Does OpenMPI always use SEND/RECV protocol between heterogeneous
processors with different endianness?
I tried btl_openib_flags to be 2 , 4 and 6 respectively to allowe RDMA,
but the bandwidth between the two heterogeneous nodes is slow, same as
the bandwidth when btl_openib_flags to be 1. Seems to me SEND/RECV is
always used no matter btl_openib_flags is. Can I force OpenMPI to use
RDMA between x86 and PPC? I only transfer MPI_BYTE, so we do not need
the support for endianness.