[petsc-dev] [petsc-users] Multigrid with defect correction

[Matthew Knepley]

On Sat, Feb 25, 2017 at 7:35 PM, Jed Brown <jedbrown at mcs.anl.gov> wrote:

> Barry Smith <bsmith at mcs.anl.gov> writes:
> >      Do you think this is a reasonable approach or am I missing
> >      something fundamental? I am assuming generally for the "higher
> >      order" DM the Mat it returns is a MATSHELL or a new matrix class
> >      built on "tensor contractions" and that kind of nonsense. I don't
> >      want to do all the coding and then have it turn out that it is
> >      totally useless for CEED etc.
>
> Well, this is exactly what we do in pTatin.
>
> I would ask, why just two discretizations?  I've always thought a better
> interface would be for Mats (and any other operators/functions) to have
> optional approximations or supplementary data attached.  We can do this
> with PetscObjectCompose, but that's hard to work with in a structured
> way.  Anyway, I think I would rather just have the Amat with ability to
> attach one or more Pmats.
>

I think that would be more convincing with a concrete use case example.
Right now
it sounds more like a additional complication for not much extra
functionality, but
maybe that is because I cannot think of when I would use it.

  Matt

-- 
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
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