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

[Danyang Su]

Hi Matt,

No, interations from both linear and nonlinear solvers are similar. The system administrator doubt that the latency in mpich makes the difference. We will test a petsc version with OpenMPI on that cluster to check if it makes difference.

Thanks, 

Danyang

On October 29, 2020 6:05:53 p.m. PDT, Matthew Knepley <knepley at gmail.com> wrote:
>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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