Actual source code: mpb_baij.c
petsc-3.10.5 2019-03-28
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      1:  #include <../src/mat/impls/baij/mpi/mpibaij.h>

      3: PetscErrorCode  MatGetMultiProcBlock_MPIBAIJ(Mat mat, MPI_Comm subComm, MatReuse scall,Mat *subMat)
      4: {
      6:   Mat_MPIBAIJ    *aij  = (Mat_MPIBAIJ*)mat->data;
      7:   Mat_SeqBAIJ    *aijB = (Mat_SeqBAIJ*)aij->B->data;
      8:   PetscMPIInt    commRank,subCommSize,subCommRank;
      9:   PetscMPIInt    *commRankMap,subRank,rank,commsize;
     10:   PetscInt       *garrayCMap,col,i,j,*nnz,newRow,newCol,*newbRow,*newbCol,k,k1;
     11:   PetscInt       bs=mat->rmap->bs;
     12:   PetscScalar    *vals,*aijBvals;

     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,MATMPIBAIJ);
     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:   PetscMalloc1(subCommSize,&commRankMap);
     36:   MPI_Allgather(&commRank,1,MPI_INT,commRankMap,1,MPI_INT,subComm);

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

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

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

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

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

     74:     PetscObjectReference((PetscObject)obj);

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

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

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

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