[petsc-dev] [Minor issue] Lag during PetscInitialize on Fedora 36 (never seen before with other OS)

[Matthew Knepley]

On Wed, Jul 27, 2022 at 9:22 AM LEDAC Pierre <Pierre.LEDAC at cea.fr> wrote:

> Hello,
>
>
> Recently migrated from Fedora34 to Fedora36, using PETSc I have some lag
> during the PetscInitialize, which
>
> disappeared if I run again immediately the binary. But after few seconds,
> the lag happens again (see below).
>
>
> I suspected MPICH 4.0.2 on Fedora36, but a small reproducer indicated the
> issue is not in MPI_Init but really during PetscInitialize
>
How do you know it is not MPI_Init()? We always call it. Could you build
PETSc using --with-mpi=0 and do the test again?

My suspicion is that it is gethostbyname() that MPI_Init() calls. This is
always what mysterious startup slowness on my machine is.

  Thanks,

      Matt


> Just annoying during testing, not very important, but did someone already
> see this ?
>
>
> Thanks,
>
>
> portable: /volatile/ledacp/petsc/src/ksp/ksp/tests (main) > time ./ex39
>
> real    0m3,593s
> user    0m0,872s
> sys    0m0,433s
> portable: /volatile/ledacp/petsc/src/ksp/ksp/tests (main) > time ./ex39
>
> real    0m0,310s
> user    0m0,884s
> sys    0m0,023s
>
> # Wait ~20 seconds then again:
>
> portable: /volatile/ledacp/petsc/src/ksp/ksp/tests (main) > time ./ex39
>
> real    0m3,507s
> user    0m0,897s
> sys    0m0,025s
> portable: /volatile/ledacp/petsc/src/ksp/ksp/tests (main) > time ./ex39
>
> real    0m0,154s
> user    0m0,725s
> sys    0m0,015s
> portable: /volatile/ledacp/petsc/src/ksp/ksp/tests (main) > time ./ex39
>
> real    0m0,176s
> user    0m0,875s
> sys    0m0,021s
>
>
> Pierre LEDAC
> Commissariat à l’énergie atomique et aux énergies alternatives
> Centre de SACLAY
> DES/ISAS/DM2S/STMF/LGLS
> Bâtiment 451 – point courrier n°43
> F-91191 Gif-sur-Yvette
> +33 1 69 08 04 03
> +33 6 83 42 05 79
>


-- 
What most experimenters take for granted before they begin their
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experiments lead.
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https://www.cse.buffalo.edu/~knepley/ <http://www.cse.buffalo.edu/~knepley/>
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