Actual source code: mpb_aij.c

petsc-3.4.2 2013-07-02
  1: #include <../src/mat/impls/aij/mpi/mpiaij.h>

  5: PetscErrorCode  MatGetMultiProcBlock_MPIAIJ(Mat mat, MPI_Comm subComm, MatReuse scall,Mat *subMat)
  6: {
  8:   Mat_MPIAIJ     *aij  = (Mat_MPIAIJ*)mat->data;
  9:   Mat_SeqAIJ     *aijB = (Mat_SeqAIJ*)aij->B->data;
 10:   PetscMPIInt    commRank,subCommSize,subCommRank;
 11:   PetscMPIInt    *commRankMap,subRank,rank,commsize;
 12:   PetscInt       *garrayCMap,col,i,j,*nnz,newRow,newCol;

 15:   MPI_Comm_size(PetscObjectComm((PetscObject)mat),&commsize);
 16:   MPI_Comm_size(subComm,&subCommSize);

 18:   /* create subMat object with the relavent layout */
 19:   if (scall == MAT_INITIAL_MATRIX) {
 20:     MatCreate(subComm,subMat);
 21:     MatSetType(*subMat,MATMPIAIJ);
 22:     MatSetSizes(*subMat,mat->rmap->n,mat->cmap->n,PETSC_DECIDE,PETSC_DECIDE);
 23:     MatSetBlockSizes(*subMat,mat->rmap->bs,mat->cmap->bs);

 25:     /* need to setup rmap and cmap before Preallocation */
 26:     PetscLayoutSetBlockSize((*subMat)->rmap,mat->rmap->bs);
 27:     PetscLayoutSetBlockSize((*subMat)->cmap,mat->cmap->bs);
 28:     PetscLayoutSetUp((*subMat)->rmap);
 29:     PetscLayoutSetUp((*subMat)->cmap);
 30:   }

 32:   /* create a map of comm_rank from subComm to comm - should commRankMap and garrayCMap be kept for reused? */
 33:   MPI_Comm_rank(PetscObjectComm((PetscObject)mat),&commRank);
 34:   MPI_Comm_rank(subComm,&subCommRank);
 35:   PetscMalloc(subCommSize*sizeof(PetscMPIInt),&commRankMap);
 36:   MPI_Allgather(&commRank,1,MPI_INT,commRankMap,1,MPI_INT,subComm);

 38:   /* Traverse garray and identify column indices [of offdiag mat] that
 39:    should be discarded. For the ones not discarded, store the newCol+1
 40:    value in garrayCMap */
 41:   PetscMalloc(aij->B->cmap->n*sizeof(PetscInt),&garrayCMap);
 42:   PetscMemzero(garrayCMap,aij->B->cmap->n*sizeof(PetscInt));
 43:   for (i=0; i<aij->B->cmap->n; i++) {
 44:     col = aij->garray[i];
 45:     for (subRank=0; subRank<subCommSize; subRank++) {
 46:       rank = commRankMap[subRank];
 47:       if ((col >= mat->cmap->range[rank]) && (col < mat->cmap->range[rank+1])) {
 48:         garrayCMap[i] = (*subMat)->cmap->range[subRank] + col - mat->cmap->range[rank]+1;
 49:         break;
 50:       }
 51:     }
 52:   }

 54:   if (scall == MAT_INITIAL_MATRIX) {
 55:     /* Now compute preallocation for the offdiag mat */
 56:     PetscMalloc(aij->B->rmap->n*sizeof(PetscInt),&nnz);
 57:     PetscMemzero(nnz,aij->B->rmap->n*sizeof(PetscInt));
 58:     for (i=0; i<aij->B->rmap->n; i++) {
 59:       for (j=aijB->i[i]; j<aijB->i[i+1]; j++) {
 60:         if (garrayCMap[aijB->j[j]]) nnz[i]++;
 61:       }
 62:     }
 63:     MatMPIAIJSetPreallocation(*(subMat),0,NULL,0,nnz);

 65:     /* reuse diag block with the new submat */
 66:     MatDestroy(&((Mat_MPIAIJ*)((*subMat)->data))->A);

 68:     ((Mat_MPIAIJ*)((*subMat)->data))->A = aij->A;

 70:     PetscObjectReference((PetscObject)aij->A);
 71:   } else if (((Mat_MPIAIJ*)(*subMat)->data)->A != aij->A) {
 72:     PetscObject obj = (PetscObject)((Mat_MPIAIJ*)((*subMat)->data))->A;

 74:     PetscObjectReference((PetscObject)obj);

 76:     ((Mat_MPIAIJ*)((*subMat)->data))->A = aij->A;

 78:     PetscObjectReference((PetscObject)aij->A);
 79:   }

 81:   /* Now traverse aij->B and insert values into subMat */
 82:   for (i=0; i<aij->B->rmap->n; i++) {
 83:     newRow = (*subMat)->rmap->range[subCommRank] + i;
 84:     for (j=aijB->i[i]; j<aijB->i[i+1]; j++) {
 85:       newCol = garrayCMap[aijB->j[j]];
 86:       if (newCol) {
 87:         newCol--; /* remove the increment */
 88:         MatSetValues(*subMat,1,&newRow,1,&newCol,(aijB->a+j),INSERT_VALUES);
 89:       }
 90:     }
 91:   }

 93:   /* assemble the submat */
 94:   MatAssemblyBegin(*subMat,MAT_FINAL_ASSEMBLY);
 95:   MatAssemblyEnd(*subMat,MAT_FINAL_ASSEMBLY);

 97:   /* deallocate temporary data */
 98:   PetscFree(commRankMap);
 99:   PetscFree(garrayCMap);
100:   if (scall == MAT_INITIAL_MATRIX) {
101:     PetscFree(nnz);
102:   }
103:   return(0);
104: }