[petsc-users] Consistent domain decomposition between DMDA and DMPLEX

[Matthew Knepley]

On Thu, Mar 21, 2019 at 8:20 PM Swarnava Ghosh via petsc-users <
petsc-users at mcs.anl.gov> wrote:

> Dear PETSc users and developers,
>
> I am new to DMPLEX and had a query regarding setting up a consistent
> domain decomposition of two meshes in PETSc.
> I have a structured finite difference grid, managed through DMDA. I have
> another unstructured finite element mesh managed through DMPLEX. Now all
> the nodes in the unstructured finite element mesh also belong to the set of
> nodes in the structured finite difference mesh (but not necessarily
> vice-versa), and the number of nodes in DMPLEX mesh is less than the number
> of nodes in DMDA mesh. How can I guarantee a consistent domain
> decomposition of the two meshes? By consistent, I mean that if a process
> has a set of nodes P from DMDA, and the same process has the set of nodes Q
> from DMPLEX, then Q is a subset of P.
>

Okay, this is not hard. DMPlexDistribute() basically distributes according
to a cell partition. You can use PetscPartitionerShell() to stick in
whatever cell partition you want. You can see me doing this here:


https://bitbucket.org/petsc/petsc/src/e2aefa968a094f48dc384fffc7d599a60aeeb591/src/dm/impls/plex/examples/tests/ex1.c#lines-261

Will that work for you?

  Thanks,

    Matt


> I look forward to your response.
>
> Sincerely,
> Swarnava
>
>

-- 
What most experimenters take for granted before they begin their
experiments is infinitely more interesting than any results to which their
experiments lead.
-- Norbert Wiener

https://www.cse.buffalo.edu/~knepley/ <http://www.cse.buffalo.edu/~knepley/>
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