Date: 2015-10-02T22:07:38+00:00

Actual source code: shell.c
petsc-3.6.2 2015-10-02
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      2: /*
      3:    This provides a simple shell for Fortran (and C programmers) to
      4:   create a very simple matrix class for use with KSP without coding
      5:   much of anything.
      6: */

      8: #include <petsc/private/matimpl.h>        /*I "petscmat.h" I*/
      9: #include <petsc/private/vecimpl.h>

     11: typedef struct {
     12:   PetscErrorCode (*destroy)(Mat);
     13:   PetscErrorCode (*mult)(Mat,Vec,Vec);
     14:   PetscErrorCode (*multtranspose)(Mat,Vec,Vec);
     15:   PetscErrorCode (*getdiagonal)(Mat,Vec);

     17:   PetscScalar vscale,vshift;
     18:   Vec         dshift;
     19:   Vec         left,right;
     20:   Vec         dshift_owned,left_owned,right_owned;
     21:   Vec         left_work,right_work;
     22:   Vec         left_add_work,right_add_work;
     23:   PetscBool   usingscaled;
     24:   void        *ctx;
     25: } Mat_Shell;
     26: /*
     27:  The most general expression for the matrix is

     29:  S = L (a A + B) R

     31:  where
     32:  A is the matrix defined by the user's function
     33:  a is a scalar multiple
     34:  L is left scaling
     35:  R is right scaling
     36:  B is a diagonal shift defined by
     37:    diag(dshift) if the vector dshift is non-NULL
     38:    vscale*identity otherwise

     40:  The following identities apply:

     42:  Scale by c:
     43:   c [L (a A + B) R] = L [(a c) A + c B] R

     45:  Shift by c:
     46:   [L (a A + B) R] + c = L [a A + (B + c Linv Rinv)] R

     48:  Diagonal scaling is achieved by simply multiplying with existing L and R vectors

     50:  In the data structure:

     52:  vscale=1.0  means no special scaling will be applied
     53:  dshift=NULL means a constant diagonal shift (fall back to vshift)
     54:  vshift=0.0  means no constant diagonal shift, note that vshift is only used if dshift is NULL
     55: */

     57: static PetscErrorCode MatMult_Shell(Mat,Vec,Vec);
     58: static PetscErrorCode MatMultTranspose_Shell(Mat,Vec,Vec);
     59: static PetscErrorCode MatGetDiagonal_Shell(Mat,Vec);

     63: static PetscErrorCode MatShellUseScaledMethods(Mat Y)
     64: {
     65:   Mat_Shell *shell = (Mat_Shell*)Y->data;

     68:   if (shell->usingscaled) return(0);
     69:   shell->mult  = Y->ops->mult;
     70:   Y->ops->mult = MatMult_Shell;
     71:   if (Y->ops->multtranspose) {
     72:     shell->multtranspose  = Y->ops->multtranspose;
     73:     Y->ops->multtranspose = MatMultTranspose_Shell;
     74:   }
     75:   if (Y->ops->getdiagonal) {
     76:     shell->getdiagonal  = Y->ops->getdiagonal;
     77:     Y->ops->getdiagonal = MatGetDiagonal_Shell;
     78:   }
     79:   shell->usingscaled = PETSC_TRUE;
     80:   return(0);
     81: }

     85: static PetscErrorCode MatShellPreScaleLeft(Mat A,Vec x,Vec *xx)
     86: {
     87:   Mat_Shell      *shell = (Mat_Shell*)A->data;

     91:   *xx = NULL;
     92:   if (!shell->left) {
     93:     *xx = x;
     94:   } else {
     95:     if (!shell->left_work) {VecDuplicate(shell->left,&shell->left_work);}
     96:     VecPointwiseMult(shell->left_work,x,shell->left);
     97:     *xx  = shell->left_work;
     98:   }
     99:   return(0);
    100: }

    104: static PetscErrorCode MatShellPreScaleRight(Mat A,Vec x,Vec *xx)
    105: {
    106:   Mat_Shell      *shell = (Mat_Shell*)A->data;

    110:   *xx = NULL;
    111:   if (!shell->right) {
    112:     *xx = x;
    113:   } else {
    114:     if (!shell->right_work) {VecDuplicate(shell->right,&shell->right_work);}
    115:     VecPointwiseMult(shell->right_work,x,shell->right);
    116:     *xx  = shell->right_work;
    117:   }
    118:   return(0);
    119: }

    123: static PetscErrorCode MatShellPostScaleLeft(Mat A,Vec x)
    124: {
    125:   Mat_Shell      *shell = (Mat_Shell*)A->data;

    129:   if (shell->left) {VecPointwiseMult(x,x,shell->left);}
    130:   return(0);
    131: }

    135: static PetscErrorCode MatShellPostScaleRight(Mat A,Vec x)
    136: {
    137:   Mat_Shell      *shell = (Mat_Shell*)A->data;

    141:   if (shell->right) {VecPointwiseMult(x,x,shell->right);}
    142:   return(0);
    143: }

    147: static PetscErrorCode MatShellShiftAndScale(Mat A,Vec X,Vec Y)
    148: {
    149:   Mat_Shell      *shell = (Mat_Shell*)A->data;

    153:   if (shell->dshift) {          /* get arrays because there is no VecPointwiseMultAdd() */
    154:     PetscInt          i,m;
    155:     const PetscScalar *x,*d;
    156:     PetscScalar       *y;
    157:     VecGetLocalSize(X,&m);
    158:     VecGetArrayRead(shell->dshift,&d);
    159:     VecGetArrayRead(X,&x);
    160:     VecGetArray(Y,&y);
    161:     for (i=0; i<m; i++) y[i] = shell->vscale*y[i] + d[i]*x[i];
    162:     VecRestoreArrayRead(shell->dshift,&d);
    163:     VecRestoreArrayRead(X,&x);
    164:     VecRestoreArray(Y,&y);
    165:   } else if (PetscAbsScalar(shell->vshift) != 0) {
    166:     VecAXPBY(Y,shell->vshift,shell->vscale,X);
    167:   } else if (shell->vscale != 1.0) {
    168:     VecScale(Y,shell->vscale);
    169:   }
    170:   return(0);
    171: }

    175: /*@
    176:     MatShellGetContext - Returns the user-provided context associated with a shell matrix.

    178:     Not Collective

    180:     Input Parameter:
    181: .   mat - the matrix, should have been created with MatCreateShell()

    183:     Output Parameter:
    184: .   ctx - the user provided context

    186:     Level: advanced

    188:     Notes:
    189:     This routine is intended for use within various shell matrix routines,
    190:     as set with MatShellSetOperation().

    192: .keywords: matrix, shell, get, context

    194: .seealso: MatCreateShell(), MatShellSetOperation(), MatShellSetContext()
    195: @*/
    196: PetscErrorCode  MatShellGetContext(Mat mat,void *ctx)
    197: {
    199:   PetscBool      flg;

    204:   PetscObjectTypeCompare((PetscObject)mat,MATSHELL,&flg);
    205:   if (flg) *(void**)ctx = ((Mat_Shell*)(mat->data))->ctx;
    206:   else SETERRQ(PetscObjectComm((PetscObject)mat),PETSC_ERR_SUP,"Cannot get context from non-shell matrix");
    207:   return(0);
    208: }

    212: PetscErrorCode MatDestroy_Shell(Mat mat)
    213: {
    215:   Mat_Shell      *shell = (Mat_Shell*)mat->data;

    218:   if (shell->destroy) {
    219:     (*shell->destroy)(mat);
    220:   }
    221:   VecDestroy(&shell->left_owned);
    222:   VecDestroy(&shell->right_owned);
    223:   VecDestroy(&shell->dshift_owned);
    224:   VecDestroy(&shell->left_work);
    225:   VecDestroy(&shell->right_work);
    226:   VecDestroy(&shell->left_add_work);
    227:   VecDestroy(&shell->right_add_work);
    228:   PetscFree(mat->data);
    229:   return(0);
    230: }

    234: PetscErrorCode MatMult_Shell(Mat A,Vec x,Vec y)
    235: {
    236:   Mat_Shell      *shell = (Mat_Shell*)A->data;
    238:   Vec            xx;

    241:   MatShellPreScaleRight(A,x,&xx);
    242:   (*shell->mult)(A,xx,y);
    243:   MatShellShiftAndScale(A,xx,y);
    244:   MatShellPostScaleLeft(A,y);
    245:   return(0);
    246: }

    250: PetscErrorCode MatMultAdd_Shell(Mat A,Vec x,Vec y,Vec z)
    251: {
    252:   Mat_Shell      *shell = (Mat_Shell*)A->data;

    256:   if (y == z) {
    257:     if (!shell->right_add_work) {VecDuplicate(z,&shell->right_add_work);}
    258:     MatMult(A,x,shell->right_add_work);
    259:     VecAXPY(z,1.0,shell->right_add_work);
    260:   } else {
    261:     MatMult(A,x,z);
    262:     VecAXPY(z,1.0,y);
    263:   }
    264:   return(0);
    265: }

    269: PetscErrorCode MatMultTranspose_Shell(Mat A,Vec x,Vec y)
    270: {
    271:   Mat_Shell      *shell = (Mat_Shell*)A->data;
    273:   Vec            xx;

    276:   MatShellPreScaleLeft(A,x,&xx);
    277:   (*shell->multtranspose)(A,xx,y);
    278:   MatShellShiftAndScale(A,xx,y);
    279:   MatShellPostScaleRight(A,y);
    280:   return(0);
    281: }

    285: PetscErrorCode MatMultTransposeAdd_Shell(Mat A,Vec x,Vec y,Vec z)
    286: {
    287:   Mat_Shell      *shell = (Mat_Shell*)A->data;

    291:   if (y == z) {
    292:     if (!shell->left_add_work) {VecDuplicate(z,&shell->left_add_work);}
    293:     MatMultTranspose(A,x,shell->left_add_work);
    294:     VecWAXPY(z,1.0,shell->left_add_work,y);
    295:   } else {
    296:     MatMultTranspose(A,x,z);
    297:     VecAXPY(z,1.0,y);
    298:   }
    299:   return(0);
    300: }

    304: PetscErrorCode MatGetDiagonal_Shell(Mat A,Vec v)
    305: {
    306:   Mat_Shell      *shell = (Mat_Shell*)A->data;

    310:   (*shell->getdiagonal)(A,v);
    311:   VecScale(v,shell->vscale);
    312:   if (shell->dshift) {
    313:     VecPointwiseMult(v,v,shell->dshift);
    314:   } else {
    315:     VecShift(v,shell->vshift);
    316:   }
    317:   if (shell->left)  {VecPointwiseMult(v,v,shell->left);}
    318:   if (shell->right) {VecPointwiseMult(v,v,shell->right);}
    319:   return(0);
    320: }

    324: PetscErrorCode MatShift_Shell(Mat Y,PetscScalar a)
    325: {
    326:   Mat_Shell      *shell = (Mat_Shell*)Y->data;

    330:   if (shell->left || shell->right || shell->dshift) {
    331:     if (!shell->dshift) {
    332:       if (!shell->dshift_owned) {VecDuplicate(shell->left ? shell->left : shell->right, &shell->dshift_owned);}
    333:       shell->dshift = shell->dshift_owned;
    334:       VecSet(shell->dshift,shell->vshift+a);
    335:     } else {VecScale(shell->dshift,a);}
    336:     if (shell->left)  {VecPointwiseDivide(shell->dshift,shell->dshift,shell->left);}
    337:     if (shell->right) {VecPointwiseDivide(shell->dshift,shell->dshift,shell->right);}
    338:   } else shell->vshift += a;
    339:   MatShellUseScaledMethods(Y);
    340:   return(0);
    341: }

    345: PetscErrorCode MatScale_Shell(Mat Y,PetscScalar a)
    346: {
    347:   Mat_Shell      *shell = (Mat_Shell*)Y->data;

    351:   shell->vscale *= a;
    352:   if (shell->dshift) {
    353:     VecScale(shell->dshift,a);
    354:   } else shell->vshift *= a;
    355:   MatShellUseScaledMethods(Y);
    356:   return(0);
    357: }

    361: static PetscErrorCode MatDiagonalScale_Shell(Mat Y,Vec left,Vec right)
    362: {
    363:   Mat_Shell      *shell = (Mat_Shell*)Y->data;

    367:   if (left) {
    368:     if (!shell->left_owned) {VecDuplicate(left,&shell->left_owned);}
    369:     if (shell->left) {
    370:       VecPointwiseMult(shell->left,shell->left,left);
    371:     } else {
    372:       shell->left = shell->left_owned;
    373:       VecCopy(left,shell->left);
    374:     }
    375:   }
    376:   if (right) {
    377:     if (!shell->right_owned) {VecDuplicate(right,&shell->right_owned);}
    378:     if (shell->right) {
    379:       VecPointwiseMult(shell->right,shell->right,right);
    380:     } else {
    381:       shell->right = shell->right_owned;
    382:       VecCopy(right,shell->right);
    383:     }
    384:   }
    385:   MatShellUseScaledMethods(Y);
    386:   return(0);
    387: }

    391: PetscErrorCode MatAssemblyEnd_Shell(Mat Y,MatAssemblyType t)
    392: {
    393:   Mat_Shell *shell = (Mat_Shell*)Y->data;

    396:   if (t == MAT_FINAL_ASSEMBLY) {
    397:     shell->vshift = 0.0;
    398:     shell->vscale = 1.0;
    399:     shell->dshift = NULL;
    400:     shell->left   = NULL;
    401:     shell->right  = NULL;
    402:     if (shell->mult) {
    403:       Y->ops->mult = shell->mult;
    404:       shell->mult  = NULL;
    405:     }
    406:     if (shell->multtranspose) {
    407:       Y->ops->multtranspose = shell->multtranspose;
    408:       shell->multtranspose  = NULL;
    409:     }
    410:     if (shell->getdiagonal) {
    411:       Y->ops->getdiagonal = shell->getdiagonal;
    412:       shell->getdiagonal  = NULL;
    413:     }
    414:     shell->usingscaled = PETSC_FALSE;
    415:   }
    416:   return(0);
    417: }

    419: extern PetscErrorCode MatConvert_Shell(Mat, MatType,MatReuse,Mat*);

    421: static struct _MatOps MatOps_Values = {0,
    422:                                        0,
    423:                                        0,
    424:                                        0,
    425:                                 /* 4*/ 0,
    426:                                        0,
    427:                                        0,
    428:                                        0,
    429:                                        0,
    430:                                        0,
    431:                                 /*10*/ 0,
    432:                                        0,
    433:                                        0,
    434:                                        0,
    435:                                        0,
    436:                                 /*15*/ 0,
    437:                                        0,
    438:                                        0,
    439:                                        MatDiagonalScale_Shell,
    440:                                        0,
    441:                                 /*20*/ 0,
    442:                                        MatAssemblyEnd_Shell,
    443:                                        0,
    444:                                        0,
    445:                                 /*24*/ 0,
    446:                                        0,
    447:                                        0,
    448:                                        0,
    449:                                        0,
    450:                                 /*29*/ 0,
    451:                                        0,
    452:                                        0,
    453:                                        0,
    454:                                        0,
    455:                                 /*34*/ 0,
    456:                                        0,
    457:                                        0,
    458:                                        0,
    459:                                        0,
    460:                                 /*39*/ 0,
    461:                                        0,
    462:                                        0,
    463:                                        0,
    464:                                        0,
    465:                                 /*44*/ 0,
    466:                                        MatScale_Shell,
    467:                                        MatShift_Shell,
    468:                                        0,
    469:                                        0,
    470:                                 /*49*/ 0,
    471:                                        0,
    472:                                        0,
    473:                                        0,
    474:                                        0,
    475:                                 /*54*/ 0,
    476:                                        0,
    477:                                        0,
    478:                                        0,
    479:                                        0,
    480:                                 /*59*/ 0,
    481:                                        MatDestroy_Shell,
    482:                                        0,
    483:                                        0,
    484:                                        0,
    485:                                 /*64*/ 0,
    486:                                        0,
    487:                                        0,
    488:                                        0,
    489:                                        0,
    490:                                 /*69*/ 0,
    491:                                        0,
    492:                                        MatConvert_Shell,
    493:                                        0,
    494:                                        0,
    495:                                 /*74*/ 0,
    496:                                        0,
    497:                                        0,
    498:                                        0,
    499:                                        0,
    500:                                 /*79*/ 0,
    501:                                        0,
    502:                                        0,
    503:                                        0,
    504:                                        0,
    505:                                 /*84*/ 0,
    506:                                        0,
    507:                                        0,
    508:                                        0,
    509:                                        0,
    510:                                 /*89*/ 0,
    511:                                        0,
    512:                                        0,
    513:                                        0,
    514:                                        0,
    515:                                 /*94*/ 0,
    516:                                        0,
    517:                                        0,
    518:                                        0,
    519:                                        0,
    520:                                 /*99*/ 0,
    521:                                        0,
    522:                                        0,
    523:                                        0,
    524:                                        0,
    525:                                /*104*/ 0,
    526:                                        0,
    527:                                        0,
    528:                                        0,
    529:                                        0,
    530:                                /*109*/ 0,
    531:                                        0,
    532:                                        0,
    533:                                        0,
    534:                                        0,
    535:                                /*114*/ 0,
    536:                                        0,
    537:                                        0,
    538:                                        0,
    539:                                        0,
    540:                                /*119*/ 0,
    541:                                        0,
    542:                                        0,
    543:                                        0,
    544:                                        0,
    545:                                /*124*/ 0,
    546:                                        0,
    547:                                        0,
    548:                                        0,
    549:                                        0,
    550:                                /*129*/ 0,
    551:                                        0,
    552:                                        0,
    553:                                        0,
    554:                                        0,
    555:                                /*134*/ 0,
    556:                                        0,
    557:                                        0,
    558:                                        0,
    559:                                        0,
    560:                                /*139*/ 0,
    561:                                        0,
    562:                                        0
    563: };

    565: /*MC
    566:    MATSHELL - MATSHELL = "shell" - A matrix type to be used to define your own matrix type -- perhaps matrix free.

    568:   Level: advanced

    570: .seealso: MatCreateShell
    571: M*/

    575: PETSC_EXTERN PetscErrorCode MatCreate_Shell(Mat A)
    576: {
    577:   Mat_Shell      *b;

    581:   PetscMemcpy(A->ops,&MatOps_Values,sizeof(struct _MatOps));

    583:   PetscNewLog(A,&b);
    584:   A->data = (void*)b;

    586:   PetscLayoutSetUp(A->rmap);
    587:   PetscLayoutSetUp(A->cmap);

    589:   b->ctx           = 0;
    590:   b->vshift        = 0.0;
    591:   b->vscale        = 1.0;
    592:   b->mult          = 0;
    593:   b->multtranspose = 0;
    594:   b->getdiagonal   = 0;
    595:   A->assembled     = PETSC_TRUE;
    596:   A->preallocated  = PETSC_FALSE;

    598:   PetscObjectChangeTypeName((PetscObject)A,MATSHELL);
    599:   return(0);
    600: }

    604: /*@C
    605:    MatCreateShell - Creates a new matrix class for use with a user-defined
    606:    private data storage format.

    608:   Collective on MPI_Comm

    610:    Input Parameters:
    611: +  comm - MPI communicator
    612: .  m - number of local rows (must be given)
    613: .  n - number of local columns (must be given)
    614: .  M - number of global rows (may be PETSC_DETERMINE)
    615: .  N - number of global columns (may be PETSC_DETERMINE)
    616: -  ctx - pointer to data needed by the shell matrix routines

    618:    Output Parameter:
    619: .  A - the matrix

    621:    Level: advanced

    623:   Usage:
    624: $    extern int mult(Mat,Vec,Vec);
    625: $    MatCreateShell(comm,m,n,M,N,ctx,&mat);
    626: $    MatShellSetOperation(mat,MATOP_MULT,(void(*)(void))mult);
    627: $    [ Use matrix for operations that have been set ]
    628: $    MatDestroy(mat);

    630:    Notes:
    631:    The shell matrix type is intended to provide a simple class to use
    632:    with KSP (such as, for use with matrix-free methods). You should not
    633:    use the shell type if you plan to define a complete matrix class.

    635:    Fortran Notes: The context can only be an integer or a PetscObject
    636:       unfortunately it cannot be a Fortran array or derived type.

    638:    PETSc requires that matrices and vectors being used for certain
    639:    operations are partitioned accordingly.  For example, when
    640:    creating a shell matrix, A, that supports parallel matrix-vector
    641:    products using MatMult(A,x,y) the user should set the number
    642:    of local matrix rows to be the number of local elements of the
    643:    corresponding result vector, y. Note that this is information is
    644:    required for use of the matrix interface routines, even though
    645:    the shell matrix may not actually be physically partitioned.
    646:    For example,

    648: $
    649: $     Vec x, y
    650: $     extern int mult(Mat,Vec,Vec);
    651: $     Mat A
    652: $
    653: $     VecCreateMPI(comm,PETSC_DECIDE,M,&y);
    654: $     VecCreateMPI(comm,PETSC_DECIDE,N,&x);
    655: $     VecGetLocalSize(y,&m);
    656: $     VecGetLocalSize(x,&n);
    657: $     MatCreateShell(comm,m,n,M,N,ctx,&A);
    658: $     MatShellSetOperation(mat,MATOP_MULT,(void(*)(void))mult);
    659: $     MatMult(A,x,y);
    660: $     MatDestroy(A);
    661: $     VecDestroy(y); VecDestroy(x);
    662: $

    664: .keywords: matrix, shell, create

    666: .seealso: MatShellSetOperation(), MatHasOperation(), MatShellGetContext(), MatShellSetContext()
    667: @*/
    668: PetscErrorCode  MatCreateShell(MPI_Comm comm,PetscInt m,PetscInt n,PetscInt M,PetscInt N,void *ctx,Mat *A)
    669: {

    673:   MatCreate(comm,A);
    674:   MatSetSizes(*A,m,n,M,N);
    675:   MatSetType(*A,MATSHELL);
    676:   MatShellSetContext(*A,ctx);
    677:   MatSetUp(*A);
    678:   return(0);
    679: }

    683: /*@
    684:     MatShellSetContext - sets the context for a shell matrix

    686:    Logically Collective on Mat

    688:     Input Parameters:
    689: +   mat - the shell matrix
    690: -   ctx - the context

    692:    Level: advanced

    694:    Fortran Notes: The context can only be an integer or a PetscObject
    695:       unfortunately it cannot be a Fortran array or derived type.

    697: .seealso: MatCreateShell(), MatShellGetContext(), MatShellGetOperation()
    698: @*/
    699: PetscErrorCode  MatShellSetContext(Mat mat,void *ctx)
    700: {
    701:   Mat_Shell      *shell = (Mat_Shell*)mat->data;
    703:   PetscBool      flg;

    707:   PetscObjectTypeCompare((PetscObject)mat,MATSHELL,&flg);
    708:   if (flg) {
    709:     shell->ctx = ctx;
    710:   } else SETERRQ(PetscObjectComm((PetscObject)mat),PETSC_ERR_SUP,"Cannot attach context to non-shell matrix");
    711:   return(0);
    712: }

    716: /*@C
    717:     MatShellSetOperation - Allows user to set a matrix operation for
    718:                            a shell matrix.

    720:    Logically Collective on Mat

    722:     Input Parameters:
    723: +   mat - the shell matrix
    724: .   op - the name of the operation
    725: -   f - the function that provides the operation.

    727:    Level: advanced

    729:     Usage:
    730: $      extern PetscErrorCode usermult(Mat,Vec,Vec);
    731: $      MatCreateShell(comm,m,n,M,N,ctx,&A);
    732: $      MatShellSetOperation(A,MATOP_MULT,(void(*)(void))usermult);

    734:     Notes:
    735:     See the file include/petscmat.h for a complete list of matrix
    736:     operations, which all have the form MATOP_<OPERATION>, where
    737:     <OPERATION> is the name (in all capital letters) of the
    738:     user interface routine (e.g., MatMult() -> MATOP_MULT).

    740:     All user-provided functions (execept for MATOP_DESTROY) should have the same calling
    741:     sequence as the usual matrix interface routines, since they
    742:     are intended to be accessed via the usual matrix interface
    743:     routines, e.g.,
    744: $       MatMult(Mat,Vec,Vec) -> usermult(Mat,Vec,Vec)

    746:     In particular each function MUST return an error code of 0 on success and
    747:     nonzero on failure.

    749:     Within each user-defined routine, the user should call
    750:     MatShellGetContext() to obtain the user-defined context that was
    751:     set by MatCreateShell().

    753:     Fortran Notes: For MatCreateVecs() the user code should check if the input left or right matrix is -1 and in that case not
    754:        generate a matrix. See src/mat/examples/tests/ex120f.F

    756: .keywords: matrix, shell, set, operation

    758: .seealso: MatCreateShell(), MatShellGetContext(), MatShellGetOperation(), MatShellSetContext()
    759: @*/
    760: PetscErrorCode  MatShellSetOperation(Mat mat,MatOperation op,void (*f)(void))
    761: {
    763:   PetscBool      flg;

    767:   switch (op) {
    768:   case MATOP_DESTROY:
    769:     PetscObjectTypeCompare((PetscObject)mat,MATSHELL,&flg);
    770:     if (flg) {
    771:       Mat_Shell *shell = (Mat_Shell*)mat->data;
    772:       shell->destroy = (PetscErrorCode (*)(Mat))f;
    773:     } else mat->ops->destroy = (PetscErrorCode (*)(Mat))f;
    774:     break;
    775:   case MATOP_VIEW:
    776:     mat->ops->view = (PetscErrorCode (*)(Mat,PetscViewer))f;
    777:     break;
    778:   case MATOP_MULT:
    779:     mat->ops->mult = (PetscErrorCode (*)(Mat,Vec,Vec))f;
    780:     if (!mat->ops->multadd) mat->ops->multadd = MatMultAdd_Shell;
    781:     break;
    782:   case MATOP_MULT_TRANSPOSE:
    783:     mat->ops->multtranspose = (PetscErrorCode (*)(Mat,Vec,Vec))f;
    784:     if (!mat->ops->multtransposeadd) mat->ops->multtransposeadd = MatMultTransposeAdd_Shell;
    785:     break;
    786:   default:
    787:     (((void(**)(void))mat->ops)[op]) = f;
    788:   }
    789:   return(0);
    790: }

    794: /*@C
    795:     MatShellGetOperation - Gets a matrix function for a shell matrix.

    797:     Not Collective

    799:     Input Parameters:
    800: +   mat - the shell matrix
    801: -   op - the name of the operation

    803:     Output Parameter:
    804: .   f - the function that provides the operation.

    806:     Level: advanced

    808:     Notes:
    809:     See the file include/petscmat.h for a complete list of matrix
    810:     operations, which all have the form MATOP_<OPERATION>, where
    811:     <OPERATION> is the name (in all capital letters) of the
    812:     user interface routine (e.g., MatMult() -> MATOP_MULT).

    814:     All user-provided functions have the same calling
    815:     sequence as the usual matrix interface routines, since they
    816:     are intended to be accessed via the usual matrix interface
    817:     routines, e.g.,
    818: $       MatMult(Mat,Vec,Vec) -> usermult(Mat,Vec,Vec)

    820:     Within each user-defined routine, the user should call
    821:     MatShellGetContext() to obtain the user-defined context that was
    822:     set by MatCreateShell().

    824: .keywords: matrix, shell, set, operation

    826: .seealso: MatCreateShell(), MatShellGetContext(), MatShellSetOperation(), MatShellSetContext()
    827: @*/
    828: PetscErrorCode  MatShellGetOperation(Mat mat,MatOperation op,void(**f)(void))
    829: {
    831:   PetscBool      flg;

    835:   if (op == MATOP_DESTROY) {
    836:     PetscObjectTypeCompare((PetscObject)mat,MATSHELL,&flg);
    837:     if (flg) {
    838:       Mat_Shell *shell = (Mat_Shell*)mat->data;
    839:       *f = (void (*)(void))shell->destroy;
    840:     } else {
    841:       *f = (void (*)(void))mat->ops->destroy;
    842:     }
    843:   } else if (op == MATOP_VIEW) {
    844:     *f = (void (*)(void))mat->ops->view;
    845:   } else {
    846:     *f = (((void (**)(void))mat->ops)[op]);
    847:   }
    848:   return(0);
    849: }