[petsc-users] Getting a vector from a DM to output VTK

[Nicholas Arnold-Medabalimi]

Hi Petsc Users

I've been having trouble consistently getting a vector generated from a DM
to output to VTK correctly. I've used ex1.c (which works properly)to try
and figure it out, but I'm still having some issues. I must be missing
something small that isn't correctly associating the section with the DM.

    DMPlexGetChart(dm, &p0, &p1);
    PetscSection section_full;
    PetscSectionCreate(PETSC_COMM_WORLD, &section_full);
    PetscSectionSetNumFields(section_full, 1);
    PetscSectionSetChart(section_full, p0, p1);
    PetscSectionSetFieldName(section_full, 0, "state");

    for (int i = c0; i < c1; i++)
    {
        PetscSectionSetDof(section_full, i, 1);
        PetscSectionSetFieldDof(section_full, i, 0, 1);
    }
    PetscSectionSetUp(section_full);
    DMSetNumFields(dm, 1);
    DMSetLocalSection(dm, section_full);
    DMCreateGlobalVector(dm, &state_full);

    int o0, o1;
    VecGetOwnershipRange(state_full, &o0, &o1);
    PetscScalar *state_full_array;
    VecGetArray(state_full, &state_full_array);

    for (int i = 0; i < (c1 - c0); i++)
    {
        int offset;
        PetscSectionGetOffset(section_full, i, &offset);
        state_full_array[offset] = 101325 + i;
    }

    VecRestoreArray(state_full, &state_full_array);


    PetscViewerCreate(PETSC_COMM_WORLD, &viewer);
    PetscViewerSetType(viewer, PETSCVIEWERVTK);
    PetscViewerFileSetMode(viewer, FILE_MODE_WRITE);
    PetscViewerFileSetName(viewer, "mesh.vtu");
    VecView(state_full, viewer);

If I run this mesh.vtu isn't generated at all. If I instead do a DMView
passing the DM it will just output the mesh correctly.

Any assistance would be greatly appreciated.

Sincerely
Nicholas


-- 
Nicholas Arnold-Medabalimi

Ph.D. Candidate
Computational Aeroscience Lab
University of Michigan
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