Cray MPI (based on mpich2) provides ways to change several internal defaults.
They are used to get a code that my user has running on an XT. I know there
are issues with the code, but if the options exist in Intel MPI, it would get us
going faster. I have looked through the Intel MPI 4.0 Beta manual, and didn't
find any equivalents, but I am asking the question in case I missed the option
or there are some undocumented options that could help:
1) MPICH_MAX_SHORT_MSG_SIZE - Determines when to use Eager vs. Rendevous protocol,
does this just sound like I_MPI_RDMA_EAGER_THRESHOLD?
2) MPICH_PTL_UNEX_EVENTS - Define the total number of unexpected events allowed
3) MPICH_UNEX_BUFFER_SIZE - Set the buffer size for the unexpected events
4) MPICH_ENV_DISPLAY - Display all settings used by the MPI
Options 2 and 3 are the most important, as I believe the code path that hangs
when run with 2000+ cores is sending too many unexpected events.