[petsc-users] Agglomeration for Multigrid on Unstructured Meshes

[Dave May]

On Tue 2. Jun 2020 at 03:30, Matthew Knepley <knepley at gmail.com> wrote:

> On Mon, Jun 1, 2020 at 7:03 PM Danyang Su <danyang.su at gmail.com> wrote:
>
>> Thanks Jed for the quick response. Yes I am asking about the
>> repartitioning of coarse grids in geometric multigrid for unstructured
>> mesh. I am happy with AMG. Thanks for letting me know.
>>
>
> All the pieces are there, we just have not had users asking for this, and
> it will take some work to put together.
>

Matt - I created a branch for you and Lawrence last year which added full
support for PLEX within Telescope. This implementation was not a fully
automated algmoeration strategy - it utilized the partition associated with
the DM returned from DMGetCoarseDM. Hence the job of building the
distributed coarse hierarchy was let to the user.

I’m pretty sure that code got merged into master as the branch also
contained several bug mixes for Telescope. Or am I mistaken?

Cheers
Dave




>   Thanks,
>
>     Matt
>
>
>> Danyang
>>
>> On 2020-06-01, 1:47 PM, "Jed Brown" <jed at jedbrown.org> wrote:
>>
>>     I assume you're talking about repartitioning of coarse grids in
>>     geometric multigrid -- that hasn't been implemented.
>>
>>
>> https://www.mcs.anl.gov/petsc/petsc-current/docs/manualpages/PC/PCTELESCOPE.html
>>
>>     But you can use an algebraic multigrid that does similar communicator
>>     reduction, and can be applied to the original global problem or just
>> on
>>     the "coarse" problem of an initial geometric hierarchy.
>>
>>     Danyang Su <danyang.su at gmail.com> writes:
>>
>>     > Dear All,
>>     >
>>     >
>>     >
>>     > I recalled there was a presentation ‘Extreme-scale multigrid
>> components with PETSc’  taling about agglomeration in parallel multigrid,
>> with future plan to extend to support unstructured meshes. Is this under
>> development or to be added?
>>     >
>>     >
>>     >
>>     > Thanks and regards,
>>     >
>>     >
>>     >
>>     > Danyang
>>
>>
>>
>
> --
> 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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