[petsc-users] PCs and MATIS

Pierre Jolivet pierre at joliv.et
Tue Dec 14 14:58:44 CST 2021

Hello Eric,
Why do you want to use a MATIS?
This solution that Barry suggested to me some time ago is perfectly functioning: https://lists.mcs.anl.gov/pipermail/petsc-dev/2020-January/025491.html <https://lists.mcs.anl.gov/pipermail/petsc-dev/2020-January/025491.html>
That’s what I do for optimized (restricted) additive Schwarz.
You can see also how to use this “trick” from Barry here: https://gitlab.com/petsc/petsc/-/commit/ba409789b0c94205af794ad85bdac232504f2b3f#2c7d367ac831f3b0c5fb767c0eb16c1ea7ae7fe0_821_821 <https://gitlab.com/petsc/petsc/-/commit/ba409789b0c94205af794ad85bdac232504f2b3f#2c7d367ac831f3b0c5fb767c0eb16c1ea7ae7fe0_821_821> (it’s in a WIP branch, and for the fine-level PCASM smoother used in PCHPDDM, but at least it’s actual code, in case you do not follow what Barry and I are saying in the old thread).


> On 14 Dec 2021, at 9:37 PM, Eric Chamberland <Eric.Chamberland at giref.ulaval.ca> wrote:
> Hi,
> We want to use an Additive Schwarz preconditioner (like PCASM) combined with overlapping meshes *and* specific boundary conditions to local (MATIS) matrices.
> At first sight, MATIS is only supported for BDDC and FETI-DP and is not working with PCASM.
> Do we have to write a new PC from scratch to combine the use of mesh overlap, MATIS and customized local matrices?
> ...or is there any working example we should look at to start from? :)
> Thanks a lot!
> Eric
> -- 
> Eric Chamberland, ing., M. Ing
> Professionnel de recherche
> GIREF/Université Laval
> (418) 656-2131 poste 41 22 42

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