Actual source code: itfunc.c

  1: #define PETSCKSP_DLL

  3: /*
  4:       Interface KSP routines that the user calls.
  5: */

 7:  #include src/ksp/ksp/kspimpl.h

 11: /*@
 12:    KSPComputeExtremeSingularValues - Computes the extreme singular values
 13:    for the preconditioned operator. Called after or during KSPSolve().

 15:    Not Collective

 17:    Input Parameter:
 18: .  ksp - iterative context obtained from KSPCreate()

 20:    Output Parameters:
 21: .  emin, emax - extreme singular values

 23:    Notes:
 24:    One must call KSPSetComputeSingularValues() before calling KSPSetUp() 
 25:    (or use the option -ksp_compute_eigenvalues) in order for this routine to work correctly.

 27:    Many users may just want to use the monitoring routine
 28:    KSPSingularValueMonitor() (which can be set with option -ksp_singmonitor)
 29:    to print the extreme singular values at each iteration of the linear solve.

 31:    Level: advanced

 33: .keywords: KSP, compute, extreme, singular, values

 35: .seealso: KSPSetComputeSingularValues(), KSPSingularValueMonitor(), KSPComputeEigenvalues()
 36: @*/
 37: PetscErrorCode PETSCKSP_DLLEXPORT KSPComputeExtremeSingularValues(KSP ksp,PetscReal *emax,PetscReal *emin)
 38: {

 45:   if (!ksp->calc_sings) {
 46:     SETERRQ(4,"Singular values not requested before KSPSetUp()");
 47:   }

 49:   if (ksp->ops->computeextremesingularvalues) {
 50:     (*ksp->ops->computeextremesingularvalues)(ksp,emax,emin);
 51:   } else {
 52:     *emin = -1.0;
 53:     *emax = -1.0;
 54:   }
 55:   return(0);
 56: }

 60: /*@
 61:    KSPComputeEigenvalues - Computes the extreme eigenvalues for the
 62:    preconditioned operator. Called after or during KSPSolve().

 64:    Not Collective

 66:    Input Parameter:
 67: +  ksp - iterative context obtained from KSPCreate()
 68: -  n - size of arrays r and c. The number of eigenvalues computed (neig) will, in 
 69:        general, be less than this.

 71:    Output Parameters:
 72: +  r - real part of computed eigenvalues
 73: .  c - complex part of computed eigenvalues
 74: -  neig - number of eigenvalues computed (will be less than or equal to n)

 76:    Options Database Keys:
 77: +  -ksp_compute_eigenvalues - Prints eigenvalues to stdout
 78: -  -ksp_plot_eigenvalues - Plots eigenvalues in an x-window display

 80:    Notes:
 81:    The number of eigenvalues estimated depends on the size of the Krylov space
 82:    generated during the KSPSolve() ; for example, with 
 83:    CG it corresponds to the number of CG iterations, for GMRES it is the number 
 84:    of GMRES iterations SINCE the last restart. Any extra space in r[] and c[]
 85:    will be ignored.

 87:    KSPComputeEigenvalues() does not usually provide accurate estimates; it is
 88:    intended only for assistance in understanding the convergence of iterative 
 89:    methods, not for eigenanalysis. 

 91:    One must call KSPSetComputeEigenvalues() before calling KSPSetUp() 
 92:    in order for this routine to work correctly.

 94:    Many users may just want to use the monitoring routine
 95:    KSPSingularValueMonitor() (which can be set with option -ksp_singmonitor)
 96:    to print the singular values at each iteration of the linear solve.

 98:    Level: advanced

100: .keywords: KSP, compute, extreme, singular, values

102: .seealso: KSPSetComputeSingularValues(), KSPSingularValueMonitor(), KSPComputeExtremeSingularValues()
103: @*/
104: PetscErrorCode PETSCKSP_DLLEXPORT KSPComputeEigenvalues(KSP ksp,PetscInt n,PetscReal *r,PetscReal *c,PetscInt *neig)
105: {

113:   if (!ksp->calc_sings) {
114:     SETERRQ(4,"Eigenvalues not requested before KSPSetUp()");
115:   }

117:   if (ksp->ops->computeeigenvalues) {
118:     (*ksp->ops->computeeigenvalues)(ksp,n,r,c,neig);
119:   } else {
120:     *neig = 0;
121:   }
122:   return(0);
123: }

127: /*@
128:    KSPSetUpOnBlocks - Sets up the preconditioner for each block in
129:    the block Jacobi, block Gauss-Seidel, and overlapping Schwarz 
130:    methods.

132:    Collective on KSP

134:    Input Parameter:
135: .  ksp - the KSP context

137:    Notes:
138:    KSPSetUpOnBlocks() is a routine that the user can optinally call for
139:    more precise profiling (via -log_summary) of the setup phase for these
140:    block preconditioners.  If the user does not call KSPSetUpOnBlocks(),
141:    it will automatically be called from within KSPSolve().
142:    
143:    Calling KSPSetUpOnBlocks() is the same as calling PCSetUpOnBlocks()
144:    on the PC context within the KSP context.

146:    Level: advanced

148: .keywords: KSP, setup, blocks

150: .seealso: PCSetUpOnBlocks(), KSPSetUp(), PCSetUp()
151: @*/
152: PetscErrorCode PETSCKSP_DLLEXPORT KSPSetUpOnBlocks(KSP ksp)
153: {

158:   PCSetUpOnBlocks(ksp->pc);
159:   return(0);
160: }

164: /*@
165:    KSPSetUp - Sets up the internal data structures for the
166:    later use of an iterative solver.

168:    Collective on KSP

170:    Input Parameter:
171: .  ksp   - iterative context obtained from KSPCreate()

173:    Level: developer

175: .keywords: KSP, setup

177: .seealso: KSPCreate(), KSPSolve(), KSPDestroy()
178: @*/
179: PetscErrorCode PETSCKSP_DLLEXPORT KSPSetUp(KSP ksp)
180: {


186:   /* reset the convergence flag from the previous solves */
187:   ksp->reason = KSP_CONVERGED_ITERATING;

189:   if (!ksp->type_name){
190:     KSPSetType(ksp,KSPGMRES);
191:   }

193:   if (ksp->setupcalled == 2) return(0);

195:   PetscLogEventBegin(KSP_SetUp,ksp,ksp->vec_rhs,ksp->vec_sol,0);

197:   if (!ksp->setupcalled) {
198:     (*ksp->ops->setup)(ksp);
199:   }

201:   /* scale the matrix if requested */
202:   if (ksp->dscale) {
203:     Mat mat,pmat;
204:     PCGetOperators(ksp->pc,&mat,&pmat,PETSC_NULL);
205:     if (mat == pmat) {
206:       PetscScalar  *xx;
207:       PetscInt          i,n;
208:       PetscTruth   zeroflag = PETSC_FALSE;

210:       if (!ksp->diagonal) { /* allocate vector to hold diagonal */
211:         MatGetVecs(pmat,&ksp->diagonal,0);
212:       }
213:       MatGetDiagonal(mat,ksp->diagonal);
214:       VecGetLocalSize(ksp->diagonal,&n);
215:       VecGetArray(ksp->diagonal,&xx);
216:       for (i=0; i<n; i++) {
217:         if (xx[i] != 0.0) xx[i] = 1.0/sqrt(PetscAbsScalar(xx[i]));
218:         else {
219:           xx[i]     = 1.0;
220:           zeroflag  = PETSC_TRUE;
221:         }
222:       }
223:       VecRestoreArray(ksp->diagonal,&xx);
224:       if (zeroflag) {
225:         PetscLogInfo((ksp,"KSPSetUp:Zero detected in diagonal of matrix, using 1 at those locations\n"));
226:       }
227:       MatDiagonalScale(mat,ksp->diagonal,ksp->diagonal);
228:       ksp->dscalefix2 = PETSC_FALSE;
229:     } else {
230:       SETERRQ(PETSC_ERR_SUP,"No support for diagonal scaling of linear system if preconditioner matrix not actual matrix");
231:     }
232:   }
233:   PetscLogEventEnd(KSP_SetUp,ksp,ksp->vec_rhs,ksp->vec_sol,0);
234:   PCSetUp(ksp->pc);
235:   if (ksp->nullsp) {
236:     PetscTruth test;
237:     PetscOptionsHasName(ksp->prefix,"-ksp_test_null_space",&test);
238:     if (test) {
239:       Mat mat;
240:       PCGetOperators(ksp->pc,&mat,PETSC_NULL,PETSC_NULL);
241:       MatNullSpaceTest(ksp->nullsp,mat);
242:     }
243:   }
244:   ksp->setupcalled = 2;
245:   return(0);
246: }

250: /*@
251:    KSPSolve - Solves linear system.

253:    Collective on KSP

255:    Parameter:
256: +  ksp - iterative context obtained from KSPCreate()
257: .  b - the right hand side vector
258: -  x - the solution 

260:    Options Database Keys:
261: +  -ksp_compute_eigenvalues - compute preconditioned operators eigenvalues
262: .  -ksp_plot_eigenvalues - plot the computed eigenvalues in an X-window
263: .  -ksp_compute_eigenvalues_explicitly - compute the eigenvalues by forming the dense operator and useing LAPACK
264: .  -ksp_plot_eigenvalues_explicitly - plot the explicitly computing eigenvalues
265: .  -ksp_view_binary - save matrix and right hand side that define linear system to the default binary viewer (can be
266:                                 read later with src/ksp/examples/tutorials/ex10.c for testing solvers)
267: .  -ksp_converged_reason - print reason for converged or diverged
268: .  -ksp_final_residual - print 2-norm of true linear system residual at the end of the solution process
269: -  -ksp_view - print the ksp data structure at the end of the system solution

271:    Notes:

273:    The operator is specified with PCSetOperators().

275:    Call KSPGetConvergedReason() to determine if the solver converged or failed and 
276:    why. The number of iterations can be obtained from KSPGetIterationNumber().
277:    
278:    If using a direct method (e.g., via the KSP solver
279:    KSPPREONLY and a preconditioner such as PCLU/PCILU),
280:    then its=1.  See KSPSetTolerances() and KSPDefaultConverged()
281:    for more details.

283:    Understanding Convergence:
284:    The routines KSPSetMonitor(), KSPComputeEigenvalues(), and
285:    KSPComputeEigenvaluesExplicitly() provide information on additional
286:    options to monitor convergence and print eigenvalue information.

288:    Level: beginner

290: .keywords: KSP, solve, linear system

292: .seealso: KSPCreate(), KSPSetUp(), KSPDestroy(), KSPSetTolerances(), KSPDefaultConverged(),
293:           KSPSolveTranspose(), KSPGetIterationNumber()
294: @*/
295: PetscErrorCode PETSCKSP_DLLEXPORT KSPSolve(KSP ksp,Vec b,Vec x)
296: {
298:   PetscMPIInt    rank;
299:   PetscTruth     flag1,flag2,viewed=PETSC_FALSE,flg;
300:   char           view[10];
301:   PetscScalar    zero = 0.0;

307: 
308:   ksp->vec_rhs = b;
309:   ksp->vec_sol = x;
310:   PetscOptionsHasName(ksp->prefix,"-ksp_view_binary",&flg);
311:   if (flg) {
312:     Mat mat;
313:     PCGetOperators(ksp->pc,&mat,PETSC_NULL,PETSC_NULL);
314:     MatView(mat,PETSC_VIEWER_BINARY_(ksp->comm));
315:     VecView(ksp->vec_rhs,PETSC_VIEWER_BINARY_(ksp->comm));
316:   }

318:   PetscLogEventBegin(KSP_Solve,ksp,ksp->vec_rhs,ksp->vec_sol,0);

320:   /* reset the residual history list if requested */
321:   if (ksp->res_hist_reset) ksp->res_hist_len = 0;

323:   PetscOptionsGetString(ksp->prefix,"-ksp_view",view,10,&flg);
324:   if (flg) {
325:     PetscStrcmp(view,"before",&viewed);
326:     if (viewed){
327:       KSPView(ksp,PETSC_VIEWER_STDOUT_(ksp->comm));
328:     }
329:   }

331:   /* KSPSetUp() scales the matrix if needed */
332:   KSPSetUp(ksp);
333:   KSPSetUpOnBlocks(ksp);

335:   ksp->transpose_solve = PETSC_FALSE;

337:   /* diagonal scale RHS if called for */
338:   if (ksp->dscale) {
339:     VecPointwiseMult(ksp->vec_rhs,ksp->vec_rhs,ksp->diagonal);
340:     /* second time in, but matrix was scaled back to original */
341:     if (ksp->dscalefix && ksp->dscalefix2) {
342:       Mat mat;

344:       PCGetOperators(ksp->pc,&mat,PETSC_NULL,PETSC_NULL);
345:       MatDiagonalScale(mat,ksp->diagonal,ksp->diagonal);
346:     }

348:     /*  scale initial guess */
349:     if (!ksp->guess_zero) {
350:       if (!ksp->truediagonal) {
351:         VecDuplicate(ksp->diagonal,&ksp->truediagonal);
352:         VecCopy(ksp->diagonal,ksp->truediagonal);
353:         VecReciprocal(ksp->truediagonal);
354:       }
355:       VecPointwiseMult(ksp->vec_sol,ksp->vec_sol,ksp->truediagonal);
356:     }
357:   }
358:   PCPreSolve(ksp->pc,ksp);

360:   if (ksp->guess_zero) { VecSet(ksp->vec_sol,zero);}
361:   if (ksp->guess_knoll) {
362:     PCApply(ksp->pc,ksp->vec_rhs,ksp->vec_sol);
363:     KSP_RemoveNullSpace(ksp,ksp->vec_sol);
364:     ksp->guess_zero = PETSC_FALSE;
365:   }
366:   (*ksp->ops->solve)(ksp);
367:   if (!ksp->reason) {
368:     SETERRQ(PETSC_ERR_PLIB,"Internal error, solver returned without setting converged reason");
369:   }
370:   if (ksp->printreason) {
371:     if (ksp->reason > 0) {
372:       PetscPrintf(ksp->comm,"Linear solve converged due to %s\n",KSPConvergedReasons[ksp->reason]);
373:     } else {
374:       PetscPrintf(ksp->comm,"Linear solve did not converge due to %s\n",KSPConvergedReasons[ksp->reason]);
375:     }
376:   }

378:   /* diagonal scale solution if called for */
379:   PCPostSolve(ksp->pc,ksp);
380:   if (ksp->dscale) {
381:     VecPointwiseMult(ksp->vec_sol,ksp->vec_sol,ksp->diagonal);
382:     /* unscale right hand side and matrix */
383:     if (ksp->dscalefix) {
384:       Mat mat;

386:       VecReciprocal(ksp->diagonal);
387:       VecPointwiseMult(ksp->vec_rhs,ksp->vec_rhs,ksp->diagonal);
388:       PCGetOperators(ksp->pc,&mat,PETSC_NULL,PETSC_NULL);
389:       MatDiagonalScale(mat,ksp->diagonal,ksp->diagonal);
390:       VecReciprocal(ksp->diagonal);
391:       ksp->dscalefix2 = PETSC_TRUE;
392:     }
393:   }
394:   PetscLogEventEnd(KSP_Solve,ksp,ksp->vec_rhs,ksp->vec_sol,0);

396:   MPI_Comm_rank(ksp->comm,&rank);

398:   PetscOptionsHasName(ksp->prefix,"-ksp_compute_eigenvalues",&flag1);
399:   PetscOptionsHasName(ksp->prefix,"-ksp_plot_eigenvalues",&flag2);
400:   if (flag1 || flag2) {
401:     PetscInt   nits,n,i,neig;
402:     PetscReal *r,*c;
403: 
404:     KSPGetIterationNumber(ksp,&nits);
405:     n = nits+2;

407:     if (!n) {
408:       PetscPrintf(ksp->comm,"Zero iterations in solver, cannot approximate any eigenvalues\n");
409:     } else {
410:       PetscMalloc(2*n*sizeof(PetscReal),&r);
411:       c = r + n;
412:       KSPComputeEigenvalues(ksp,n,r,c,&neig);
413:       if (flag1) {
414:         PetscPrintf(ksp->comm,"Iteratively computed eigenvalues\n");
415:         for (i=0; i<neig; i++) {
416:           if (c[i] >= 0.0) {PetscPrintf(ksp->comm,"%g + %gi\n",r[i],c[i]);}
417:           else             {PetscPrintf(ksp->comm,"%g - %gi\n",r[i],-c[i]);}
418:         }
419:       }
420:       if (flag2 && !rank) {
421:         PetscViewer viewer;
422:         PetscDraw   draw;
423:         PetscDrawSP drawsp;

425:         PetscViewerDrawOpen(PETSC_COMM_SELF,0,"Iteratively Computed Eigenvalues",
426:                                PETSC_DECIDE,PETSC_DECIDE,300,300,&viewer);
427:         PetscViewerDrawGetDraw(viewer,0,&draw);
428:         PetscDrawSPCreate(draw,1,&drawsp);
429:         for (i=0; i<neig; i++) {
430:           PetscDrawSPAddPoint(drawsp,r+i,c+i);
431:         }
432:         PetscDrawSPDraw(drawsp);
433:         PetscDrawSPDestroy(drawsp);
434:         PetscViewerDestroy(viewer);
435:       }
436:       PetscFree(r);
437:     }
438:   }

440:   PetscOptionsHasName(ksp->prefix,"-ksp_compute_eigenvalues_explicitly",&flag1);
441:   PetscOptionsHasName(ksp->prefix,"-ksp_plot_eigenvalues_explicitly",&flag2);
442:   if (flag1 || flag2) {
443:     PetscInt       n,i;
444:     PetscReal *r,*c;
445:     VecGetSize(ksp->vec_sol,&n);
446:     PetscMalloc(2*n*sizeof(PetscReal),&r);
447:     c = r + n;
448:     KSPComputeEigenvaluesExplicitly(ksp,n,r,c);
449:     if (flag1) {
450:       PetscPrintf(ksp->comm,"Explicitly computed eigenvalues\n");
451:       for (i=0; i<n; i++) {
452:         if (c[i] >= 0.0) {PetscPrintf(ksp->comm,"%g + %gi\n",r[i],c[i]);}
453:         else             {PetscPrintf(ksp->comm,"%g - %gi\n",r[i],-c[i]);}
454:       }
455:     }
456:     if (flag2 && !rank) {
457:       PetscViewer viewer;
458:       PetscDraw   draw;
459:       PetscDrawSP drawsp;

461:       PetscViewerDrawOpen(PETSC_COMM_SELF,0,"Explicitly Computed Eigenvalues",0,320,300,300,&viewer);
462:       PetscViewerDrawGetDraw(viewer,0,&draw);
463:       PetscDrawSPCreate(draw,1,&drawsp);
464:       for (i=0; i<n; i++) {
465:         PetscDrawSPAddPoint(drawsp,r+i,c+i);
466:       }
467:       PetscDrawSPDraw(drawsp);
468:       PetscDrawSPDestroy(drawsp);
469:       PetscViewerDestroy(viewer);
470:     }
471:     PetscFree(r);
472:   }

474:   PetscOptionsHasName(ksp->prefix,"-ksp_view_operator",&flag2);
475:   if (flag2) {
476:     Mat A,B;
477:     PCGetOperators(ksp->pc,&A,PETSC_NULL,PETSC_NULL);
478:     MatComputeExplicitOperator(A,&B);
479:     PetscViewerPushFormat(PETSC_VIEWER_STDOUT_(ksp->comm),PETSC_VIEWER_ASCII_MATLAB);
480:     MatView(B,PETSC_VIEWER_STDOUT_(ksp->comm));
481:     PetscViewerPopFormat(PETSC_VIEWER_STDOUT_(ksp->comm));
482:     MatDestroy(B);
483:   }
484:   PetscOptionsHasName(ksp->prefix,"-ksp_view_operator_binary",&flag2);
485:   if (flag2) {
486:     Mat A,B;
487:     PCGetOperators(ksp->pc,&A,PETSC_NULL,PETSC_NULL);
488:     MatComputeExplicitOperator(A,&B);
489:     MatView(B,PETSC_VIEWER_BINARY_(ksp->comm));
490:     MatDestroy(B);
491:   }
492:   PetscOptionsHasName(ksp->prefix,"-ksp_view_preconditioned_operator_binary",&flag2);
493:   if (flag2) {
494:     Mat B;
495:     KSPComputeExplicitOperator(ksp,&B);
496:     MatView(B,PETSC_VIEWER_BINARY_(ksp->comm));
497:     MatDestroy(B);
498:   }
499:   if (!viewed) {
500:     PetscOptionsHasName(ksp->prefix,"-ksp_view",&flg);
501:     if (flg) {
502:       KSPView(ksp,PETSC_VIEWER_STDOUT_(ksp->comm));
503:     }
504:   }
505:   PetscOptionsHasName(ksp->prefix,"-ksp_final_residual",&flg);
506:   if (flg) {
507:     Mat         A;
508:     Vec         t;
509:     PetscScalar mone = -1.0;
510:     PetscReal   norm;
511:     if (ksp->dscale && !ksp->dscalefix) SETERRQ(PETSC_ERR_ARG_WRONGSTATE,"Cannot compute final scale with -ksp_diagonal_scale except also with -ksp_diagonal_scale_fix");
512:     PCGetOperators(ksp->pc,&A,0,0);
513:     VecDuplicate(ksp->vec_sol,&t);
514:     KSP_MatMult(ksp,A,ksp->vec_sol,t);
515:     VecWAXPY(t,mone,t,ksp->vec_rhs);
516:     VecNorm(t,NORM_2,&norm);
517:     VecDestroy(t);
518:     PetscPrintf(ksp->comm,"KSP final norm of residual %g\n",norm);
519:   }
520:   return(0);
521: }

525: /*@
526:    KSPSolveTranspose - Solves the transpose of a linear system. Usually
527:    accessed through KSPSolveTranspose().

529:    Collective on KSP

531:    Input Parameter:
532: +  ksp - iterative context obtained from KSPCreate()
533: .  b - right hand side vector
534: -  x - solution vector

536:    Note:
537:    Currently only supported by KSPType of KSPPREONLY. This routine is usally 
538:    only used internally by the BiCG solver on the subblocks in BJacobi and ASM.

540:    Level: developer

542: .keywords: KSP, solve, linear system

544: .seealso: KSPCreate(), KSPSetUp(), KSPDestroy(), KSPSetTolerances(), KSPDefaultConverged(),
545:           KSPSolve()
546: @*/
547: PetscErrorCode PETSCKSP_DLLEXPORT KSPSolveTranspose(KSP ksp,Vec b,Vec x)
548: {
550:   PetscScalar    zero = 0.0;


557:   ksp->vec_rhs = b;
558:   ksp->vec_sol = x;
559:   KSPSetUp(ksp);
560:   if (ksp->guess_zero) { VecSet(ksp->vec_sol,zero);}
561:   ksp->transpose_solve = PETSC_TRUE;
562:   (*ksp->ops->solve)(ksp);
563:   return(0);
564: }

568: /*@C
569:    KSPDestroy - Destroys KSP context.

571:    Collective on KSP

573:    Input Parameter:
574: .  ksp - iterative context obtained from KSPCreate()

576:    Level: beginner

578: .keywords: KSP, destroy

580: .seealso: KSPCreate(), KSPSetUp(), KSPSolve()
581: @*/
582: PetscErrorCode PETSCKSP_DLLEXPORT KSPDestroy(KSP ksp)
583: {
585:   PetscInt       i;

589:   if (--ksp->refct > 0) return(0);

591:   /* if memory was published with AMS then destroy it */
592:   PetscObjectDepublish(ksp);

594:   if (ksp->ops->destroy) {
595:     (*ksp->ops->destroy)(ksp);
596:   }
597:   for (i=0; i<ksp->numbermonitors; i++) {
598:     if (ksp->monitordestroy[i]) {
599:       (*ksp->monitordestroy[i])(ksp->monitorcontext[i]);
600:     }
601:   }
602:   PCDestroy(ksp->pc);
603:   if (ksp->diagonal) {VecDestroy(ksp->diagonal);}
604:   if (ksp->truediagonal) {VecDestroy(ksp->truediagonal);}
605:   if (ksp->nullsp) {MatNullSpaceDestroy(ksp->nullsp);}
606:   PetscHeaderDestroy(ksp);
607:   return(0);
608: }

612: /*@
613:     KSPSetPreconditionerSide - Sets the preconditioning side.

615:     Collective on KSP

617:     Input Parameter:
618: .   ksp - iterative context obtained from KSPCreate()

620:     Output Parameter:
621: .   side - the preconditioning side, where side is one of
622: .vb
623:       PC_LEFT - left preconditioning (default)
624:       PC_RIGHT - right preconditioning
625:       PC_SYMMETRIC - symmetric preconditioning
626: .ve

628:     Options Database Keys:
629: +   -ksp_left_pc - Sets left preconditioning
630: .   -ksp_right_pc - Sets right preconditioning
631: -   -ksp_symmetric_pc - Sets symmetric preconditioning

633:     Notes:
634:     Left preconditioning is used by default.  Symmetric preconditioning is
635:     currently available only for the KSPQCG method. Note, however, that
636:     symmetric preconditioning can be emulated by using either right or left
637:     preconditioning and a pre or post processing step.

639:     Level: intermediate

641: .keywords: KSP, set, right, left, symmetric, side, preconditioner, flag

643: .seealso: KSPGetPreconditionerSide()
644: @*/
645: PetscErrorCode PETSCKSP_DLLEXPORT KSPSetPreconditionerSide(KSP ksp,PCSide side)
646: {
649:   ksp->pc_side = side;
650:   return(0);
651: }

655: /*@C
656:     KSPGetPreconditionerSide - Gets the preconditioning side.

658:     Not Collective

660:     Input Parameter:
661: .   ksp - iterative context obtained from KSPCreate()

663:     Output Parameter:
664: .   side - the preconditioning side, where side is one of
665: .vb
666:       PC_LEFT - left preconditioning (default)
667:       PC_RIGHT - right preconditioning
668:       PC_SYMMETRIC - symmetric preconditioning
669: .ve

671:     Level: intermediate

673: .keywords: KSP, get, right, left, symmetric, side, preconditioner, flag

675: .seealso: KSPSetPreconditionerSide()
676: @*/
677: PetscErrorCode PETSCKSP_DLLEXPORT KSPGetPreconditionerSide(KSP ksp,PCSide *side)
678: {
682:   *side = ksp->pc_side;
683:   return(0);
684: }

688: /*@
689:    KSPGetTolerances - Gets the relative, absolute, divergence, and maximum
690:    iteration tolerances used by the default KSP convergence tests. 

692:    Not Collective

694:    Input Parameter:
695: .  ksp - the Krylov subspace context
696:   
697:    Output Parameters:
698: +  rtol - the relative convergence tolerance
699: .  abstol - the absolute convergence tolerance
700: .  dtol - the divergence tolerance
701: -  maxits - maximum number of iterations

703:    Notes:
704:    The user can specify PETSC_NULL for any parameter that is not needed.

706:    Level: intermediate

708: .keywords: KSP, get, tolerance, absolute, relative, divergence, convergence,
709:            maximum, iterations

711: .seealso: KSPSetTolerances()
712: @*/
713: PetscErrorCode PETSCKSP_DLLEXPORT KSPGetTolerances(KSP ksp,PetscReal *rtol,PetscReal *abstol,PetscReal *dtol,PetscInt *maxits)
714: {
717:   if (abstol)   *abstol   = ksp->abstol;
718:   if (rtol)   *rtol   = ksp->rtol;
719:   if (dtol)   *dtol   = ksp->divtol;
720:   if (maxits) *maxits = ksp->max_it;
721:   return(0);
722: }

726: /*@
727:    KSPSetTolerances - Sets the relative, absolute, divergence, and maximum
728:    iteration tolerances used by the default KSP convergence testers. 

730:    Collective on KSP

732:    Input Parameters:
733: +  ksp - the Krylov subspace context
734: .  rtol - the relative convergence tolerance
735:    (relative decrease in the residual norm)
736: .  abstol - the absolute convergence tolerance 
737:    (absolute size of the residual norm)
738: .  dtol - the divergence tolerance
739:    (amount residual can increase before KSPDefaultConverged()
740:    concludes that the method is diverging)
741: -  maxits - maximum number of iterations to use

743:    Options Database Keys:
744: +  -ksp_atol <abstol> - Sets abstol
745: .  -ksp_rtol <rtol> - Sets rtol
746: .  -ksp_divtol <dtol> - Sets dtol
747: -  -ksp_max_it <maxits> - Sets maxits

749:    Notes:
750:    Use PETSC_DEFAULT to retain the default value of any of the tolerances.

752:    See KSPDefaultConverged() for details on the use of these parameters
753:    in the default convergence test.  See also KSPSetConvergenceTest() 
754:    for setting user-defined stopping criteria.

756:    Level: intermediate

758: .keywords: KSP, set, tolerance, absolute, relative, divergence, 
759:            convergence, maximum, iterations

761: .seealso: KSPGetTolerances(), KSPDefaultConverged(), KSPSetConvergenceTest()
762: @*/
763: PetscErrorCode PETSCKSP_DLLEXPORT KSPSetTolerances(KSP ksp,PetscReal rtol,PetscReal abstol,PetscReal dtol,PetscInt maxits)
764: {
767:   if (abstol != PETSC_DEFAULT)   ksp->abstol   = abstol;
768:   if (rtol != PETSC_DEFAULT)   ksp->rtol   = rtol;
769:   if (dtol != PETSC_DEFAULT)   ksp->divtol = dtol;
770:   if (maxits != PETSC_DEFAULT) ksp->max_it = maxits;
771:   return(0);
772: }

776: /*@
777:    KSPSetInitialGuessNonzero - Tells the iterative solver that the 
778:    initial guess is nonzero; otherwise KSP assumes the initial guess
779:    is to be zero (and thus zeros it out before solving).

781:    Collective on KSP

783:    Input Parameters:
784: +  ksp - iterative context obtained from KSPCreate()
785: -  flg - PETSC_TRUE indicates the guess is non-zero, PETSC_FALSE indicates the guess is zero

787:    Level: beginner

789:    Notes:
790:     If this is not called the X vector is zeroed in the call to KSPSolve().

792: .keywords: KSP, set, initial guess, nonzero

794: .seealso: KSPGetInitialGuessNonzero(), KSPSetInitialGuessKnoll(), KSPGetInitialGuessKnoll()
795: @*/
796: PetscErrorCode PETSCKSP_DLLEXPORT KSPSetInitialGuessNonzero(KSP ksp,PetscTruth flg)
797: {
799:   ksp->guess_zero   = (PetscTruth)!(int)flg;
800:   return(0);
801: }

805: /*@
806:    KSPGetInitialGuessNonzero - Determines whether the KSP solver is using
807:    a zero initial guess.

809:    Not Collective

811:    Input Parameter:
812: .  ksp - iterative context obtained from KSPCreate()

814:    Output Parameter:
815: .  flag - PETSC_TRUE if guess is nonzero, else PETSC_FALSE

817:    Level: intermediate

819: .keywords: KSP, set, initial guess, nonzero

821: .seealso: KSPSetInitialGuessNonzero(), KSPSetInitialGuessKnoll(), KSPGetInitialGuessKnoll()
822: @*/
823: PetscErrorCode PETSCKSP_DLLEXPORT KSPGetInitialGuessNonzero(KSP ksp,PetscTruth *flag)
824: {
826:   if (ksp->guess_zero) *flag = PETSC_FALSE;
827:   else                 *flag = PETSC_TRUE;
828:   return(0);
829: }

833: /*@
834:    KSPSetInitialGuessKnoll - Tells the iterative solver to use PCApply(pc,b,..) to compute the initial guess (The Knoll trick)

836:    Collective on KSP

838:    Input Parameters:
839: +  ksp - iterative context obtained from KSPCreate()
840: -  flg - PETSC_TRUE or PETSC_FALSE

842:    Level: advanced


845: .keywords: KSP, set, initial guess, nonzero

847: .seealso: KSPGetInitialGuessKnoll(), KSPSetInitialGuessNonzero(), KSPGetInitialGuessNonzero()
848: @*/
849: PetscErrorCode PETSCKSP_DLLEXPORT KSPSetInitialGuessKnoll(KSP ksp,PetscTruth flg)
850: {
852:   ksp->guess_knoll   = flg;
853:   return(0);
854: }

858: /*@
859:    KSPGetInitialGuessKnoll - Determines whether the KSP solver is using the Knoll trick (using PCApply(pc,b,...) to compute
860:      the initial guess

862:    Not Collective

864:    Input Parameter:
865: .  ksp - iterative context obtained from KSPCreate()

867:    Output Parameter:
868: .  flag - PETSC_TRUE if using Knoll trick, else PETSC_FALSE

870:    Level: advanced

872: .keywords: KSP, set, initial guess, nonzero

874: .seealso: KSPSetInitialGuessKnoll(), KSPSetInitialGuessNonzero(), KSPGetInitialGuessNonzero()
875: @*/
876: PetscErrorCode PETSCKSP_DLLEXPORT KSPGetInitialGuessKnoll(KSP ksp,PetscTruth *flag)
877: {
879:   *flag = ksp->guess_knoll;
880:   return(0);
881: }

885: /*@
886:    KSPGetComputeSingularValues - Gets the flag indicating whether the extreme singular 
887:    values will be calculated via a Lanczos or Arnoldi process as the linear 
888:    system is solved.

890:    Collective on KSP

892:    Input Parameter:
893: .  ksp - iterative context obtained from KSPCreate()

895:    Output Parameter:
896: .  flg - PETSC_TRUE or PETSC_FALSE

898:    Options Database Key:
899: .  -ksp_singmonitor - Activates KSPSetComputeSingularValues()

901:    Notes:
902:    Currently this option is not valid for all iterative methods.

904:    Many users may just want to use the monitoring routine
905:    KSPSingularValueMonitor() (which can be set with option -ksp_singmonitor)
906:    to print the singular values at each iteration of the linear solve.

908:    Level: advanced

910: .keywords: KSP, set, compute, singular values

912: .seealso: KSPComputeExtremeSingularValues(), KSPSingularValueMonitor()
913: @*/
914: PetscErrorCode PETSCKSP_DLLEXPORT KSPGetComputeSingularValues(KSP ksp,PetscTruth *flg)
915: {
919:   *flg = ksp->calc_sings;
920:   return(0);
921: }

925: /*@
926:    KSPSetComputeSingularValues - Sets a flag so that the extreme singular 
927:    values will be calculated via a Lanczos or Arnoldi process as the linear 
928:    system is solved.

930:    Collective on KSP

932:    Input Parameters:
933: +  ksp - iterative context obtained from KSPCreate()
934: -  flg - PETSC_TRUE or PETSC_FALSE

936:    Options Database Key:
937: .  -ksp_singmonitor - Activates KSPSetComputeSingularValues()

939:    Notes:
940:    Currently this option is not valid for all iterative methods.

942:    Many users may just want to use the monitoring routine
943:    KSPSingularValueMonitor() (which can be set with option -ksp_singmonitor)
944:    to print the singular values at each iteration of the linear solve.

946:    Level: advanced

948: .keywords: KSP, set, compute, singular values

950: .seealso: KSPComputeExtremeSingularValues(), KSPSingularValueMonitor()
951: @*/
952: PetscErrorCode PETSCKSP_DLLEXPORT KSPSetComputeSingularValues(KSP ksp,PetscTruth flg)
953: {
956:   ksp->calc_sings  = flg;
957:   return(0);
958: }

962: /*@
963:    KSPGetComputeEigenvalues - Gets the flag indicating that the extreme eigenvalues
964:    values will be calculated via a Lanczos or Arnoldi process as the linear 
965:    system is solved.

967:    Collective on KSP

969:    Input Parameter:
970: .  ksp - iterative context obtained from KSPCreate()

972:    Output Parameter:
973: .  flg - PETSC_TRUE or PETSC_FALSE

975:    Notes:
976:    Currently this option is not valid for all iterative methods.

978:    Level: advanced

980: .keywords: KSP, set, compute, eigenvalues

982: .seealso: KSPComputeEigenvalues(), KSPComputeEigenvaluesExplicitly()
983: @*/
984: PetscErrorCode PETSCKSP_DLLEXPORT KSPGetComputeEigenvalues(KSP ksp,PetscTruth *flg)
985: {
989:   *flg = ksp->calc_sings;
990:   return(0);
991: }

995: /*@
996:    KSPSetComputeEigenvalues - Sets a flag so that the extreme eigenvalues
997:    values will be calculated via a Lanczos or Arnoldi process as the linear 
998:    system is solved.

1000:    Collective on KSP

1002:    Input Parameters:
1003: +  ksp - iterative context obtained from KSPCreate()
1004: -  flg - PETSC_TRUE or PETSC_FALSE

1006:    Notes:
1007:    Currently this option is not valid for all iterative methods.

1009:    Level: advanced

1011: .keywords: KSP, set, compute, eigenvalues

1013: .seealso: KSPComputeEigenvalues(), KSPComputeEigenvaluesExplicitly()
1014: @*/
1015: PetscErrorCode PETSCKSP_DLLEXPORT KSPSetComputeEigenvalues(KSP ksp,PetscTruth flg)
1016: {
1019:   ksp->calc_sings  = flg;
1020:   return(0);
1021: }

1025: /*@C
1026:    KSPGetRhs - Gets the right-hand-side vector for the linear system to
1027:    be solved.

1029:    Not Collective

1031:    Input Parameter:
1032: .  ksp - iterative context obtained from KSPCreate()

1034:    Output Parameter:
1035: .  r - right-hand-side vector

1037:    Level: developer

1039: .keywords: KSP, get, right-hand-side, rhs

1041: .seealso: KSPGetSolution(), KSPSolve()
1042: @*/
1043: PetscErrorCode PETSCKSP_DLLEXPORT KSPGetRhs(KSP ksp,Vec *r)
1044: {
1047:   *r = ksp->vec_rhs;
1048:   return(0);
1049: }

1053: /*@C
1054:    KSPGetSolution - Gets the location of the solution for the 
1055:    linear system to be solved.  Note that this may not be where the solution
1056:    is stored during the iterative process; see KSPBuildSolution().

1058:    Not Collective

1060:    Input Parameters:
1061: .  ksp - iterative context obtained from KSPCreate()

1063:    Output Parameters:
1064: .  v - solution vector

1066:    Level: developer

1068: .keywords: KSP, get, solution

1070: .seealso: KSPGetRhs(),  KSPBuildSolution(), KSPSolve()
1071: @*/
1072: PetscErrorCode PETSCKSP_DLLEXPORT KSPGetSolution(KSP ksp,Vec *v)
1073: {
1077:   *v = ksp->vec_sol;
1078:   return(0);
1079: }

1083: /*@
1084:    KSPSetPC - Sets the preconditioner to be used to calculate the 
1085:    application of the preconditioner on a vector. 

1087:    Collective on KSP

1089:    Input Parameters:
1090: +  ksp - iterative context obtained from KSPCreate()
1091: -  pc   - the preconditioner object

1093:    Notes:
1094:    Use KSPGetPC() to retrieve the preconditioner context (for example,
1095:    to free it at the end of the computations).

1097:    Level: developer

1099: .keywords: KSP, set, precondition, Binv

1101: .seealso: KSPGetPC()
1102: @*/
1103: PetscErrorCode PETSCKSP_DLLEXPORT KSPSetPC(KSP ksp,PC pc)
1104: {

1111:   if (ksp->pc) {PCDestroy(ksp->pc);}
1112:   ksp->pc = pc;
1113:   PetscObjectReference((PetscObject)ksp->pc);
1114:   return(0);
1115: }

1119: /*@C
1120:    KSPGetPC - Returns a pointer to the preconditioner context
1121:    set with KSPSetPC().

1123:    Not Collective

1125:    Input Parameters:
1126: .  ksp - iterative context obtained from KSPCreate()

1128:    Output Parameter:
1129: .  pc - preconditioner context

1131:    Level: developer

1133: .keywords: KSP, get, preconditioner, Binv

1135: .seealso: KSPSetPC()
1136: @*/
1137: PetscErrorCode PETSCKSP_DLLEXPORT KSPGetPC(KSP ksp,PC *pc)
1138: {
1142:   *pc = ksp->pc;
1143:   return(0);
1144: }

1148: /*@C
1149:    KSPSetMonitor - Sets an ADDITIONAL function to be called at every iteration to monitor 
1150:    the residual/error etc.
1151:       
1152:    Collective on KSP

1154:    Input Parameters:
1155: +  ksp - iterative context obtained from KSPCreate()
1156: .  monitor - pointer to function (if this is PETSC_NULL, it turns off monitoring
1157: .  mctx    - [optional] context for private data for the
1158:              monitor routine (use PETSC_NULL if no context is desired)
1159: -  monitordestroy - [optional] routine that frees monitor context
1160:           (may be PETSC_NULL)

1162:    Calling Sequence of monitor:
1163: $     monitor (KSP ksp, int it, PetscReal rnorm, void *mctx)

1165: +  ksp - iterative context obtained from KSPCreate()
1166: .  it - iteration number
1167: .  rnorm - (estimated) 2-norm of (preconditioned) residual
1168: -  mctx  - optional monitoring context, as set by KSPSetMonitor()

1170:    Options Database Keys:
1171: +    -ksp_monitor        - sets KSPDefaultMonitor()
1172: .    -ksp_truemonitor    - sets KSPTrueMonitor()
1173: .    -ksp_xmonitor       - sets line graph monitor,
1174:                            uses KSPLGMonitorCreate()
1175: .    -ksp_xtruemonitor   - sets line graph monitor,
1176:                            uses KSPLGMonitorCreate()
1177: .    -ksp_singmonitor    - sets KSPSingularValueMonitor()
1178: -    -ksp_cancelmonitors - cancels all monitors that have
1179:                           been hardwired into a code by 
1180:                           calls to KSPSetMonitor(), but
1181:                           does not cancel those set via
1182:                           the options database.

1184:    Notes:  
1185:    The default is to do nothing.  To print the residual, or preconditioned 
1186:    residual if KSPSetNormType(ksp,KSP_PRECONDITIONED_NORM) was called, use 
1187:    KSPDefaultMonitor() as the monitoring routine, with a null monitoring 
1188:    context. 

1190:    Several different monitoring routines may be set by calling
1191:    KSPSetMonitor() multiple times; all will be called in the 
1192:    order in which they were set.

1194:    Level: beginner

1196: .keywords: KSP, set, monitor

1198: .seealso: KSPDefaultMonitor(), KSPLGMonitorCreate(), KSPClearMonitor()
1199: @*/
1200: PetscErrorCode PETSCKSP_DLLEXPORT KSPSetMonitor(KSP ksp,PetscErrorCode (*monitor)(KSP,PetscInt,PetscReal,void*),void *mctx,PetscErrorCode (*monitordestroy)(void*))
1201: {
1204:   if (ksp->numbermonitors >= MAXKSPMONITORS) {
1205:     SETERRQ(PETSC_ERR_ARG_OUTOFRANGE,"Too many KSP monitors set");
1206:   }
1207:   ksp->monitor[ksp->numbermonitors]           = monitor;
1208:   ksp->monitordestroy[ksp->numbermonitors]    = monitordestroy;
1209:   ksp->monitorcontext[ksp->numbermonitors++]  = (void*)mctx;
1210:   return(0);
1211: }

1215: /*@
1216:    KSPClearMonitor - Clears all monitors for a KSP object.

1218:    Collective on KSP

1220:    Input Parameters:
1221: .  ksp - iterative context obtained from KSPCreate()

1223:    Options Database Key:
1224: .  -ksp_cancelmonitors - Cancels all monitors that have
1225:     been hardwired into a code by calls to KSPSetMonitor(), 
1226:     but does not cancel those set via the options database.

1228:    Level: intermediate

1230: .keywords: KSP, set, monitor

1232: .seealso: KSPDefaultMonitor(), KSPLGMonitorCreate(), KSPSetMonitor()
1233: @*/
1234: PetscErrorCode PETSCKSP_DLLEXPORT KSPClearMonitor(KSP ksp)
1235: {
1238:   ksp->numbermonitors = 0;
1239:   return(0);
1240: }

1244: /*@C
1245:    KSPGetMonitorContext - Gets the monitoring context, as set by 
1246:    KSPSetMonitor() for the FIRST monitor only.

1248:    Not Collective

1250:    Input Parameter:
1251: .  ksp - iterative context obtained from KSPCreate()

1253:    Output Parameter:
1254: .  ctx - monitoring context

1256:    Level: intermediate

1258: .keywords: KSP, get, monitor, context

1260: .seealso: KSPDefaultMonitor(), KSPLGMonitorCreate()
1261: @*/
1262: PetscErrorCode PETSCKSP_DLLEXPORT KSPGetMonitorContext(KSP ksp,void **ctx)
1263: {
1266:   *ctx =      (ksp->monitorcontext[0]);
1267:   return(0);
1268: }

1272: /*@
1273:    KSPSetResidualHistory - Sets the array used to hold the residual history.
1274:    If set, this array will contain the residual norms computed at each
1275:    iteration of the solver.

1277:    Not Collective

1279:    Input Parameters:
1280: +  ksp - iterative context obtained from KSPCreate()
1281: .  a   - array to hold history
1282: .  na  - size of a
1283: -  reset - PETSC_TRUE indicates the history counter is reset to zero
1284:            for each new linear solve

1286:    Level: advanced

1288:    Notes: The array is NOT freed by PETSc so the user needs to keep track of 
1289:            it and destroy once the KSP object is destroyed.

1291:    If 'na' is PETSC_DECIDE or 'a' is PETSC_NULL, then a default array of
1292:    length 1000 is allocated.

1294: .keywords: KSP, set, residual, history, norm

1296: .seealso: KSPGetResidualHistory()

1298: @*/
1299: PetscErrorCode PETSCKSP_DLLEXPORT KSPSetResidualHistory(KSP ksp,PetscReal a[],PetscInt na,PetscTruth reset)
1300: {

1305:   if (na != PETSC_DECIDE && a) {
1306:     ksp->res_hist        = a;
1307:     ksp->res_hist_max    = na;
1308:   } else {
1309:     ksp->res_hist_max    = 1000;
1310:     PetscMalloc(ksp->res_hist_max*sizeof(PetscReal),&ksp->res_hist);
1311:   }
1312:   ksp->res_hist_len    = 0;
1313:   ksp->res_hist_reset  = reset;


1316:   return(0);
1317: }

1321: /*@C
1322:    KSPGetResidualHistory - Gets the array used to hold the residual history
1323:    and the number of residuals it contains.

1325:    Not Collective

1327:    Input Parameter:
1328: .  ksp - iterative context obtained from KSPCreate()

1330:    Output Parameters:
1331: +  a   - pointer to array to hold history (or PETSC_NULL)
1332: -  na  - number of used entries in a (or PETSC_NULL)

1334:    Level: advanced

1336:    Notes:
1337:      Can only be called after a KSPSetResidualHistory() otherwise a and na are set to zero

1339:      The Fortran version of this routine has a calling sequence
1340: $   call KSPGetResidualHistory(KSP ksp, integer na, integer ierr)

1342: .keywords: KSP, get, residual, history, norm

1344: .seealso: KSPGetResidualHistory()

1346: @*/
1347: PetscErrorCode PETSCKSP_DLLEXPORT KSPGetResidualHistory(KSP ksp,PetscReal *a[],PetscInt *na)
1348: {
1351:   if (a)  *a = ksp->res_hist;
1352:   if (na) *na = ksp->res_hist_len;
1353:   return(0);
1354: }

1358: /*@C
1359:    KSPSetConvergenceTest - Sets the function to be used to determine
1360:    convergence.  

1362:    Collective on KSP

1364:    Input Parameters:
1365: +  ksp - iterative context obtained from KSPCreate()
1366: .  converge - pointer to int function
1367: -  cctx    - context for private data for the convergence routine (may be null)

1369:    Calling sequence of converge:
1370: $     converge (KSP ksp, int it, PetscReal rnorm, KSPConvergedReason *reason,void *mctx)

1372: +  ksp - iterative context obtained from KSPCreate()
1373: .  it - iteration number
1374: .  rnorm - (estimated) 2-norm of (preconditioned) residual
1375: .  reason - the reason why it has converged or diverged
1376: -  cctx  - optional convergence context, as set by KSPSetConvergenceTest()


1379:    Notes:
1380:    Must be called after the KSP type has been set so put this after
1381:    a call to KSPSetType(), or KSPSetFromOptions().

1383:    The default convergence test, KSPDefaultConverged(), aborts if the 
1384:    residual grows to more than 10000 times the initial residual.

1386:    The default is a combination of relative and absolute tolerances.  
1387:    The residual value that is tested may be an approximation; routines 
1388:    that need exact values should compute them.

1390:    In the default PETSc convergence test, the precise values of reason
1391:    are macros such as KSP_CONVERGED_RTOL, which are defined in petscksp.h.

1393:    Level: advanced

1395: .keywords: KSP, set, convergence, test, context

1397: .seealso: KSPDefaultConverged(), KSPGetConvergenceContext()
1398: @*/
1399: PetscErrorCode PETSCKSP_DLLEXPORT KSPSetConvergenceTest(KSP ksp,PetscErrorCode (*converge)(KSP,PetscInt,PetscReal,KSPConvergedReason*,void*),void *cctx)
1400: {
1403:   ksp->converged = converge;
1404:   ksp->cnvP      = (void*)cctx;
1405:   return(0);
1406: }

1410: /*@C
1411:    KSPGetConvergenceContext - Gets the convergence context set with 
1412:    KSPSetConvergenceTest().  

1414:    Not Collective

1416:    Input Parameter:
1417: .  ksp - iterative context obtained from KSPCreate()

1419:    Output Parameter:
1420: .  ctx - monitoring context

1422:    Level: advanced

1424: .keywords: KSP, get, convergence, test, context

1426: .seealso: KSPDefaultConverged(), KSPSetConvergenceTest()
1427: @*/
1428: PetscErrorCode PETSCKSP_DLLEXPORT KSPGetConvergenceContext(KSP ksp,void **ctx)
1429: {
1432:   *ctx = ksp->cnvP;
1433:   return(0);
1434: }

1438: /*@C
1439:    KSPBuildSolution - Builds the approximate solution in a vector provided.
1440:    This routine is NOT commonly needed (see KSPSolve()).

1442:    Collective on KSP

1444:    Input Parameter:
1445: .  ctx - iterative context obtained from KSPCreate()

1447:    Output Parameter: 
1448:    Provide exactly one of
1449: +  v - location to stash solution.   
1450: -  V - the solution is returned in this location. This vector is created 
1451:        internally. This vector should NOT be destroyed by the user with
1452:        VecDestroy().

1454:    Notes:
1455:    This routine can be used in one of two ways
1456: .vb
1457:       KSPBuildSolution(ksp,PETSC_NULL,&V);
1458:    or
1459:       KSPBuildSolution(ksp,v,PETSC_NULL); 
1460: .ve
1461:    In the first case an internal vector is allocated to store the solution
1462:    (the user cannot destroy this vector). In the second case the solution
1463:    is generated in the vector that the user provides. Note that for certain 
1464:    methods, such as KSPCG, the second case requires a copy of the solution,
1465:    while in the first case the call is essentially free since it simply 
1466:    returns the vector where the solution already is stored.

1468:    Level: advanced

1470: .keywords: KSP, build, solution

1472: .seealso: KSPGetSolution(), KSPBuildResidual()
1473: @*/
1474: PetscErrorCode PETSCKSP_DLLEXPORT KSPBuildSolution(KSP ksp,Vec v,Vec *V)
1475: {

1480:   if (!V && !v) SETERRQ(PETSC_ERR_ARG_WRONG,"Must provide either v or V");
1481:   if (!V) V = &v;
1482:   (*ksp->ops->buildsolution)(ksp,v,V);
1483:   return(0);
1484: }

1488: /*@C
1489:    KSPBuildResidual - Builds the residual in a vector provided.

1491:    Collective on KSP

1493:    Input Parameter:
1494: .  ksp - iterative context obtained from KSPCreate()

1496:    Output Parameters:
1497: +  v - optional location to stash residual.  If v is not provided,
1498:        then a location is generated.
1499: .  t - work vector.  If not provided then one is generated.
1500: -  V - the residual

1502:    Notes:
1503:    Regardless of whether or not v is provided, the residual is 
1504:    returned in V.

1506:    Level: advanced

1508: .keywords: KSP, build, residual

1510: .seealso: KSPBuildSolution()
1511: @*/
1512: PetscErrorCode PETSCKSP_DLLEXPORT KSPBuildResidual(KSP ksp,Vec t,Vec v,Vec *V)
1513: {
1515:   PetscTruth     flag = PETSC_FALSE;
1516:   Vec            w = v,tt = t;

1520:   if (!w) {
1521:     VecDuplicate(ksp->vec_rhs,&w);
1522:     PetscLogObjectParent((PetscObject)ksp,w);
1523:   }
1524:   if (!tt) {
1525:     VecDuplicate(ksp->vec_rhs,&tt); flag = PETSC_TRUE;
1526:     PetscLogObjectParent((PetscObject)ksp,tt);
1527:   }
1528:   (*ksp->ops->buildresidual)(ksp,tt,w,V);
1529:   if (flag) {VecDestroy(tt);}
1530:   return(0);
1531: }

1535: /*@
1536:    KSPSetDiagonalScale - Tells KSP to symmetrically diagonally scale the system
1537:      before solving. This actually CHANGES the matrix (and right hand side).

1539:    Collective on KSP

1541:    Input Parameter:
1542: +  ksp - the KSP context
1543: -  scale - PETSC_TRUE or PETSC_FALSE

1545:    Options Database Key:
1546: +   -ksp_diagonal_scale - 
1547: -   -ksp_diagonal_scale_fix - scale the matrix back AFTER the solve 


1550:     BE CAREFUL with this routine: it actually scales the matrix and right 
1551:     hand side that define the system. After the system is solved the matrix
1552:     and right hand side remain scaled.

1554:     This routine is only used if the matrix and preconditioner matrix are
1555:     the same thing.
1556:  
1557:     If you use this with the PCType Eisenstat preconditioner than you can 
1558:     use the PCEisenstatNoDiagonalScaling() option, or -pc_eisenstat_no_diagonal_scaling
1559:     to save some unneeded, redundant flops.

1561:    Level: intermediate

1563: .keywords: KSP, set, options, prefix, database

1565: .seealso: KSPGetDiagonalScale(), KSPSetDiagonalScaleFix()
1566: @*/
1567: PetscErrorCode PETSCKSP_DLLEXPORT KSPSetDiagonalScale(KSP ksp,PetscTruth scale)
1568: {
1571:   ksp->dscale = scale;
1572:   return(0);
1573: }

1577: /*@C
1578:    KSPGetDiagonalScale - Checks if KSP solver scales the matrix and
1579:                           right hand side

1581:    Not Collective

1583:    Input Parameter:
1584: .  ksp - the KSP context

1586:    Output Parameter:
1587: .  scale - PETSC_TRUE or PETSC_FALSE

1589:    Notes:
1590:     BE CAREFUL with this routine: it actually scales the matrix and right 
1591:     hand side that define the system. After the system is solved the matrix
1592:     and right hand side remain scaled.

1594:     This routine is only used if the matrix and preconditioner matrix are
1595:     the same thing.

1597:    Level: intermediate

1599: .keywords: KSP, set, options, prefix, database

1601: .seealso: KSPSetDiagonalScale(), KSPSetDiagonalScaleFix()
1602: @*/
1603: PetscErrorCode PETSCKSP_DLLEXPORT KSPGetDiagonalScale(KSP ksp,PetscTruth *scale)
1604: {
1608:   *scale = ksp->dscale;
1609:   return(0);
1610: }

1614: /*@
1615:    KSPSetDiagonalScaleFix - Tells KSP to diagonally scale the system
1616:      back after solving.

1618:    Collective on KSP

1620:    Input Parameter:
1621: +  ksp - the KSP context
1622: -  fix - PETSC_TRUE to scale back after the system solve, PETSC_FALSE to not 
1623:          rescale (default)

1625:    Notes:
1626:      Must be called after KSPSetDiagonalScale()

1628:      Using this will slow things down, because it rescales the matrix before and
1629:      after each linear solve. This is intended mainly for testing to allow one
1630:      to easily get back the original system to make sure the solution computed is
1631:      accurate enough.

1633:     This routine is only used if the matrix and preconditioner matrix are
1634:     the same thing.

1636:    Level: intermediate

1638: .keywords: KSP, set, options, prefix, database

1640: .seealso: KSPGetDiagonalScale(), KSPSetDiagonalScale(), KSPGetDiagonalScaleFix()
1641: @*/
1642: PetscErrorCode PETSCKSP_DLLEXPORT KSPSetDiagonalScaleFix(KSP ksp,PetscTruth fix)
1643: {
1646:   ksp->dscalefix = fix;
1647:   return(0);
1648: }

1652: /*@
1653:    KSPGetDiagonalScaleFix - Determines if KSP diagonally scales the system
1654:      back after solving.

1656:    Collective on KSP

1658:    Input Parameter:
1659: .  ksp - the KSP context

1661:    Output Parameter:
1662: .  fix - PETSC_TRUE to scale back after the system solve, PETSC_FALSE to not 
1663:          rescale (default)

1665:    Notes:
1666:      Must be called after KSPSetDiagonalScale()

1668:      If PETSC_TRUE will slow things down, because it rescales the matrix before and
1669:      after each linear solve. This is intended mainly for testing to allow one
1670:      to easily get back the original system to make sure the solution computed is
1671:      accurate enough.

1673:     This routine is only used if the matrix and preconditioner matrix are
1674:     the same thing.

1676:    Level: intermediate

1678: .keywords: KSP, set, options, prefix, database

1680: .seealso: KSPGetDiagonalScale(), KSPSetDiagonalScale(), KSPSetDiagonalScaleFix()
1681: @*/
1682: PetscErrorCode PETSCKSP_DLLEXPORT KSPGetDiagonalScaleFix(KSP ksp,PetscTruth *fix)
1683: {
1687:   *fix = ksp->dscalefix;
1688:   return(0);
1689: }