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.