[petsc-users] DMAdaptLabel with triangle mesh

[Matthew Knepley]

On Mon, Aug 31, 2020 at 9:45 AM Thibault Bridel-Bertomeu <
thibault.bridelbertomeu at gmail.com> wrote:

> Hi Matt,
>
> OK so I tried to replicate the problem starting from one of the tests in
> PETSc repo.
> I found
> https://gitlab.com/petsc/petsc/-/blob/master/src/dm/impls/plex/tests/ex20.c that
> actually uses DMAdaptLabel.
> Just add
>
> {
>  DM <https://www.mcs.anl.gov/petsc/petsc-current/docs/manualpages/DM/DM.html#DM> gdm;
>  DMPlexConstructGhostCells <https://www.mcs.anl.gov/petsc/petsc-current/docs/manualpages/DMPLEX/DMPlexConstructGhostCells.html#DMPlexConstructGhostCells>(dm, NULL, NULL, &gdm); DMDestroy <https://www.mcs.anl.gov/petsc/petsc-current/docs/manualpages/DM/DMDestroy.html#DMDestroy>(&dm);
>
>  dm   = gdm;
>
> }
>
> after line 24 where the box mesh is generated. Then compile and run with ex20 -dim 2.It should tell you that Triangle 18 has an invalid vertex index.
> That's the minimal example that I found that replicates the problem.
>
> Ah, okay. p4est knows to discard the ghost cells. I can add that to
Triangle.

> Regarding the serial character of the technique, I tried with a distributed mesh and it works.
>
> Hmm, it can't work. Maybe it appears to work. Triangle knows nothing about
parallelism. So this must be feeding the local mesh to triangle and
replacing it by
a refined mesh, but the parallel boundaries will not be correct, and might
not even match up.

  Thanks,

     Matt

> So do you mean that intrinsically it gathers all the cells on the master proc before proceeding to the coarsening & refinement and only then broadcast the info back to the other processors ?
>
> Thanks,
>
> Thibault
>
> Le lun. 31 août 2020 à 12:55, Matthew Knepley <knepley at gmail.com> a
> écrit :
>
>> On Mon, Aug 31, 2020 at 5:34 AM Thibault Bridel-Bertomeu <
>> thibault.bridelbertomeu at gmail.com> wrote:
>>
>>> Dear all,
>>>
>>> I have recently been playing around with the AMR capabilities embedded
>>> in PETSc for quad meshes using p4est. Based on the TS tutorial ex11, I was
>>> able to incorporate the AMR into a pre-existing code with different metrics
>>> for the adaptation process.
>>> Now I would like to do something similar using tri meshes. I read that
>>> compiling PETSc with Triangle (in 2D and Tetgen for 3D) gives access to
>>> refinement and coarsening capabilities on triangular meshes.When I try to
>>> execute the code with a triangular mesh (that i manipulate as a DMPLEX), it
>>> yields "Triangle 1700 has an invalid vertex index" when trying to adapt the
>>> mesh (the initial mesh indeed has 1700 cells). From what i could tell, it
>>> comes from the reconstruct method called by the triangulate method of
>>> triangle.c, the latter being called by either *DMPlexGenerate_Triangle *
>>> or *DMPlexRefine_Triangle *in PETSc, I cannot be sure.
>>>
>>> In substance, the code is the same as in ex11.c and the crash occurs in
>>> the first adaptation pass, i.e. an equivalent in ex11 is that it crashes
>>> after the SetInitialCondition in the first if (useAMR) located line 1835
>>> when it calls adaptToleranceFVM (which I copied basically so the code is
>>> the same).
>>>
>>> Is the automatic mesh refinement feature on tri meshes supposed to work
>>> or am I trying something that has not been completed yet ?
>>>
>>
>> It is supposed to work, and does for some tests in the library. I stopped
>> using it because it is inherently serial and it is isotropic. However, it
>> should be fixed.
>> Is there something I can run to help me track down the problem?
>>
>>   Thanks,
>>
>>      Matt
>>
>>
>>> Thank you very much for your help, as always.
>>>
>>> Thibault Bridel-Bertomeu
>>> —
>>> Eng, MSc, PhD
>>> Research Engineer
>>> CEA/CESTA
>>> 33114 LE BARP
>>> Tel.: (+33)557046924
>>> Mob.: (+33)611025322
>>> Mail: thibault.bridelbertomeu 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/>
>>
>

-- 
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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