Actual source code: shellcnv.c

 2:  #include src/mat/matimpl.h
 3:  #include vecimpl.h
  4: 
  7: PetscErrorCode MatConvert_Shell(Mat oldmat,const MatType newtype,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:   comm = 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:   PetscMalloc((m+1)*sizeof(int),&rows);
 25:   for (i=0; i<m; i++) {rows[i] = start + i;}

 27:   MatCreate(comm,m,M,M,M,&mat);
 28:   MatSetType(mat,newtype);
 29:   MatSetBlockSize(mat,oldmat->bs);

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

 37:     MatMult(oldmat,in,out);
 38: 
 39:     VecGetArray(out,&array);
 40:     MatSetValues(mat,m,rows,1,&i,array,INSERT_VALUES);
 41:     VecRestoreArray(out,&array);

 43:   }
 44:   PetscFree(rows);
 45:   VecDestroy(in);
 46:   VecDestroy(out);
 47:   MatAssemblyBegin(mat,MAT_FINAL_ASSEMBLY);
 48:   MatAssemblyEnd(mat,MAT_FINAL_ASSEMBLY);

 50:   /* Fake support for "inplace" convert. */
 51:   if (*newmat == oldmat) {
 52:     MatDestroy(oldmat);
 53:   }
 54:   *newmat = mat;
 55:   return(0);
 56: }