Actual source code: ex3.c

petsc-master 2019-09-23
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  1: static char help[] = "Newton methods to solve u'' + u^{2} = f in parallel.\n\
  2: This example employs a user-defined monitoring routine and optionally a user-defined\n\
  3: routine to check candidate iterates produced by line search routines.\n\
  4: The command line options include:\n\
  5:   -pre_check_iterates : activate checking of iterates\n\
  6:   -post_check_iterates : activate checking of iterates\n\
  7:   -check_tol <tol>: set tolerance for iterate checking\n\
  8:   -user_precond : activate a (trivial) user-defined preconditioner\n\n";

 10: /*T
 11:    Concepts: SNES^basic parallel example
 12:    Concepts: SNES^setting a user-defined monitoring routine
 13:    Processors: n
 14: T*/



 18: /*
 19:    Include "petscdm.h" so that we can use data management objects (DMs)
 20:    Include "petscdmda.h" so that we can use distributed arrays (DMDAs).
 21:    Include "petscsnes.h" so that we can use SNES solvers.  Note that this
 22:    file automatically includes:
 23:      petscsys.h    - base PETSc routines
 24:      petscvec.h    - vectors
 25:      petscmat.h    - matrices
 26:      petscis.h     - index sets
 27:      petscksp.h    - Krylov subspace methods
 28:      petscviewer.h - viewers
 29:      petscpc.h     - preconditioners
 30:      petscksp.h    - linear solvers
 31: */

 33:  #include <petscdm.h>
 34:  #include <petscdmda.h>
 35:  #include <petscsnes.h>

 37: /*
 38:    User-defined routines.
 39: */
 40: PetscErrorCode FormJacobian(SNES,Vec,Mat,Mat,void*);
 41: PetscErrorCode FormFunction(SNES,Vec,Vec,void*);
 42: PetscErrorCode FormInitialGuess(Vec);
 43: PetscErrorCode Monitor(SNES,PetscInt,PetscReal,void*);
 44: PetscErrorCode PreCheck(SNESLineSearch,Vec,Vec,PetscBool*,void*);
 45: PetscErrorCode PostCheck(SNESLineSearch,Vec,Vec,Vec,PetscBool*,PetscBool*,void*);
 46: PetscErrorCode PostSetSubKSP(SNESLineSearch,Vec,Vec,Vec,PetscBool*,PetscBool*,void*);
 47: PetscErrorCode MatrixFreePreconditioner(PC,Vec,Vec);

 49: /*
 50:    User-defined application context
 51: */
 52: typedef struct {
 53:   DM          da;      /* distributed array */
 54:   Vec         F;       /* right-hand-side of PDE */
 55:   PetscMPIInt rank;    /* rank of processor */
 56:   PetscMPIInt size;    /* size of communicator */
 57:   PetscReal   h;       /* mesh spacing */
 58:   PetscBool   sjerr;   /* if or not to test jacobian domain error */
 59: } ApplicationCtx;

 61: /*
 62:    User-defined context for monitoring
 63: */
 64: typedef struct {
 65:   PetscViewer viewer;
 66: } MonitorCtx;

 68: /*
 69:    User-defined context for checking candidate iterates that are
 70:    determined by line search methods
 71: */
 72: typedef struct {
 73:   Vec            last_step;  /* previous iterate */
 74:   PetscReal      tolerance;  /* tolerance for changes between successive iterates */
 75:   ApplicationCtx *user;
 76: } StepCheckCtx;

 78: typedef struct {
 79:   PetscInt its0; /* num of prevous outer KSP iterations */
 80: } SetSubKSPCtx;

 82: int main(int argc,char **argv)
 83: {
 84:   SNES           snes;                 /* SNES context */
 85:   SNESLineSearch linesearch;           /* SNESLineSearch context */
 86:   Mat            J;                    /* Jacobian matrix */
 87:   ApplicationCtx ctx;                  /* user-defined context */
 88:   Vec            x,r,U,F;              /* vectors */
 89:   MonitorCtx     monP;                 /* monitoring context */
 90:   StepCheckCtx   checkP;               /* step-checking context */
 91:   SetSubKSPCtx   checkP1;
 92:   PetscBool      pre_check,post_check,post_setsubksp; /* flag indicating whether we're checking candidate iterates */
 93:   PetscScalar    xp,*FF,*UU,none = -1.0;
 95:   PetscInt       its,N = 5,i,maxit,maxf,xs,xm;
 96:   PetscReal      abstol,rtol,stol,norm;
 97:   PetscBool      flg;


100:   PetscInitialize(&argc,&argv,(char*)0,help);if (ierr) return ierr;
101:   MPI_Comm_rank(PETSC_COMM_WORLD,&ctx.rank);
102:   MPI_Comm_size(PETSC_COMM_WORLD,&ctx.size);
103:   PetscOptionsGetInt(NULL,NULL,"-n",&N,NULL);
104:   ctx.h = 1.0/(N-1);
105:   ctx.sjerr = PETSC_FALSE;
106:   PetscOptionsGetBool(NULL,NULL,"-test_jacobian_domain_error",&ctx.sjerr,NULL);

108:   /* - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -
109:      Create nonlinear solver context
110:      - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - */

112:   SNESCreate(PETSC_COMM_WORLD,&snes);

114:   /* - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -
115:      Create vector data structures; set function evaluation routine
116:      - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - */

118:   /*
119:      Create distributed array (DMDA) to manage parallel grid and vectors
120:   */
121:   DMDACreate1d(PETSC_COMM_WORLD,DM_BOUNDARY_NONE,N,1,1,NULL,&ctx.da);
122:   DMSetFromOptions(ctx.da);
123:   DMSetUp(ctx.da);

125:   /*
126:      Extract global and local vectors from DMDA; then duplicate for remaining
127:      vectors that are the same types
128:   */
129:   DMCreateGlobalVector(ctx.da,&x);
130:   VecDuplicate(x,&r);
131:   VecDuplicate(x,&F); ctx.F = F;
132:   VecDuplicate(x,&U);

134:   /*
135:      Set function evaluation routine and vector.  Whenever the nonlinear
136:      solver needs to compute the nonlinear function, it will call this
137:      routine.
138:       - Note that the final routine argument is the user-defined
139:         context that provides application-specific data for the
140:         function evaluation routine.
141:   */
142:   SNESSetFunction(snes,r,FormFunction,&ctx);

144:   /* - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -
145:      Create matrix data structure; set Jacobian evaluation routine
146:      - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - */

148:   MatCreate(PETSC_COMM_WORLD,&J);
149:   MatSetSizes(J,PETSC_DECIDE,PETSC_DECIDE,N,N);
150:   MatSetFromOptions(J);
151:   MatSeqAIJSetPreallocation(J,3,NULL);
152:   MatMPIAIJSetPreallocation(J,3,NULL,3,NULL);

154:   /*
155:      Set Jacobian matrix data structure and default Jacobian evaluation
156:      routine.  Whenever the nonlinear solver needs to compute the
157:      Jacobian matrix, it will call this routine.
158:       - Note that the final routine argument is the user-defined
159:         context that provides application-specific data for the
160:         Jacobian evaluation routine.
161:   */
162:   SNESSetJacobian(snes,J,J,FormJacobian,&ctx);

164:   /*
165:      Optionally allow user-provided preconditioner
166:    */
167:   PetscOptionsHasName(NULL,NULL,"-user_precond",&flg);
168:   if (flg) {
169:     KSP ksp;
170:     PC  pc;
171:     SNESGetKSP(snes,&ksp);
172:     KSPGetPC(ksp,&pc);
173:     PCSetType(pc,PCSHELL);
174:     PCShellSetApply(pc,MatrixFreePreconditioner);
175:   }

177:   /* - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -
178:      Customize nonlinear solver; set runtime options
179:    - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - */

181:   /*
182:      Set an optional user-defined monitoring routine
183:   */
184:   PetscViewerDrawOpen(PETSC_COMM_WORLD,0,0,0,0,400,400,&monP.viewer);
185:   SNESMonitorSet(snes,Monitor,&monP,0);

187:   /*
188:      Set names for some vectors to facilitate monitoring (optional)
189:   */
190:   PetscObjectSetName((PetscObject)x,"Approximate Solution");
191:   PetscObjectSetName((PetscObject)U,"Exact Solution");

193:   /*
194:      Set SNES/KSP/KSP/PC runtime options, e.g.,
195:          -snes_view -snes_monitor -ksp_type <ksp> -pc_type <pc>
196:   */
197:   SNESSetFromOptions(snes);

199:   /*
200:      Set an optional user-defined routine to check the validity of candidate
201:      iterates that are determined by line search methods
202:   */
203:   SNESGetLineSearch(snes, &linesearch);
204:   PetscOptionsHasName(NULL,NULL,"-post_check_iterates",&post_check);

206:   if (post_check) {
207:     PetscPrintf(PETSC_COMM_WORLD,"Activating post step checking routine\n");
208:     SNESLineSearchSetPostCheck(linesearch,PostCheck,&checkP);
209:     VecDuplicate(x,&(checkP.last_step));

211:     checkP.tolerance = 1.0;
212:     checkP.user      = &ctx;

214:     PetscOptionsGetReal(NULL,NULL,"-check_tol",&checkP.tolerance,NULL);
215:   }

217:   PetscOptionsHasName(NULL,NULL,"-post_setsubksp",&post_setsubksp);
218:   if (post_setsubksp) {
219:     PetscPrintf(PETSC_COMM_WORLD,"Activating post setsubksp\n");
220:     SNESLineSearchSetPostCheck(linesearch,PostSetSubKSP,&checkP1);
221:   }

223:   PetscOptionsHasName(NULL,NULL,"-pre_check_iterates",&pre_check);
224:   if (pre_check) {
225:     PetscPrintf(PETSC_COMM_WORLD,"Activating pre step checking routine\n");
226:     SNESLineSearchSetPreCheck(linesearch,PreCheck,&checkP);
227:   }

229:   /*
230:      Print parameters used for convergence testing (optional) ... just
231:      to demonstrate this routine; this information is also printed with
232:      the option -snes_view
233:   */
234:   SNESGetTolerances(snes,&abstol,&rtol,&stol,&maxit,&maxf);
235:   PetscPrintf(PETSC_COMM_WORLD,"atol=%g, rtol=%g, stol=%g, maxit=%D, maxf=%D\n",(double)abstol,(double)rtol,(double)stol,maxit,maxf);

237:   /* - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -
238:      Initialize application:
239:      Store right-hand-side of PDE and exact solution
240:    - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - */

242:   /*
243:      Get local grid boundaries (for 1-dimensional DMDA):
244:        xs, xm - starting grid index, width of local grid (no ghost points)
245:   */
246:   DMDAGetCorners(ctx.da,&xs,NULL,NULL,&xm,NULL,NULL);

248:   /*
249:      Get pointers to vector data
250:   */
251:   DMDAVecGetArray(ctx.da,F,&FF);
252:   DMDAVecGetArray(ctx.da,U,&UU);

254:   /*
255:      Compute local vector entries
256:   */
257:   xp = ctx.h*xs;
258:   for (i=xs; i<xs+xm; i++) {
259:     FF[i] = 6.0*xp + PetscPowScalar(xp+1.e-12,6.0); /* +1.e-12 is to prevent 0^6 */
260:     UU[i] = xp*xp*xp;
261:     xp   += ctx.h;
262:   }

264:   /*
265:      Restore vectors
266:   */
267:   DMDAVecRestoreArray(ctx.da,F,&FF);
268:   DMDAVecRestoreArray(ctx.da,U,&UU);

270:   /* - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -
271:      Evaluate initial guess; then solve nonlinear system
272:    - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - */

274:   /*
275:      Note: The user should initialize the vector, x, with the initial guess
276:      for the nonlinear solver prior to calling SNESSolve().  In particular,
277:      to employ an initial guess of zero, the user should explicitly set
278:      this vector to zero by calling VecSet().
279:   */
280:   FormInitialGuess(x);
281:   SNESSolve(snes,NULL,x);
282:   SNESGetIterationNumber(snes,&its);
283:   PetscPrintf(PETSC_COMM_WORLD,"Number of SNES iterations = %D\n",its);

285:   /* - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -
286:      Check solution and clean up
287:    - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - */

289:   /*
290:      Check the error
291:   */
292:   VecAXPY(x,none,U);
293:   VecNorm(x,NORM_2,&norm);
294:   PetscPrintf(PETSC_COMM_WORLD,"Norm of error %g Iterations %D\n",(double)norm,its);
295:   if (ctx.sjerr) {
296:     SNESType       snestype;
297:     SNESGetType(snes,&snestype);
298:     PetscPrintf(PETSC_COMM_WORLD,"SNES Type %s\n",snestype);
299:   }

301:   /*
302:      Free work space.  All PETSc objects should be destroyed when they
303:      are no longer needed.
304:   */
305:   PetscViewerDestroy(&monP.viewer);
306:   if (post_check) {VecDestroy(&checkP.last_step);}
307:   VecDestroy(&x);
308:   VecDestroy(&r);
309:   VecDestroy(&U);
310:   VecDestroy(&F);
311:   MatDestroy(&J);
312:   SNESDestroy(&snes);
313:   DMDestroy(&ctx.da);
314:   PetscFinalize();
315:   return ierr;
316: }

318: /* ------------------------------------------------------------------- */
319: /*
320:    FormInitialGuess - Computes initial guess.

322:    Input/Output Parameter:
323: .  x - the solution vector
324: */
325: PetscErrorCode FormInitialGuess(Vec x)
326: {
328:   PetscScalar    pfive = .50;

331:   VecSet(x,pfive);
332:   return(0);
333: }

335: /* ------------------------------------------------------------------- */
336: /*
337:    FormFunction - Evaluates nonlinear function, F(x).

339:    Input Parameters:
340: .  snes - the SNES context
341: .  x - input vector
342: .  ctx - optional user-defined context, as set by SNESSetFunction()

344:    Output Parameter:
345: .  f - function vector

347:    Note:
348:    The user-defined context can contain any application-specific
349:    data needed for the function evaluation.
350: */
351: PetscErrorCode FormFunction(SNES snes,Vec x,Vec f,void *ctx)
352: {
353:   ApplicationCtx *user = (ApplicationCtx*) ctx;
354:   DM             da    = user->da;
355:   PetscScalar    *xx,*ff,*FF,d;
357:   PetscInt       i,M,xs,xm;
358:   Vec            xlocal;

361:   DMGetLocalVector(da,&xlocal);
362:   /*
363:      Scatter ghost points to local vector, using the 2-step process
364:         DMGlobalToLocalBegin(), DMGlobalToLocalEnd().
365:      By placing code between these two statements, computations can
366:      be done while messages are in transition.
367:   */
368:   DMGlobalToLocalBegin(da,x,INSERT_VALUES,xlocal);
369:   DMGlobalToLocalEnd(da,x,INSERT_VALUES,xlocal);

371:   /*
372:      Get pointers to vector data.
373:        - The vector xlocal includes ghost point; the vectors x and f do
374:          NOT include ghost points.
375:        - Using DMDAVecGetArray() allows accessing the values using global ordering
376:   */
377:   DMDAVecGetArray(da,xlocal,&xx);
378:   DMDAVecGetArray(da,f,&ff);
379:   DMDAVecGetArray(da,user->F,&FF);

381:   /*
382:      Get local grid boundaries (for 1-dimensional DMDA):
383:        xs, xm  - starting grid index, width of local grid (no ghost points)
384:   */
385:   DMDAGetCorners(da,&xs,NULL,NULL,&xm,NULL,NULL);
386:   DMDAGetInfo(da,NULL,&M,NULL,NULL,NULL,NULL,NULL,NULL,NULL,NULL,NULL,NULL,NULL);

388:   /*
389:      Set function values for boundary points; define local interior grid point range:
390:         xsi - starting interior grid index
391:         xei - ending interior grid index
392:   */
393:   if (xs == 0) { /* left boundary */
394:     ff[0] = xx[0];
395:     xs++;xm--;
396:   }
397:   if (xs+xm == M) {  /* right boundary */
398:     ff[xs+xm-1] = xx[xs+xm-1] - 1.0;
399:     xm--;
400:   }

402:   /*
403:      Compute function over locally owned part of the grid (interior points only)
404:   */
405:   d = 1.0/(user->h*user->h);
406:   for (i=xs; i<xs+xm; i++) ff[i] = d*(xx[i-1] - 2.0*xx[i] + xx[i+1]) + xx[i]*xx[i] - FF[i];

408:   /*
409:      Restore vectors
410:   */
411:   DMDAVecRestoreArray(da,xlocal,&xx);
412:   DMDAVecRestoreArray(da,f,&ff);
413:   DMDAVecRestoreArray(da,user->F,&FF);
414:   DMRestoreLocalVector(da,&xlocal);
415:   return(0);
416: }

418: /* ------------------------------------------------------------------- */
419: /*
420:    FormJacobian - Evaluates Jacobian matrix.

422:    Input Parameters:
423: .  snes - the SNES context
424: .  x - input vector
425: .  dummy - optional user-defined context (not used here)

427:    Output Parameters:
428: .  jac - Jacobian matrix
429: .  B - optionally different preconditioning matrix
430: .  flag - flag indicating matrix structure
431: */
432: PetscErrorCode FormJacobian(SNES snes,Vec x,Mat jac,Mat B,void *ctx)
433: {
434:   ApplicationCtx *user = (ApplicationCtx*) ctx;
435:   PetscScalar    *xx,d,A[3];
437:   PetscInt       i,j[3],M,xs,xm;
438:   DM             da = user->da;

441:   if (user->sjerr) {
442:     SNESSetJacobianDomainError(snes);
443:     return(0);
444:   }
445:   /*
446:      Get pointer to vector data
447:   */
448:   DMDAVecGetArrayRead(da,x,&xx);
449:   DMDAGetCorners(da,&xs,NULL,NULL,&xm,NULL,NULL);

451:   /*
452:     Get range of locally owned matrix
453:   */
454:   DMDAGetInfo(da,NULL,&M,NULL,NULL,NULL,NULL,NULL,NULL,NULL,NULL,NULL,NULL,NULL);

456:   /*
457:      Determine starting and ending local indices for interior grid points.
458:      Set Jacobian entries for boundary points.
459:   */

461:   if (xs == 0) {  /* left boundary */
462:     i = 0; A[0] = 1.0;

464:     MatSetValues(jac,1,&i,1,&i,A,INSERT_VALUES);
465:     xs++;xm--;
466:   }
467:   if (xs+xm == M) { /* right boundary */
468:     i    = M-1;
469:     A[0] = 1.0;
470:     MatSetValues(jac,1,&i,1,&i,A,INSERT_VALUES);
471:     xm--;
472:   }

474:   /*
475:      Interior grid points
476:       - Note that in this case we set all elements for a particular
477:         row at once.
478:   */
479:   d = 1.0/(user->h*user->h);
480:   for (i=xs; i<xs+xm; i++) {
481:     j[0] = i - 1; j[1] = i; j[2] = i + 1;
482:     A[0] = A[2] = d; A[1] = -2.0*d + 2.0*xx[i];
483:     MatSetValues(jac,1,&i,3,j,A,INSERT_VALUES);
484:   }

486:   /*
487:      Assemble matrix, using the 2-step process:
488:        MatAssemblyBegin(), MatAssemblyEnd().
489:      By placing code between these two statements, computations can be
490:      done while messages are in transition.

492:      Also, restore vector.
493:   */

495:   MatAssemblyBegin(jac,MAT_FINAL_ASSEMBLY);
496:   DMDAVecRestoreArrayRead(da,x,&xx);
497:   MatAssemblyEnd(jac,MAT_FINAL_ASSEMBLY);

499:   return(0);
500: }

502: /* ------------------------------------------------------------------- */
503: /*
504:    Monitor - Optional user-defined monitoring routine that views the
505:    current iterate with an x-window plot. Set by SNESMonitorSet().

507:    Input Parameters:
508:    snes - the SNES context
509:    its - iteration number
510:    norm - 2-norm function value (may be estimated)
511:    ctx - optional user-defined context for private data for the
512:          monitor routine, as set by SNESMonitorSet()

514:    Note:
515:    See the manpage for PetscViewerDrawOpen() for useful runtime options,
516:    such as -nox to deactivate all x-window output.
517:  */
518: PetscErrorCode Monitor(SNES snes,PetscInt its,PetscReal fnorm,void *ctx)
519: {
521:   MonitorCtx     *monP = (MonitorCtx*) ctx;
522:   Vec            x;

525:   PetscPrintf(PETSC_COMM_WORLD,"iter = %D,SNES Function norm %g\n",its,(double)fnorm);
526:   SNESGetSolution(snes,&x);
527:   VecView(x,monP->viewer);
528:   return(0);
529: }

531: /* ------------------------------------------------------------------- */
532: /*
533:    PreCheck - Optional user-defined routine that checks the validity of
534:    candidate steps of a line search method.  Set by SNESLineSearchSetPreCheck().

536:    Input Parameters:
537:    snes - the SNES context
538:    xcurrent - current solution
539:    y - search direction and length

541:    Output Parameters:
542:    y         - proposed step (search direction and length) (possibly changed)
543:    changed_y - tells if the step has changed or not
544:  */
545: PetscErrorCode PreCheck(SNESLineSearch linesearch,Vec xcurrent,Vec y, PetscBool *changed_y, void * ctx)
546: {
548:   *changed_y = PETSC_FALSE;
549:   return(0);
550: }

552: /* ------------------------------------------------------------------- */
553: /*
554:    PostCheck - Optional user-defined routine that checks the validity of
555:    candidate steps of a line search method.  Set by SNESLineSearchSetPostCheck().

557:    Input Parameters:
558:    snes - the SNES context
559:    ctx  - optional user-defined context for private data for the
560:           monitor routine, as set by SNESLineSearchSetPostCheck()
561:    xcurrent - current solution
562:    y - search direction and length
563:    x    - the new candidate iterate

565:    Output Parameters:
566:    y    - proposed step (search direction and length) (possibly changed)
567:    x    - current iterate (possibly modified)

569:  */
570: PetscErrorCode PostCheck(SNESLineSearch linesearch,Vec xcurrent,Vec y,Vec x,PetscBool  *changed_y,PetscBool  *changed_x, void * ctx)
571: {
573:   PetscInt       i,iter,xs,xm;
574:   StepCheckCtx   *check;
575:   ApplicationCtx *user;
576:   PetscScalar    *xa,*xa_last,tmp;
577:   PetscReal      rdiff;
578:   DM             da;
579:   SNES           snes;

582:   *changed_x = PETSC_FALSE;
583:   *changed_y = PETSC_FALSE;

585:   SNESLineSearchGetSNES(linesearch, &snes);
586:   check = (StepCheckCtx*)ctx;
587:   user  = check->user;
588:   SNESGetIterationNumber(snes,&iter);

590:   /* iteration 1 indicates we are working on the second iteration */
591:   if (iter > 0) {
592:     da   = user->da;
593:     PetscPrintf(PETSC_COMM_WORLD,"Checking candidate step at iteration %D with tolerance %g\n",iter,(double)check->tolerance);

595:     /* Access local array data */
596:     DMDAVecGetArray(da,check->last_step,&xa_last);
597:     DMDAVecGetArray(da,x,&xa);
598:     DMDAGetCorners(da,&xs,NULL,NULL,&xm,NULL,NULL);

600:     /*
601:        If we fail the user-defined check for validity of the candidate iterate,
602:        then modify the iterate as we like.  (Note that the particular modification
603:        below is intended simply to demonstrate how to manipulate this data, not
604:        as a meaningful or appropriate choice.)
605:     */
606:     for (i=xs; i<xs+xm; i++) {
607:       if (!PetscAbsScalar(xa[i])) rdiff = 2*check->tolerance;
608:       else rdiff = PetscAbsScalar((xa[i] - xa_last[i])/xa[i]);
609:       if (rdiff > check->tolerance) {
610:         tmp        = xa[i];
611:         xa[i]      = .5*(xa[i] + xa_last[i]);
612:         *changed_x = PETSC_TRUE;
613:         PetscPrintf(PETSC_COMM_WORLD,"  Altering entry %D: x=%g, x_last=%g, diff=%g, x_new=%g\n",i,(double)PetscAbsScalar(tmp),(double)PetscAbsScalar(xa_last[i]),(double)rdiff,(double)PetscAbsScalar(xa[i]));
614:       }
615:     }
616:     DMDAVecRestoreArray(da,check->last_step,&xa_last);
617:     DMDAVecRestoreArray(da,x,&xa);
618:   }
619:   VecCopy(x,check->last_step);
620:   return(0);
621: }

623: /* ------------------------------------------------------------------- */
624: /*
625:    PostSetSubKSP - Optional user-defined routine that reset SubKSP options when hierarchical bjacobi PC is used
626:    e.g,
627:      mpiexec -n 8 ./ex3 -nox -n 10000 -ksp_type fgmres -pc_type bjacobi -pc_bjacobi_blocks 4 -sub_ksp_type gmres -sub_ksp_max_it 3 -post_setsubksp -sub_ksp_rtol 1.e-16
628:    Set by SNESLineSearchSetPostCheck().

630:    Input Parameters:
631:    linesearch - the LineSearch context
632:    xcurrent - current solution
633:    y - search direction and length
634:    x    - the new candidate iterate

636:    Output Parameters:
637:    y    - proposed step (search direction and length) (possibly changed)
638:    x    - current iterate (possibly modified)

640:  */
641: PetscErrorCode PostSetSubKSP(SNESLineSearch linesearch,Vec xcurrent,Vec y,Vec x,PetscBool  *changed_y,PetscBool  *changed_x, void * ctx)
642: {
644:   SetSubKSPCtx   *check;
645:   PetscInt       iter,its,sub_its,maxit;
646:   KSP            ksp,sub_ksp,*sub_ksps;
647:   PC             pc;
648:   PetscReal      ksp_ratio;
649:   SNES           snes;

652:   SNESLineSearchGetSNES(linesearch, &snes);
653:   check   = (SetSubKSPCtx*)ctx;
654:   SNESGetIterationNumber(snes,&iter);
655:   SNESGetKSP(snes,&ksp);
656:   KSPGetPC(ksp,&pc);
657:   PCBJacobiGetSubKSP(pc,NULL,NULL,&sub_ksps);
658:   sub_ksp = sub_ksps[0];
659:   KSPGetIterationNumber(ksp,&its);      /* outer KSP iteration number */
660:   KSPGetIterationNumber(sub_ksp,&sub_its); /* inner KSP iteration number */

662:   if (iter) {
663:     PetscPrintf(PETSC_COMM_WORLD,"    ...PostCheck snes iteration %D, ksp_it %D %D, subksp_it %D\n",iter,check->its0,its,sub_its);
664:     ksp_ratio = ((PetscReal)(its))/check->its0;
665:     maxit     = (PetscInt)(ksp_ratio*sub_its + 0.5);
666:     if (maxit < 2) maxit = 2;
667:     KSPSetTolerances(sub_ksp,PETSC_DEFAULT,PETSC_DEFAULT,PETSC_DEFAULT,maxit);
668:     PetscPrintf(PETSC_COMM_WORLD,"    ...ksp_ratio %g, new maxit %D\n\n",(double)ksp_ratio,maxit);
669:   }
670:   check->its0 = its; /* save current outer KSP iteration number */
671:   return(0);
672: }

674: /* ------------------------------------------------------------------- */
675: /*
676:    MatrixFreePreconditioner - This routine demonstrates the use of a
677:    user-provided preconditioner.  This code implements just the null
678:    preconditioner, which of course is not recommended for general use.

680:    Input Parameters:
681: +  pc - preconditioner
682: -  x - input vector

684:    Output Parameter:
685: .  y - preconditioned vector
686: */
687: PetscErrorCode MatrixFreePreconditioner(PC pc,Vec x,Vec y)
688: {
690:   VecCopy(x,y);
691:   return 0;
692: }


695: /*TEST

697:    test:
698:       args: -nox -snes_monitor_cancel -snes_monitor_short -ksp_gmres_cgs_refinement_type refine_always

700:    test:
701:       suffix: 2
702:       nsize: 3
703:       args: -nox -pc_type asm -mat_type mpiaij -snes_monitor_cancel -snes_monitor_short -ksp_gmres_cgs_refinement_type refine_always

705:    test:
706:       suffix: 3
707:       nsize: 2
708:       args: -nox -snes_monitor_cancel -snes_monitor_short -ksp_gmres_cgs_refinement_type refine_always

710:    test:
711:       suffix: 4
712:       args: -nox -pre_check_iterates -post_check_iterates

714:    test:
715:       suffix: 5
716:       requires: double !complex !single
717:       nsize: 2
718:       args: -nox -snes_test_jacobian  -snes_test_jacobian_view

720:    test:
721:       suffix: 6
722:       requires: double !complex !single
723:       nsize: 4
724:       args: -test_jacobian_domain_error -snes_converged_reason -snes_check_jacobian_domain_error 1

726:    test:
727:       suffix: 7
728:       requires: double !complex !single
729:       nsize: 4
730:       args: -test_jacobian_domain_error -snes_converged_reason -snes_type newtontr -snes_check_jacobian_domain_error 1

732:    test:
733:       suffix: 8
734:       requires: double !complex !single
735:       nsize: 4
736:       args: -test_jacobian_domain_error -snes_converged_reason -snes_type vinewtonrsls -snes_check_jacobian_domain_error 1

738:    test:
739:       suffix: 9
740:       requires: double !complex !single
741:       nsize: 4
742:       args: -test_jacobian_domain_error -snes_converged_reason -snes_type vinewtonssls -snes_check_jacobian_domain_error 1

744:    test:
745:       suffix: 10
746:       requires: double !complex !single
747:       nsize: 4
748:       args: -test_jacobian_domain_error -snes_converged_reason -snes_type qn -snes_qn_scale_type jacobian -snes_check_jacobian_domain_error 1

750:    test:
751:       suffix: 11
752:       requires: double !complex !single
753:       nsize: 4
754:       args: -test_jacobian_domain_error -snes_converged_reason -snes_type ms -snes_check_jacobian_domain_error 1

756: TEST*/