[petsc-users] Quite different behaviours of PETSc solver on different clusters

[Matthew Knepley]

On Thu, Oct 29, 2020 at 3:04 PM Su,D.S. Danyang <dsu at eoas.ubc.ca> wrote:

> Dear PETSc users,
>
>
>
> This is a question bother me for some time. I have the same code running
> on different clusters and both clusters have good speedup. However, I
> noticed some thing quite strange. On one cluster, the solver is quite
> stable in computing time while on another cluster, the solver is unstable
> in computing time. As shown in the figure below, the local calculation
> almost has no communication and the computing time in this part is quite
> stable. However, PETSc solver on Cluster B jumps quite a lot and the
> performance is not as good as Cluster A, even though the local calculation
> is a little better on Cluster B. There are some difference on hardware and
> PETSc configuration and optimization. Cluster A uses OpenMPI + GCC compiler
> and Cluster B uses MPICH + GCC compiler. The number of processors used is
> 128 on Cluster A and 120 on Cluster B. I also tested different number of
> processors but the problem is the same. Does anyone have any idea which
> part might cause this problem?
>

First question: Does the solver take more iterates when the time bumps up?

  Thanks,

    Matt


>
>
>
>
> Thanks and regards,
>
>
>
> Danyang
>
>
>


-- 
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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