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Re: Fwd: Dropping Open MPI 32 bit support




On 27/03/2021 17:38, Wouter Verhelst wrote:
Hi Alastair,

On Thu, Mar 11, 2021 at 04:44:05PM +0000, Alastair McKinstry wrote:
    See the mail below from the OpenMPI maintainers.

    This would mean our options are:
    (1) Drop MPI for 32-bit archs.

    (2) Use MPICH for 32-bit archs,  OpenMPI for 64 bit

    (3) Use MPICH for everything.

    My experience is that OpenMPI is more mature for new fabrics, etc (UCX)  -
    I wasn't able to get UCX to work with MPICH in time for Bullseye, so I'm
    not favouring (3).  I'd rather not drop MPI for 32-bit systems in general
    - while I don't expect proper HPC to run on these, its one of the simplest
    ways of adding parallelism, and there will be systems with large numbers
    of 32-bit cores.
We're just talking about defaults here, right?

I think if we switch the default to MPICH but make it reasonably easy
for someone to switch to OpenMPI, then that's good enough.

Alternatively, option 2 (so long as we're only talking about defaults)
is fine too.

Dropping MPI for any architecture that we otherwise fully support seems
inappropriate.

Yes, we're talking about defaults. I agree dropping MPI is inappropriate for supported archs.


--
Alastair McKinstry, <alastair@sceal.ie>, <mckinstry@debian.org>, https://diaspora.sceal.ie/u/amckinstry
Misentropy: doubting that the Universe is becoming more disordered.


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