[petsc-users] set block size on AMG systems

[Matthew Knepley]

On Sun, Mar 24, 2013 at 6:35 AM, Nico Schlömer <nico.schloemer at gmail.com>wrote:

> >
> http://www.mcs.anl.gov/petsc/petsc-dev/docs/manualpages/Mat/MatSetBlockSize.html
>
> Thanks!
>
> > For complex-valued problems, you're likely better off using complex
> numbers.
>
> Does PETSc support complex arithmetic natively? That'd be another
> reason for getting complex-value support into FEniCS.


Yes.

  Matt


>
> --Nico
>
>
>
> On Sat, Mar 23, 2013 at 8:29 PM, Jed Brown <jedbrown at mcs.anl.gov> wrote:
> >
> http://www.mcs.anl.gov/petsc/petsc-dev/docs/manualpages/Mat/MatSetBlockSize.html
> >
> > PCML, PCHYPRE, and PCGAMG pay attention to this parameter if no richer
> > information (like near-null spaces) is provided.
> >
> > For complex-valued problems, you're likely better off using complex
> numbers.
> >
> >
> > On Sat, Mar 23, 2013 at 2:25 PM, Nico Schlömer <nico.schloemer at gmail.com
> >
> > wrote:
> >>
> >> Hi,
> >>
> >> I've got this linear system consisting of 2x2 blocks (acutally coming
> >> from a real-imaginary formulation of a complex-valued problem) and I'd
> >> like to precondition the linear solves with AMG. Things are already
> >> working well when taking the defaults, but I guess one could achieve
> >> way better when telling AMG about the 2x2 structure. Trilinos' ML does
> >> this by a parameter "PDE equations". -- Is there something comparable
> >> in the PETSc world?
> >>
> >> --Nico
> >
> >
>



-- 
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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