Actual source code: ex16.c
petsc-dev 2014-02-02
1: #include <petscsnes.h>
2: #include <petscdmda.h>
4: static char help[]=
5: "This example is an implementation of minimal surface area with \n\
6: a plate problem from the TAO package (examples/plate2.c) \n\
7: This example is based on a problem from the MINPACK-2 test suite.\n\
8: Given a rectangular 2-D domain, boundary values along the edges of \n\
9: the domain, and a plate represented by lower boundary conditions, \n\
10: the objective is to find the surface with the minimal area that \n\
11: satisfies the boundary conditions.\n\
12: The command line options are:\n\
13: -bmx <bxg>, where <bxg> = number of grid points under plate in 1st direction\n\
14: -bmy <byg>, where <byg> = number of grid points under plate in 2nd direction\n\
15: -bheight <ht>, where <ht> = height of the plate\n\
16: -start <st>, where <st> =0 for zero vector, <st> != 0 \n\
17: for an average of the boundary conditions\n\n";
19: /*
20: User-defined application context - contains data needed by the
21: application-provided call-back routines, FormJacobian() and
22: FormFunction().
23: */
25: typedef struct {
26: DM da;
27: Vec Bottom, Top, Left, Right;
28: PetscScalar bheight;
29: PetscInt mx,my,bmx,bmy;
30: } AppCtx;
33: /* -------- User-defined Routines --------- */
35: PetscErrorCode MSA_BoundaryConditions(AppCtx*);
36: PetscErrorCode MSA_InitialPoint(AppCtx*, Vec);
37: PetscErrorCode MSA_Plate(Vec,Vec,void*);
38: PetscErrorCode FormGradient(SNES, Vec, Vec, void*);
39: PetscErrorCode FormJacobian(SNES, Vec, Mat*, Mat*, MatStructure*,void*);
43: int main(int argc, char **argv)
44: {
46: Vec x,r; /* solution and residual vectors */
47: Vec xl,xu; /* Bounds on the variables */
48: SNES snes; /* nonlinear solver context */
49: Mat J; /* Jacobian matrix */
50: AppCtx user; /* user-defined work context */
51: PetscBool flg;
53: /* Initialize PETSc */
54: PetscInitialize(&argc, &argv, (char*)0, help);
56: #if defined(PETSC_USE_COMPLEX)
57: SETERRQ(PETSC_COMM_WORLD,PETSC_ERR_SUP,"This example does not work for scalar type complex\n");
58: #endif
60: /* Create distributed array to manage the 2d grid */
61: DMDACreate2d(PETSC_COMM_WORLD, DMDA_BOUNDARY_NONE, DMDA_BOUNDARY_NONE,DMDA_STENCIL_BOX,-10,-10,PETSC_DECIDE,PETSC_DECIDE,1,1,NULL,NULL,&user.da);
62: DMDAGetIerr(user.da,PETSC_IGNORE,&user.mx,&user.my,PETSC_IGNORE,PETSC_IGNORE,PETSC_IGNORE,PETSC_IGNORE,PETSC_IGNORE,PETSC_IGNORE,PETSC_IGNORE,PETSC_IGNORE,PETSC_IGNORE,PETSC_IGNORE);
64: user.bheight = 0.1;
65: PetscOptionsGetScalar(NULL,"-bheight",&user.bheight,&flg);
67: user.bmx = user.mx/2; user.bmy = user.my/2;
68: PetscOptionsGetInt(NULL,"-bmx",&user.bmx,&flg);
69: PetscOptionsGetInt(NULL,"-bmy",&user.bmy,&flg);
71: PetscPrintf(PETSC_COMM_WORLD,"\n---- Minimum Surface Area With Plate Problem -----\n");
72: PetscPrintf(PETSC_COMM_WORLD,"mx:%d, my:%d, bmx:%d, bmy:%d, height:%4.2f\n",
73: user.mx,user.my,user.bmx,user.bmy,user.bheight);
75: /* Extract global vectors from DMDA; */
76: DMCreateGlobalVector(user.da,&x);
77: VecDuplicate(x, &r);
79: DMSetMatType(user.da,MATAIJ);
80: DMCreateMatrix(user.da,&J);
82: /* Create nonlinear solver context */
83: SNESCreate(PETSC_COMM_WORLD,&snes);
85: /* Set function evaluation and Jacobian evaluation routines */
86: SNESSetDM(snes,user.da);
87: SNESSetFunction(snes,r,FormGradient,&user);
88: SNESSetJacobian(snes,J,J,FormJacobian,&user);
90: /* Set the boundary conditions */
91: MSA_BoundaryConditions(&user);
93: /* Set initial solution guess */
94: MSA_InitialPoint(&user, x);
96: SNESSetFromOptions(snes);
98: /* Set Bounds on variables */
99: VecDuplicate(x, &xl);
100: VecDuplicate(x, &xu);
101: MSA_Plate(xl,xu,&user);
103: SNESVISetVariableBounds(snes,xl,xu);
105: /* Solve the application */
106: SNESSolve(snes,NULL,x);
108: PetscOptionsHasName(NULL,"-view_sol",&flg);
109: if (flg) { VecView(x,PETSC_VIEWER_STDOUT_WORLD); }
111: /* Free memory */
112: VecDestroy(&x);
113: VecDestroy(&xl);
114: VecDestroy(&xu);
115: VecDestroy(&r);
116: MatDestroy(&J);
117: SNESDestroy(&snes);
119: /* Free user-created data structures */
120: DMDestroy(&user.da);
121: VecDestroy(&user.Bottom);
122: VecDestroy(&user.Top);
123: VecDestroy(&user.Left);
124: VecDestroy(&user.Right);
126: PetscFinalize();
128: return 0;
129: }
131: /* -------------------------------------------------------------------- */
135: /* FormGradient - Evaluates gradient of f.
137: Input Parameters:
138: . snes - the SNES context
139: . X - input vector
140: . ptr - optional user-defined context, as set by SNESSetFunction()
142: Output Parameters:
143: . G - vector containing the newly evaluated gradient
144: */
145: PetscErrorCode FormGradient(SNES snes, Vec X, Vec G, void *ptr)
146: {
147: AppCtx *user = (AppCtx*) ptr;
148: int ierr;
149: PetscInt i,j;
150: PetscInt mx=user->mx, my=user->my;
151: PetscScalar hx=1.0/(mx+1),hy=1.0/(my+1), hydhx=hy/hx, hxdhy=hx/hy;
152: PetscScalar f1,f2,f3,f4,f5,f6,d1,d2,d3,d4,d5,d6,d7,d8,xc,xl,xr,xt,xb,xlt,xrb;
153: PetscScalar df1dxc,df2dxc,df3dxc,df4dxc,df5dxc,df6dxc;
154: PetscScalar **g, **x;
155: PetscInt xs,xm,ys,ym;
156: Vec localX;
157: PetscScalar *top,*bottom,*left,*right;
160: /* Initialize vector to zero */
161: VecSet(G,0.0);
163: /* Get local vector */
164: DMGetLocalVector(user->da,&localX);
165: VecGetArray(user->Top,&top);
166: VecGetArray(user->Bottom,&bottom);
167: VecGetArray(user->Left,&left);
168: VecGetArray(user->Right,&right);
170: /* Get ghost points */
171: DMGlobalToLocalBegin(user->da,X,INSERT_VALUES,localX);
172: DMGlobalToLocalEnd(user->da,X,INSERT_VALUES,localX);
173: /* Get pointers to local vector data */
174: DMDAVecGetArray(user->da,localX, &x);
175: DMDAVecGetArray(user->da,G, &g);
177: DMDAGetCorners(user->da,&xs,&ys,NULL,&xm,&ym,NULL);
178: /* Compute function over the locally owned part of the mesh */
179: for (j=ys; j < ys+ym; j++) {
180: for (i=xs; i< xs+xm; i++) {
182: xc = x[j][i];
183: xlt=xrb=xl=xr=xb=xt=xc;
185: if (i==0) { /* left side */
186: xl = left[j-ys+1];
187: xlt = left[j-ys+2];
188: } else xl = x[j][i-1];
190: if (j==0) { /* bottom side */
191: xb = bottom[i-xs+1];
192: xrb = bottom[i-xs+2];
193: } else xb = x[j-1][i];
195: if (i+1 == mx) { /* right side */
196: xr = right[j-ys+1];
197: xrb = right[j-ys];
198: } else xr = x[j][i+1];
200: if (j+1==0+my) { /* top side */
201: xt = top[i-xs+1];
202: xlt = top[i-xs];
203: } else xt = x[j+1][i];
205: if (i>0 && j+1<my) xlt = x[j+1][i-1]; /* left top side */
206: if (j>0 && i+1<mx) xrb = x[j-1][i+1]; /* right bottom */
208: d1 = (xc-xl);
209: d2 = (xc-xr);
210: d3 = (xc-xt);
211: d4 = (xc-xb);
212: d5 = (xr-xrb);
213: d6 = (xrb-xb);
214: d7 = (xlt-xl);
215: d8 = (xt-xlt);
217: df1dxc = d1*hydhx;
218: df2dxc = (d1*hydhx + d4*hxdhy);
219: df3dxc = d3*hxdhy;
220: df4dxc = (d2*hydhx + d3*hxdhy);
221: df5dxc = d2*hydhx;
222: df6dxc = d4*hxdhy;
224: d1 /= hx;
225: d2 /= hx;
226: d3 /= hy;
227: d4 /= hy;
228: d5 /= hy;
229: d6 /= hx;
230: d7 /= hy;
231: d8 /= hx;
233: f1 = PetscSqrtReal(1.0 + d1*d1 + d7*d7);
234: f2 = PetscSqrtReal(1.0 + d1*d1 + d4*d4);
235: f3 = PetscSqrtReal(1.0 + d3*d3 + d8*d8);
236: f4 = PetscSqrtReal(1.0 + d3*d3 + d2*d2);
237: f5 = PetscSqrtReal(1.0 + d2*d2 + d5*d5);
238: f6 = PetscSqrtReal(1.0 + d4*d4 + d6*d6);
240: df1dxc /= f1;
241: df2dxc /= f2;
242: df3dxc /= f3;
243: df4dxc /= f4;
244: df5dxc /= f5;
245: df6dxc /= f6;
247: g[j][i] = (df1dxc+df2dxc+df3dxc+df4dxc+df5dxc+df6dxc)/2.0;
249: }
250: }
252: /* Restore vectors */
253: DMDAVecRestoreArray(user->da,localX, &x);
254: DMDAVecRestoreArray(user->da,G, &g);
255: DMRestoreLocalVector(user->da,&localX);
257: VecRestoreArray(user->Left,&left);
258: VecRestoreArray(user->Top,&top);
259: VecRestoreArray(user->Bottom,&bottom);
260: VecRestoreArray(user->Right,&right);
262: PetscLogFlops(67*mx*my);
263: return(0);
264: }
266: /* ------------------------------------------------------------------- */
269: /*
270: FormJacobian - Evaluates Jacobian matrix.
272: Input Parameters:
273: . snes - SNES context
274: . X - input vector
275: . ptr - optional user-defined context, as set by SNESSetJacobian()
277: Output Parameters:
278: . tH - Jacobian matrix
280: */
281: PetscErrorCode FormJacobian(SNES snes, Vec X, Mat *tH, Mat *tHPre, MatStructure *flag, void *ptr)
282: {
283: AppCtx *user = (AppCtx*) ptr;
284: Mat H = *tH;
286: PetscInt i,j,k;
287: PetscInt mx=user->mx, my=user->my;
288: MatStencil row,col[7];
289: PetscScalar hx=1.0/(mx+1), hy=1.0/(my+1), hydhx=hy/hx, hxdhy=hx/hy;
290: PetscScalar f1,f2,f3,f4,f5,f6,d1,d2,d3,d4,d5,d6,d7,d8,xc,xl,xr,xt,xb,xlt,xrb;
291: PetscScalar hl,hr,ht,hb,hc,htl,hbr;
292: PetscScalar **x, v[7];
293: PetscBool assembled;
294: PetscInt xs,xm,ys,ym;
295: Vec localX;
296: PetscScalar *top,*bottom,*left,*right;
299: /* Set various matrix options */
300: MatAssembled(H,&assembled);
301: if (assembled) {MatZeroEntries(H);}
302: *flag=SAME_NONZERO_PATTERN;
304: /* Get local vectors */
305: DMGetLocalVector(user->da,&localX);
306: VecGetArray(user->Top,&top);
307: VecGetArray(user->Bottom,&bottom);
308: VecGetArray(user->Left,&left);
309: VecGetArray(user->Right,&right);
311: /* Get ghost points */
312: DMGlobalToLocalBegin(user->da,X,INSERT_VALUES,localX);
313: DMGlobalToLocalEnd(user->da,X,INSERT_VALUES,localX);
315: /* Get pointers to vector data */
316: DMDAVecGetArray(user->da,localX, &x);
318: DMDAGetCorners(user->da,&xs,&ys,NULL,&xm,&ym,NULL);
319: /* Compute Jacobian over the locally owned part of the mesh */
320: for (j=ys; j< ys+ym; j++) {
321: for (i=xs; i< xs+xm; i++) {
322: xc = x[j][i];
323: xlt=xrb=xl=xr=xb=xt=xc;
325: /* Left */
326: if (i==0) {
327: xl = left[j+1];
328: xlt = left[j+2];
329: } else xl = x[j][i-1];
331: /* Bottom */
332: if (j==0) {
333: xb = bottom[i+1];
334: xrb = bottom[i+2];
335: } else xb = x[j-1][i];
337: /* Right */
338: if (i+1 == mx) {
339: xr = right[j+1];
340: xrb = right[j];
341: } else xr = x[j][i+1];
343: /* Top */
344: if (j+1==my) {
345: xt = top[i+1];
346: xlt = top[i];
347: } else xt = x[j+1][i];
349: /* Top left */
350: if (i>0 && j+1<my) xlt = x[j+1][i-1];
352: /* Bottom right */
353: if (j>0 && i+1<mx) xrb = x[j-1][i+1];
355: d1 = (xc-xl)/hx;
356: d2 = (xc-xr)/hx;
357: d3 = (xc-xt)/hy;
358: d4 = (xc-xb)/hy;
359: d5 = (xrb-xr)/hy;
360: d6 = (xrb-xb)/hx;
361: d7 = (xlt-xl)/hy;
362: d8 = (xlt-xt)/hx;
364: f1 = PetscSqrtReal(1.0 + d1*d1 + d7*d7);
365: f2 = PetscSqrtReal(1.0 + d1*d1 + d4*d4);
366: f3 = PetscSqrtReal(1.0 + d3*d3 + d8*d8);
367: f4 = PetscSqrtReal(1.0 + d3*d3 + d2*d2);
368: f5 = PetscSqrtReal(1.0 + d2*d2 + d5*d5);
369: f6 = PetscSqrtReal(1.0 + d4*d4 + d6*d6);
372: hl = (-hydhx*(1.0+d7*d7)+d1*d7)/(f1*f1*f1)+
373: (-hydhx*(1.0+d4*d4)+d1*d4)/(f2*f2*f2);
374: hr = (-hydhx*(1.0+d5*d5)+d2*d5)/(f5*f5*f5)+
375: (-hydhx*(1.0+d3*d3)+d2*d3)/(f4*f4*f4);
376: ht = (-hxdhy*(1.0+d8*d8)+d3*d8)/(f3*f3*f3)+
377: (-hxdhy*(1.0+d2*d2)+d2*d3)/(f4*f4*f4);
378: hb = (-hxdhy*(1.0+d6*d6)+d4*d6)/(f6*f6*f6)+
379: (-hxdhy*(1.0+d1*d1)+d1*d4)/(f2*f2*f2);
381: hbr = -d2*d5/(f5*f5*f5) - d4*d6/(f6*f6*f6);
382: htl = -d1*d7/(f1*f1*f1) - d3*d8/(f3*f3*f3);
384: hc = hydhx*(1.0+d7*d7)/(f1*f1*f1) + hxdhy*(1.0+d8*d8)/(f3*f3*f3) +
385: hydhx*(1.0+d5*d5)/(f5*f5*f5) + hxdhy*(1.0+d6*d6)/(f6*f6*f6) +
386: (hxdhy*(1.0+d1*d1)+hydhx*(1.0+d4*d4)-2*d1*d4)/(f2*f2*f2) +
387: (hxdhy*(1.0+d2*d2)+hydhx*(1.0+d3*d3)-2*d2*d3)/(f4*f4*f4);
389: hl/=2.0; hr/=2.0; ht/=2.0; hb/=2.0; hbr/=2.0; htl/=2.0; hc/=2.0;
391: k = 0;
392: row.i = i;row.j = j;
393: /* Bottom */
394: if (j>0) {
395: v[k] = hb;
396: col[k].i = i; col[k].j=j-1; k++;
397: }
399: /* Bottom right */
400: if (j>0 && i < mx -1) {
401: v[k] = hbr;
402: col[k].i = i+1; col[k].j = j-1; k++;
403: }
405: /* left */
406: if (i>0) {
407: v[k] = hl;
408: col[k].i = i-1; col[k].j = j; k++;
409: }
411: /* Centre */
412: v[k]= hc; col[k].i= row.i; col[k].j = row.j; k++;
414: /* Right */
415: if (i < mx-1) {
416: v[k] = hr;
417: col[k].i= i+1; col[k].j = j;k++;
418: }
420: /* Top left */
421: if (i>0 && j < my-1) {
422: v[k] = htl;
423: col[k].i = i-1;col[k].j = j+1; k++;
424: }
426: /* Top */
427: if (j < my-1) {
428: v[k] = ht;
429: col[k].i = i; col[k].j = j+1; k++;
430: }
432: MatSetValuesStencil(H,1,&row,k,col,v,INSERT_VALUES);
433: }
434: }
436: VecRestoreArray(user->Left,&left);
437: VecRestoreArray(user->Top,&top);
438: VecRestoreArray(user->Bottom,&bottom);
439: VecRestoreArray(user->Right,&right);
441: /* Assemble the matrix */
442: MatAssemblyBegin(H,MAT_FINAL_ASSEMBLY);
443: DMDAVecRestoreArray(user->da,localX,&x);
444: MatAssemblyEnd(H,MAT_FINAL_ASSEMBLY);
445: DMRestoreLocalVector(user->da,&localX);
447: PetscLogFlops(199*mx*my);
448: return(0);
449: }
451: /* ------------------------------------------------------------------- */
454: /*
455: MSA_BoundaryConditions - Calculates the boundary conditions for
456: the region.
458: Input Parameter:
459: . user - user-defined application context
461: Output Parameter:
462: . user - user-defined application context
463: */
464: PetscErrorCode MSA_BoundaryConditions(AppCtx * user)
465: {
467: PetscInt i,j,k,limit=0,maxits=5;
468: PetscInt mx=user->mx,my=user->my;
469: PetscInt xs,ys,xm,ym;
470: PetscInt bsize=0, lsize=0, tsize=0, rsize=0;
471: PetscScalar one =1.0, two=2.0, three=3.0, tol=1e-10;
472: PetscScalar fnorm,det,hx,hy,xt=0,yt=0;
473: PetscScalar u1,u2,nf1,nf2,njac11,njac12,njac21,njac22;
474: PetscScalar b=-0.5, t=0.5, l=-0.5, r=0.5;
475: PetscScalar *boundary;
476: Vec Bottom,Top,Right,Left;
477: PetscScalar scl=1.0;
478: PetscBool flg;
481: DMDAGetCorners(user->da,&xs,&ys,NULL,&xm,&ym,NULL);
483: bsize=xm+2; lsize=ym+2; rsize=ym+2; tsize=xm+2;
485: VecCreateMPI(PETSC_COMM_WORLD,bsize,PETSC_DECIDE,&Bottom);
486: VecCreateMPI(PETSC_COMM_WORLD,tsize,PETSC_DECIDE,&Top);
487: VecCreateMPI(PETSC_COMM_WORLD,lsize,PETSC_DECIDE,&Left);
488: VecCreateMPI(PETSC_COMM_WORLD,rsize,PETSC_DECIDE,&Right);
490: user->Top = Top;
491: user->Left = Left;
492: user->Bottom = Bottom;
493: user->Right = Right;
495: hx= (r-l)/(mx+1); hy=(t-b)/(my+1);
497: for (j=0; j<4; j++) {
498: if (j==0) {
499: yt = b;
500: xt = l+hx*xs;
501: limit = bsize;
502: VecGetArray(Bottom,&boundary);
503: } else if (j==1) {
504: yt = t;
505: xt = l+hx*xs;
506: limit= tsize;
507: VecGetArray(Top,&boundary);
508: } else if (j==2) {
509: yt = b+hy*ys;
510: xt = l;
511: limit= lsize;
512: VecGetArray(Left,&boundary);
513: } else { /* if (j==3) */
514: yt = b+hy*ys;
515: xt = r;
516: limit= rsize;
517: VecGetArray(Right,&boundary);
518: }
520: for (i=0; i<limit; i++) {
521: u1=xt;
522: u2=-yt;
523: for (k=0; k<maxits; k++) {
524: nf1 = u1 + u1*u2*u2 - u1*u1*u1/three-xt;
525: nf2 = -u2 - u1*u1*u2 + u2*u2*u2/three-yt;
526: fnorm = PetscSqrtReal(nf1*nf1+nf2*nf2);
527: if (fnorm <= tol) break;
528: njac11 = one+u2*u2-u1*u1;
529: njac12 = two*u1*u2;
530: njac21 = -two*u1*u2;
531: njac22 = -one - u1*u1 + u2*u2;
532: det = njac11*njac22-njac21*njac12;
533: u1 = u1-(njac22*nf1-njac12*nf2)/det;
534: u2 = u2-(njac11*nf2-njac21*nf1)/det;
535: }
537: boundary[i]=u1*u1-u2*u2;
538: if (j==0 || j==1) xt=xt+hx;
539: else yt=yt+hy; /* if (j==2 || j==3) */
540: }
542: if (j==0) {
543: VecRestoreArray(Bottom,&boundary);
544: } else if (j==1) {
545: VecRestoreArray(Top,&boundary);
546: } else if (j==2) {
547: VecRestoreArray(Left,&boundary);
548: } else if (j==3) {
549: VecRestoreArray(Right,&boundary);
550: }
552: }
554: /* Scale the boundary if desired */
556: PetscOptionsGetReal(NULL,"-bottom",&scl,&flg);
557: if (flg) {
558: VecScale(Bottom, scl);
559: }
561: PetscOptionsGetReal(NULL,"-top",&scl,&flg);
562: if (flg) {
563: VecScale(Top, scl);
564: }
566: PetscOptionsGetReal(NULL,"-right",&scl,&flg);
567: if (flg) {
568: VecScale(Right, scl);
569: }
571: PetscOptionsGetReal(NULL,"-left",&scl,&flg);
572: if (flg) {
573: VecScale(Left, scl);
574: }
575: return(0);
576: }
578: /* ------------------------------------------------------------------- */
581: /*
582: MSA_InitialPoint - Calculates the initial guess in one of three ways.
584: Input Parameters:
585: . user - user-defined application context
586: . X - vector for initial guess
588: Output Parameters:
589: . X - newly computed initial guess
590: */
591: PetscErrorCode MSA_InitialPoint(AppCtx * user, Vec X)
592: {
594: PetscInt start =-1,i,j;
595: PetscScalar zero =0.0;
596: PetscBool flg;
597: PetscScalar *left,*right,*bottom,*top;
600: PetscOptionsGetInt(NULL,"-start",&start,&flg);
602: if (flg && start==0) { /* The zero vector is reasonable */
604: VecSet(X, zero);
605: /* PLogIerr(user,"Min. Surface Area Problem: Start with 0 vector \n"); */
608: } else { /* Take an average of the boundary conditions */
609: PetscInt mx=user->mx,my=user->my;
610: PetscScalar **x;
611: PetscInt xs,xm,ys,ym;
613: VecGetArray(user->Top,&top);
614: VecGetArray(user->Bottom,&bottom);
615: VecGetArray(user->Left,&left);
616: VecGetArray(user->Right,&right);
618: /* Get pointers to vector data */
619: DMDAVecGetArray(user->da,X,&x);
620: DMDAGetCorners(user->da,&xs,&ys,NULL,&xm,&ym,NULL);
622: /* Perform local computations */
623: for (j=ys; j<ys+ym; j++) {
624: for (i=xs; i< xs+xm; i++) {
625: x[j][i] = ((j+1)*bottom[i-xs+1]/my+(my-j+1)*top[i-xs+1]/(my+2)+
626: (i+1)*left[j-ys+1]/mx+(mx-i+1)*right[j-ys+1]/(mx+2))/2.0;
627: }
628: }
630: /* Restore vectors */
631: DMDAVecRestoreArray(user->da,X,&x);
632: VecRestoreArray(user->Left,&left);
633: VecRestoreArray(user->Top,&top);
634: VecRestoreArray(user->Bottom,&bottom);
635: VecRestoreArray(user->Right,&right);
636: }
637: return(0);
638: }
642: /*
643: MSA_Plate - Calculates an obstacle for surface to stretch over.
644: */
645: PetscErrorCode MSA_Plate(Vec XL,Vec XU,void *ctx)
646: {
647: AppCtx *user=(AppCtx*)ctx;
649: PetscInt i,j;
650: PetscInt xs,ys,xm,ym;
651: PetscInt mx=user->mx, my=user->my, bmy, bmx;
652: PetscScalar t1,t2,t3;
653: PetscScalar **xl;
654: PetscScalar lb=-PETSC_INFINITY, ub=PETSC_INFINITY;
655: PetscBool cylinder;
657: user->bmy = PetscMax(0,user->bmy);user->bmy = PetscMin(my,user->bmy);
658: user->bmx = PetscMax(0,user->bmx);user->bmx = PetscMin(mx,user->bmx);
660: bmy=user->bmy, bmx=user->bmx;
662: DMDAGetCorners(user->da,&xs,&ys,NULL,&xm,&ym,NULL);
663: VecSet(XL, lb);
664: DMDAVecGetArray(user->da,XL,&xl);
665: VecSet(XU, ub);
667: PetscOptionsHasName(NULL,"-cylinder",&cylinder);
668: /* Compute the optional lower box */
669: if (cylinder) {
670: for (i=xs; i< xs+xm; i++) {
671: for (j=ys; j<ys+ym; j++) {
672: t1=(2.0*i-mx)*bmy;
673: t2=(2.0*j-my)*bmx;
674: t3=bmx*bmx*bmy*bmy;
675: if (t1*t1 + t2*t2 <= t3) xl[j][i] = user->bheight;
676: }
677: }
678: } else {
679: /* Compute the optional lower box */
680: for (i=xs; i< xs+xm; i++) {
681: for (j=ys; j<ys+ym; j++) {
682: if (i>=(mx-bmx)/2 && i<mx-(mx-bmx)/2 &&
683: j>=(my-bmy)/2 && j<my-(my-bmy)/2) {
684: xl[j][i] = user->bheight;
685: }
686: }
687: }
688: }
690: DMDAVecRestoreArray(user->da,XL,&xl);
691: return(0);
692: }