On 07/29/2013 10:18 PM, Underwood, Keith D wrote:

And, um, technically, if loads can be hoisted across the MPI_Recv, then the MPI_Recv semantics are incorrect and you have to have a memory barrier in MPI_Recv.

Why is reordering not permitted for two unrelated memory loads? AFAIK, ARM allows that. -- Pavan Balaji http://www.mcs.anl.gov/~balaji