To maintain compatibility with a major HPC center I upgraded(?) from
OpenMPI 1.1.4 to OpenMPI 1.2 on my local cluster.
In testing on my local cluster, 13 dual-Opteron Linux boxes with dual
gigabit ethernet, I discovered that my program runs slower using
OpenMPI 1.2 then OpenMPI 1.1.4 (780.3 versus 402.4 seconds with 3
processes--tested twice to be certain).
This particular version of my program was designed to minimize the
amount of communications and the only MPI calls that get used a lot
are MPI_SEND and MPI_RECV with MPI_PACKED data (so MPI_PACK and
MPI_UNPACK also get used a lot).
Was there a known problem with OpenMPI 1.2 (r14027) and ethernet
communication that got fixed later?
The same executable run at the major center seems fine, but they have