how big can I go

[Matthew Knepley]

On Wed, Jun 17, 2009 at 1:51 PM, Yann Tambouret <yannpaul at bu.edu> wrote:

> Hi,
>
> I'm new to PETSc and I'm try to solve a linear system that has nine terms
> per equation, along the diagonal. I'd like to use a  bluegene machine to
> solve for a large number of unknowns (10's of millions). Does anyone have
> advice for such problem? Which algorithms scale best on such a machine?


We have run problems on BG/P with hundreds of millions of unknowns. However,
the algorithm/solver is always highly
system dependent. The right idea is to run lots of small examples,
preferably on your laptop to understand the system you
want to solve. Then scale up in stages. At each stage, something new usually
becomes important, and you handle that
aspect. The right thing to look at is the output of -log_summary and the
iteration counts.

  Matt


>
> I can of course provide more detail, so please don't hesitate to ask.
>
> Thanks,
>
> Yann
>
-- 
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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