[petsc-users] shell preconditioner for Schur complement

[Matthew Knepley]

On Thu, Feb 11, 2021 at 10:53 AM Matteo Semplice <
matteo.semplice at uninsubria.it> wrote:

>
> Il 11/02/21 06:41, Barry Smith ha scritto:
> >    Best to just look at the code to see exactly what it is doing:
> src/ksp/pc/impls/fieldsplit/fieldsplit.c  function
> PCApply_FieldSplit_Schur()
> >
> >    There is no particular "scaling" applied to the vectors. It might be
> easiest to track through the computational process with the debugger (you
> can call VecView(v,0) in the debugger anytime to see the current vector) to
> see why the "scaling" seems to change.
> >
> >    Barry
>
> Found!
>
> It came from the initial rescaling b->b/norm(b) in the fgmres for the
> entire matrix.
>

I see. I did not document it because it is internal to the solver, but the
subsolvers can see it :)
Glad you got it worked out.

 Thanks,

    Matt


> We are now set and we can concentrate on our routine.
>
> Thanks a lot Matthew and Barry!
>
> Matteo & Elena
>
> --
> Prof. Matteo Semplice
> Università degli Studi dell’Insubria
> Dipartimento di Scienza e Alta Tecnologia – DiSAT
> Professore Associato
> Via Valleggio, 11 – 22100 Como (CO) – Italia
> tel.: +39 031 2386316
>
>

-- 
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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