nf = 0, of = 0;

204:     PetscCall(PetscSectionCreateSubsection(section, numFields, fields, &subsection));
205:     PetscCall(DMSetLocalSection(*subdm, subsection));
206:     PetscCall(PetscSectionDestroy(&subsection));
207:     for (f = 0; f < numFields; ++f) {
208:       (*subdm)->nullspaceConstructors[f] = dm->nullspaceConstructors[fields[f]];
209:       if ((*subdm)->nullspaceConstructors[f]) {
210:         haveNull = PETSC_TRUE;
211:         nf       = f;
212:         of       = fields[f];
213:       }
214:     }
215:     if (dm->probs) {
216:       PetscCall(DMSetNumFields(*subdm, numFields));
217:       for (f = 0; f < numFields; ++f) {
218:         PetscObject disc;

220:         PetscCall(DMGetField(dm, fields[f], NULL, &disc));
221:         PetscCall(DMSetField(*subdm, f, NULL, disc));
222:       }
223:       PetscCall(DMCreateDS(*subdm));
224:       if (numFields == 1 && is) {
225:         PetscObject disc, space, pmat;

227:         PetscCall(DMGetField(*subdm, 0, NULL, &disc));
228:         PetscCall(PetscObjectQuery(disc, "nullspace", &space));
229:         if (space) PetscCall(PetscObjectCompose((PetscObject)*is, "nullspace", space));
230:         PetscCall(PetscObjectQuery(disc, "nearnullspace", &space));
231:         if (space) PetscCall(PetscObjectCompose((PetscObject)*is, "nearnullspace", space));
232:         PetscCall(PetscObjectQuery(disc, "pmat", &pmat));
233:         if (pmat) PetscCall(PetscObjectCompose((PetscObject)*is, "pmat", pmat));
234:       }
235:       /* Check if DSes record their DM fields */
236:       if (dm->probs[0].fields) {
237:         PetscInt d, e;

239:         for (d = 0, e = 0; d < dm->Nds && e < (*subdm)->Nds; ++d) {
240:           const PetscInt  Nf = dm->probs[d].ds->Nf;
241:           const PetscInt *fld;
242:           PetscInt        f, g;

244:           PetscCall(ISGetIndices(dm->probs[d].fields, &fld));
245:           for (f = 0; f < Nf; ++f) {
246:             for (g = 0; g < numFields; ++g)
247:               if (fld[f] == fields[g]) break;
248:             if (g < numFields) break;
249:           }
250:           PetscCall(ISRestoreIndices(dm->probs[d].fields, &fld));
251:           if (f == Nf) continue;
252:           PetscCall(PetscDSCopyConstants(dm->probs[d].ds, (*subdm)->probs[e].ds));
253:           PetscCall(PetscDSCopyBoundary(dm->probs[d].ds, numFields, fields, (*subdm)->probs[e].ds));
254:           /* Translate DM fields to DS fields */
255:           {
256:             IS              infields, dsfields;
257:             const PetscInt *fld, *ofld;
258:             PetscInt       *fidx;
259:             PetscInt        onf, nf, f, g;

261:             PetscCall(ISCreateGeneral(PETSC_COMM_SELF, numFields, fields, PETSC_USE_POINTER, &infields));
262:             PetscCall(ISIntersect(infields, dm->probs[d].fields, &dsfields));
263:             PetscCall(ISDestroy(&infields));
264:             PetscCall(ISGetLocalSize(dsfields, &nf));
265:             PetscCheck(nf, PETSC_COMM_SELF, PETSC_ERR_PLIB, "DS cannot be supported on 0 fields");
266:             PetscCall(ISGetIndices(dsfields, &fld));
267:             PetscCall(ISGetLocalSize(dm->probs[d].fields, &onf));
268:             PetscCall(ISGetIndices(dm->probs[d].fields, &ofld));
269:             PetscCall(PetscMalloc1(nf, &fidx));
270:             for (f = 0, g = 0; f < onf && g < nf; ++f) {
271:               if (ofld[f] == fld[g]) fidx[g++] = f;
272:             }
273:             PetscCall(ISRestoreIndices(dm->probs[d].fields, &ofld));
274:             PetscCall(ISRestoreIndices(dsfields, &fld));
275:             PetscCall(ISDestroy(&dsfields));
276:             PetscCall(PetscDSSelectDiscretizations(dm->probs[0].ds, nf, fidx, (*subdm)->probs[0].ds));
277:             PetscCall(PetscDSSelectEquations(dm->probs[0].ds, nf, fidx, (*subdm)->probs[0].ds));
278:             PetscCall(PetscFree(fidx));
279:           }
280:           ++e;
281:         }
282:       } else {
283:         PetscCall(PetscDSCopyConstants(dm->probs[0].ds, (*subdm)->probs[0].ds));
284:         PetscCall(PetscDSCopyBoundary(dm->probs[0].ds, PETSC_DETERMINE, NULL, (*subdm)->probs[0].ds));
285:         PetscCall(PetscDSSelectDiscretizations(dm->probs[0].ds, numFields, fields, (*subdm)->probs[0].ds));
286:         PetscCall(PetscDSSelectEquations(dm->probs[0].ds, numFields, fields, (*subdm)->probs[0].ds));
287:       }
288:     }
289:     if (haveNull && is) {
290:       MatNullSpace nullSpace;

292:       PetscCall((*(*subdm)->nullspaceConstructors[nf])(*subdm, of, nf, &nullSpace));
293:       PetscCall(PetscObjectCompose((PetscObject)*is, "nullspace", (PetscObject)nullSpace));
294:       PetscCall(MatNullSpaceDestroy(&nullSpace));
295:     }
296:     if (dm->coarseMesh) PetscCall(DMCreateSubDM(dm->coarseMesh, numFields, fields, NULL, &(*subdm)->coarseMesh));
297:   }
298:   PetscFunctionReturn(PETSC_SUCCESS);
299: }

301: /*@C
302:   DMCreateSectionSuperDM - Returns an arrays of ISes and DM+Section encapsulating a superproblem defined by the DM+Sections passed in.

304:   Not collective

306:   Input Parameters:
307: + dms - The DM objects
308: - len - The number of DMs

310:   Output Parameters:
311: + is - The global indices for the subproblem, or NULL
312: - superdm - The DM for the superproblem, which must already have be cloned

314:   Note: This handles all information in the DM class and the PetscSection. This is used as the basis for creating subDMs in specialized classes,
315:   such as Plex and Forest.

317:   Level: intermediate

319: .seealso `DMCreateSuperDM()`, `DMGetLocalSection()`, `DMPlexSetMigrationSF()`, `DMView()`
320: @*/
321: PetscErrorCode DMCreateSectionSuperDM(DM dms[], PetscInt len, IS **is, DM *superdm)
322: {
323:   MPI_Comm     comm;
324:   PetscSection supersection, *sections, *sectionGlobals;
325:   PetscInt    *Nfs, Nf = 0, f, supf, oldf = -1, nullf = -1, i;
326:   PetscBool    haveNull = PETSC_FALSE;

328:   PetscFunctionBegin;
329:   PetscCall(PetscObjectGetComm((PetscObject)dms[0], &comm));
330:   /* Pull out local and global sections */
331:   PetscCall(PetscMalloc3(len, &Nfs, len, &sections, len, &sectionGlobals));
332:   for (i = 0; i < len; ++i) {
333:     PetscCall(DMGetLocalSection(dms[i], &sections[i]));
334:     PetscCall(DMGetGlobalSection(dms[i], &sectionGlobals[i]));
335:     PetscCheck(sections[i], comm, PETSC_ERR_ARG_WRONG, "Must set default section for DM before splitting fields");
336:     PetscCheck(sectionGlobals[i], comm, PETSC_ERR_ARG_WRONG, "Must set default global section for DM before splitting fields");
337:     PetscCall(PetscSectionGetNumFields(sections[i], &Nfs[i]));
338:     Nf += Nfs[i];
339:   }
340:   /* Create the supersection */
341:   PetscCall(PetscSectionCreateSupersection(sections, len, &supersection));
342:   PetscCall(DMSetLocalSection(*superdm, supersection));
343:   /* Create ISes */
344:   if (is) {
345:     PetscSection supersectionGlobal;
346:     PetscInt     bs = -1, startf = 0;

348:     PetscCall(PetscMalloc1(len, is));
349:     PetscCall(DMGetGlobalSection(*superdm, &supersectionGlobal));
350:     for (i = 0; i < len; startf += Nfs[i], ++i) {
351:       PetscInt *subIndices;
352:       PetscInt  subSize, subOff, pStart, pEnd, p, start, end, dummy;

354:       PetscCall(PetscSectionGetChart(sectionGlobals[i], &pStart, &pEnd));
355:       PetscCall(PetscSectionGetConstrainedStorageSize(sectionGlobals[i], &subSize));
356:       PetscCall(PetscMalloc1(subSize, &subIndices));
357:       for (p = pStart, subOff = 0; p < pEnd; ++p) {
358:         PetscInt gdof, gcdof, gtdof, d;

360:         PetscCall(PetscSectionGetDof(sectionGlobals[i], p, &gdof));
361:         PetscCall(PetscSectionGetConstraintDof(sections[i], p, &gcdof));
362:         gtdof = gdof - gcdof;
363:         if (gdof > 0 && gtdof) {
364:           if (bs < 0) {
365:             bs = gtdof;
366:           } else if (bs != gtdof) {
367:             bs = 1;
368:           }
369:           PetscCall(DMGetGlobalFieldOffset_Private(*superdm, p, startf, &start, &dummy));
370:           PetscCall(DMGetGlobalFieldOffset_Private(*superdm, p, startf + Nfs[i] - 1, &dummy, &end));
371:           PetscCheck(end - start == gtdof, PETSC_COMM_SELF, PETSC_ERR_ARG_SIZ, "Invalid number of global dofs %" PetscInt_FMT " != %" PetscInt_FMT " for dm %" PetscInt_FMT " on point %" PetscInt_FMT, end - start, gtdof, i, p);
372:           for (d = start; d < end; ++d, ++subOff) subIndices[subOff] = d;
373:         }
374:       }
375:       PetscCall(ISCreateGeneral(comm, subSize, subIndices, PETSC_OWN_POINTER, &(*is)[i]));
376:       /* Must have same blocksize on all procs (some might have no points) */
377:       {
378:         PetscInt bs = -1, bsLocal[2], bsMinMax[2];

380:         bsLocal[0] = bs < 0 ? PETSC_MAX_INT : bs;
381:         bsLocal[1] = bs;
382:         PetscCall(PetscGlobalMinMaxInt(comm, bsLocal, bsMinMax));
383:         if (bsMinMax[0] != bsMinMax[1]) {
384:           bs = 1;
385:         } else {
386:           bs = bsMinMax[0];
387:         }
388:         PetscCall(ISSetBlockSize((*is)[i], bs));
389:       }
390:     }
391:   }
392:   /* Preserve discretizations */
393:   if (len && dms[0]->probs) {
394:     PetscCall(DMSetNumFields(*superdm, Nf));
395:     for (i = 0, supf = 0; i < len; ++i) {
396:       for (f = 0; f < Nfs[i]; ++f, ++supf) {
397:         PetscObject disc;

399:         PetscCall(DMGetField(dms[i], f, NULL, &disc));
400:         PetscCall(DMSetField(*superdm, supf, NULL, disc));
401:       }
402:     }
403:     PetscCall(DMCreateDS(*superdm));
404:   }
405:   /* Preserve nullspaces */
406:   for (i = 0, supf = 0; i < len; ++i) {
407:     for (f = 0; f < Nfs[i]; ++f, ++supf) {
408:       (*superdm)->nullspaceConstructors[supf] = dms[i]->nullspaceConstructors[f];
409:       if ((*superdm)->nullspaceConstructors[supf]) {
410:         haveNull = PETSC_TRUE;
411:         nullf    = supf;
412:         oldf     = f;
413:       }
414:     }
415:   }
416:   /* Attach nullspace to IS */
417:   if (haveNull && is) {
418:     MatNullSpace nullSpace;

420:     PetscCall((*(*superdm)->nullspaceConstructors[nullf])(*superdm, oldf, nullf, &nullSpace));
421:     PetscCall(PetscObjectCompose((PetscObject)(*is)[nullf], "nullspace", (PetscObject)nullSpace));
422:     PetscCall(MatNullSpaceDestroy(&nullSpace));
423:   }
424:   PetscCall(PetscSectionDestroy(&supersection));
425:   PetscCall(PetscFree3(Nfs, sections, sectionGlobals));
426:   PetscFunctionReturn(PETSC_SUCCESS);
427: }