[petsc-users] Question on KSPSetReusePreconditioner

Matthew Knepley knepley at gmail.com
Thu Apr 18 11:32:18 CDT 2019

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.



> 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/>
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