[petsc-dev] default MPI in debian/ubuntu: openmpi vs mpich

[Drew Parsons]

Thanks Jed, I'll pass that on to the debian thread.  Normalising the MPI 
ABI sounds like a useful goal.

Drew

On 2018-12-08 13:15, Jed Brown wrote:
> The Open MPI API is better for developers due to better type safety 
> (all
> handles in MPICH are typedef'd to int). Most major commercial vendors
> are organized around variants of MPICH (where there is collective ABI
> standardization). Open MPI is more modular so most vendor stuff goes
> into their plugins (for those vendors working with OMPI).
> 
> I think a good solution for Linux distros (and many others) would be to
> make a library that is ABI compatible with OMPI, but dispatches through
> to MPICH.  There exists a (messy) open source demonstration.
> 
>   https://github.com/cea-hpc/wi4mpi/
> 
> 
> Drew Parsons via petsc-dev <petsc-dev at mcs.anl.gov> writes:
> 
>> Hi PETSc developers,
>> 
>> Debian (and therefore Ubuntu) currently uses openmpi as the default 
>> MPI
>> implementation. Some developers have encouraged us to switch to mpich,
>> partly on experience of less bugs with mpich, partly around openmpi
>> development policies.
>> 
>> We're amenable to the idea but don't want to rush. The next Debian
>> stable release is coming soon (around February) and we'd anticipate a
>> lot of transition bugs (for instance scalapack currently builds for 
>> both
>> openmpi and mpich, build tests pass openmpi but fail mpich).
>> 
>> Equally importantly, pmix is in an uncertain state for mpich (and 
>> we've
>> just finished closing outstanding pmix bugs with openmpi3. openmpi3 is
>> stable now).  Alastair McKinstry, the lead Debian MPI developer, 
>> thinks
>> pmix support should be in order before going ahead with a transition 
>> to
>> mpich, especially for container support (singularity).
>> 
>> There's a discussion thread on Debian-Science at [1] (cc: to
>> debian-release [2]).  I'm writing to invite you to add your own
>> experience to these discussions.
>> 
>> Best regards,
>> Drew Parsons
>> Debian Developer / Debian Science member
>> 
>> [1]  https://lists.debian.org/debian-science/2018/12/msg00017.html
>> [2]  https://lists.debian.org/debian-release/2018/12/msg00162.html