Adrian, i just fixed this in the master (https://github.com/open-mpi/ompi/commit/d14daf40d041f7a0a8e9d85b3bfd5eb570495fd2)
the root cause is a corner case was not handled correctly : MPI_Type_hvector(20000, 1, 0, MPI_INT, &type); type has extent = 4 *but* size = 80000 ob1 used to test only the extent to determine whether the message should be sent inlined or not extent <= 256 means try to send the message inline that meant a fragment of size 80000 (which is greater than 65536 e.g. max default size for IB) was allocated, and that failed. now both extent and size are tested, so the message is not sent inline, and it just works. Cheers, Gilles
