Actual source code: ex3.c

petsc-3.7.1 2016-05-15
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  2: static char help[] = "Newton methods to solve u'' + u^{2} = f in parallel.\n\
  3: This example employs a user-defined monitoring routine and optionally a user-defined\n\
  4: routine to check candidate iterates produced by line search routines.  This code also\n\
  5: demonstrates use of the macro __FUNCT__ to define routine names for use in error handling.\n\
  6: The command line options include:\n\
  7:   -pre_check_iterates : activate checking of iterates\n\
  8:   -post_check_iterates : activate checking of iterates\n\
  9:   -check_tol <tol>: set tolerance for iterate checking\n\n";

 11: /*T
 12:    Concepts: SNES^basic parallel example
 13:    Concepts: SNES^setting a user-defined monitoring routine
 14:    Concepts: error handling^using the macro __FUNCT__ to define routine names;
 15:    Processors: n
 16: T*/

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

 30: #include <petscdm.h>
 31: #include <petscdmda.h>
 32: #include <petscsnes.h>

 34: /*
 35:    User-defined routines.  Note that immediately before each routine below,
 36:    we define the macro __FUNCT__ to be a string containing the routine name.
 37:    If defined, this macro is used in the PETSc error handlers to provide a
 38:    complete traceback of routine names.  All PETSc library routines use this
 39:    macro, and users can optionally employ it as well in their application
 40:    codes.  Note that users can get a traceback of PETSc errors regardless of
 41:    whether they define __FUNCT__ in application codes; this macro merely
 42:    provides the added traceback detail of the application routine names.
 43: */
 44: PetscErrorCode FormJacobian(SNES,Vec,Mat,Mat,void*);
 45: PetscErrorCode FormFunction(SNES,Vec,Vec,void*);
 46: PetscErrorCode FormInitialGuess(Vec);
 47: PetscErrorCode Monitor(SNES,PetscInt,PetscReal,void*);
 48: PetscErrorCode PreCheck(SNESLineSearch,Vec,Vec,PetscBool*,void*);
 49: PetscErrorCode PostCheck(SNESLineSearch,Vec,Vec,Vec,PetscBool*,PetscBool*,void*);
 50: PetscErrorCode PostSetSubKSP(SNESLineSearch,Vec,Vec,Vec,PetscBool*,PetscBool*,void*);
 51: PetscErrorCode MatrixFreePreconditioner(PC,Vec,Vec);

 53: /*
 54:    User-defined application context
 55: */
 56: typedef struct {
 57:   DM          da;      /* distributed array */
 58:   Vec         F;       /* right-hand-side of PDE */
 59:   PetscMPIInt rank;    /* rank of processor */
 60:   PetscMPIInt size;    /* size of communicator */
 61:   PetscReal   h;       /* mesh spacing */
 62: } ApplicationCtx;

 64: /*
 65:    User-defined context for monitoring
 66: */
 67: typedef struct {
 68:   PetscViewer viewer;
 69: } MonitorCtx;

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

 81: typedef struct {
 82:   PetscInt its0; /* num of prevous outer KSP iterations */
 83: } SetSubKSPCtx;

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


105:   PetscInitialize(&argc,&argv,(char*)0,help);
106:   MPI_Comm_rank(PETSC_COMM_WORLD,&ctx.rank);
107:   MPI_Comm_size(PETSC_COMM_WORLD,&ctx.size);
108:   PetscOptionsGetInt(NULL,NULL,"-n",&N,NULL);
109:   ctx.h = 1.0/(N-1);

111:   /* - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -
112:      Create nonlinear solver context
113:      - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - */

115:   SNESCreate(PETSC_COMM_WORLD,&snes);

117:   /* - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -
118:      Create vector data structures; set function evaluation routine
119:      - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - */

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

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

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

145:   /* - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -
146:      Create matrix data structure; set Jacobian evaluation routine
147:      - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - */

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

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

165:   /*
166:      Optional allow user provided preconditioner
167:    */
168:   PetscOptionsHasName(NULL,NULL,"-user_precond",&flg);
169:   if (flg) {
170:     KSP ksp;
171:     PC  pc;
172:     SNESGetKSP(snes,&ksp);
173:     KSPGetPC(ksp,&pc);
174:     PCSetType(pc,PCSHELL);
175:     PCShellSetApply(pc,MatrixFreePreconditioner);
176:   }

178:   /* - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -
179:      Customize nonlinear solver; set runtime options
180:    - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - */

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

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

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

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

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

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

215:     PetscOptionsGetReal(NULL,NULL,"-check_tol",&checkP.tolerance,NULL);
216:   }

218:   PetscOptionsHasName(NULL,NULL,"-post_setsubksp",&post_setsubksp);
219:   if (post_setsubksp) {
220:     PetscPrintf(PETSC_COMM_WORLD,"Activating post setsubksp\n");
221:     SNESLineSearchSetPostCheck(linesearch,PostSetSubKSP,&checkP1);
222:   }

224:   PetscOptionsHasName(NULL,NULL,"-pre_check_iterates",&pre_check);
225:   if (pre_check) {
226:     PetscPrintf(PETSC_COMM_WORLD,"Activating pre step checking routine\n");
227:     SNESLineSearchSetPreCheck(linesearch,PreCheck,&checkP);
228:   }

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

238:   /* - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -
239:      Initialize application:
240:      Store right-hand-side of PDE and exact solution
241:    - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - */

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

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

255:   /*
256:      Compute local vector entries
257:   */
258:   xp = ctx.h*xs;
259:   for (i=xs; i<xs+xm; i++) {
260:     FF[i] = 6.0*xp + PetscPowScalar(xp+1.e-12,6.0); /* +1.e-12 is to prevent 0^6 */
261:     UU[i] = xp*xp*xp;
262:     xp   += ctx.h;
263:   }

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

271:   /* - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -
272:      Evaluate initial guess; then solve nonlinear system
273:    - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - */

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

286:   /* - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -
287:      Check solution and clean up
288:    - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - */

290:   /*
291:      Check the error
292:   */
293:   VecAXPY(x,none,U);
294:   VecNorm(x,NORM_2,&norm);
295:   PetscPrintf(PETSC_COMM_WORLD,"Norm of error %g Iterations %D\n",(double)norm,its);

297:   /*
298:      Free work space.  All PETSc objects should be destroyed when they
299:      are no longer needed.
300:   */
301:   PetscViewerDestroy(&monP.viewer);
302:   if (post_check) {VecDestroy(&checkP.last_step);}
303:   VecDestroy(&x);
304:   VecDestroy(&r);
305:   VecDestroy(&U);
306:   VecDestroy(&F);
307:   MatDestroy(&J);
308:   SNESDestroy(&snes);
309:   DMDestroy(&ctx.da);
310:   PetscFinalize();
311:   return(0);
312: }
313: /* ------------------------------------------------------------------- */
316: /*
317:    FormInitialGuess - Computes initial guess.

319:    Input/Output Parameter:
320: .  x - the solution vector
321: */
322: PetscErrorCode FormInitialGuess(Vec x)
323: {
325:   PetscScalar    pfive = .50;

328:   VecSet(x,pfive);
329:   return(0);
330: }
331: /* ------------------------------------------------------------------- */
334: /*
335:    FormFunction - Evaluates nonlinear function, F(x).

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

342:    Output Parameter:
343: .  f - function vector

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

359:   DMGetLocalVector(da,&xlocal);
360:   /*
361:      Scatter ghost points to local vector, using the 2-step process
362:         DMGlobalToLocalBegin(), DMGlobalToLocalEnd().
363:      By placing code between these two statements, computations can
364:      be done while messages are in transition.
365:   */
366:   DMGlobalToLocalBegin(da,x,INSERT_VALUES,xlocal);
367:   DMGlobalToLocalEnd(da,x,INSERT_VALUES,xlocal);

369:   /*
370:      Get pointers to vector data.
371:        - The vector xlocal includes ghost point; the vectors x and f do
372:          NOT include ghost points.
373:        - Using DMDAVecGetArray() allows accessing the values using global ordering
374:   */
375:   DMDAVecGetArray(da,xlocal,&xx);
376:   DMDAVecGetArray(da,f,&ff);
377:   DMDAVecGetArray(da,user->F,&FF);

379:   /*
380:      Get local grid boundaries (for 1-dimensional DMDA):
381:        xs, xm  - starting grid index, width of local grid (no ghost points)
382:   */
383:   DMDAGetCorners(da,&xs,NULL,NULL,&xm,NULL,NULL);
384:   DMDAGetInfo(da,NULL,&M,NULL,NULL,NULL,NULL,NULL,NULL,NULL,NULL,NULL,NULL,NULL);

386:   /*
387:      Set function values for boundary points; define local interior grid point range:
388:         xsi - starting interior grid index
389:         xei - ending interior grid index
390:   */
391:   if (xs == 0) { /* left boundary */
392:     ff[0] = xx[0];
393:     xs++;xm--;
394:   }
395:   if (xs+xm == M) {  /* right boundary */
396:     ff[xs+xm-1] = xx[xs+xm-1] - 1.0;
397:     xm--;
398:   }

400:   /*
401:      Compute function over locally owned part of the grid (interior points only)
402:   */
403:   d = 1.0/(user->h*user->h);
404:   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];

406:   /*
407:      Restore vectors
408:   */
409:   DMDAVecRestoreArray(da,xlocal,&xx);
410:   DMDAVecRestoreArray(da,f,&ff);
411:   DMDAVecRestoreArray(da,user->F,&FF);
412:   DMRestoreLocalVector(da,&xlocal);
413:   return(0);
414: }
415: /* ------------------------------------------------------------------- */
418: /*
419:    FormJacobian - Evaluates Jacobian matrix.

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

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

440:   /*
441:      Get pointer to vector data
442:   */
443:   DMDAVecGetArrayRead(da,x,&xx);
444:   DMDAGetCorners(da,&xs,NULL,NULL,&xm,NULL,NULL);

446:   /*
447:     Get range of locally owned matrix
448:   */
449:   DMDAGetInfo(da,NULL,&M,NULL,NULL,NULL,NULL,NULL,NULL,NULL,NULL,NULL,NULL,NULL);

451:   /*
452:      Determine starting and ending local indices for interior grid points.
453:      Set Jacobian entries for boundary points.
454:   */

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

459:     MatSetValues(jac,1,&i,1,&i,A,INSERT_VALUES);
460:     xs++;xm--;
461:   }
462:   if (xs+xm == M) { /* right boundary */
463:     i    = M-1;
464:     A[0] = 1.0;
465:     MatSetValues(jac,1,&i,1,&i,A,INSERT_VALUES);
466:     xm--;
467:   }

469:   /*
470:      Interior grid points
471:       - Note that in this case we set all elements for a particular
472:         row at once.
473:   */
474:   d = 1.0/(user->h*user->h);
475:   for (i=xs; i<xs+xm; i++) {
476:     j[0] = i - 1; j[1] = i; j[2] = i + 1;
477:     A[0] = A[2] = d; A[1] = -2.0*d + 2.0*xx[i];
478:     MatSetValues(jac,1,&i,3,j,A,INSERT_VALUES);
479:   }

481:   /*
482:      Assemble matrix, using the 2-step process:
483:        MatAssemblyBegin(), MatAssemblyEnd().
484:      By placing code between these two statements, computations can be
485:      done while messages are in transition.

487:      Also, restore vector.
488:   */

490:   MatAssemblyBegin(jac,MAT_FINAL_ASSEMBLY);
491:   DMDAVecRestoreArrayRead(da,x,&xx);
492:   MatAssemblyEnd(jac,MAT_FINAL_ASSEMBLY);

494:   return(0);
495: }
496: /* ------------------------------------------------------------------- */
499: /*
500:    Monitor - Optional user-defined monitoring routine that views the
501:    current iterate with an x-window plot. Set by SNESMonitorSet().

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

510:    Note:
511:    See the manpage for PetscViewerDrawOpen() for useful runtime options,
512:    such as -nox to deactivate all x-window output.
513:  */
514: PetscErrorCode Monitor(SNES snes,PetscInt its,PetscReal fnorm,void *ctx)
515: {
517:   MonitorCtx     *monP = (MonitorCtx*) ctx;
518:   Vec            x;

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

527: /* ------------------------------------------------------------------- */
530: /*
531:    PreCheck - Optional user-defined routine that checks the validity of
532:    candidate steps of a line search method.  Set by SNESLineSearchSetPreCheck().

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

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

550: /* ------------------------------------------------------------------- */
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",
614:                                  i,(double)PetscAbsScalar(tmp),(double)PetscAbsScalar(xa_last[i]),(double)rdiff,(double)PetscAbsScalar(xa[i]));
615:       }
616:     }
617:     DMDAVecRestoreArray(da,check->last_step,&xa_last);
618:     DMDAVecRestoreArray(da,x,&xa);
619:   }
620:   VecCopy(x,check->last_step);
621:   return(0);
622: }


625: /* ------------------------------------------------------------------- */
628: /*
629:    PostSetSubKSP - Optional user-defined routine that reset SubKSP options when hierarchical bjacobi PC is used
630:    e.g,
631:      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
632:    Set by SNESLineSearchSetPostCheck().

634:    Input Parameters:
635:    linesearch - the LineSearch context
636:    xcurrent - current solution
637:    y - search direction and length
638:    x    - the new candidate iterate

640:    Output Parameters:
641:    y    - proposed step (search direction and length) (possibly changed)
642:    x    - current iterate (possibly modified)

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

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

666:   if (iter) {
667:     PetscPrintf(PETSC_COMM_WORLD,"    ...PostCheck snes iteration %D, ksp_it %d %d, subksp_it %d\n",iter,check->its0,its,sub_its);
668:     ksp_ratio = ((PetscReal)(its))/check->its0;
669:     maxit     = (PetscInt)(ksp_ratio*sub_its + 0.5);
670:     if (maxit < 2) maxit = 2;
671:     KSPSetTolerances(sub_ksp,PETSC_DEFAULT,PETSC_DEFAULT,PETSC_DEFAULT,maxit);
672:     PetscPrintf(PETSC_COMM_WORLD,"    ...ksp_ratio %g, new maxit %d\n\n",ksp_ratio,maxit);
673:   }
674:   check->its0 = its; /* save current outer KSP iteration number */
675:   return(0);
676: }

678: /* ------------------------------------------------------------------- */
679: /*
680:    MatrixFreePreconditioner - This routine demonstrates the use of a
681:    user-provided preconditioner.  This code implements just the null
682:    preconditioner, which of course is not recommended for general use.

684:    Input Parameters:
685: +  pc - preconditioner
686: -  x - input vector

688:    Output Parameter:
689: .  y - preconditioned vector
690: */
691: PetscErrorCode MatrixFreePreconditioner(PC pc,Vec x,Vec y)
692: {
694:   VecCopy(x,y);
695:   return 0;
696: }