[petsc-users] how to check if cell is local owned in DMPlex

[Matthew Knepley]

On Fri, Mar 2, 2018 at 1:41 PM, Danyang Su <danyang.su at gmail.com> wrote:

>
> On 18-02-19 03:30 PM, Matthew Knepley wrote:
>
> On Mon, Feb 19, 2018 at 3:11 PM, Danyang Su <danyang.su at gmail.com> wrote:
>
>> Hi Matt,
>>
>> Would you please let me know how to check if a cell is local owned? When
>> overlap is 0 in DMPlexDistribute, all the cells are local owned. How about
>> overlap > 0? It sounds like impossible to check by node because a cell can
>> be local owned even if none of the nodes in this cell is local owned.
>>
>
> If a cell is in the PetscSF, then it is not locally owned. The local nodes
> in the SF are sorted, so I use
> PetscFindInt (http://www.mcs.anl.gov/petsc/petsc-current/docs/
> manualpages/Sys/PetscFindInt.html).
>
> Hi Matt,
>
> Would you please give me a little more about how to mark the ghost cells
> when overlap > 0? What do you mean a cell is in the PetscSF? I use
> PetscSFView to export the graph (original mesh file pile.vtk) and it
> exports all the cells, including the ghost cells (PETScSFView.txt).
>

Yes, I will send you some sample code when I get time. The first problem is
that you are looking at a different PetscSF. This looks like the
one returned by DMPlexDistribute(). This is mapping the serial mesh to the
parallel mesh. You want


http://www.mcs.anl.gov/petsc/petsc-current/docs/manualpages/DM/DMGetPointSF.html

Then you can look at


https://bitbucket.org/petsc/petsc/src/1788fc36644e622df8cb1a0de85676ccc5af0239/src/dm/impls/plex/plexsubmesh.c?at=master&fileviewer=file-view-default#plexsubmesh.c-683

I get the pointSF, get out the list of leaves, and find points in it using
PetscFindInt()

  Thanks,

    Matt


> Thanks,
>
> Danyang
>
>
>   Thanks,
>
>     Matt
>
>
>> Thanks,
>>
>> Danyang
>>
> --
> 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.caam.rice.edu/%7Emk51/>
>
>
>


-- 
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.caam.rice.edu/~mk51/>
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