Actual source code: mpb_aij.c
petsc-dev 2014-02-02
1: #include <../src/mat/impls/aij/mpi/mpiaij.h>
5: PetscErrorCode MatGetMultiProcBlock_MPIAIJ(Mat mat, MPI_Comm subComm, MatReuse scall,Mat *subMat)
6: {
8: Mat_MPIAIJ *aij = (Mat_MPIAIJ*)mat->data;
9: Mat_SeqAIJ *aijB = (Mat_SeqAIJ*)aij->B->data;
10: PetscMPIInt commRank,subCommSize,subCommRank;
11: PetscMPIInt *commRankMap,subRank,rank,commsize;
12: PetscInt *garrayCMap,col,i,j,*nnz,newRow,newCol;
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,MATMPIAIJ);
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 column indices [of offdiag mat] that
39: should be discarded. For the ones not discarded, store the newCol+1
40: value in garrayCMap */
41: PetscCalloc1(aij->B->cmap->n,&garrayCMap);
42: for (i=0; i<aij->B->cmap->n; i++) {
43: col = aij->garray[i];
44: for (subRank=0; subRank<subCommSize; subRank++) {
45: rank = commRankMap[subRank];
46: if ((col >= mat->cmap->range[rank]) && (col < mat->cmap->range[rank+1])) {
47: garrayCMap[i] = (*subMat)->cmap->range[subRank] + col - mat->cmap->range[rank]+1;
48: break;
49: }
50: }
51: }
53: if (scall == MAT_INITIAL_MATRIX) {
54: /* Now compute preallocation for the offdiag mat */
55: PetscCalloc1(aij->B->rmap->n,&nnz);
56: for (i=0; i<aij->B->rmap->n; i++) {
57: for (j=aijB->i[i]; j<aijB->i[i+1]; j++) {
58: if (garrayCMap[aijB->j[j]]) nnz[i]++;
59: }
60: }
61: MatMPIAIJSetPreallocation(*(subMat),0,NULL,0,nnz);
63: /* reuse diag block with the new submat */
64: MatDestroy(&((Mat_MPIAIJ*)((*subMat)->data))->A);
66: ((Mat_MPIAIJ*)((*subMat)->data))->A = aij->A;
68: PetscObjectReference((PetscObject)aij->A);
69: } else if (((Mat_MPIAIJ*)(*subMat)->data)->A != aij->A) {
70: PetscObject obj = (PetscObject)((Mat_MPIAIJ*)((*subMat)->data))->A;
72: PetscObjectReference((PetscObject)obj);
74: ((Mat_MPIAIJ*)((*subMat)->data))->A = aij->A;
76: PetscObjectReference((PetscObject)aij->A);
77: }
79: /* Now traverse aij->B and insert values into subMat */
80: for (i=0; i<aij->B->rmap->n; i++) {
81: newRow = (*subMat)->rmap->range[subCommRank] + i;
82: for (j=aijB->i[i]; j<aijB->i[i+1]; j++) {
83: newCol = garrayCMap[aijB->j[j]];
84: if (newCol) {
85: newCol--; /* remove the increment */
86: MatSetValues(*subMat,1,&newRow,1,&newCol,(aijB->a+j),INSERT_VALUES);
87: }
88: }
89: }
91: /* assemble the submat */
92: MatAssemblyBegin(*subMat,MAT_FINAL_ASSEMBLY);
93: MatAssemblyEnd(*subMat,MAT_FINAL_ASSEMBLY);
95: /* deallocate temporary data */
96: PetscFree(commRankMap);
97: PetscFree(garrayCMap);
98: if (scall == MAT_INITIAL_MATRIX) {
99: PetscFree(nnz);
100: }
101: return(0);
102: }