[petsc-users] Galerkin multigrid coarsening

[Jed Brown]

Torquil Macdonald Sørensen <torquil at gmail.com> writes:
> This question was similar to my recent unanswered one:
>
> http://lists.mcs.anl.gov/pipermail/petsc-users/2014-January/020382.html

That's why I Cc'd you.

> I just tried jed/pcmg-galerkin-rap, and it seems to work fineI verified
> that the coarse system matrix is R*A*P, for a two-level PCMG. I'm first
> calling PCMGSetInterpolation() with a matrix P, and then
> PCMGSetInterpolation() with a matrix R. Previously R was ignored, and I got
>
> A_c = P^T*A*P
>
> With jed/pcmg-galerkin-rap, I'm getting:
>
> A_c = R*A*P
>
> So now I can experiment with using R or P^T, which is very nice!

Thanks for testing.

> I did not have an opportunity to test what happens if I don't set any
> restriction, but I'm hoping it will then use P^T, as before.

Yes, it will.
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