1:  #include <petsc/private/matimpl.h>
  2:  #include <petsc/private/isimpl.h>

  4: static PetscErrorCode MatColoringApply_Natural(MatColoring mc,ISColoring *iscoloring)
  5: {
  6:   PetscErrorCode  ierr;
  7:   PetscInt        start,end,i,bs = 1,n;
  8:   ISColoringValue *colors;
  9:   MPI_Comm        comm;
 10:   PetscBool       flg1,flg2;
 11:   Mat             mat     = mc->mat;
 12:   Mat             mat_seq = mc->mat;
 13:   PetscMPIInt     size;
 14:   ISColoring      iscoloring_seq;
 15:   ISColoringValue *colors_loc;
 16:   PetscInt        rstart,rend,N_loc,nc;

 19:   /* this is ugly way to get blocksize but cannot call MatGetBlockSize() because AIJ can have bs > 1 */
 20:   PetscObjectTypeCompare((PetscObject)mat,MATSEQBAIJ,&flg1);
 21:   PetscObjectTypeCompare((PetscObject)mat,MATMPIBAIJ,&flg2);
 22:   if (flg1 || flg2) {
 23:     MatGetBlockSize(mat,&bs);
 24:   }

 26:   PetscObjectGetComm((PetscObject)mat,&comm);
 27:   MPI_Comm_size(comm,&size);
 28:   if (size > 1) {
 29:     /* create a sequential iscoloring on all processors */
 30:     MatGetSeqNonzeroStructure(mat,&mat_seq);
 31:   }

 33:   MatGetSize(mat_seq,&n,NULL);
 34:   MatGetOwnershipRange(mat_seq,&start,&end);
 35:   n    = n/bs;
 36:   if (n > IS_COLORING_MAX-1) SETERRQ(PETSC_COMM_SELF,PETSC_ERR_SUP,"Maximum color size exceeded");

 38:   start = start/bs;
 39:   end   = end/bs;
 40:   PetscMalloc1(end-start+1,&colors);
 41:   for (i=start; i<end; i++) {
 42:     colors[i-start] = (ISColoringValue)i;
 43:   }
 44:   ISColoringCreate(comm,n,end-start,colors,PETSC_OWN_POINTER,iscoloring);

 46:   if (size > 1) {
 47:     MatDestroySeqNonzeroStructure(&mat_seq);

 49:     /* convert iscoloring_seq to a parallel iscoloring */
 50:     iscoloring_seq = *iscoloring;
 51:     rstart         = mat->rmap->rstart/bs;
 52:     rend           = mat->rmap->rend/bs;
 53:     N_loc          = rend - rstart; /* number of local nodes */

 55:     /* get local colors for each local node */
 56:     PetscMalloc1(N_loc+1,&colors_loc);
 57:     for (i=rstart; i<rend; i++) {
 58:       colors_loc[i-rstart] = iscoloring_seq->colors[i];
 59:     }
 60:     /* create a parallel iscoloring */
 61:     nc   = iscoloring_seq->n;
 62:     ISColoringCreate(comm,nc,N_loc,colors_loc,PETSC_OWN_POINTER,iscoloring);
 63:     ISColoringDestroy(&iscoloring_seq);
 64:   }
 65:   return(0);
 66: }

 68: PETSC_EXTERN PetscErrorCode MatColoringCreate_Natural(MatColoring mc)
 69: {
 71:     mc->data                = NULL;
 72:     mc->ops->apply          = MatColoringApply_Natural;
 73:     mc->ops->view           = NULL;
 74:     mc->ops->destroy        = NULL;
 75:     mc->ops->setfromoptions = NULL;
 76:     return(0);
 77: }