It's used for compressing the startup time messages in PMIx. I.e., the traffic for when you "mpirun ...".
It's mostly beneficial when launching very large MPI jobs. If you're only launching across several nodes, the performance improvement isn't really noticeable. -- Jeff Squyres jsquy...@cisco.com ________________________________________ From: users <users-boun...@lists.open-mpi.org> on behalf of Matt Thompson via users <users@lists.open-mpi.org> Sent: Monday, January 31, 2022 10:53 AM To: Open MPI Users Cc: Matt Thompson Subject: [OMPI users] Building Open MPI without zlib: what might go wrong/different? Open MPI List, Recently in trying to build some libraries with NVHPC + Open MPI, I hit an error building HDF5 where it died at configure time saying that the zlib that Open MPI wanted to link to (my system one) was incompatible with the zlib I built in my libraries leading up to HDF5. So, in the end I "fixed" my issue by adding: --without-zlib to my configure line for Open MPI and rebuilt. And hey, it worked. HDF5 built. And Hello world still works as well. But I'm now wondering: what might I be missing now? Zlib isn't required by the MPI Standard (as far as I can tell), so I'm guessing it's not functionality but rather performance? Just curious, Matt -- Matt Thompson “The fact is, this is about us identifying what we do best and finding more ways of doing less of it better” -- Director of Better Anna Rampton
