[petsc-users] DMPlexCreateFromDAG in parallel

[Asitav Mishra]

Matt,

Thank you very much for your prompt response. Between the two solutions
suggested by you, solution (1) would be tough since it would be difficult
to ensure non-repeating vertices between processors.
Would you be able to provide an example for the solution (2), that is using
CreateFromDAG() on multiple processes.
For example, how can we set up PetscSF for the simple case of two triangles
(cells: 0 and 1) sharing a face (with vertices: 1, 2) with cell 0 in proc 0
and cell 1 in proc 1?

        2
      / | \
    /   |   \
   /    |    \
 0  0 | 1  3
   \    |    /
     \  |   /
      \ | /
        1

Any help would be great. Thanks again.
Asitav

On Sat, Sep 28, 2019 at 1:20 AM Matthew Knepley <knepley at gmail.com> wrote:

> On Wed, Sep 25, 2019 at 5:56 PM Asitav Mishra via petsc-users <
> petsc-users at mcs.anl.gov> wrote:
>
>> Hi,
>>
>> I have a native distributed mesh graph across multiple processors, using
>> which I would want to create DMPlex mesh using DMPlexCreateFromDAG. I see
>> in Petsc plex/examples that DMPlexCreateFromDAG creates DM only from master
>> processor and then the DM is distributed across multiple (one-to-many)
>> processors. My question is: is it possible to create DAG locally in each
>> processor and then build the global DM? If yes, are there any such examples?
>>
>
> 1) If you do not mind us redistributing the mesh on input, then you can
> probably do what you want using
>
>
> https://www.mcs.anl.gov/petsc/petsc-current/docs/manualpages/DMPLEX/DMPlexCreateFromCellListParallel.html
>
> Note that the input to this function wants a unique set of vertices from
> each process, so each vertex must come from only one processes.
>
>  2) If that does not work, you can certainly call CreateFromDAG() on
> multiple processes. However, then you must manually create the PetscSF
>      which describes how the mesh is connected in parallel. If this is
> what you need to do, I can give you instructions but at that point we should
>      probably make an example that does it.
>
>   Thanks,
>
>     Matt
>
>
>> Best,
>> Asitav
>>
>
>
> --
> 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/>
>


-- 
Asitav Mishra, PhD
Research Engineer II, NIA
-------------- next part --------------
An HTML attachment was scrubbed...
URL: <http://lists.mcs.anl.gov/pipermail/petsc-users/attachments/20191001/f1164cf9/attachment.html>