[petsc-users] Finding which cell an arbitrary point belongs to in DMPlex

[Matthew Knepley]

On Mon, Sep 14, 2020 at 6:15 PM Jeremy Theler <jeremy at seamplex.com> wrote:

> Hello all
>
> Say I have a fully-interpolated 3D DMPlex and a point with arbitrary
> coordinates x,y,z. What's the most efficient way to know which cell
> this point belongs to in parallel? Cells can be either tets or hexes.
>

I should make a tutorial on this, but have not had time so far.

The intention is that you use


https://www.mcs.anl.gov/petsc/petsc-current/docs/manualpages/DM/DMLocatePoints.html

This will just brute force search unless you also give

  -dm_plex_hash_location

which builds a grid hash to accelerate it. I should probably expose

  DMPlexLocatePoint_Internal()

which handles the single cell queries. If you just had one point, that
might make it simpler,
although you would still write your own loop. If your intention is to
interpolate a field at these
locations, I created


https://www.mcs.anl.gov/petsc/petsc-current/docs/manualpages/SNES/DMInterpolationCreate.html

which no one but me uses so far, but I think it is convenient.

  Thanks,

    Matt


> Regards
> --
> jeremy theler
> www.seamplex.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/>
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