Actual source code: shellcnv.c
petsc-3.7.1 2016-05-15
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      2: #include <petsc/private/matimpl.h>        /*I "petscmat.h" I*/
      3: #include <petsc/private/vecimpl.h>

      7: PETSC_INTERN PetscErrorCode MatConvert_Shell(Mat oldmat, MatType newtype,MatReuse reuse,Mat *newmat)
      8: {
      9:   Mat            mat;
     10:   Vec            in,out;
     12:   PetscInt       i,M,m,*rows,start,end;
     13:   MPI_Comm       comm;
     14:   PetscScalar    *array,zero = 0.0,one = 1.0;

     17:   PetscObjectGetComm((PetscObject)oldmat,&comm);

     19:   MatGetOwnershipRange(oldmat,&start,&end);
     20:   VecCreateMPI(comm,end-start,PETSC_DECIDE,&in);
     21:   VecDuplicate(in,&out);
     22:   VecGetSize(in,&M);
     23:   VecGetLocalSize(in,&m);
     24:   PetscMalloc1(m+1,&rows);
     25:   for (i=0; i<m; i++) rows[i] = start + i;

     27:   MatCreate(comm,&mat);
     28:   MatSetSizes(mat,m,M,M,M);
     29:   MatSetType(mat,newtype);
     30:   MatSetBlockSizesFromMats(mat,oldmat,oldmat);
     31:   MatSetUp(mat);

     33:   for (i=0; i<M; i++) {
     34:     VecSet(in,zero);
     35:     VecSetValues(in,1,&i,&one,INSERT_VALUES);
     36:     VecAssemblyBegin(in);
     37:     VecAssemblyEnd(in);

     39:     MatMult(oldmat,in,out);

     41:     VecGetArray(out,&array);
     42:     MatSetValues(mat,m,rows,1,&i,array,INSERT_VALUES);
     43:     VecRestoreArray(out,&array);

     45:   }
     46:   PetscFree(rows);
     47:   VecDestroy(&in);
     48:   VecDestroy(&out);
     49:   MatAssemblyBegin(mat,MAT_FINAL_ASSEMBLY);
     50:   MatAssemblyEnd(mat,MAT_FINAL_ASSEMBLY);

     52:   if (reuse == MAT_INPLACE_MATRIX) {
     53:     MatHeaderReplace(oldmat,&mat);
     54:   } else {
     55:     *newmat = mat;
     56:   }
     57:   return(0);
     58: }