Actual source code: mpb_aij.c
1: #include <../src/mat/impls/aij/mpi/mpiaij.h>
3: PetscErrorCode MatGetMultiProcBlock_MPIAIJ(Mat mat, MPI_Comm subComm, MatReuse scall, Mat *subMat)
4: {
5: Mat_MPIAIJ *aij = (Mat_MPIAIJ *)mat->data;
6: Mat_SeqAIJ *aijB = (Mat_SeqAIJ *)aij->B->data;
7: PetscMPIInt subCommSize, subCommRank;
8: PetscMPIInt *commRankMap, subRank, rank, commRank;
9: PetscInt *garrayCMap, col, i, j, *nnz, newRow, newCol;
11: MPI_Comm_size(subComm, &subCommSize);
12: MPI_Comm_rank(subComm, &subCommRank);
13: MPI_Comm_rank(PetscObjectComm((PetscObject)mat), &commRank);
15: /* create subMat object with the relevant layout */
16: if (scall == MAT_INITIAL_MATRIX) {
17: MatCreate(subComm, subMat);
18: MatSetType(*subMat, MATMPIAIJ);
19: MatSetSizes(*subMat, mat->rmap->n, mat->cmap->n, PETSC_DECIDE, PETSC_DECIDE);
20: MatSetBlockSizesFromMats(*subMat, mat, mat);
22: /* need to setup rmap and cmap before Preallocation */
23: PetscLayoutSetUp((*subMat)->rmap);
24: PetscLayoutSetUp((*subMat)->cmap);
25: }
27: /* create a map of comm_rank from subComm to comm - should commRankMap and garrayCMap be kept for reused? */
28: PetscMalloc1(subCommSize, &commRankMap);
29: MPI_Allgather(&commRank, 1, MPI_INT, commRankMap, 1, MPI_INT, subComm);
31: /* Traverse garray and identify column indices [of offdiag mat] that
32: should be discarded. For the ones not discarded, store the newCol+1
33: value in garrayCMap */
34: PetscCalloc1(aij->B->cmap->n, &garrayCMap);
35: for (i = 0; i < aij->B->cmap->n; i++) {
36: col = aij->garray[i];
37: for (subRank = 0; subRank < subCommSize; subRank++) {
38: rank = commRankMap[subRank];
39: if ((col >= mat->cmap->range[rank]) && (col < mat->cmap->range[rank + 1])) {
40: garrayCMap[i] = (*subMat)->cmap->range[subRank] + col - mat->cmap->range[rank] + 1;
41: break;
42: }
43: }
44: }
46: if (scall == MAT_INITIAL_MATRIX) {
47: /* Compute preallocation for the offdiag mat */
48: PetscCalloc1(aij->B->rmap->n, &nnz);
49: for (i = 0; i < aij->B->rmap->n; i++) {
50: for (j = aijB->i[i]; j < aijB->i[i + 1]; j++) {
51: if (garrayCMap[aijB->j[j]]) nnz[i]++;
52: }
53: }
54: MatMPIAIJSetPreallocation(*(subMat), 0, NULL, 0, nnz);
56: /* reuse diag block with the new submat */
57: MatDestroy(&((Mat_MPIAIJ *)((*subMat)->data))->A);
58: ((Mat_MPIAIJ *)((*subMat)->data))->A = aij->A;
59: PetscObjectReference((PetscObject)aij->A);
60: } else if (((Mat_MPIAIJ *)(*subMat)->data)->A != aij->A) {
61: PetscObject obj = (PetscObject)((Mat_MPIAIJ *)((*subMat)->data))->A;
62: PetscObjectReference((PetscObject)obj);
63: ((Mat_MPIAIJ *)((*subMat)->data))->A = aij->A;
64: PetscObjectReference((PetscObject)aij->A);
65: }
67: /* Traverse aij->B and insert values into subMat */
68: if ((*subMat)->assembled) {
69: (*subMat)->was_assembled = PETSC_TRUE;
70: (*subMat)->assembled = PETSC_FALSE;
71: }
72: for (i = 0; i < aij->B->rmap->n; i++) {
73: newRow = (*subMat)->rmap->range[subCommRank] + i;
74: for (j = aijB->i[i]; j < aijB->i[i + 1]; j++) {
75: newCol = garrayCMap[aijB->j[j]];
76: if (newCol) {
77: newCol--; /* remove the increment */
78: MatSetValues_MPIAIJ(*subMat, 1, &newRow, 1, &newCol, (aijB->a + j), INSERT_VALUES);
79: }
80: }
81: }
82: MatAssemblyBegin(*subMat, MAT_FINAL_ASSEMBLY);
83: MatAssemblyEnd(*subMat, MAT_FINAL_ASSEMBLY);
85: /* deallocate temporary data */
86: PetscFree(commRankMap);
87: PetscFree(garrayCMap);
88: if (scall == MAT_INITIAL_MATRIX) PetscFree(nnz);
89: return 0;
90: }