[Trilinos-Users] IfPack_AdditiveSchwarz with custom blocks

[Chris Siefert]

Nate,

Ifpack_AdditiveSchwarz won't do that for you.

But you can achieve the same effect with OverlappingRowMatrix, the 
partitioners and BlockRelaxation.

Tom Benson has some some work on Vanka-smoothing in Ifpack2 that might 
be a template for how to do that in regular old Ifpack.

See: ifpack/test/vanka/TomVankaTest.cpp

Also, feel free to email me off-list if you have additional questions.

-Chris


On 03/31/2015 02:39 PM, Roberts, Nathan V. wrote:
> Dear Trilinos-Users,
>
> I'm using an IfPack_AdditiveSchwarz smoother as a component in a preconditioner.  At present, the way this works is that the Schwarz blocks are "greedy" in that they use all the locally-available coefficients in the matrix; there is just one Schwarz block on each MPI rank.  For a variety of reasons, including the fact that I'd like to do some strong scaling experiments, I would like to be able to specify smaller blocks, so that there may be several on each MPI rank.
>
> To be specific, in one use case, what I'd like is to have one Schwarz block per cell in my finite element discretization.  Since I know what rows correspond to that cell, in principle it's simple for me to provide the rows that I want for the Schwarz block.
>
> Is this something that I can reasonably do with IfPack_AdditiveSchwarz?
>
> Thanks for any assistance you can provide.
>
> Regards,
> Nate
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