/*$Id: precon.c,v 1.216 2001/08/21 21:03:13 bsmith Exp $*/ /* The PC (preconditioner) interface routines, callable by users. */ #include "src/sles/pc/pcimpl.h" /*I "petscsles.h" I*/ /* Logging support */ int PC_COOKIE; int PC_SetUp, PC_SetUpOnBlocks, PC_Apply, PC_ApplyCoarse, PC_ApplyMultiple, PC_ApplySymmetricLeft; int PC_ApplySymmetricRight, PC_ModifySubMatrices; EXTERN int SLESInitializePackage(char *); #undef __FUNCT__ #define __FUNCT__ "PCNullSpaceAttach" /*@C PCNullSpaceAttach - attaches a null space to a preconditioner object. This null space will be removed from the resulting vector whenever the preconditioner is applied. Collective on PC Input Parameters: + pc - the preconditioner context - nullsp - the null space object Level: developer Notes: Overwrites any previous null space that may have been attached Users manual sections: . sec_singular .keywords: PC, destroy, null space .seealso: PCCreate(), PCSetUp(), MatNullSpaceCreate(), MatNullSpace @*/ int PCNullSpaceAttach(PC pc,MatNullSpace nullsp) { int ierr; PetscFunctionBegin; PetscValidHeaderSpecific(pc,PC_COOKIE); PetscValidHeaderSpecific(nullsp,MAT_NULLSPACE_COOKIE); if (pc->nullsp) { ierr = MatNullSpaceDestroy(pc->nullsp);CHKERRQ(ierr); } pc->nullsp = nullsp; ierr = PetscObjectReference((PetscObject)nullsp);CHKERRQ(ierr); PetscFunctionReturn(0); } #undef __FUNCT__ #define __FUNCT__ "PCDestroy" /*@C PCDestroy - Destroys PC context that was created with PCCreate(). Collective on PC Input Parameter: . pc - the preconditioner context Level: developer .keywords: PC, destroy .seealso: PCCreate(), PCSetUp() @*/ int PCDestroy(PC pc) { int ierr; PetscFunctionBegin; PetscValidHeaderSpecific(pc,PC_COOKIE); if (--pc->refct > 0) PetscFunctionReturn(0); /* if memory was published with AMS then destroy it */ ierr = PetscObjectDepublish(pc);CHKERRQ(ierr); if (pc->ops->destroy) {ierr = (*pc->ops->destroy)(pc);CHKERRQ(ierr);} if (pc->nullsp) {ierr = MatNullSpaceDestroy(pc->nullsp);CHKERRQ(ierr);} if (pc->diagonalscaleright) {ierr = VecDestroy(pc->diagonalscaleright);CHKERRQ(ierr);} if (pc->diagonalscaleleft) {ierr = VecDestroy(pc->diagonalscaleleft);CHKERRQ(ierr);} PetscLogObjectDestroy(pc); PetscHeaderDestroy(pc); PetscFunctionReturn(0); } #undef __FUNCT__ #define __FUNCT__ "PCDiagonalScale" /*@C PCDiagonalScale - Indicates if the preconditioner applies an additional left and right scaling as needed by certain time-stepping codes. Collective on PC Input Parameter: . pc - the preconditioner context Output Parameter: . flag - PETSC_TRUE if it applies the scaling Level: developer Notes: If this returns PETSC_TRUE then the system solved via the Krylov method is $ D M A D^{-1} y = D M b for left preconditioning or $ D A M D^{-1} z = D b for right preconditioning .keywords: PC .seealso: PCCreate(), PCSetUp(), PCDiagonalScaleLeft(), PCDiagonalScaleRight(), PCDiagonalScaleSet() @*/ int PCDiagonalScale(PC pc,PetscTruth *flag) { PetscFunctionBegin; PetscValidHeaderSpecific(pc,PC_COOKIE); *flag = pc->diagonalscale; PetscFunctionReturn(0); } #undef __FUNCT__ #define __FUNCT__ "PCDiagonalScaleSet" /*@ PCDiagonalScaleSet - Indicates the left scaling to use to apply an additional left and right scaling as needed by certain time-stepping codes. Collective on PC Input Parameters: + pc - the preconditioner context - s - scaling vector Level: intermediate Notes: The system solved via the Krylov method is $ D M A D^{-1} y = D M b for left preconditioning or $ D A M D^{-1} z = D b for right preconditioning PCDiagonalScaleLeft() scales a vector by D. PCDiagonalScaleRight() scales a vector by D^{-1}. .keywords: PC .seealso: PCCreate(), PCSetUp(), PCDiagonalScaleLeft(), PCDiagonalScaleRight(), PCDiagonalScale() @*/ int PCDiagonalScaleSet(PC pc,Vec s) { int ierr; PetscFunctionBegin; PetscValidHeaderSpecific(pc,PC_COOKIE); PetscValidHeaderSpecific(s,VEC_COOKIE); pc->diagonalscale = PETSC_TRUE; if (pc->diagonalscaleleft) { ierr = VecDestroy(pc->diagonalscaleleft);CHKERRQ(ierr); } pc->diagonalscaleleft = s; ierr = PetscObjectReference((PetscObject)s);CHKERRQ(ierr); if (!pc->diagonalscaleright) { ierr = VecDuplicate(s,&pc->diagonalscaleright);CHKERRQ(ierr); } ierr = VecCopy(s,pc->diagonalscaleright);CHKERRQ(ierr); ierr = VecReciprocal(pc->diagonalscaleright);CHKERRQ(ierr); PetscFunctionReturn(0); } #undef __FUNCT__ #define __FUNCT__ "PCDiagonalScaleLeft" /*@C PCDiagonalScaleLeft - Indicates the left scaling to use to apply an additional left and right scaling as needed by certain time-stepping codes. Collective on PC Input Parameters: + pc - the preconditioner context . in - input vector + out - scaled vector (maybe the same as in) Level: intermediate Notes: The system solved via the Krylov method is $ D M A D^{-1} y = D M b for left preconditioning or $ D A M D^{-1} z = D b for right preconditioning PCDiagonalScaleLeft() scales a vector by D. PCDiagonalScaleRight() scales a vector by D^{-1}. If diagonal scaling is turned off and in is not out then in is copied to out .keywords: PC .seealso: PCCreate(), PCSetUp(), PCDiagonalScaleSet(), PCDiagonalScaleRight(), PCDiagonalScale() @*/ int PCDiagonalScaleLeft(PC pc,Vec in,Vec out) { int ierr; PetscFunctionBegin; PetscValidHeaderSpecific(pc,PC_COOKIE); PetscValidHeaderSpecific(in,VEC_COOKIE); PetscValidHeaderSpecific(out,VEC_COOKIE); if (pc->diagonalscale) { ierr = VecPointwiseMult(pc->diagonalscaleleft,in,out);CHKERRQ(ierr); } else if (in != out) { ierr = VecCopy(in,out);CHKERRQ(ierr); } PetscFunctionReturn(0); } #undef __FUNCT__ #define __FUNCT__ "PCDiagonalScaleRight" /*@C PCDiagonalScaleRight - Scales a vector by the right scaling as needed by certain time-stepping codes. Collective on PC Input Parameters: + pc - the preconditioner context . in - input vector + out - scaled vector (maybe the same as in) Level: intermediate Notes: The system solved via the Krylov method is $ D M A D^{-1} y = D M b for left preconditioning or $ D A M D^{-1} z = D b for right preconditioning PCDiagonalScaleLeft() scales a vector by D. PCDiagonalScaleRight() scales a vector by D^{-1}. If diagonal scaling is turned off and in is not out then in is copied to out .keywords: PC .seealso: PCCreate(), PCSetUp(), PCDiagonalScaleLeft(), PCDiagonalScaleSet(), PCDiagonalScale() @*/ int PCDiagonalScaleRight(PC pc,Vec in,Vec out) { int ierr; PetscFunctionBegin; PetscValidHeaderSpecific(pc,PC_COOKIE); PetscValidHeaderSpecific(in,VEC_COOKIE); PetscValidHeaderSpecific(out,VEC_COOKIE); if (pc->diagonalscale) { ierr = VecPointwiseMult(pc->diagonalscaleright,in,out);CHKERRQ(ierr); } else if (in != out) { ierr = VecCopy(in,out);CHKERRQ(ierr); } PetscFunctionReturn(0); } #undef __FUNCT__ #define __FUNCT__ "PCPublish_Petsc" static int PCPublish_Petsc(PetscObject obj) { #if defined(PETSC_HAVE_AMS) PC v = (PC) obj; int ierr; #endif PetscFunctionBegin; #if defined(PETSC_HAVE_AMS) /* if it is already published then return */ if (v->amem >=0) PetscFunctionReturn(0); ierr = PetscObjectPublishBaseBegin(obj);CHKERRQ(ierr); ierr = PetscObjectPublishBaseEnd(obj);CHKERRQ(ierr); #endif PetscFunctionReturn(0); } #undef __FUNCT__ #define __FUNCT__ "PCCreate" /*@C PCCreate - Creates a preconditioner context. Collective on MPI_Comm Input Parameter: . comm - MPI communicator Output Parameter: . pc - location to put the preconditioner context Notes: The default preconditioner on one processor is PCILU with 0 fill on more then one it is PCBJACOBI with ILU() on each processor. Level: developer .keywords: PC, create, context .seealso: PCSetUp(), PCApply(), PCDestroy() @*/ int PCCreate(MPI_Comm comm,PC *newpc) { PC pc; int ierr; PetscFunctionBegin; PetscValidPointer(newpc) *newpc = 0; #ifndef PETSC_USE_DYNAMIC_LIBRARIES ierr = SLESInitializePackage(PETSC_NULL); CHKERRQ(ierr); #endif PetscHeaderCreate(pc,_p_PC,struct _PCOps,PC_COOKIE,-1,"PC",comm,PCDestroy,PCView); PetscLogObjectCreate(pc); pc->bops->publish = PCPublish_Petsc; pc->vec = 0; pc->mat = 0; pc->setupcalled = 0; pc->nullsp = 0; pc->data = 0; pc->diagonalscale = PETSC_FALSE; pc->diagonalscaleleft = 0; pc->diagonalscaleright = 0; pc->ops->destroy = 0; pc->ops->apply = 0; pc->ops->applytranspose = 0; pc->ops->applyBA = 0; pc->ops->applyBAtranspose = 0; pc->ops->applyrichardson = 0; pc->ops->view = 0; pc->ops->getfactoredmatrix = 0; pc->ops->applysymmetricright = 0; pc->ops->applysymmetricleft = 0; pc->ops->setuponblocks = 0; pc->modifysubmatrices = 0; pc->modifysubmatricesP = 0; *newpc = pc; ierr = PetscPublishAll(pc);CHKERRQ(ierr); PetscFunctionReturn(0); } /* -------------------------------------------------------------------------------*/ #undef __FUNCT__ #define __FUNCT__ "PCApply" /*@ PCApply - Applies the preconditioner to a vector. Collective on PC and Vec Input Parameters: + pc - the preconditioner context - x - input vector Output Parameter: . y - output vector Level: developer .keywords: PC, apply .seealso: PCApplyTranspose(), PCApplyBAorAB() @*/ int PCApply(PC pc,Vec x,Vec y) { int ierr; PetscFunctionBegin; PetscValidHeaderSpecific(pc,PC_COOKIE); PetscValidHeaderSpecific(x,VEC_COOKIE); PetscValidHeaderSpecific(y,VEC_COOKIE); if (x == y) SETERRQ(PETSC_ERR_ARG_IDN,"x and y must be different vectors"); if (pc->setupcalled < 2) { ierr = PCSetUp(pc);CHKERRQ(ierr); } ierr = PetscLogEventBegin(PC_Apply,pc,x,y,0);CHKERRQ(ierr); ierr = (*pc->ops->apply)(pc,x,y);CHKERRQ(ierr); ierr = PetscLogEventEnd(PC_Apply,pc,x,y,0);CHKERRQ(ierr); /* Remove null space from preconditioned vector y */ if (pc->nullsp) { ierr = MatNullSpaceRemove(pc->nullsp,y,PETSC_NULL);CHKERRQ(ierr); } PetscFunctionReturn(0); } #undef __FUNCT__ #define __FUNCT__ "PCApplySymmetricLeft" /*@ PCApplySymmetricLeft - Applies the left part of a symmetric preconditioner to a vector. Collective on PC and Vec Input Parameters: + pc - the preconditioner context - x - input vector Output Parameter: . y - output vector Notes: Currently, this routine is implemented only for PCICC and PCJACOBI preconditioners. Level: developer .keywords: PC, apply, symmetric, left .seealso: PCApply(), PCApplySymmetricRight() @*/ int PCApplySymmetricLeft(PC pc,Vec x,Vec y) { int ierr; PetscFunctionBegin; PetscValidHeaderSpecific(pc,PC_COOKIE); PetscValidHeaderSpecific(x,VEC_COOKIE); PetscValidHeaderSpecific(y,VEC_COOKIE); if (!pc->ops->applysymmetricleft) SETERRQ(1,"PC does not have left symmetric apply"); if (pc->setupcalled < 2) { ierr = PCSetUp(pc);CHKERRQ(ierr); } ierr = PetscLogEventBegin(PC_ApplySymmetricLeft,pc,x,y,0);CHKERRQ(ierr); ierr = (*pc->ops->applysymmetricleft)(pc,x,y);CHKERRQ(ierr); ierr = PetscLogEventEnd(PC_ApplySymmetricLeft,pc,x,y,0);CHKERRQ(ierr); PetscFunctionReturn(0); } #undef __FUNCT__ #define __FUNCT__ "PCApplySymmetricRight" /*@ PCApplySymmetricRight - Applies the right part of a symmetric preconditioner to a vector. Collective on PC and Vec Input Parameters: + pc - the preconditioner context - x - input vector Output Parameter: . y - output vector Level: developer Notes: Currently, this routine is implemented only for PCICC and PCJACOBI preconditioners. .keywords: PC, apply, symmetric, right .seealso: PCApply(), PCApplySymmetricLeft() @*/ int PCApplySymmetricRight(PC pc,Vec x,Vec y) { int ierr; PetscFunctionBegin; PetscValidHeaderSpecific(pc,PC_COOKIE); PetscValidHeaderSpecific(x,VEC_COOKIE); PetscValidHeaderSpecific(y,VEC_COOKIE); if (!pc->ops->applysymmetricright) SETERRQ(1,"PC does not have left symmetric apply"); if (pc->setupcalled < 2) { ierr = PCSetUp(pc);CHKERRQ(ierr); } ierr = PetscLogEventBegin(PC_ApplySymmetricRight,pc,x,y,0);CHKERRQ(ierr); ierr = (*pc->ops->applysymmetricright)(pc,x,y);CHKERRQ(ierr); ierr = PetscLogEventEnd(PC_ApplySymmetricRight,pc,x,y,0);CHKERRQ(ierr); PetscFunctionReturn(0); } #undef __FUNCT__ #define __FUNCT__ "PCApplyTranspose" /*@ PCApplyTranspose - Applies the transpose of preconditioner to a vector. Collective on PC and Vec Input Parameters: + pc - the preconditioner context - x - input vector Output Parameter: . y - output vector Level: developer .keywords: PC, apply, transpose .seealso: PCApplyTranspose(), PCApplyBAorAB(), PCApplyBAorABTranspose() @*/ int PCApplyTranspose(PC pc,Vec x,Vec y) { int ierr; PetscFunctionBegin; PetscValidHeaderSpecific(pc,PC_COOKIE); PetscValidHeaderSpecific(x,VEC_COOKIE); PetscValidHeaderSpecific(y,VEC_COOKIE); if (x == y) SETERRQ(PETSC_ERR_ARG_IDN,"x and y must be different vectors"); if (!pc->ops->applytranspose) SETERRQ(PETSC_ERR_SUP," "); if (pc->setupcalled < 2) { ierr = PCSetUp(pc);CHKERRQ(ierr); } ierr = PetscLogEventBegin(PC_Apply,pc,x,y,0);CHKERRQ(ierr); ierr = (*pc->ops->applytranspose)(pc,x,y);CHKERRQ(ierr); ierr = PetscLogEventEnd(PC_Apply,pc,x,y,0);CHKERRQ(ierr); PetscFunctionReturn(0); } #undef __FUNCT__ #define __FUNCT__ "PCApplyBAorAB" /*@ PCApplyBAorAB - Applies the preconditioner and operator to a vector. Collective on PC and Vec Input Parameters: + pc - the preconditioner context . side - indicates the preconditioner side, one of PC_LEFT, PC_RIGHT, or PC_SYMMETRIC . x - input vector - work - work vector Output Parameter: . y - output vector Level: developer .keywords: PC, apply, operator .seealso: PCApply(), PCApplyTranspose(), PCApplyBAorABTranspose() @*/ int PCApplyBAorAB(PC pc,PCSide side,Vec x,Vec y,Vec work) { int ierr; PetscFunctionBegin; PetscValidHeaderSpecific(pc,PC_COOKIE); PetscValidHeaderSpecific(x,VEC_COOKIE); PetscValidHeaderSpecific(y,VEC_COOKIE); PetscValidHeaderSpecific(work,VEC_COOKIE); if (x == y) SETERRQ(PETSC_ERR_ARG_IDN,"x and y must be different vectors"); if (side != PC_LEFT && side != PC_SYMMETRIC && side != PC_RIGHT) { SETERRQ(PETSC_ERR_ARG_OUTOFRANGE,"Side must be right, left, or symmetric"); } if (pc->diagonalscale && side == PC_SYMMETRIC) { SETERRQ(1,"Cannot include diagonal scaling with symmetric preconditioner application"); } if (pc->setupcalled < 2) { ierr = PCSetUp(pc);CHKERRQ(ierr); } if (pc->diagonalscale) { if (pc->ops->applyBA) { Vec work2; /* this is expensive, but to fix requires a second work vector argument to PCApplyBAorAB() */ ierr = VecDuplicate(x,&work2);CHKERRQ(ierr); ierr = PCDiagonalScaleRight(pc,x,work2);CHKERRQ(ierr); ierr = (*pc->ops->applyBA)(pc,side,work2,y,work);CHKERRQ(ierr); /* Remove null space from preconditioned vector y */ if (pc->nullsp) { ierr = MatNullSpaceRemove(pc->nullsp,y,PETSC_NULL);CHKERRQ(ierr); } ierr = PCDiagonalScaleLeft(pc,y,y);CHKERRQ(ierr); ierr = VecDestroy(work2);CHKERRQ(ierr); } else if (side == PC_RIGHT) { ierr = PCDiagonalScaleRight(pc,x,y);CHKERRQ(ierr); ierr = PCApply(pc,y,work);CHKERRQ(ierr); ierr = MatMult(pc->mat,work,y);CHKERRQ(ierr); ierr = PCDiagonalScaleLeft(pc,y,y);CHKERRQ(ierr); } else if (side == PC_LEFT) { ierr = PCDiagonalScaleRight(pc,x,y);CHKERRQ(ierr); ierr = MatMult(pc->mat,y,work);CHKERRQ(ierr); ierr = PCApply(pc,work,y);CHKERRQ(ierr); ierr = PCDiagonalScaleLeft(pc,y,y);CHKERRQ(ierr); } else if (side == PC_SYMMETRIC) { SETERRQ(1,"Cannot provide diagonal scaling with symmetric application of preconditioner"); } } else { if (pc->ops->applyBA) { ierr = (*pc->ops->applyBA)(pc,side,x,y,work);CHKERRQ(ierr); /* Remove null space from preconditioned vector y */ if (pc->nullsp) { ierr = MatNullSpaceRemove(pc->nullsp,y,PETSC_NULL);CHKERRQ(ierr); } } else if (side == PC_RIGHT) { ierr = PCApply(pc,x,work);CHKERRQ(ierr); ierr = MatMult(pc->mat,work,y);CHKERRQ(ierr); } else if (side == PC_LEFT) { ierr = MatMult(pc->mat,x,work);CHKERRQ(ierr); ierr = PCApply(pc,work,y);CHKERRQ(ierr); } else if (side == PC_SYMMETRIC) { /* There's an extra copy here; maybe should provide 2 work vectors instead? */ ierr = PCApplySymmetricRight(pc,x,work);CHKERRQ(ierr); ierr = MatMult(pc->mat,work,y);CHKERRQ(ierr); ierr = VecCopy(y,work);CHKERRQ(ierr); ierr = PCApplySymmetricLeft(pc,work,y);CHKERRQ(ierr); } } PetscFunctionReturn(0); } #undef __FUNCT__ #define __FUNCT__ "PCApplyBAorABTranspose" /*@ PCApplyBAorABTranspose - Applies the transpose of the preconditioner and operator to a vector. That is, applies tr(B) * tr(A) with left preconditioning, not tr(B*A) = tr(A)*tr(B). Collective on PC and Vec Input Parameters: + pc - the preconditioner context . side - indicates the preconditioner side, one of PC_LEFT, PC_RIGHT, or PC_SYMMETRIC . x - input vector - work - work vector Output Parameter: . y - output vector Level: developer .keywords: PC, apply, operator, transpose .seealso: PCApply(), PCApplyTranspose(), PCApplyBAorAB() @*/ int PCApplyBAorABTranspose(PC pc,PCSide side,Vec x,Vec y,Vec work) { int ierr; PetscFunctionBegin; PetscValidHeaderSpecific(pc,PC_COOKIE); PetscValidHeaderSpecific(x,VEC_COOKIE); PetscValidHeaderSpecific(y,VEC_COOKIE); PetscValidHeaderSpecific(work,VEC_COOKIE); if (x == y) SETERRQ(PETSC_ERR_ARG_IDN,"x and y must be different vectors"); if (pc->ops->applyBAtranspose) { ierr = (*pc->ops->applyBAtranspose)(pc,side,x,y,work);CHKERRQ(ierr); PetscFunctionReturn(0); } if (side != PC_LEFT && side != PC_RIGHT) { SETERRQ(PETSC_ERR_ARG_OUTOFRANGE,"Side must be right or left"); } if (pc->setupcalled < 2) { ierr = PCSetUp(pc);CHKERRQ(ierr); } if (side == PC_RIGHT) { ierr = PCApplyTranspose(pc,x,work);CHKERRQ(ierr); ierr = MatMultTranspose(pc->mat,work,y);CHKERRQ(ierr); } else if (side == PC_LEFT) { ierr = MatMultTranspose(pc->mat,x,work);CHKERRQ(ierr); ierr = PCApplyTranspose(pc,work,y);CHKERRQ(ierr); } /* add support for PC_SYMMETRIC */ PetscFunctionReturn(0); /* actually will never get here */ } /* -------------------------------------------------------------------------------*/ #undef __FUNCT__ #define __FUNCT__ "PCApplyRichardsonExists" /*@ PCApplyRichardsonExists - Determines whether a particular preconditioner has a built-in fast application of Richardson's method. Not Collective Input Parameter: . pc - the preconditioner Output Parameter: . exists - PETSC_TRUE or PETSC_FALSE Level: developer .keywords: PC, apply, Richardson, exists .seealso: PCApplyRichardson() @*/ int PCApplyRichardsonExists(PC pc,PetscTruth *exists) { PetscFunctionBegin; PetscValidHeaderSpecific(pc,PC_COOKIE); PetscValidIntPointer(exists); if (pc->ops->applyrichardson) *exists = PETSC_TRUE; else *exists = PETSC_FALSE; PetscFunctionReturn(0); } #undef __FUNCT__ #define __FUNCT__ "PCApplyRichardson" /*@ PCApplyRichardson - Applies several steps of Richardson iteration with the particular preconditioner. This routine is usually used by the Krylov solvers and not the application code directly. Collective on PC Input Parameters: + pc - the preconditioner context . x - the initial guess . w - one work vector . rtol - relative decrease in residual norm convergence criteria . atol - absolute residual norm convergence criteria . dtol - divergence residual norm increase criteria - its - the number of iterations to apply. Output Parameter: . y - the solution Notes: Most preconditioners do not support this function. Use the command PCApplyRichardsonExists() to determine if one does. Except for the multigrid PC this routine ignores the convergence tolerances and always runs for the number of iterations Level: developer .keywords: PC, apply, Richardson .seealso: PCApplyRichardsonExists() @*/ int PCApplyRichardson(PC pc,Vec x,Vec y,Vec w,PetscReal rtol,PetscReal atol, PetscReal dtol,int its) { int ierr; PetscFunctionBegin; PetscValidHeaderSpecific(pc,PC_COOKIE); PetscValidHeaderSpecific(x,VEC_COOKIE); PetscValidHeaderSpecific(y,VEC_COOKIE); PetscValidHeaderSpecific(w,VEC_COOKIE); if (!pc->ops->applyrichardson) SETERRQ(PETSC_ERR_SUP," "); if (pc->setupcalled < 2) { ierr = PCSetUp(pc);CHKERRQ(ierr); } ierr = (*pc->ops->applyrichardson)(pc,x,y,w,rtol,atol,dtol,its);CHKERRQ(ierr); PetscFunctionReturn(0); } /* a setupcall of 0 indicates never setup, 1 needs to be resetup, 2 does not need any changes. */ #undef __FUNCT__ #define __FUNCT__ "PCSetUp" /*@ PCSetUp - Prepares for the use of a preconditioner. Collective on PC Input Parameter: . pc - the preconditioner context Level: developer .keywords: PC, setup .seealso: PCCreate(), PCApply(), PCDestroy() @*/ int PCSetUp(PC pc) { int ierr; PetscTruth flg; PetscFunctionBegin; PetscValidHeaderSpecific(pc,PC_COOKIE); if (pc->setupcalled > 1) { PetscLogInfo(pc,"PCSetUp:Setting PC with identical preconditioner\n"); PetscFunctionReturn(0); } else if (pc->setupcalled == 0) { PetscLogInfo(pc,"PCSetUp:Setting up new PC\n"); } else if (pc->flag == SAME_NONZERO_PATTERN) { PetscLogInfo(pc,"PCSetUp:Setting up PC with same nonzero pattern\n"); } else { PetscLogInfo(pc,"PCSetUp:Setting up PC with different nonzero pattern\n"); } ierr = PetscLogEventBegin(PC_SetUp,pc,0,0,0);CHKERRQ(ierr); if (!pc->vec) {SETERRQ(PETSC_ERR_ARG_WRONGSTATE,"Vector must be set first");} if (!pc->mat) {SETERRQ(PETSC_ERR_ARG_WRONGSTATE,"Matrix must be set first");} if (!pc->type_name) { int size; ierr = MPI_Comm_size(pc->comm,&size);CHKERRQ(ierr); if (size == 1) { ierr = PetscTypeCompare((PetscObject)pc->pmat,MATSEQSBAIJ,&flg);CHKERRQ(ierr); if (flg) { /* for sbaij mat */ ierr = PCSetType(pc,PCICC);CHKERRQ(ierr); } else { ierr = PCSetType(pc,PCILU);CHKERRQ(ierr); } } else { ierr = PCSetType(pc,PCBJACOBI);CHKERRQ(ierr); } } if (pc->ops->setup) { ierr = (*pc->ops->setup)(pc);CHKERRQ(ierr); } pc->setupcalled = 2; if (pc->nullsp) { PetscTruth test; ierr = PetscOptionsHasName(pc->prefix,"-pc_test_null_space",&test);CHKERRQ(ierr); if (test) { ierr = MatNullSpaceTest(pc->nullsp,pc->mat);CHKERRQ(ierr); } } ierr = PetscLogEventEnd(PC_SetUp,pc,0,0,0);CHKERRQ(ierr); PetscFunctionReturn(0); } #undef __FUNCT__ #define __FUNCT__ "PCSetUpOnBlocks" /*@ PCSetUpOnBlocks - Sets up the preconditioner for each block in the block Jacobi, block Gauss-Seidel, and overlapping Schwarz methods. Collective on PC Input Parameters: . pc - the preconditioner context Level: developer .keywords: PC, setup, blocks .seealso: PCCreate(), PCApply(), PCDestroy(), PCSetUp() @*/ int PCSetUpOnBlocks(PC pc) { int ierr; PetscFunctionBegin; PetscValidHeaderSpecific(pc,PC_COOKIE); if (!pc->ops->setuponblocks) PetscFunctionReturn(0); ierr = PetscLogEventBegin(PC_SetUpOnBlocks,pc,0,0,0);CHKERRQ(ierr); ierr = (*pc->ops->setuponblocks)(pc);CHKERRQ(ierr); ierr = PetscLogEventEnd(PC_SetUpOnBlocks,pc,0,0,0);CHKERRQ(ierr); PetscFunctionReturn(0); } #undef __FUNCT__ #define __FUNCT__ "PCSetModifySubMatrices" /*@ PCSetModifySubMatrices - Sets a user-defined routine for modifying the submatrices that arise within certain subdomain-based preconditioners. The basic submatrices are extracted from the preconditioner matrix as usual; the user can then alter these (for example, to set different boundary conditions for each submatrix) before they are used for the local solves. Collective on PC Input Parameters: + pc - the preconditioner context . func - routine for modifying the submatrices - ctx - optional user-defined context (may be null) Calling sequence of func: $ func (PC pc,int nsub,IS *row,IS *col,Mat *submat,void *ctx); . row - an array of index sets that contain the global row numbers that comprise each local submatrix . col - an array of index sets that contain the global column numbers that comprise each local submatrix . submat - array of local submatrices - ctx - optional user-defined context for private data for the user-defined func routine (may be null) Notes: PCSetModifySubMatrices() MUST be called before SLESSetUp() and SLESSolve(). A routine set by PCSetModifySubMatrices() is currently called within the block Jacobi (PCBJACOBI) and additive Schwarz (PCASM) preconditioners. All other preconditioners ignore this routine. Level: advanced .keywords: PC, set, modify, submatrices .seealso: PCModifySubMatrices() @*/ int PCSetModifySubMatrices(PC pc,int(*func)(PC,int,IS*,IS*,Mat*,void*),void *ctx) { PetscFunctionBegin; PetscValidHeaderSpecific(pc,PC_COOKIE); pc->modifysubmatrices = func; pc->modifysubmatricesP = ctx; PetscFunctionReturn(0); } #undef __FUNCT__ #define __FUNCT__ "PCModifySubMatrices" /*@ PCModifySubMatrices - Calls an optional user-defined routine within certain preconditioners if one has been set with PCSetModifySubMarices(). Collective on PC Input Parameters: + pc - the preconditioner context . nsub - the number of local submatrices . row - an array of index sets that contain the global row numbers that comprise each local submatrix . col - an array of index sets that contain the global column numbers that comprise each local submatrix . submat - array of local submatrices - ctx - optional user-defined context for private data for the user-defined routine (may be null) Output Parameter: . submat - array of local submatrices (the entries of which may have been modified) Notes: The user should NOT generally call this routine, as it will automatically be called within certain preconditioners (currently block Jacobi, additive Schwarz) if set. The basic submatrices are extracted from the preconditioner matrix as usual; the user can then alter these (for example, to set different boundary conditions for each submatrix) before they are used for the local solves. Level: developer .keywords: PC, modify, submatrices .seealso: PCSetModifySubMatrices() @*/ int PCModifySubMatrices(PC pc,int nsub,IS *row,IS *col,Mat *submat,void *ctx) { int ierr; PetscFunctionBegin; if (!pc->modifysubmatrices) PetscFunctionReturn(0); ierr = PetscLogEventBegin(PC_ModifySubMatrices,pc,0,0,0);CHKERRQ(ierr); ierr = (*pc->modifysubmatrices)(pc,nsub,row,col,submat,ctx);CHKERRQ(ierr); ierr = PetscLogEventEnd(PC_ModifySubMatrices,pc,0,0,0);CHKERRQ(ierr); PetscFunctionReturn(0); } #undef __FUNCT__ #define __FUNCT__ "PCSetOperators" /*@ PCSetOperators - Sets the matrix associated with the linear system and a (possibly) different one associated with the preconditioner. Collective on PC and Mat Input Parameters: + pc - the preconditioner context . Amat - the matrix associated with the linear system . Pmat - the matrix to be used in constructing the preconditioner, usually the same as Amat. - flag - flag indicating information about the preconditioner matrix structure during successive linear solves. This flag is ignored the first time a linear system is solved, and thus is irrelevant when solving just one linear system. Notes: The flag can be used to eliminate unnecessary work in the preconditioner during the repeated solution of linear systems of the same size. The available options are + SAME_PRECONDITIONER - Pmat is identical during successive linear solves. This option is intended for folks who are using different Amat and Pmat matrices and wish to reuse the same preconditioner matrix. For example, this option saves work by not recomputing incomplete factorization for ILU/ICC preconditioners. . SAME_NONZERO_PATTERN - Pmat has the same nonzero structure during successive linear solves. - DIFFERENT_NONZERO_PATTERN - Pmat does not have the same nonzero structure. Caution: If you specify SAME_NONZERO_PATTERN, PETSc believes your assertion and does not check the structure of the matrix. If you erroneously claim that the structure is the same when it actually is not, the new preconditioner will not function correctly. Thus, use this optimization feature carefully! If in doubt about whether your preconditioner matrix has changed structure or not, use the flag DIFFERENT_NONZERO_PATTERN. More Notes about Repeated Solution of Linear Systems: PETSc does NOT reset the matrix entries of either Amat or Pmat to zero after a linear solve; the user is completely responsible for matrix assembly. See the routine MatZeroEntries() if desiring to zero all elements of a matrix. Level: intermediate .keywords: PC, set, operators, matrix, linear system .seealso: PCGetOperators(), MatZeroEntries() @*/ int PCSetOperators(PC pc,Mat Amat,Mat Pmat,MatStructure flag) { int ierr; PetscTruth isbjacobi,isrowbs; PetscFunctionBegin; PetscValidHeaderSpecific(pc,PC_COOKIE); PetscValidHeaderSpecific(Amat,MAT_COOKIE); PetscValidHeaderSpecific(Pmat,MAT_COOKIE); /* BlockSolve95 cannot use default BJacobi preconditioning */ ierr = PetscTypeCompare((PetscObject)Amat,MATMPIROWBS,&isrowbs);CHKERRQ(ierr); if (isrowbs) { ierr = PetscTypeCompare((PetscObject)pc,PCBJACOBI,&isbjacobi);CHKERRQ(ierr); if (isbjacobi) { ierr = PCSetType(pc,PCILU);CHKERRQ(ierr); PetscLogInfo(pc,"PCSetOperators:Switching default PC to PCILU since BS95 doesn't support PCBJACOBI\n"); } } pc->mat = Amat; pc->pmat = Pmat; if (pc->setupcalled == 2 && flag != SAME_PRECONDITIONER) { pc->setupcalled = 1; } pc->flag = flag; PetscFunctionReturn(0); } #undef __FUNCT__ #define __FUNCT__ "PCGetOperators" /*@C PCGetOperators - Gets the matrix associated with the linear system and possibly a different one associated with the preconditioner. Not collective, though parallel Mats are returned if the PC is parallel Input Parameter: . pc - the preconditioner context Output Parameters: + mat - the matrix associated with the linear system . pmat - matrix associated with the preconditioner, usually the same as mat. - flag - flag indicating information about the preconditioner matrix structure. See PCSetOperators() for details. Level: intermediate .keywords: PC, get, operators, matrix, linear system .seealso: PCSetOperators() @*/ int PCGetOperators(PC pc,Mat *mat,Mat *pmat,MatStructure *flag) { PetscFunctionBegin; PetscValidHeaderSpecific(pc,PC_COOKIE); if (mat) *mat = pc->mat; if (pmat) *pmat = pc->pmat; if (flag) *flag = pc->flag; PetscFunctionReturn(0); } #undef __FUNCT__ #define __FUNCT__ "PCSetVector" /*@ PCSetVector - Sets a vector associated with the preconditioner. Collective on PC and Vec Input Parameters: + pc - the preconditioner context - vec - the vector Notes: The vector must be set so that the preconditioner knows what type of vector to allocate if necessary. Level: intermediate .keywords: PC, set, vector .seealso: PCGetVector() @*/ int PCSetVector(PC pc,Vec vec) { PetscFunctionBegin; PetscValidHeaderSpecific(pc,PC_COOKIE); PetscValidHeaderSpecific(vec,VEC_COOKIE); PetscCheckSameComm(pc,vec); pc->vec = vec; PetscFunctionReturn(0); } #undef __FUNCT__ #define __FUNCT__ "PCGetVector" /*@ PCGetVector - Gets a vector associated with the preconditioner; if the vector was not get set it will return a 0 pointer. Not collective, but vector is shared by all processors that share the PC Input Parameter: . pc - the preconditioner context Output Parameter: . vec - the vector Level: intermediate .keywords: PC, get, vector .seealso: PCSetVector() @*/ int PCGetVector(PC pc,Vec *vec) { PetscFunctionBegin; PetscValidHeaderSpecific(pc,PC_COOKIE); *vec = pc->vec; PetscFunctionReturn(0); } #undef __FUNCT__ #define __FUNCT__ "PCGetFactoredMatrix" /*@C PCGetFactoredMatrix - Gets the factored matrix from the preconditioner context. This routine is valid only for the LU, incomplete LU, Cholesky, and incomplete Cholesky methods. Not Collective on PC though Mat is parallel if PC is parallel Input Parameters: . pc - the preconditioner context Output parameters: . mat - the factored matrix Level: advanced .keywords: PC, get, factored, matrix @*/ int PCGetFactoredMatrix(PC pc,Mat *mat) { int ierr; PetscFunctionBegin; PetscValidHeaderSpecific(pc,PC_COOKIE); if (pc->ops->getfactoredmatrix) { ierr = (*pc->ops->getfactoredmatrix)(pc,mat);CHKERRQ(ierr); } PetscFunctionReturn(0); } #undef __FUNCT__ #define __FUNCT__ "PCSetOptionsPrefix" /*@C PCSetOptionsPrefix - Sets the prefix used for searching for all PC options in the database. Collective on PC Input Parameters: + pc - the preconditioner context - prefix - the prefix string to prepend to all PC option requests Notes: A hyphen (-) must NOT be given at the beginning of the prefix name. The first character of all runtime options is AUTOMATICALLY the hyphen. Level: advanced .keywords: PC, set, options, prefix, database .seealso: PCAppendOptionsPrefix(), PCGetOptionsPrefix() @*/ int PCSetOptionsPrefix(PC pc,char *prefix) { int ierr; PetscFunctionBegin; PetscValidHeaderSpecific(pc,PC_COOKIE); ierr = PetscObjectSetOptionsPrefix((PetscObject)pc,prefix);CHKERRQ(ierr); PetscFunctionReturn(0); } #undef __FUNCT__ #define __FUNCT__ "PCAppendOptionsPrefix" /*@C PCAppendOptionsPrefix - Appends to the prefix used for searching for all PC options in the database. Collective on PC Input Parameters: + pc - the preconditioner context - prefix - the prefix string to prepend to all PC option requests Notes: A hyphen (-) must NOT be given at the beginning of the prefix name. The first character of all runtime options is AUTOMATICALLY the hyphen. Level: advanced .keywords: PC, append, options, prefix, database .seealso: PCSetOptionsPrefix(), PCGetOptionsPrefix() @*/ int PCAppendOptionsPrefix(PC pc,char *prefix) { int ierr; PetscFunctionBegin; PetscValidHeaderSpecific(pc,PC_COOKIE); ierr = PetscObjectAppendOptionsPrefix((PetscObject)pc,prefix);CHKERRQ(ierr); PetscFunctionReturn(0); } #undef __FUNCT__ #define __FUNCT__ "PCGetOptionsPrefix" /*@C PCGetOptionsPrefix - Gets the prefix used for searching for all PC options in the database. Not Collective Input Parameters: . pc - the preconditioner context Output Parameters: . prefix - pointer to the prefix string used, is returned Notes: On the fortran side, the user should pass in a string 'prifix' of sufficient length to hold the prefix. Level: advanced .keywords: PC, get, options, prefix, database .seealso: PCSetOptionsPrefix(), PCAppendOptionsPrefix() @*/ int PCGetOptionsPrefix(PC pc,char **prefix) { int ierr; PetscFunctionBegin; PetscValidHeaderSpecific(pc,PC_COOKIE); ierr = PetscObjectGetOptionsPrefix((PetscObject)pc,prefix);CHKERRQ(ierr); PetscFunctionReturn(0); } #undef __FUNCT__ #define __FUNCT__ "PCPreSolve" /*@ PCPreSolve - Optional pre-solve phase, intended for any preconditioner-specific actions that must be performed before the iterative solve itself. Collective on PC Input Parameters: + pc - the preconditioner context - ksp - the Krylov subspace context Level: developer Sample of Usage: .vb PCPreSolve(pc,ksp); KSPSolve(ksp,its); PCPostSolve(pc,ksp); .ve Notes: The pre-solve phase is distinct from the PCSetUp() phase. SLESSolve() calls this directly, so is rarely called by the user. .keywords: PC, pre-solve .seealso: PCPostSolve() @*/ int PCPreSolve(PC pc,KSP ksp) { int ierr; Vec x,rhs; Mat A,B; PetscFunctionBegin; PetscValidHeaderSpecific(pc,PC_COOKIE); ierr = KSPGetSolution(ksp,&x);CHKERRQ(ierr); ierr = KSPGetRhs(ksp,&rhs);CHKERRQ(ierr); /* Scale the system and have the matrices use the scaled form only if the two matrices are actually the same (and hence have the same scaling */ ierr = PCGetOperators(pc,&A,&B,PETSC_NULL);CHKERRQ(ierr); if (A == B) { ierr = MatScaleSystem(pc->mat,x,rhs);CHKERRQ(ierr); ierr = MatUseScaledForm(pc->mat,PETSC_TRUE);CHKERRQ(ierr); } if (pc->ops->presolve) { ierr = (*pc->ops->presolve)(pc,ksp,x,rhs);CHKERRQ(ierr); } PetscFunctionReturn(0); } #undef __FUNCT__ #define __FUNCT__ "PCPostSolve" /*@ PCPostSolve - Optional post-solve phase, intended for any preconditioner-specific actions that must be performed after the iterative solve itself. Collective on PC Input Parameters: + pc - the preconditioner context - ksp - the Krylov subspace context Sample of Usage: .vb PCPreSolve(pc,ksp); KSPSolve(ksp,its); PCPostSolve(pc,ksp); .ve Note: SLESSolve() calls this routine directly, so it is rarely called by the user. Level: developer .keywords: PC, post-solve .seealso: PCPreSolve(), SLESSolve() @*/ int PCPostSolve(PC pc,KSP ksp) { int ierr; Vec x,rhs; Mat A,B; PetscFunctionBegin; PetscValidHeaderSpecific(pc,PC_COOKIE); ierr = KSPGetSolution(ksp,&x);CHKERRQ(ierr); ierr = KSPGetRhs(ksp,&rhs);CHKERRQ(ierr); if (pc->ops->postsolve) { ierr = (*pc->ops->postsolve)(pc,ksp,x,rhs);CHKERRQ(ierr); } /* Scale the system and have the matrices use the scaled form only if the two matrices are actually the same (and hence have the same scaling */ ierr = PCGetOperators(pc,&A,&B,PETSC_NULL);CHKERRQ(ierr); if (A == B) { ierr = MatUnScaleSystem(pc->mat,x,rhs);CHKERRQ(ierr); ierr = MatUseScaledForm(pc->mat,PETSC_FALSE);CHKERRQ(ierr); } PetscFunctionReturn(0); } #undef __FUNCT__ #define __FUNCT__ "PCView" /*@C PCView - Prints the PC data structure. Collective on PC Input Parameters: + PC - the PC context - viewer - optional visualization context Note: The available visualization contexts include + PETSC_VIEWER_STDOUT_SELF - standard output (default) - PETSC_VIEWER_STDOUT_WORLD - synchronized standard output where only the first processor opens the file. All other processors send their data to the first processor to print. The user can open an alternative visualization contexts with PetscViewerASCIIOpen() (output to a specified file). Level: developer .keywords: PC, view .seealso: KSPView(), PetscViewerASCIIOpen() @*/ int PCView(PC pc,PetscViewer viewer) { PCType cstr; int ierr; PetscTruth mat_exists,isascii,isstring; PetscViewerFormat format; PetscFunctionBegin; PetscValidHeaderSpecific(pc,PC_COOKIE); if (!viewer) viewer = PETSC_VIEWER_STDOUT_(pc->comm); PetscValidHeaderSpecific(viewer,PETSC_VIEWER_COOKIE); PetscCheckSameComm(pc,viewer); ierr = PetscTypeCompare((PetscObject)viewer,PETSC_VIEWER_ASCII,&isascii);CHKERRQ(ierr); ierr = PetscTypeCompare((PetscObject)viewer,PETSC_VIEWER_STRING,&isstring);CHKERRQ(ierr); if (isascii) { ierr = PetscViewerGetFormat(viewer,&format);CHKERRQ(ierr); if (pc->prefix) { ierr = PetscViewerASCIIPrintf(viewer,"PC Object:(%s)\n",pc->prefix);CHKERRQ(ierr); } else { ierr = PetscViewerASCIIPrintf(viewer,"PC Object:\n");CHKERRQ(ierr); } ierr = PCGetType(pc,&cstr);CHKERRQ(ierr); if (cstr) { ierr = PetscViewerASCIIPrintf(viewer," type: %s\n",cstr);CHKERRQ(ierr); } else { ierr = PetscViewerASCIIPrintf(viewer," type: not yet set\n");CHKERRQ(ierr); } if (pc->ops->view) { ierr = PetscViewerASCIIPushTab(viewer);CHKERRQ(ierr); ierr = (*pc->ops->view)(pc,viewer);CHKERRQ(ierr); ierr = PetscViewerASCIIPopTab(viewer);CHKERRQ(ierr); } ierr = PetscObjectExists((PetscObject)pc->mat,&mat_exists);CHKERRQ(ierr); if (mat_exists) { ierr = PetscViewerPushFormat(viewer,PETSC_VIEWER_ASCII_INFO);CHKERRQ(ierr); if (pc->pmat == pc->mat) { ierr = PetscViewerASCIIPrintf(viewer," linear system matrix = precond matrix:\n");CHKERRQ(ierr); ierr = PetscViewerASCIIPushTab(viewer);CHKERRQ(ierr); ierr = MatView(pc->mat,viewer);CHKERRQ(ierr); ierr = PetscViewerASCIIPopTab(viewer);CHKERRQ(ierr); } else { ierr = PetscObjectExists((PetscObject)pc->pmat,&mat_exists);CHKERRQ(ierr); if (mat_exists) { ierr = PetscViewerASCIIPrintf(viewer," linear system matrix followed by preconditioner matrix:\n");CHKERRQ(ierr); } else { ierr = PetscViewerASCIIPrintf(viewer," linear system matrix:\n");CHKERRQ(ierr); } ierr = PetscViewerASCIIPushTab(viewer);CHKERRQ(ierr); ierr = MatView(pc->mat,viewer);CHKERRQ(ierr); if (mat_exists) {ierr = MatView(pc->pmat,viewer);CHKERRQ(ierr);} ierr = PetscViewerASCIIPopTab(viewer);CHKERRQ(ierr); } ierr = PetscViewerPopFormat(viewer);CHKERRQ(ierr); } } else if (isstring) { ierr = PCGetType(pc,&cstr);CHKERRQ(ierr); ierr = PetscViewerStringSPrintf(viewer," %-7.7s",cstr);CHKERRQ(ierr); if (pc->ops->view) {ierr = (*pc->ops->view)(pc,viewer);CHKERRQ(ierr);} } else { SETERRQ1(1,"Viewer type %s not supported by PC",((PetscObject)viewer)->type_name); } PetscFunctionReturn(0); } /*MC PCRegisterDynamic - Adds a method to the preconditioner package. Synopsis: int PCRegisterDynamic(char *name_solver,char *path,char *name_create,int (*routine_create)(PC)) Not collective Input Parameters: + name_solver - name of a new user-defined solver . path - path (either absolute or relative) the library containing this solver . name_create - name of routine to create method context - routine_create - routine to create method context Notes: PCRegisterDynamic() may be called multiple times to add several user-defined preconditioners. If dynamic libraries are used, then the fourth input argument (routine_create) is ignored. Sample usage: .vb PCRegisterDynamic("my_solver","/home/username/my_lib/lib/libO/solaris/mylib", "MySolverCreate",MySolverCreate); .ve Then, your solver can be chosen with the procedural interface via $ PCSetType(pc,"my_solver") or at runtime via the option $ -pc_type my_solver Level: advanced Notes: ${PETSC_ARCH}, ${PETSC_DIR}, ${PETSC_LIB_DIR}, ${BOPT}, or ${any environmental variable} occuring in pathname will be replaced with appropriate values. If your function is not being put into a shared library then use PCRegister() instead .keywords: PC, register .seealso: PCRegisterAll(), PCRegisterDestroy() M*/ #undef __FUNCT__ #define __FUNCT__ "PCRegister" /*@C PCRegister - See PCRegisterDynamic() Level: advanced @*/ int PCRegister(char *sname,char *path,char *name,int (*function)(PC)) { int ierr; char fullname[256]; PetscFunctionBegin; ierr = PetscFListConcat(path,name,fullname);CHKERRQ(ierr); ierr = PetscFListAdd(&PCList,sname,fullname,(void (*)(void))function);CHKERRQ(ierr); PetscFunctionReturn(0); } #undef __FUNCT__ #define __FUNCT__ "PCComputeExplicitOperator" /*@ PCComputeExplicitOperator - Computes the explicit preconditioned operator. Collective on PC Input Parameter: . pc - the preconditioner object Output Parameter: . mat - the explict preconditioned operator Notes: This computation is done by applying the operators to columns of the identity matrix. Currently, this routine uses a dense matrix format when 1 processor is used and a sparse format otherwise. This routine is costly in general, and is recommended for use only with relatively small systems. Level: advanced .keywords: PC, compute, explicit, operator @*/ int PCComputeExplicitOperator(PC pc,Mat *mat) { Vec in,out; int ierr,i,M,m,size,*rows,start,end; MPI_Comm comm; PetscScalar *array,zero = 0.0,one = 1.0; PetscFunctionBegin; PetscValidHeaderSpecific(pc,PC_COOKIE); PetscValidPointer(mat); comm = pc->comm; ierr = MPI_Comm_size(comm,&size);CHKERRQ(ierr); ierr = PCGetVector(pc,&in);CHKERRQ(ierr); ierr = VecDuplicate(in,&out);CHKERRQ(ierr); ierr = VecGetOwnershipRange(in,&start,&end);CHKERRQ(ierr); ierr = VecGetSize(in,&M);CHKERRQ(ierr); ierr = VecGetLocalSize(in,&m);CHKERRQ(ierr); ierr = PetscMalloc((m+1)*sizeof(int),&rows);CHKERRQ(ierr); for (i=0; i