[petsc-dev] Unions of IS and MatNest

[Matthew Knepley]

On Thu, Mar 12, 2020 at 5:59 PM Jed Brown <jed at jedbrown.org> wrote:

> Pierre Jolivet <pierre.jolivet at enseeiht.fr> writes:
>
> > Hello,
> > Has there been any follow-up on this
> https://lists.mcs.anl.gov/pipermail/petsc-users/2015-January/024020.html <
> https://lists.mcs.anl.gov/pipermail/petsc-users/2015-January/024020.html>?
> > Given a 3x3 MatNest A = [A_00,0,0 ; 0,A_11,0 ; 0,0,A_22], I’d like to
> setup a two-way fieldsplit coupling [A_00,0 ; 0,A_11] and [A_22] but I
> can’t figure out the proper options.
>
> Are you looking for a Schur split or additive/multiplicative?
>

-pc_fieldsplit_field_0 0,1 -pc_fieldsplit_field_1 2 -pc_fieldsplit_type
schur

I believe.

   Matt


> > Jed, in this answer
> https://lists.mcs.anl.gov/pipermail/petsc-users/2015-January/023993.html <
> https://lists.mcs.anl.gov/pipermail/petsc-users/2015-January/023993.html>,
> you recommend not to use MatNest. What would you recommend instead?
>
> See src/snes/examples/tutorials/ex28.c for my preferred approach.
>


-- 
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/>
-------------- next part --------------
An HTML attachment was scrubbed...
URL: <http://lists.mcs.anl.gov/pipermail/petsc-dev/attachments/20200312/de4efd82/attachment.html>