[petsc-dev] Mark, what's the rational for keeping the Chebyshev tuning inside GAMG?

[Mark Adams]

On Fri, Feb 20, 2015 at 11:46 PM, Barry Smith <bsmith at mcs.anl.gov> wrote:

>
>   Mark,
>
>    What's the rational for keeping the Chebyshev tuning inside GAMG that
> duplicates that is already support by KSPChebyshev ? I'd like to remove
> this chunk of code from GAMG since it is duplicative and instead make sure
> that the Chebyshev tuning  inside the KSPChebyshev provides everything that
> is needed.
>
>    Also in particular what about the /* zeroing out BC rows -- needed for
> crazy matrices */ should this be ported to KSPChebyshev ?
>

This is a fix for a matrix that has a norm << X, but X is put on the
diagonal for BCs.  You then get X as the eigen estimate.  We should
probably remove this ...


>
>     /* create cheby smoothers */
>     for (lidx = 1, level = pc_gamg->Nlevels-2; lidx <= fine_level; lidx++,
> level--) {
>       KSP       smoother;
>       PetscBool flag,flag2;
>       PC        subpc;
>
>       ierr = PCMGGetSmoother(pc, lidx, &smoother);CHKERRQ(ierr);
>       ierr = KSPGetPC(smoother, &subpc);CHKERRQ(ierr);
>
>       /* do my own cheby */
>
> Thanks
>
>    Barry
>
>
>
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