Actual source code: ex3.c

petsc-dev 2014-07-25
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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:   -check_iterates : activate checking of iterates\n\
  8:   -check_tol <tol>: set tolerance for iterate checking\n\n";

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

 17: /*
 18:    Include "petscdraw.h" so that we can use distributed arrays (DMDAs).
 19:    Include "petscdraw.h" so that we can use PETSc drawing routines.
 20:    Include "petscsnes.h" so that we can use SNES solvers.  Note that this
 21:    file automatically includes:
 22:      petscsys.h       - base PETSc routines   petscvec.h - vectors
 23:      petscmat.h - matrices
 24:      petscis.h     - index sets            petscksp.h - Krylov subspace methods
 25:      petscviewer.h - viewers               petscpc.h  - preconditioners
 26:      petscksp.h   - linear solvers
 27: */

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

 33: /*
 34:    User-defined routines.  Note that immediately before each routine below,
 35:    we define the macro __FUNCT__ to be a string containing the routine name.
 36:    If defined, this macro is used in the PETSc error handlers to provide a
 37:    complete traceback of routine names.  All PETSc library routines use this
 38:    macro, and users can optionally employ it as well in their application
 39:    codes.  Note that users can get a traceback of PETSc errors regardless of
 40:    whether they define __FUNCT__ in application codes; this macro merely
 41:    provides the added traceback detail of the application routine names.
 42: */
 43: PetscErrorCode FormJacobian(SNES,Vec,Mat,Mat,void*);
 44: PetscErrorCode FormFunction(SNES,Vec,Vec,void*);
 45: PetscErrorCode FormInitialGuess(Vec);
 46: PetscErrorCode Monitor(SNES,PetscInt,PetscReal,void*);
 47: PetscErrorCode PreCheck(SNESLineSearch,Vec,Vec,PetscBool*,void*);
 48: PetscErrorCode PostCheck(SNESLineSearch,Vec,Vec,Vec,PetscBool*,PetscBool*,void*);
 49: PetscErrorCode PostSetSubKSP(SNESLineSearch,Vec,Vec,Vec,PetscBool*,PetscBool*,void*);
 50: PetscErrorCode MatrixFreePreconditioner(PC,Vec,Vec);

 52: /*
 53:    User-defined application context
 54: */
 55: typedef struct {
 56:   DM          da;      /* distributed array */
 57:   Vec         F;       /* right-hand-side of PDE */
 58:   PetscMPIInt rank;    /* rank of processor */
 59:   PetscMPIInt size;    /* size of communicator */
 60:   PetscReal   h;       /* mesh spacing */
 61: } ApplicationCtx;

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

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

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

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


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

110:   /* - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -
111:      Create nonlinear solver context
112:      - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - */

114:   SNESCreate(PETSC_COMM_WORLD,&snes);

116:   /* - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -
117:      Create vector data structures; set function evaluation routine
118:      - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - */

120:   /*
121:      Create distributed array (DMDA) to manage parallel grid and vectors
122:   */
123:   DMDACreate1d(PETSC_COMM_WORLD,DM_BOUNDARY_NONE,N,1,1,NULL,&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:      Optional allow user provided preconditioner
166:    */
167:   PetscOptionsHasName(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,"-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,"-check_tol",&checkP.tolerance,NULL);
215:   }

217:   PetscOptionsHasName(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,"-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);

296:   /*
297:      Free work space.  All PETSc objects should be destroyed when they
298:      are no longer needed.
299:   */
300:   PetscViewerDestroy(&monP.viewer);
301:   if (post_check) {VecDestroy(&checkP.last_step);}
302:   VecDestroy(&x);
303:   VecDestroy(&r);
304:   VecDestroy(&U);
305:   VecDestroy(&F);
306:   MatDestroy(&J);
307:   SNESDestroy(&snes);
308:   DMDestroy(&ctx.da);
309:   PetscFinalize();
310:   return(0);
311: }
312: /* ------------------------------------------------------------------- */
315: /*
316:    FormInitialGuess - Computes initial guess.

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

327:   VecSet(x,pfive);
328:   return(0);
329: }
330: /* ------------------------------------------------------------------- */
333: /*
334:    FormFunction - Evaluates nonlinear function, F(x).

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

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

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

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

368:   /*
369:      Get pointers to vector data.
370:        - The vector xlocal includes ghost point; the vectors x and f do
371:          NOT include ghost points.
372:        - Using DMDAVecGetArray() allows accessing the values using global ordering
373:   */
374:   DMDAVecGetArray(da,xlocal,&xx);
375:   DMDAVecGetArray(da,f,&ff);
376:   DMDAVecGetArray(da,user->F,&FF);

378:   /*
379:      Get local grid boundaries (for 1-dimensional DMDA):
380:        xs, xm  - starting grid index, width of local grid (no ghost points)
381:   */
382:   DMDAGetCorners(da,&xs,NULL,NULL,&xm,NULL,NULL);
383:   DMDAGetInfo(da,NULL,&M,NULL,NULL,NULL,NULL,NULL,NULL,
384:                      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:   DMDAVecGetArray(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,
450:                      NULL,NULL,NULL,NULL,NULL);

452:   /*
453:      Determine starting and ending local indices for interior grid points.
454:      Set Jacobian entries for boundary points.
455:   */

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

460:     MatSetValues(jac,1,&i,1,&i,A,INSERT_VALUES);
461:     xs++;xm--;
462:   }
463:   if (xs+xm == M) { /* right boundary */
464:     i    = M-1;
465:     A[0] = 1.0;
466:     MatSetValues(jac,1,&i,1,&i,A,INSERT_VALUES);
467:     xm--;
468:   }

470:   /*
471:      Interior grid points
472:       - Note that in this case we set all elements for a particular
473:         row at once.
474:   */
475:   d = 1.0/(user->h*user->h);
476:   for (i=xs; i<xs+xm; i++) {
477:     j[0] = i - 1; j[1] = i; j[2] = i + 1;
478:     A[0] = A[2] = d; A[1] = -2.0*d + 2.0*xx[i];
479:     MatSetValues(jac,1,&i,3,j,A,INSERT_VALUES);
480:   }

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

488:      Also, restore vector.
489:   */

491:   MatAssemblyBegin(jac,MAT_FINAL_ASSEMBLY);
492:   DMDAVecRestoreArray(da,x,&xx);
493:   MatAssemblyEnd(jac,MAT_FINAL_ASSEMBLY);

495:   return(0);
496: }
497: /* ------------------------------------------------------------------- */
500: /*
501:    Monitor - Optional user-defined monitoring routine that views the
502:    current iterate with an x-window plot. Set by SNESMonitorSet().

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

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

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

528: /* ------------------------------------------------------------------- */
531: /*
532:    PreCheck - Optional user-defined routine that checks the validity of
533:    candidate steps of a line search method.  Set by SNESLineSearchSetPreCheck().

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

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

551: /* ------------------------------------------------------------------- */
554: /*
555:    PostCheck - Optional user-defined routine that checks the validity of
556:    candidate steps of a line search method.  Set by SNESLineSearchSetPostCheck().

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

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

570:  */
571: PetscErrorCode PostCheck(SNESLineSearch linesearch,Vec xcurrent,Vec y,Vec x,PetscBool  *changed_y,PetscBool  *changed_x, void * ctx)
572: {
574:   PetscInt       i,iter,xs,xm;
575:   StepCheckCtx   *check;
576:   ApplicationCtx *user;
577:   PetscScalar    *xa,*xa_last,tmp;
578:   PetscReal      rdiff;
579:   DM             da;
580:   SNES           snes;

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

586:   SNESLineSearchGetSNES(linesearch, &snes);
587:   check = (StepCheckCtx*)ctx;
588:   user  = check->user;
589:   SNESGetIterationNumber(snes,&iter);
590:   SNESLineSearchGetPreCheck(linesearch, NULL, (void**)&check);

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

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

602:     /*
603:        If we fail the user-defined check for validity of the candidate iterate,
604:        then modify the iterate as we like.  (Note that the particular modification
605:        below is intended simply to demonstrate how to manipulate this data, not
606:        as a meaningful or appropriate choice.)
607:     */
608:     for (i=xs; i<xs+xm; i++) {
609:       if (!PetscAbsScalar(xa[i])) rdiff = 2*check->tolerance;
610:       else rdiff = PetscAbsScalar((xa[i] - xa_last[i])/xa[i]);
611:       if (rdiff > check->tolerance) {
612:         tmp        = xa[i];
613:         xa[i]      = .5*(xa[i] + xa_last[i]);
614:         *changed_x = PETSC_TRUE;
615:         PetscPrintf(PETSC_COMM_WORLD,"  Altering entry %D: x=%g, x_last=%g, diff=%g, x_new=%g\n",
616:                                  i,(double)PetscAbsScalar(tmp),(double)PetscAbsScalar(xa_last[i]),(double)rdiff,(double)PetscAbsScalar(xa[i]));
617:       }
618:     }
619:     DMDAVecRestoreArray(da,check->last_step,&xa_last);
620:     DMDAVecRestoreArray(da,x,&xa);
621:   }
622:   VecCopy(x,check->last_step);
623:   return(0);
624: }


627: /* ------------------------------------------------------------------- */
630: /*
631:    PostSetSubKSP - Optional user-defined routine that reset SubKSP options when hierarchical bjacobi PC is used
632:    e.g,
633:      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
634:    Set by SNESLineSearchSetPostCheck().

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

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

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

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

668:   if (iter) {
669:     PetscPrintf(PETSC_COMM_WORLD,"    ...PostCheck snes iteration %D, ksp_it %d %d, subksp_it %d\n",iter,check->its0,its,sub_its);
670:     ksp_ratio = ((PetscReal)(its))/check->its0;
671:     maxit     = (PetscInt)(ksp_ratio*sub_its + 0.5);
672:     if (maxit < 2) maxit = 2;
673:     KSPSetTolerances(sub_ksp,PETSC_DEFAULT,PETSC_DEFAULT,PETSC_DEFAULT,maxit);
674:     PetscPrintf(PETSC_COMM_WORLD,"    ...ksp_ratio %g, new maxit %d\n\n",ksp_ratio,maxit);
675:   }
676:   check->its0 = its; /* save current outer KSP iteration number */
677:   return(0);
678: }

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

686:    Input Parameters:
687: +  pc - preconditioner
688: -  x - input vector

690:    Output Parameter:
691: .  y - preconditioned vector
692: */
693: PetscErrorCode MatrixFreePreconditioner(PC pc,Vec x,Vec y)
694: {
696:   VecCopy(x,y);
697:   return 0;
698: }