[petsc-users] DMPlex Traversal

[Nicholas Arnold-Medabalimi]

Hi

Currently, I am just trying to replace the mesh management in an existing
code using DMPlex. So I am distributing the DMPlex and then passing the
mesh information and translating the PetscSF information off into the
existing MPI solver. So I think using the cone and support should be fine.
It does happen repeatedly during the run time but with a different
distribution each time so I think GetAdjacency will cover my use case.

Thank you for the clarification

Sincerely
Nicholas


On Fri, Dec 2, 2022 at 6:49 AM Matthew Knepley <knepley at gmail.com> wrote:

> On Fri, Dec 2, 2022 at 5:16 AM Nicholas Arnold-Medabalimi <
> narnoldm at umich.edu> wrote:
>
>> Hi Petsc Users
>>
>> I have become familiar with usage of DMPlexGet(Restore)TransitiveClosure
>> as well as general traversal of the graph using DMPlexGetCone and
>> GetSupport.
>>
>> I was wondering if there is a more trivial way to get access to adjacent
>> points of the same Stratum.
>>
>> For example, I have an 2D mesh. I have identified the point value of a
>> cell of interest and I would like to get the point value of the surrounding
>> cells. So far the way I get that is I descend a level using GetCone and
>> then for each constituent point (face in this case) call GetSupport (which
>> yields the adjacent cell and the original cell) and discard the original
>> cell.
>>
>> Is there a direct function call that achieves this? I've looked a bit
>> into the Adjacency commands but they seem to be more for variable influence
>> (FV or FE) and using them seems to throw an error.
>>
>
> It is important to lay out why you want to do this, because it influences
> the choice of implementation.
>
> If you just want to discover topology, then doing it using Cone and
> Support is fine. This is what GetAdjacency is doing underneath.
>
> However, if you want to repeatedly do this, which most people do for
> dof traversal, then you should make an index. There are two cases
> of this in Plexx right now, but we could easily have more. GetAdjacency is
> used to construct the sparsity pattern for the Jacobian, which
> serves as an index. Also GetClosure is used to construct the closure index
> which we use when setting values since this is a common
> operation in FE.
>
> What do you want to do with this?
>
>   Thanks,
>
>      Matt
>
>
>> Sincerely
>> Nicholas
>>
>> --
>> Nicholas Arnold-Medabalimi
>>
>> Ph.D. Candidate
>> Computational Aeroscience Lab
>> University of Michigan
>>
>
>
> --
> 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/>
>


-- 
Nicholas Arnold-Medabalimi

Ph.D. Candidate
Computational Aeroscience Lab
University of Michigan
-------------- next part --------------
An HTML attachment was scrubbed...
URL: <http://lists.mcs.anl.gov/pipermail/petsc-users/attachments/20221202/0a7cffcb/attachment.html>