[petsc-users] Scalability problem using PETSc with local installed OpenMPI

[Matthew Knepley]

On Tue, Oct 10, 2023 at 9:28 AM Gong Yujie <yc17470 at connect.um.edu.mo>
wrote:

> Dear PETSc developers,
>
> I installed OpenMPI3 first and then installed PETSc with that mpi.
> Currently, I'm facing a scalability issue, in detail, I tested that using
> OpenMPI to calculate an addition of two distributed arrays and I get a good
> scalability. The problem is when I calculate the addition of two vectors in
> PETSc, I don't have any scalability. For the same size of the problem,
> PETSc costs a lot much time than merely using OpenMPI.
>
> My PETSc version is 3.16.0 and the version of OpenMPI is 3.1.4. Hope you
> can give me some suggestions.
>

1. For any performance question, we really need to see the output of
-log_view for each run.

2. I am not sure I understand your question. Vector addition does not
involve communication. Thus it will scale perfectly in the absence of load
imbalance.

  Thanks,

      Matt


> Best Regards,
> Yujie
>
-- 
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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