[petsc-users] PetscSF "One-Sided" vs. "Two-Sided"

[Matthew Knepley]

On Wed, May 31, 2023 at 6:37 PM Ferrand, Jesus A. <FERRANJ2 at my.erau.edu>
wrote:

> Dear PETSc team:
>
> For one of my applications, I need to know which owned DAG  points in a
> (DMPlex) are other ranks' ghosts.
> Say, rank-0 has some point "x" (which it owns) and it shows up in, say,
> rank-1 as a ghost numbered "y".
> Then, if I inspect the "Point" PestcSF,  in rank-1 there should be a leaf
> for "y" that records rank-0 and the value of "x", right?
> However, back in rank-0, the same PetscSF has no record that "x" is "y" in
> rank-1 (and potentially "z","a","b",... in additional ranks).
>
> Is this what, in PetscSF terminology, is referred to as "One-Sided"?
>
> If so, I think what I am really asking is how can I obtain a "Two-Sided"
> version of the PointSF?
>

You need

  https://petsc.org/main/manualpages/PetscSF/PetscSFComputeDegreeBegin/

If the point is not in the leaf list (owned) and has rootdegree > 1
(shared), it is your point.

  Thanks,

     Matt


> Sincerely:
>
> *J.A. Ferrand*
>
> Embry-Riddle Aeronautical University - Daytona Beach - FL
> Ph.D. Candidate, Aerospace Engineering
>
> M.Sc. Aerospace Engineering
>
> B.Sc. Aerospace Engineering
>
> B.Sc. Computational Mathematics
>
>
> *Phone:* (386)-843-1829
>
> *Email(s):* ferranj2 at my.erau.edu
>
>     jesus.ferrand at gmail.com
>


-- 
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/>
-------------- next part --------------
An HTML attachment was scrubbed...
URL: <http://lists.mcs.anl.gov/pipermail/petsc-users/attachments/20230531/6ecdd3f1/attachment.html>