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

[Drew Parsons]

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