In message http://www.open-mpi.org/community/lists/users/
2007/03/2889.php I found this comment:
"The only way to get any
benefit from the MPI_Bsend is to have a progress thread which take
care of the pending communications in the background. Such thread is
not enabled by default in Open MPI."
I understand this won't be portable, but how do you enable a sender
progress thread in Open MPI?