[petsc-users] Domain decomposition using DMPLEX

[Swarnava Ghosh]

Hi Barry,

 "Why do you need a cuboidal domain decomposition?"

I gave it some thought. I don't always need a cuboidal decomposition. But I
would need something that essentially minimized the surface area of the
faces of each decomposition. Is there a way to get this? Could you please
direct me to a reference a reference where I can read about the domain
decomposition strategies used in petsc dmplex.

Sincerely,
Swarnava

On Mon, Nov 25, 2019 at 9:02 PM Smith, Barry F. <bsmith at mcs.anl.gov> wrote:

>
> "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?"
>
>   No definitely not. Why do you need a cuboidal domain decomposition?
>
>   Barry
>
>
> > On Nov 25, 2019, at 10:45 PM, Swarnava Ghosh <swarnava89 at gmail.com>
> wrote:
> >
> > 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/
>
>
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