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Re: OpenMPI 5.0 to be 32-bit only ?

On 07/02/2023 10:27, Drew Parsons wrote:
On 2023-02-07 10:54, Alastair McKinstry wrote:

I've been pinged by the upstream maintainer of OpenMPI    Jefff
Squyres as to our opinions on maintaining 32-bit support.

See a  thread here: https://github.com/open-mpi/ompi/pull/11282

If 32-bit support is dropped in OMPI we can switch to MPICH as the
default on those archs instead, but the core problem remains: how much
can we support and test on 32-bit?

Switching to mpich would in any case be supported by a lot of our upstream developers.  In various different projects we hear them recommending mpich and occasionally expressing discontent with bugs in openmpi.

I've heard this, but at the same time heard that one of the benefits of OpenMPI is the larger test suite and infrastructure, which is puzzling.

My experience is that OpenMPI is faster on release of support for new systems such as PMIx, UCX; this shakes out bugs there first before MPICH;

also MPICH has at times been harder to build, looking like many configurations are not tested as well.

Can you point to the upstream bugs?

To make it simpler for ourselves, we could also consider just switching to mpich altogether as default.  Are there reasons to prefer 64-bit OMPI over MPICH?



Alastair McKinstry,
GPG: 82383CE9165B347C787081A2CBE6BB4E5D9AD3A5
ph: +353 87 6847928 e: alastair@sceal.ie, im: @sceal.ie:mckinstry

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