Date: 2021-03-03T22:26:19+00:00

Actual source code: mpb_baij.c
petsc-3.14.5 2021-03-03
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      1: #include <../src/mat/impls/baij/mpi/mpibaij.h>

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

     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,MATMPIBAIJ);
     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 blocked 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/bs,&garrayCMap);
     42:   for (i=0; i<aij->B->cmap->n/bs; i++) {
     43:     col = aij->garray[i]; /* blocked column index */
     44:     for (subRank=0; subRank<subCommSize; subRank++) {
     45:       rank = commRankMap[subRank];
     46:       if ((col >= mat->cmap->range[rank]/bs) && (col < mat->cmap->range[rank+1]/bs)) {
     47:         garrayCMap[i] = (((*subMat)->cmap->range[subRank]- mat->cmap->range[rank])/bs + col + 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/bs,&nnz);
     56:     for (i=0; i<aij->B->rmap->n/bs; i++) {
     57:       for (j=aijB->i[i]; j<aijB->i[i+1]; j++) {
     58:         if (garrayCMap[aijB->j[j]]) nnz[i]++;
     59:       }
     60:     }
     61:     MatMPIBAIJSetPreallocation(*(subMat),bs,0,NULL,0,nnz);

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

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

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

     72:     PetscObjectReference((PetscObject)obj);

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

     76:     PetscObjectReference((PetscObject)aij->A);
     77:   }

     79:   /* Now traverse aij->B and insert values into subMat */
     80:   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++) {
     96:             vals[k1+k*bs] = *aijBvals++;
     97:           }
     98:         }
     99:         MatSetValues(*subMat,bs,newbRow,bs,newbCol,vals,INSERT_VALUES);
    100:       }
    101:     }
    102:   }
    103:   MatAssemblyBegin(*subMat,MAT_FINAL_ASSEMBLY);
    104:   MatAssemblyEnd(*subMat,MAT_FINAL_ASSEMBLY);

    106:   /* deallocate temporary data */
    107:   PetscFree3(newbRow,newbCol,vals);
    108:   PetscFree(commRankMap);
    109:   PetscFree(garrayCMap);
    110:   if (scall == MAT_INITIAL_MATRIX) {
    111:     PetscFree(nnz);
    112:   }
    113:   return(0);
    114: }