1: #include <../src/mat/impls/baij/mpi/mpibaij.h>

  5: PetscErrorCode  MatGetMultiProcBlock_MPIBAIJ(Mat mat, MPI_Comm subComm, MatReuse scall,Mat *subMat)
  6: {
  8:   Mat_MPIBAIJ    *aij  = (Mat_MPIBAIJ*)mat->data;
  9:   Mat_SeqBAIJ    *aijB = (Mat_SeqBAIJ*)aij->B->data;
 10:   PetscMPIInt    commRank,subCommSize,subCommRank;
 11:   PetscMPIInt    *commRankMap,subRank,rank,commsize;
 12:   PetscInt       *garrayCMap,col,i,j,*nnz,newRow,newCol,*newbRow,*newbCol,k,k1;
 13:   PetscInt       bs=mat->rmap->bs;
 14:   PetscScalar    *vals,*aijBvals;

 17:   MPI_Comm_size(PetscObjectComm((PetscObject)mat),&commsize);
 18:   MPI_Comm_size(subComm,&subCommSize);

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

 27:     /* need to setup rmap and cmap before Preallocation */
 28:     PetscLayoutSetBlockSize((*subMat)->rmap,mat->rmap->bs);
 29:     PetscLayoutSetBlockSize((*subMat)->cmap,mat->cmap->bs);
 30:     PetscLayoutSetUp((*subMat)->rmap);
 31:     PetscLayoutSetUp((*subMat)->cmap);
 32:   }

 34:   /* create a map of comm_rank from subComm to comm - should commRankMap and garrayCMap be kept for reused? */
 35:   MPI_Comm_rank(PetscObjectComm((PetscObject)mat),&commRank);
 36:   MPI_Comm_rank(subComm,&subCommRank);
 37:   PetscMalloc1(subCommSize,&commRankMap);
 38:   MPI_Allgather(&commRank,1,MPI_INT,commRankMap,1,MPI_INT,subComm);

 40:   /* Traverse garray and identify blocked column indices [of offdiag mat] that
 41:    should be discarded. For the ones not discarded, store the newCol+1
 42:    value in garrayCMap */
 43:   PetscMalloc1(aij->B->cmap->n/bs,&garrayCMap);
 44:   PetscMemzero(garrayCMap,aij->B->cmap->n/bs*sizeof(PetscInt));
 45:   for (i=0; i<aij->B->cmap->n/bs; i++) {
 46:     col = aij->garray[i]; /* blocked column index */
 47:     for (subRank=0; subRank<subCommSize; subRank++) {
 48:       rank = commRankMap[subRank];
 49:       if ((col >= mat->cmap->range[rank]/bs) && (col < mat->cmap->range[rank+1]/bs)) {
 50:         garrayCMap[i] = (((*subMat)->cmap->range[subRank]- mat->cmap->range[rank])/bs + col + 1);
 51:         break;
 52:       }
 53:     }
 54:   }

 56:   if (scall == MAT_INITIAL_MATRIX) {
 57:     /* Now compute preallocation for the offdiag mat */
 58:     PetscMalloc1(aij->B->rmap->n/bs,&nnz);
 59:     PetscMemzero(nnz,aij->B->rmap->n/bs*sizeof(PetscInt));
 60:     for (i=0; i<aij->B->rmap->n/bs; i++) {
 61:       for (j=aijB->i[i]; j<aijB->i[i+1]; j++) {
 62:         if (garrayCMap[aijB->j[j]]) nnz[i]++;
 63:       }
 64:     }
 65:     MatMPIBAIJSetPreallocation(*(subMat),bs,0,NULL,0,nnz);

 67:     /* reuse diag block with the new submat */
 68:     MatDestroy(&((Mat_MPIBAIJ*)((*subMat)->data))->A);

 70:     ((Mat_MPIBAIJ*)((*subMat)->data))->A = aij->A;

 72:     PetscObjectReference((PetscObject)aij->A);
 73:   } else if (((Mat_MPIBAIJ*)(*subMat)->data)->A != aij->A) {
 74:     PetscObject obj = (PetscObject)((Mat_MPIBAIJ*)((*subMat)->data))->A;

 76:     PetscObjectReference((PetscObject)obj);

 78:     ((Mat_MPIBAIJ*)((*subMat)->data))->A = aij->A;

 80:     PetscObjectReference((PetscObject)aij->A);
 81:   }

 83:   /* Now traverse aij->B and insert values into subMat */
 84:   PetscMalloc3(bs,&newbRow,bs,&newbCol,bs*bs,&vals);
 85:   for (i=0; i<aij->B->rmap->n/bs; i++) {
 86:     newRow = (*subMat)->rmap->range[subCommRank] + i*bs;
 87:     for (j=aijB->i[i]; j<aijB->i[i+1]; j++) {
 88:       newCol = garrayCMap[aijB->j[j]];
 89:       if (newCol) {
 90:         newCol--; /* remove the increment */
 91:         newCol *= bs;
 92:         for (k=0; k<bs; k++) {
 93:           newbRow[k] = newRow + k;
 94:           newbCol[k] = newCol + k;
 95:         }
 96:         /* copy column-oriented aijB->a into row-oriented vals */
 97:         aijBvals = aijB->a + j*bs*bs;
 98:         for (k1=0; k1<bs; k1++) {
 99:           for (k=0; k<bs; k++) {
100:             vals[k1+k*bs] = *aijBvals++;
101:           }
102:         }
103:         MatSetValues(*subMat,bs,newbRow,bs,newbCol,vals,INSERT_VALUES);
104:       }
105:     }
106:   }
107:   MatAssemblyBegin(*subMat,MAT_FINAL_ASSEMBLY);
108:   MatAssemblyEnd(*subMat,MAT_FINAL_ASSEMBLY);

110:   /* deallocate temporary data */
111:   PetscFree3(newbRow,newbCol,vals);
112:   PetscFree(commRankMap);
113:   PetscFree(garrayCMap);
114:   if (scall == MAT_INITIAL_MATRIX) {
115:     PetscFree(nnz);
116:   }
117:   return(0);
118: }