[petsc-users] Domain decomposition using DMPLEX

[Swarnava Ghosh]

Hi Matt,


https://arxiv.org/pdf/1907.02604.pdf

On Mon, Nov 25, 2019 at 7:54 PM Matthew Knepley <knepley at gmail.com> wrote:

> On Mon, Nov 25, 2019 at 6:25 PM Swarnava Ghosh <swarnava89 at gmail.com>
> wrote:
>
>> Dear PETSc users and developers,
>>
>> I am working with dmplex to distribute a 3D unstructured mesh made of
>> tetrahedrons in a cuboidal domain. I had a few queries:
>> 1) Is there any way of ensuring load balancing based on the number of
>> vertices per MPI process.
>>
>
> You can now call DMPlexRebalanceSharedPoints() to try and get better
> balance of vertices.
>
>
  Thank you for pointing out this function!


> 2) As the global domain is cuboidal, is the resulting domain decomposition
>> also cuboidal on every MPI process? If not, is there a way to ensure this?
>> For example in DMDA, the default domain decomposition for a cuboidal domain
>> is cuboidal.
>>
>
> It sounds like you do not want something that is actually unstructured.
> Rather, it seems like you want to
> take a DMDA type thing and split it into tets. You can get a cuboidal
> decomposition of a hex mesh easily.
> Call DMPlexCreateBoxMesh() with one cell for every process, distribute,
> and then uniformly refine. This
> will not quite work for tets since the mesh partitioner will tend to
> violate that constraint. You could:
>
> No, I have an unstructured mesh that increases in resolution away from the
center of the cuboid. See Figure: 5 in the ArXiv paper
https://arxiv.org/pdf/1907.02604.pdf  for a slice through the midplane of
the cuboid.  Given this type of mesh, will dmplex do a cuboidal domain
decomposition?

Sincerely,
SG


>   a) Prescribe the distribution yourself using the Shell partitioner type
>
> or
>
>   b) Write a refiner that turns hexes into tets
>
> We already have a refiner that turns tets into hexes, but we never wrote
> the other direction because it was not clear
> that it was useful.
>
>   Thanks,
>
>      Matt
>
>
>> Sincerely,
>> SG
>>
>
>
> --
> 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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