[petsc-users] Partitioning does not work

[Orxan Shibliyev]

I modified ex11.c: Tests MatMeshToDual()
<http://www.mcs.anl.gov/petsc/petsc-current/src/mat/examples/tutorials/ex11.c.html>
in order to partition the unstructured grid provided in Petsc documentation
<http://www.mcs.anl.gov/petsc/petsc-current/docs/manual.pdf>, page 71. The
resulting code is as follows but *MatView()* does not print entries of
matrix, *dual* whereas in the original example it does. Why?

static char help[] = "Tests MatMeshToDual()\n\n";

/*T
Concepts: Mat^mesh partitioning
Processors: n
T*/

/*
   Include "petscmat.h" so that we can use matrices.
   automatically includes:
   petscsys.h       - base PETSc routines   petscvec.h    - vectors
   petscmat.h    - matrices
   petscis.h     - index sets            petscviewer.h - viewers
   */
#include <petscmat.h>

#undef __FUNCT__
#define __FUNCT__ "main"
int main(int argc,char **args)
{
    Mat             mesh,dual;
    PetscErrorCode  ierr;
    PetscInt        Nvertices = 4;       /* total number of vertices */
    PetscInt        ncells    = 2;       /* number cells on this process */
    PetscInt        *ii,*jj;
    PetscMPIInt     size,rank;
    MatPartitioning part;
    IS              is;

    PetscInitialize(&argc,&args,(char*)0,help);
    ierr = MPI_Comm_size(MPI_COMM_WORLD,&size);CHKERRQ(ierr);
    if (size != 2) SETERRQ(PETSC_COMM_WORLD,PETSC_ERR_SUP,"This example is
for exactly two processes");
    ierr = MPI_Comm_rank(MPI_COMM_WORLD,&rank);CHKERRQ(ierr);

    ierr  = PetscMalloc1(3,&ii);CHKERRQ(ierr);
    ierr  = PetscMalloc1(3,&jj);CHKERRQ(ierr);
    if (rank == 0) {
        ii[0] = 0; ii[1] = 2; ii[2] = 3;
        jj[0] = 2; jj[1] = 3; jj[2] = 3;
    } else {
        ii[0] = 0; ii[1] = 1; ii[2] = 3;
        jj[0] = 0; jj[1] = 0; jj[2] = 1;
    }
    ierr =
MatCreateMPIAdj(MPI_COMM_WORLD,ncells,Nvertices,ii,jj,NULL,&mesh);CHKERRQ(ierr);
    ierr = MatMeshToCellGraph(mesh,2,&dual);CHKERRQ(ierr);
    ierr = MatView(dual,PETSC_VIEWER_STDOUT_WORLD);CHKERRQ(ierr);

    ierr = MatPartitioningCreate(MPI_COMM_WORLD,&part);CHKERRQ(ierr);
    ierr = MatPartitioningSetAdjacency(part,dual);CHKERRQ(ierr);
    ierr = MatPartitioningSetFromOptions(part);CHKERRQ(ierr);
    ierr = MatPartitioningApply(part,&is);CHKERRQ(ierr);
    ierr = ISView(is,PETSC_VIEWER_STDOUT_WORLD);CHKERRQ(ierr);
    ierr = ISDestroy(&is);CHKERRQ(ierr);
    ierr = MatPartitioningDestroy(&part);CHKERRQ(ierr);

    ierr = MatDestroy(&mesh);CHKERRQ(ierr);
    ierr = MatDestroy(&dual);CHKERRQ(ierr);
    ierr = PetscFinalize();
    return 0;
}
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