Actual source code: itcreate.c
petsc-3.10.5 2019-03-28
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      2: /*
      3:      The basic KSP routines, Create, View etc. are here.
      4: */
      5:  #include <petsc/private/kspimpl.h>

      7: /* Logging support */
      8: PetscClassId  KSP_CLASSID;
      9: PetscClassId  DMKSP_CLASSID;
     10: PetscClassId  KSPGUESS_CLASSID;
     11: PetscLogEvent KSP_GMRESOrthogonalization, KSP_SetUp, KSP_Solve;

     13: /*
     14:    Contains the list of registered KSP routines
     15: */
     16: PetscFunctionList KSPList              = 0;
     17: PetscBool         KSPRegisterAllCalled = PETSC_FALSE;

     19: /*@C
     20:   KSPLoad - Loads a KSP that has been stored in binary  with KSPView().

     22:   Collective on PetscViewer

     24:   Input Parameters:
     25: + newdm - the newly loaded KSP, this needs to have been created with KSPCreate() or
     26:            some related function before a call to KSPLoad().
     27: - viewer - binary file viewer, obtained from PetscViewerBinaryOpen()

     29:    Level: intermediate

     31:   Notes:
     32:    The type is determined by the data in the file, any type set into the KSP before this call is ignored.

     34:   Notes for advanced users:
     35:   Most users should not need to know the details of the binary storage
     36:   format, since KSPLoad() and KSPView() completely hide these details.
     37:   But for anyone who's interested, the standard binary matrix storage
     38:   format is
     39: .vb
     40:      has not yet been determined
     41: .ve

     43: .seealso: PetscViewerBinaryOpen(), KSPView(), MatLoad(), VecLoad()
     44: @*/
     45: PetscErrorCode  KSPLoad(KSP newdm, PetscViewer viewer)
     46: {
     48:   PetscBool      isbinary;
     49:   PetscInt       classid;
     50:   char           type[256];
     51:   PC             pc;

     56:   PetscObjectTypeCompare((PetscObject)viewer,PETSCVIEWERBINARY,&isbinary);
     57:   if (!isbinary) SETERRQ(PETSC_COMM_SELF,PETSC_ERR_ARG_WRONG,"Invalid viewer; open viewer with PetscViewerBinaryOpen()");

     59:   PetscViewerBinaryRead(viewer,&classid,1,NULL,PETSC_INT);
     60:   if (classid != KSP_FILE_CLASSID) SETERRQ(PetscObjectComm((PetscObject)newdm),PETSC_ERR_ARG_WRONG,"Not KSP next in file");
     61:   PetscViewerBinaryRead(viewer,type,256,NULL,PETSC_CHAR);
     62:   KSPSetType(newdm, type);
     63:   if (newdm->ops->load) {
     64:     (*newdm->ops->load)(newdm,viewer);
     65:   }
     66:   KSPGetPC(newdm,&pc);
     67:   PCLoad(pc,viewer);
     68:   return(0);
     69: }

     71:  #include <petscdraw.h>
     72: #if defined(PETSC_HAVE_SAWS)
     73:  #include <petscviewersaws.h>
     74: #endif
     75: /*@C
     76:    KSPView - Prints the KSP data structure.

     78:    Collective on KSP

     80:    Input Parameters:
     81: +  ksp - the Krylov space context
     82: -  viewer - visualization context

     84:    Options Database Keys:
     85: .  -ksp_view - print the ksp data structure at the end of a KSPSolve call

     87:    Note:
     88:    The available visualization contexts include
     89: +     PETSC_VIEWER_STDOUT_SELF - standard output (default)
     90: -     PETSC_VIEWER_STDOUT_WORLD - synchronized standard
     91:          output where only the first processor opens
     92:          the file.  All other processors send their
     93:          data to the first processor to print.

     95:    The user can open an alternative visualization context with
     96:    PetscViewerASCIIOpen() - output to a specified file.

     98:    Level: beginner

    100: .keywords: KSP, view

    102: .seealso: PCView(), PetscViewerASCIIOpen()
    103: @*/
    104: PetscErrorCode  KSPView(KSP ksp,PetscViewer viewer)
    105: {
    107:   PetscBool      iascii,isbinary,isdraw;
    108: #if defined(PETSC_HAVE_SAWS)
    109:   PetscBool      issaws;
    110: #endif

    114:   if (!viewer) {
    115:     PetscViewerASCIIGetStdout(PetscObjectComm((PetscObject)ksp),&viewer);
    116:   }

    120:   PetscObjectTypeCompare((PetscObject)viewer,PETSCVIEWERASCII,&iascii);
    121:   PetscObjectTypeCompare((PetscObject)viewer,PETSCVIEWERBINARY,&isbinary);
    122:   PetscObjectTypeCompare((PetscObject)viewer,PETSCVIEWERDRAW,&isdraw);
    123: #if defined(PETSC_HAVE_SAWS)
    124:   PetscObjectTypeCompare((PetscObject)viewer,PETSCVIEWERSAWS,&issaws);
    125: #endif
    126:   if (iascii) {
    127:     PetscObjectPrintClassNamePrefixType((PetscObject)ksp,viewer);
    128:     if (ksp->ops->view) {
    129:       PetscViewerASCIIPushTab(viewer);
    130:       (*ksp->ops->view)(ksp,viewer);
    131:       PetscViewerASCIIPopTab(viewer);
    132:     }
    133:     if (ksp->guess_zero) {
    134:       PetscViewerASCIIPrintf(viewer,"  maximum iterations=%D, initial guess is zero\n",ksp->max_it);
    135:     } else {
    136:       PetscViewerASCIIPrintf(viewer,"  maximum iterations=%D, nonzero initial guess\n", ksp->max_it);
    137:     }
    138:     if (ksp->guess_knoll) {PetscViewerASCIIPrintf(viewer,"  using preconditioner applied to right hand side for initial guess\n");}
    139:     PetscViewerASCIIPrintf(viewer,"  tolerances:  relative=%g, absolute=%g, divergence=%g\n",(double)ksp->rtol,(double)ksp->abstol,(double)ksp->divtol);
    140:     if (ksp->pc_side == PC_RIGHT) {
    141:       PetscViewerASCIIPrintf(viewer,"  right preconditioning\n");
    142:     } else if (ksp->pc_side == PC_SYMMETRIC) {
    143:       PetscViewerASCIIPrintf(viewer,"  symmetric preconditioning\n");
    144:     } else {
    145:       PetscViewerASCIIPrintf(viewer,"  left preconditioning\n");
    146:     }
    147:     if (ksp->guess) {
    148:       PetscViewerASCIIPushTab(viewer);
    149:       KSPGuessView(ksp->guess,viewer);
    150:       PetscViewerASCIIPopTab(viewer);
    151:     }
    152:     if (ksp->dscale) {PetscViewerASCIIPrintf(viewer,"  diagonally scaled system\n");}
    153:     PetscViewerASCIIPrintf(viewer,"  using %s norm type for convergence test\n",KSPNormTypes[ksp->normtype]);
    154:   } else if (isbinary) {
    155:     PetscInt    classid = KSP_FILE_CLASSID;
    156:     MPI_Comm    comm;
    157:     PetscMPIInt rank;
    158:     char        type[256];

    160:     PetscObjectGetComm((PetscObject)ksp,&comm);
    161:     MPI_Comm_rank(comm,&rank);
    162:     if (!rank) {
    163:       PetscViewerBinaryWrite(viewer,&classid,1,PETSC_INT,PETSC_FALSE);
    164:       PetscStrncpy(type,((PetscObject)ksp)->type_name,256);
    165:       PetscViewerBinaryWrite(viewer,type,256,PETSC_CHAR,PETSC_FALSE);
    166:     }
    167:     if (ksp->ops->view) {
    168:       (*ksp->ops->view)(ksp,viewer);
    169:     }
    170:   } else if (isdraw) {
    171:     PetscDraw draw;
    172:     char      str[36];
    173:     PetscReal x,y,bottom,h;
    174:     PetscBool flg;

    176:     PetscViewerDrawGetDraw(viewer,0,&draw);
    177:     PetscDrawGetCurrentPoint(draw,&x,&y);
    178:     PetscObjectTypeCompare((PetscObject)ksp,KSPPREONLY,&flg);
    179:     if (!flg) {
    180:       PetscStrncpy(str,"KSP: ",sizeof(str));
    181:       PetscStrlcat(str,((PetscObject)ksp)->type_name,sizeof(str));
    182:       PetscDrawStringBoxed(draw,x,y,PETSC_DRAW_RED,PETSC_DRAW_BLACK,str,NULL,&h);
    183:       bottom = y - h;
    184:     } else {
    185:       bottom = y;
    186:     }
    187:     PetscDrawPushCurrentPoint(draw,x,bottom);
    188: #if defined(PETSC_HAVE_SAWS)
    189:   } else if (issaws) {
    190:     PetscMPIInt rank;
    191:     const char  *name;

    193:     PetscObjectGetName((PetscObject)ksp,&name);
    194:     MPI_Comm_rank(PETSC_COMM_WORLD,&rank);
    195:     if (!((PetscObject)ksp)->amsmem && !rank) {
    196:       char       dir[1024];

    198:       PetscObjectViewSAWs((PetscObject)ksp,viewer);
    199:       PetscSNPrintf(dir,1024,"/PETSc/Objects/%s/its",name);
    200:       PetscStackCallSAWs(SAWs_Register,(dir,&ksp->its,1,SAWs_READ,SAWs_INT));
    201:       if (!ksp->res_hist) {
    202:         KSPSetResidualHistory(ksp,NULL,PETSC_DECIDE,PETSC_TRUE);
    203:       }
    204:       PetscSNPrintf(dir,1024,"/PETSc/Objects/%s/res_hist",name);
    205:       PetscStackCallSAWs(SAWs_Register,(dir,ksp->res_hist,10,SAWs_READ,SAWs_DOUBLE));
    206:     }
    207: #endif
    208:   } else if (ksp->ops->view) {
    209:     (*ksp->ops->view)(ksp,viewer);
    210:   }
    211:   if (!ksp->skippcsetfromoptions) {
    212:     if (!ksp->pc) {KSPGetPC(ksp,&ksp->pc);}
    213:     PCView(ksp->pc,viewer);
    214:   }
    215:   if (isdraw) {
    216:     PetscDraw draw;
    217:     PetscViewerDrawGetDraw(viewer,0,&draw);
    218:     PetscDrawPopCurrentPoint(draw);
    219:   }
    220:   return(0);
    221: }

    224: /*@
    225:    KSPSetNormType - Sets the norm that is used for convergence testing.

    227:    Logically Collective on KSP

    229:    Input Parameter:
    230: +  ksp - Krylov solver context
    231: -  normtype - one of
    232: $   KSP_NORM_NONE - skips computing the norm, this should only be used if you are using
    233: $                 the Krylov method as a smoother with a fixed small number of iterations.
    234: $                 Implicitly sets KSPConvergedSkip as KSP convergence test.
    235: $   KSP_NORM_PRECONDITIONED - the default for left preconditioned solves, uses the l2 norm
    236: $                 of the preconditioned residual P^{-1}(b - A x)
    237: $   KSP_NORM_UNPRECONDITIONED - uses the l2 norm of the true b - Ax residual.
    238: $   KSP_NORM_NATURAL - supported  by KSPCG, KSPCR, KSPCGNE, KSPCGS

    241:    Options Database Key:
    242: .   -ksp_norm_type <none,preconditioned,unpreconditioned,natural>

    244:    Notes:
    245:    Not all combinations of preconditioner side (see KSPSetPCSide()) and norm type are supported by all Krylov methods.
    246:    If only one is set, PETSc tries to automatically change the other to find a compatible pair.  If no such combination
    247:    is supported, PETSc will generate an error.

    249:    Developer Notes:
    250:    Supported combinations of norm and preconditioner side are set using KSPSetSupportedNorm().

    252:    Level: advanced

    254: .keywords: KSP, create, context, norms

    256: .seealso: KSPSetUp(), KSPSolve(), KSPDestroy(), KSPConvergedSkip(), KSPSetCheckNormIteration(), KSPSetPCSide(), KSPGetPCSide(), KSPNormType
    257: @*/
    258: PetscErrorCode  KSPSetNormType(KSP ksp,KSPNormType normtype)
    259: {
    263:   ksp->normtype = ksp->normtype_set = normtype;
    264:   return(0);
    265: }

    267: /*@
    268:    KSPSetCheckNormIteration - Sets the first iteration at which the norm of the residual will be
    269:      computed and used in the convergence test.

    271:    Logically Collective on KSP

    273:    Input Parameter:
    274: +  ksp - Krylov solver context
    275: -  it  - use -1 to check at all iterations

    277:    Notes:
    278:    Currently only works with KSPCG, KSPBCGS and KSPIBCGS

    280:    Use KSPSetNormType(ksp,KSP_NORM_NONE) to never check the norm

    282:    On steps where the norm is not computed, the previous norm is still in the variable, so if you run with, for example,
    283:     -ksp_monitor the residual norm will appear to be unchanged for several iterations (though it is not really unchanged).
    284:    Level: advanced

    286: .keywords: KSP, create, context, norms

    288: .seealso: KSPSetUp(), KSPSolve(), KSPDestroy(), KSPConvergedSkip(), KSPSetNormType()
    289: @*/
    290: PetscErrorCode  KSPSetCheckNormIteration(KSP ksp,PetscInt it)
    291: {
    295:   ksp->chknorm = it;
    296:   return(0);
    297: }

    299: /*@
    300:    KSPSetLagNorm - Lags the residual norm calculation so that it is computed as part of the MPI_Allreduce() for
    301:    computing the inner products for the next iteration.  This can reduce communication costs at the expense of doing
    302:    one additional iteration.

    305:    Logically Collective on KSP

    307:    Input Parameter:
    308: +  ksp - Krylov solver context
    309: -  flg - PETSC_TRUE or PETSC_FALSE

    311:    Options Database Keys:
    312: .  -ksp_lag_norm - lag the calculated residual norm

    314:    Notes:
    315:    Currently only works with KSPIBCGS.

    317:    Use KSPSetNormType(ksp,KSP_NORM_NONE) to never check the norm

    319:    If you lag the norm and run with, for example, -ksp_monitor, the residual norm reported will be the lagged one.
    320:    Level: advanced

    322: .keywords: KSP, create, context, norms

    324: .seealso: KSPSetUp(), KSPSolve(), KSPDestroy(), KSPConvergedSkip(), KSPSetNormType(), KSPSetCheckNormIteration()
    325: @*/
    326: PetscErrorCode  KSPSetLagNorm(KSP ksp,PetscBool flg)
    327: {
    331:   ksp->lagnorm = flg;
    332:   return(0);
    333: }

    335: /*@
    336:    KSPSetSupportedNorm - Sets a norm and preconditioner side supported by a KSP

    338:    Logically Collective

    340:    Input Arguments:
    341: +  ksp - Krylov method
    342: .  normtype - supported norm type
    343: .  pcside - preconditioner side that can be used with this norm
    344: -  priority - positive integer preference for this combination; larger values have higher priority

    346:    Level: developer

    348:    Notes:
    349:    This function should be called from the implementation files KSPCreate_XXX() to declare
    350:    which norms and preconditioner sides are supported. Users should not need to call this
    351:    function.

    353: .seealso: KSPSetNormType(), KSPSetPCSide()
    354: @*/
    355: PetscErrorCode KSPSetSupportedNorm(KSP ksp,KSPNormType normtype,PCSide pcside,PetscInt priority)
    356: {

    360:   ksp->normsupporttable[normtype][pcside] = priority;
    361:   return(0);
    362: }

    364: PetscErrorCode KSPNormSupportTableReset_Private(KSP ksp)
    365: {

    369:   PetscMemzero(ksp->normsupporttable,sizeof(ksp->normsupporttable));
    370:   ksp->pc_side  = ksp->pc_side_set;
    371:   ksp->normtype = ksp->normtype_set;
    372:   return(0);
    373: }

    375: PetscErrorCode KSPSetUpNorms_Private(KSP ksp,PetscBool errorifnotsupported,KSPNormType *normtype,PCSide *pcside)
    376: {
    377:   PetscInt i,j,best,ibest = 0,jbest = 0;

    380:   best = 0;
    381:   for (i=0; i<KSP_NORM_MAX; i++) {
    382:     for (j=0; j<PC_SIDE_MAX; j++) {
    383:       if ((ksp->normtype == KSP_NORM_DEFAULT || ksp->normtype == i) && (ksp->pc_side == PC_SIDE_DEFAULT || ksp->pc_side == j) && (ksp->normsupporttable[i][j] > best)) {
    384:         best  = ksp->normsupporttable[i][j];
    385:         ibest = i;
    386:         jbest = j;
    387:       }
    388:     }
    389:   }
    390:   if (best < 1 && errorifnotsupported) {
    391:     if (ksp->normtype == KSP_NORM_DEFAULT && ksp->pc_side == PC_SIDE_DEFAULT) SETERRQ1(PetscObjectComm((PetscObject)ksp),PETSC_ERR_PLIB,"The %s KSP implementation did not call KSPSetSupportedNorm()",((PetscObject)ksp)->type_name);
    392:     if (ksp->normtype == KSP_NORM_DEFAULT) SETERRQ2(PetscObjectComm((PetscObject)ksp),PETSC_ERR_SUP,"KSP %s does not support %s",((PetscObject)ksp)->type_name,PCSides[ksp->pc_side]);
    393:     if (ksp->pc_side == PC_SIDE_DEFAULT) SETERRQ2(PetscObjectComm((PetscObject)ksp),PETSC_ERR_SUP,"KSP %s does not support %s",((PetscObject)ksp)->type_name,KSPNormTypes[ksp->normtype]);
    394:     SETERRQ3(PetscObjectComm((PetscObject)ksp),PETSC_ERR_SUP,"KSP %s does not support %s with %s",((PetscObject)ksp)->type_name,KSPNormTypes[ksp->normtype],PCSides[ksp->pc_side]);
    395:   }
    396:   if (normtype) *normtype = (KSPNormType)ibest;
    397:   if (pcside)   *pcside   = (PCSide)jbest;
    398:   return(0);
    399: }

    401: /*@
    402:    KSPGetNormType - Gets the norm that is used for convergence testing.

    404:    Not Collective

    406:    Input Parameter:
    407: .  ksp - Krylov solver context

    409:    Output Parameter:
    410: .  normtype - norm that is used for convergence testing

    412:    Level: advanced

    414: .keywords: KSP, create, context, norms

    416: .seealso: KSPNormType, KSPSetNormType(), KSPConvergedSkip()
    417: @*/
    418: PetscErrorCode  KSPGetNormType(KSP ksp, KSPNormType *normtype)
    419: {

    425:   KSPSetUpNorms_Private(ksp,PETSC_TRUE,&ksp->normtype,&ksp->pc_side);
    426:   *normtype = ksp->normtype;
    427:   return(0);
    428: }

    430: #if defined(PETSC_HAVE_SAWS)
    431:  #include <petscviewersaws.h>
    432: #endif

    434: /*@
    435:    KSPSetOperators - Sets the matrix associated with the linear system
    436:    and a (possibly) different one associated with the preconditioner.

    438:    Collective on KSP and Mat

    440:    Input Parameters:
    441: +  ksp - the KSP context
    442: .  Amat - the matrix that defines the linear system
    443: -  Pmat - the matrix to be used in constructing the preconditioner, usually the same as Amat.

    445:    Notes:

    447:     If you know the operator Amat has a null space you can use MatSetNullSpace() and MatSetTransposeNullSpace() to supply the null
    448:     space to Amat and the KSP solvers will automatically use that null space as needed during the solution process.

    450:     All future calls to KSPSetOperators() must use the same size matrices!

    452:     Passing a NULL for Amat or Pmat removes the matrix that is currently used.

    454:     If you wish to replace either Amat or Pmat but leave the other one untouched then
    455:     first call KSPGetOperators() to get the one you wish to keep, call PetscObjectReference()
    456:     on it and then pass it back in in your call to KSPSetOperators().

    458:     Level: beginner

    460:    Alternative usage: If the operators have NOT been set with KSP/PCSetOperators() then the operators
    461:       are created in PC and returned to the user. In this case, if both operators
    462:       mat and pmat are requested, two DIFFERENT operators will be returned. If
    463:       only one is requested both operators in the PC will be the same (i.e. as
    464:       if one had called KSP/PCSetOperators() with the same argument for both Mats).
    465:       The user must set the sizes of the returned matrices and their type etc just
    466:       as if the user created them with MatCreate(). For example,

    468: $         KSP/PCGetOperators(ksp/pc,&mat,NULL); is equivalent to
    469: $           set size, type, etc of mat

    471: $         MatCreate(comm,&mat);
    472: $         KSP/PCSetOperators(ksp/pc,mat,mat);
    473: $         PetscObjectDereference((PetscObject)mat);
    474: $           set size, type, etc of mat

    476:      and

    478: $         KSP/PCGetOperators(ksp/pc,&mat,&pmat); is equivalent to
    479: $           set size, type, etc of mat and pmat

    481: $         MatCreate(comm,&mat);
    482: $         MatCreate(comm,&pmat);
    483: $         KSP/PCSetOperators(ksp/pc,mat,pmat);
    484: $         PetscObjectDereference((PetscObject)mat);
    485: $         PetscObjectDereference((PetscObject)pmat);
    486: $           set size, type, etc of mat and pmat

    488:     The rational for this support is so that when creating a TS, SNES, or KSP the hierarchy
    489:     of underlying objects (i.e. SNES, KSP, PC, Mat) and their livespans can be completely
    490:     managed by the top most level object (i.e. the TS, SNES, or KSP). Another way to look
    491:     at this is when you create a SNES you do not NEED to create a KSP and attach it to
    492:     the SNES object (the SNES object manages it for you). Similarly when you create a KSP
    493:     you do not need to attach a PC to it (the KSP object manages the PC object for you).
    494:     Thus, why should YOU have to create the Mat and attach it to the SNES/KSP/PC, when
    495:     it can be created for you?

    497: .keywords: KSP, set, operators, matrix, preconditioner, linear system

    499: .seealso: KSPSolve(), KSPGetPC(), PCGetOperators(), PCSetOperators(), KSPGetOperators(), KSPSetComputeOperators(), KSPSetComputeInitialGuess(), KSPSetComputeRHS()
    500: @*/
    501: PetscErrorCode  KSPSetOperators(KSP ksp,Mat Amat,Mat Pmat)
    502: {

    511:   if (!ksp->pc) {KSPGetPC(ksp,&ksp->pc);}
    512:   PCSetOperators(ksp->pc,Amat,Pmat);
    513:   if (ksp->setupstage == KSP_SETUP_NEWRHS) ksp->setupstage = KSP_SETUP_NEWMATRIX;  /* so that next solve call will call PCSetUp() on new matrix */
    514:   return(0);
    515: }

    517: /*@
    518:    KSPGetOperators - Gets the matrix associated with the linear system
    519:    and a (possibly) different one associated with the preconditioner.

    521:    Collective on KSP and Mat

    523:    Input Parameter:
    524: .  ksp - the KSP context

    526:    Output Parameters:
    527: +  Amat - the matrix that defines the linear system
    528: -  Pmat - the matrix to be used in constructing the preconditioner, usually the same as Amat.

    530:     Level: intermediate

    532:    Notes:
    533:     DOES NOT increase the reference counts of the matrix, so you should NOT destroy them.

    535: .keywords: KSP, set, get, operators, matrix, preconditioner, linear system

    537: .seealso: KSPSolve(), KSPGetPC(), PCGetOperators(), PCSetOperators(), KSPSetOperators(), KSPGetOperatorsSet()
    538: @*/
    539: PetscErrorCode  KSPGetOperators(KSP ksp,Mat *Amat,Mat *Pmat)
    540: {

    545:   if (!ksp->pc) {KSPGetPC(ksp,&ksp->pc);}
    546:   PCGetOperators(ksp->pc,Amat,Pmat);
    547:   return(0);
    548: }

    550: /*@C
    551:    KSPGetOperatorsSet - Determines if the matrix associated with the linear system and
    552:    possibly a different one associated with the preconditioner have been set in the KSP.

    554:    Not collective, though the results on all processes should be the same

    556:    Input Parameter:
    557: .  pc - the KSP context

    559:    Output Parameters:
    560: +  mat - the matrix associated with the linear system was set
    561: -  pmat - matrix associated with the preconditioner was set, usually the same

    563:    Level: intermediate

    565: .keywords: KSP, get, operators, matrix, linear system

    567: .seealso: PCSetOperators(), KSPGetOperators(), KSPSetOperators(), PCGetOperators(), PCGetOperatorsSet()
    568: @*/
    569: PetscErrorCode  KSPGetOperatorsSet(KSP ksp,PetscBool  *mat,PetscBool  *pmat)
    570: {

    575:   if (!ksp->pc) {KSPGetPC(ksp,&ksp->pc);}
    576:   PCGetOperatorsSet(ksp->pc,mat,pmat);
    577:   return(0);
    578: }

    580: /*@C
    581:    KSPSetPreSolve - Sets a function that is called before every KSPSolve() is started

    583:    Logically Collective on KSP

    585:    Input Parameters:
    586: +   ksp - the solver object
    587: .   presolve - the function to call before the solve
    588: -   prectx - any context needed by the function

    590:    Level: developer

    592: .keywords: KSP, create, context

    594: .seealso: KSPSetUp(), KSPSolve(), KSPDestroy(), KSP, KSPSetPostSolve()
    595: @*/
    596: PetscErrorCode  KSPSetPreSolve(KSP ksp,PetscErrorCode (*presolve)(KSP,Vec,Vec,void*),void *prectx)
    597: {
    600:   ksp->presolve = presolve;
    601:   ksp->prectx   = prectx;
    602:   return(0);
    603: }

    605: /*@C
    606:    KSPSetPostSolve - Sets a function that is called after every KSPSolve() completes (whether it converges or not)

    608:    Logically Collective on KSP

    610:    Input Parameters:
    611: +   ksp - the solver object
    612: .   postsolve - the function to call after the solve
    613: -   postctx - any context needed by the function

    615:    Level: developer

    617: .keywords: KSP, create, context

    619: .seealso: KSPSetUp(), KSPSolve(), KSPDestroy(), KSP, KSPSetPreSolve()
    620: @*/
    621: PetscErrorCode  KSPSetPostSolve(KSP ksp,PetscErrorCode (*postsolve)(KSP,Vec,Vec,void*),void *postctx)
    622: {
    625:   ksp->postsolve = postsolve;
    626:   ksp->postctx   = postctx;
    627:   return(0);
    628: }

    630: /*@
    631:    KSPCreate - Creates the default KSP context.

    633:    Collective on MPI_Comm

    635:    Input Parameter:
    636: .  comm - MPI communicator

    638:    Output Parameter:
    639: .  ksp - location to put the KSP context

    641:    Notes:
    642:    The default KSP type is GMRES with a restart of 30, using modified Gram-Schmidt
    643:    orthogonalization.

    645:    Level: beginner

    647: .keywords: KSP, create, context

    649: .seealso: KSPSetUp(), KSPSolve(), KSPDestroy(), KSP
    650: @*/
    651: PetscErrorCode  KSPCreate(MPI_Comm comm,KSP *inksp)
    652: {
    653:   KSP            ksp;
    655:   void           *ctx;

    659:   *inksp = 0;
    660:   KSPInitializePackage();

    662:   PetscHeaderCreate(ksp,KSP_CLASSID,"KSP","Krylov Method","KSP",comm,KSPDestroy,KSPView);

    664:   ksp->max_it  = 10000;
    665:   ksp->pc_side = ksp->pc_side_set = PC_SIDE_DEFAULT;
    666:   ksp->rtol    = 1.e-5;
    667: #if defined(PETSC_USE_REAL_SINGLE)
    668:   ksp->abstol  = 1.e-25;
    669: #else
    670:   ksp->abstol  = 1.e-50;
    671: #endif
    672:   ksp->divtol  = 1.e4;

    674:   ksp->chknorm        = -1;
    675:   ksp->normtype       = ksp->normtype_set = KSP_NORM_DEFAULT;
    676:   ksp->rnorm          = 0.0;
    677:   ksp->its            = 0;
    678:   ksp->guess_zero     = PETSC_TRUE;
    679:   ksp->calc_sings     = PETSC_FALSE;
    680:   ksp->res_hist       = NULL;
    681:   ksp->res_hist_alloc = NULL;
    682:   ksp->res_hist_len   = 0;
    683:   ksp->res_hist_max   = 0;
    684:   ksp->res_hist_reset = PETSC_TRUE;
    685:   ksp->numbermonitors = 0;
    686:   ksp->setfromoptionscalled = 0;

    688:   KSPConvergedDefaultCreate(&ctx);
    689:   KSPSetConvergenceTest(ksp,KSPConvergedDefault,ctx,KSPConvergedDefaultDestroy);
    690:   ksp->ops->buildsolution = KSPBuildSolutionDefault;
    691:   ksp->ops->buildresidual = KSPBuildResidualDefault;

    693:   ksp->vec_sol    = 0;
    694:   ksp->vec_rhs    = 0;
    695:   ksp->pc         = 0;
    696:   ksp->data       = 0;
    697:   ksp->nwork      = 0;
    698:   ksp->work       = 0;
    699:   ksp->reason     = KSP_CONVERGED_ITERATING;
    700:   ksp->setupstage = KSP_SETUP_NEW;

    702:   KSPNormSupportTableReset_Private(ksp);

    704:   *inksp = ksp;
    705:   return(0);
    706: }

    708: /*@C
    709:    KSPSetType - Builds KSP for a particular solver.

    711:    Logically Collective on KSP

    713:    Input Parameters:
    714: +  ksp      - the Krylov space context
    715: -  type - a known method

    717:    Options Database Key:
    718: .  -ksp_type  <method> - Sets the method; use -help for a list
    719:     of available methods (for instance, cg or gmres)

    721:    Notes:
    722:    See "petsc/include/petscksp.h" for available methods (for instance,
    723:    KSPCG or KSPGMRES).

    725:   Normally, it is best to use the KSPSetFromOptions() command and
    726:   then set the KSP type from the options database rather than by using
    727:   this routine.  Using the options database provides the user with
    728:   maximum flexibility in evaluating the many different Krylov methods.
    729:   The KSPSetType() routine is provided for those situations where it
    730:   is necessary to set the iterative solver independently of the command
    731:   line or options database.  This might be the case, for example, when
    732:   the choice of iterative solver changes during the execution of the
    733:   program, and the user's application is taking responsibility for
    734:   choosing the appropriate method.  In other words, this routine is
    735:   not for beginners.

    737:   Level: intermediate

    739:   Developer Note: KSPRegister() is used to add Krylov types to KSPList from which they
    740:   are accessed by KSPSetType().

    742: .keywords: KSP, set, method

    744: .seealso: PCSetType(), KSPType, KSPRegister(), KSPCreate()

    746: @*/
    747: PetscErrorCode  KSPSetType(KSP ksp, KSPType type)
    748: {
    749:   PetscErrorCode ierr,(*r)(KSP);
    750:   PetscBool      match;
    751:   void           *ctx;

    757:   PetscObjectTypeCompare((PetscObject)ksp,type,&match);
    758:   if (match) return(0);

    760:    PetscFunctionListFind(KSPList,type,&r);
    761:   if (!r) SETERRQ1(PetscObjectComm((PetscObject)ksp),PETSC_ERR_ARG_UNKNOWN_TYPE,"Unable to find requested KSP type %s",type);
    762:   /* Destroy the previous private KSP context */
    763:   if (ksp->ops->destroy) {
    764:     (*ksp->ops->destroy)(ksp);
    765:     ksp->ops->destroy = NULL;
    766:   }
    767:   /* Reinitialize function pointers in KSPOps structure */
    768:   PetscMemzero(ksp->ops,sizeof(struct _KSPOps));
    769:   KSPConvergedDefaultCreate(&ctx);
    770:   KSPSetConvergenceTest(ksp,KSPConvergedDefault,ctx,KSPConvergedDefaultDestroy);
    771:   ksp->ops->buildsolution = KSPBuildSolutionDefault;
    772:   ksp->ops->buildresidual = KSPBuildResidualDefault;
    773:   KSPNormSupportTableReset_Private(ksp);
    774:   /* Call the KSPCreate_XXX routine for this particular Krylov solver */
    775:   ksp->setupstage = KSP_SETUP_NEW;
    776:   PetscObjectChangeTypeName((PetscObject)ksp,type);
    777:   (*r)(ksp);
    778:   return(0);
    779: }

    781: /*@C
    782:    KSPGetType - Gets the KSP type as a string from the KSP object.

    784:    Not Collective

    786:    Input Parameter:
    787: .  ksp - Krylov context

    789:    Output Parameter:
    790: .  name - name of KSP method

    792:    Level: intermediate

    794: .keywords: KSP, get, method, name

    796: .seealso: KSPSetType()
    797: @*/
    798: PetscErrorCode  KSPGetType(KSP ksp,KSPType *type)
    799: {
    803:   *type = ((PetscObject)ksp)->type_name;
    804:   return(0);
    805: }

    807: /*@C
    808:   KSPRegister -  Adds a method to the Krylov subspace solver package.

    810:    Not Collective

    812:    Input Parameters:
    813: +  name_solver - name of a new user-defined solver
    814: -  routine_create - routine to create method context

    816:    Notes:
    817:    KSPRegister() may be called multiple times to add several user-defined solvers.

    819:    Sample usage:
    820: .vb
    821:    KSPRegister("my_solver",MySolverCreate);
    822: .ve

    824:    Then, your solver can be chosen with the procedural interface via
    825: $     KSPSetType(ksp,"my_solver")
    826:    or at runtime via the option
    827: $     -ksp_type my_solver

    829:    Level: advanced

    831: .keywords: KSP, register

    833: .seealso: KSPRegisterAll(), KSPRegisterDestroy()

    835: @*/
    836: PetscErrorCode  KSPRegister(const char sname[],PetscErrorCode (*function)(KSP))
    837: {

    841:   KSPInitializePackage();
    842:   PetscFunctionListAdd(&KSPList,sname,function);
    843:   return(0);
    844: }