Actual source code: mpb_baij.c

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

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

     13:   PetscFunctionBegin;
     14:   PetscCallMPI(MPI_Comm_size(PetscObjectComm((PetscObject)mat), &commsize));
     15:   PetscCallMPI(MPI_Comm_size(subComm, &subCommSize));

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

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

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

     37:   /* Traverse garray and identify blocked column indices [of offdiag mat] that
     38:    should be discarded. For the ones not discarded, store the newCol+1
     39:    value in garrayCMap */
     40:   PetscCall(PetscCalloc1(aij->B->cmap->n / bs, &garrayCMap));
     41:   for (i = 0; i < aij->B->cmap->n / bs; i++) {
     42:     col = aij->garray[i]; /* blocked column index */
     43:     for (subRank = 0; subRank < subCommSize; subRank++) {
     44:       rank = commRankMap[subRank];
     45:       if ((col >= mat->cmap->range[rank] / bs) && (col < mat->cmap->range[rank + 1] / bs)) {
     46:         garrayCMap[i] = (((*subMat)->cmap->range[subRank] - mat->cmap->range[rank]) / bs + col + 1);
     47:         break;
     48:       }
     49:     }
     50:   }

     52:   if (scall == MAT_INITIAL_MATRIX) {
     53:     /* Now compute preallocation for the offdiag mat */
     54:     PetscCall(PetscCalloc1(aij->B->rmap->n / bs, &nnz));
     55:     for (i = 0; i < aij->B->rmap->n / bs; i++) {
     56:       for (j = aijB->i[i]; j < aijB->i[i + 1]; j++) {
     57:         if (garrayCMap[aijB->j[j]]) nnz[i]++;
     58:       }
     59:     }
     60:     PetscCall(MatMPIBAIJSetPreallocation(*(subMat), bs, 0, NULL, 0, nnz));

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

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

     67:     PetscCall(PetscObjectReference((PetscObject)aij->A));
     68:   } else if (((Mat_MPIBAIJ *)(*subMat)->data)->A != aij->A) {
     69:     PetscObject obj = (PetscObject)((Mat_MPIBAIJ *)((*subMat)->data))->A;

     71:     PetscCall(PetscObjectReference(obj));

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

     75:     PetscCall(PetscObjectReference((PetscObject)aij->A));
     76:   }

     78:   /* Now traverse aij->B and insert values into subMat */
     79:   /* Does not need PetscShmgetAllocateArray() since temporary */
     80:   PetscCall(PetscMalloc3(bs, &newbRow, bs, &newbCol, bs * bs, &vals));
     81:   for (i = 0; i < aij->B->rmap->n / bs; i++) {
     82:     newRow = (*subMat)->rmap->range[subCommRank] + i * bs;
     83:     for (j = aijB->i[i]; j < aijB->i[i + 1]; j++) {
     84:       newCol = garrayCMap[aijB->j[j]];
     85:       if (newCol) {
     86:         newCol--; /* remove the increment */
     87:         newCol *= bs;
     88:         for (k = 0; k < bs; k++) {
     89:           newbRow[k] = newRow + k;
     90:           newbCol[k] = newCol + k;
     91:         }
     92:         /* copy column-oriented aijB->a into row-oriented vals */
     93:         aijBvals = aijB->a + j * bs * bs;
     94:         for (k1 = 0; k1 < bs; k1++) {
     95:           for (k = 0; k < bs; k++) vals[k1 + k * bs] = *aijBvals++;
     96:         }
     97:         PetscCall(MatSetValues(*subMat, bs, newbRow, bs, newbCol, vals, INSERT_VALUES));
     98:       }
     99:     }
    100:   }
    101:   PetscCall(MatAssemblyBegin(*subMat, MAT_FINAL_ASSEMBLY));
    102:   PetscCall(MatAssemblyEnd(*subMat, MAT_FINAL_ASSEMBLY));

    104:   /* deallocate temporary data */
    105:   PetscCall(PetscFree3(newbRow, newbCol, vals));
    106:   PetscCall(PetscFree(commRankMap));
    107:   PetscCall(PetscFree(garrayCMap));
    108:   if (scall == MAT_INITIAL_MATRIX) PetscCall(PetscFree(nnz));
    109:   PetscFunctionReturn(PETSC_SUCCESS);
    110: }