1 #include <../src/mat/impls/aij/mpi/mpiaij.h>
2
MatGetMultiProcBlock_MPIAIJ(Mat mat,MPI_Comm subComm,MatReuse scall,Mat * subMat)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;
10
11 PetscFunctionBegin;
12 PetscCallMPI(MPI_Comm_size(subComm, &subCommSize));
13 PetscCallMPI(MPI_Comm_rank(subComm, &subCommRank));
14 PetscCallMPI(MPI_Comm_rank(PetscObjectComm((PetscObject)mat), &commRank));
15
16 /* create subMat object with the relevant layout */
17 if (scall == MAT_INITIAL_MATRIX) {
18 PetscCall(MatCreate(subComm, subMat));
19 PetscCall(MatSetType(*subMat, MATMPIAIJ));
20 PetscCall(MatSetSizes(*subMat, mat->rmap->n, mat->cmap->n, PETSC_DECIDE, PETSC_DECIDE));
21 PetscCall(MatSetBlockSizesFromMats(*subMat, mat, mat));
22
23 /* need to setup rmap and cmap before Preallocation */
24 PetscCall(PetscLayoutSetUp((*subMat)->rmap));
25 PetscCall(PetscLayoutSetUp((*subMat)->cmap));
26 }
27
28 /* create a map of comm_rank from subComm to comm - should commRankMap and garrayCMap be kept for reused? */
29 PetscCall(PetscMalloc1(subCommSize, &commRankMap));
30 PetscCallMPI(MPI_Allgather(&commRank, 1, MPI_INT, commRankMap, 1, MPI_INT, subComm));
31
32 /* Traverse garray and identify column indices [of offdiag mat] that
33 should be discarded. For the ones not discarded, store the newCol+1
34 value in garrayCMap */
35 PetscCall(PetscCalloc1(aij->B->cmap->n, &garrayCMap));
36 for (i = 0; i < aij->B->cmap->n; i++) {
37 col = aij->garray[i];
38 for (subRank = 0; subRank < subCommSize; subRank++) {
39 rank = commRankMap[subRank];
40 if ((col >= mat->cmap->range[rank]) && (col < mat->cmap->range[rank + 1])) {
41 garrayCMap[i] = (*subMat)->cmap->range[subRank] + col - mat->cmap->range[rank] + 1;
42 break;
43 }
44 }
45 }
46
47 if (scall == MAT_INITIAL_MATRIX) {
48 /* Compute preallocation for the offdiag mat */
49 PetscCall(PetscCalloc1(aij->B->rmap->n, &nnz));
50 for (i = 0; i < aij->B->rmap->n; i++) {
51 for (j = aijB->i[i]; j < aijB->i[i + 1]; j++) {
52 if (garrayCMap[aijB->j[j]]) nnz[i]++;
53 }
54 }
55 PetscCall(MatMPIAIJSetPreallocation(*(subMat), 0, NULL, 0, nnz));
56
57 /* reuse diag block with the new submat */
58 PetscCall(MatDestroy(&((Mat_MPIAIJ *)((*subMat)->data))->A));
59 ((Mat_MPIAIJ *)((*subMat)->data))->A = aij->A;
60 PetscCall(PetscObjectReference((PetscObject)aij->A));
61 } else if (((Mat_MPIAIJ *)(*subMat)->data)->A != aij->A) {
62 PetscObject obj = (PetscObject)((Mat_MPIAIJ *)((*subMat)->data))->A;
63 PetscCall(PetscObjectReference(obj));
64 ((Mat_MPIAIJ *)((*subMat)->data))->A = aij->A;
65 PetscCall(PetscObjectReference((PetscObject)aij->A));
66 }
67
68 /* Traverse aij->B and insert values into subMat */
69 if ((*subMat)->assembled) {
70 (*subMat)->was_assembled = PETSC_TRUE;
71 (*subMat)->assembled = PETSC_FALSE;
72 }
73 for (i = 0; i < aij->B->rmap->n; i++) {
74 newRow = (*subMat)->rmap->range[subCommRank] + i;
75 for (j = aijB->i[i]; j < aijB->i[i + 1]; j++) {
76 newCol = garrayCMap[aijB->j[j]];
77 if (newCol) {
78 newCol--; /* remove the increment */
79 PetscCall(MatSetValues_MPIAIJ(*subMat, 1, &newRow, 1, &newCol, aijB->a + j, INSERT_VALUES));
80 }
81 }
82 }
83 PetscCall(MatAssemblyBegin(*subMat, MAT_FINAL_ASSEMBLY));
84 PetscCall(MatAssemblyEnd(*subMat, MAT_FINAL_ASSEMBLY));
85
86 /* deallocate temporary data */
87 PetscCall(PetscFree(commRankMap));
88 PetscCall(PetscFree(garrayCMap));
89 if (scall == MAT_INITIAL_MATRIX) PetscCall(PetscFree(nnz));
90 PetscFunctionReturn(PETSC_SUCCESS);
91 }
92