prometheus related question,

[Matthew Knepley]

Block matrices can use block smoothers, which invert whole blocks exactly.
This can
be much more effective than point smoothers if you actually have block
structure in
the matrix.

  Matt

On Thu, May 21, 2009 at 10:45 PM, Ryan Yan <vyan2000 at gmail.com> wrote:

> Hi all,
> I did a numerical experiment of ksp solve on a large sparse matrix.
>
> For the first step, I load the matrix from petsc readable files. If I load
> the matrix as a MPIAIJ matrix and then apply the prometheus preconditioner
> with GMRES, it will not converge in 10000 iterations.
>
> However, if I load the matrix as a MPIBAIJ matrix and then apply the
> prometheus preconditioner  with GEMRES, it will converge with in 800
> iterations
>
> Can anyone please provide some hints on how to explain this numerical
> result.
>
> Thanks a lot,
>
> Yan
>



-- 
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
-------------- next part --------------
An HTML attachment was scrubbed...
URL: <http://lists.mcs.anl.gov/pipermail/petsc-users/attachments/20090521/f1aebfb1/attachment.htm>