[petsc-users] Question on KSPSetReusePreconditioner

[Matthew Knepley]

On Thu, Apr 18, 2019 at 2:46 PM Yuyun Yang <yyang85 at stanford.edu> wrote:

> Let’s say I’m using HYPRE’s boomeramg preconditioner. Could we say
> anything about convergence/pc construction time if the matrix changes
> significantly from one solve to the next vs. slightly changes?
>

Hypre does not store anything (I believe), so it does not matter at all.

  Thanks,

     Matt


>
>
> Thanks,
>
> Yuyun
>
>
>
> *From:* Matthew Knepley <knepley at gmail.com>
> *Sent:* Thursday, April 18, 2019 9:32 AM
> *To:* Yuyun Yang <yyang85 at stanford.edu>
> *Cc:* petsc-users at mcs.anl.gov
> *Subject:* Re: [petsc-users] Question on KSPSetReusePreconditioner
>
>
>
> On Thu, Apr 18, 2019 at 11:44 AM Yuyun Yang via petsc-users <
> petsc-users at mcs.anl.gov> wrote:
>
> Hello team,
>
>
>
> I have a question on when I should be setting KSPSetReusePreconditioner to
> PETSC_TRUE or PETSC_FALSE. It made a pretty big difference in the solutions
> I get when I ran my code testing both settings, so is recalculating the
> preconditioner better since it will make the convergence faster and the
> solution more accurate? On the other hand, if the operator is updated every
> time step (but same nonzero pattern), will reconstructing the pc become
> time-consuming?
>
>
>
> We cannot say anything since it (at least) depends on a) how much your
> matrix changes from one solve to the next, and b)  what preconditioner you
> are reusing.
>
>
>
>   Thanks,
>
>
>
>     Matt
>
>
>
>
>
> Thank you!
>
> Yuyun
>
>
>
>
> --
>
> 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/>
>


-- 
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-users/attachments/20190418/1ae5f5b3/attachment.html>