Actual source code: mpb_baij.c
petsc-3.7.1 2016-05-15
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      1: #include <../src/mat/impls/baij/mpi/mpibaij.h>

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

     17:   MPI_Comm_size(PetscObjectComm((PetscObject)mat),&commsize);
     18:   MPI_Comm_size(subComm,&subCommSize);

     20:   /* create subMat object with the relavent layout */
     21:   if (scall == MAT_INITIAL_MATRIX) {
     22:     MatCreate(subComm,subMat);
     23:     MatSetType(*subMat,MATMPIBAIJ);
     24:     MatSetSizes(*subMat,mat->rmap->n,mat->cmap->n,PETSC_DECIDE,PETSC_DECIDE);
     25:     MatSetBlockSizes(*subMat,mat->rmap->bs,mat->cmap->bs);

     27:     /* need to setup rmap and cmap before Preallocation */
     28:     PetscLayoutSetBlockSize((*subMat)->rmap,mat->rmap->bs);
     29:     PetscLayoutSetBlockSize((*subMat)->cmap,mat->cmap->bs);
     30:     PetscLayoutSetUp((*subMat)->rmap);
     31:     PetscLayoutSetUp((*subMat)->cmap);
     32:   }

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

     40:   /* Traverse garray and identify blocked column indices [of offdiag mat] that
     41:    should be discarded. For the ones not discarded, store the newCol+1
     42:    value in garrayCMap */
     43:   PetscMalloc1(aij->B->cmap->n/bs,&garrayCMap);
     44:   PetscMemzero(garrayCMap,aij->B->cmap->n/bs*sizeof(PetscInt));
     45:   for (i=0; i<aij->B->cmap->n/bs; i++) {
     46:     col = aij->garray[i]; /* blocked column index */
     47:     for (subRank=0; subRank<subCommSize; subRank++) {
     48:       rank = commRankMap[subRank];
     49:       if ((col >= mat->cmap->range[rank]/bs) && (col < mat->cmap->range[rank+1]/bs)) {
     50:         garrayCMap[i] = (((*subMat)->cmap->range[subRank]- mat->cmap->range[rank])/bs + col + 1);
     51:         break;
     52:       }
     53:     }
     54:   }

     56:   if (scall == MAT_INITIAL_MATRIX) {
     57:     /* Now compute preallocation for the offdiag mat */
     58:     PetscMalloc1(aij->B->rmap->n/bs,&nnz);
     59:     PetscMemzero(nnz,aij->B->rmap->n/bs*sizeof(PetscInt));
     60:     for (i=0; i<aij->B->rmap->n/bs; i++) {
     61:       for (j=aijB->i[i]; j<aijB->i[i+1]; j++) {
     62:         if (garrayCMap[aijB->j[j]]) nnz[i]++;
     63:       }
     64:     }
     65:     MatMPIBAIJSetPreallocation(*(subMat),bs,0,NULL,0,nnz);

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

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

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

     76:     PetscObjectReference((PetscObject)obj);

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

     80:     PetscObjectReference((PetscObject)aij->A);
     81:   }

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

    110:   /* deallocate temporary data */
    111:   PetscFree3(newbRow,newbCol,vals);
    112:   PetscFree(commRankMap);
    113:   PetscFree(garrayCMap);
    114:   if (scall == MAT_INITIAL_MATRIX) {
    115:     PetscFree(nnz);
    116:   }
    117:   return(0);
    118: }