Dear Jeff, Dear Gilles, Dear All, now is all more clear. I use CALL MPI_ISEND and CALL MPI_IRECV. Each CPU send once and revive once, this implies that I have REQUEST(2) for WAITALL. However, sometimes dome CPU does not send or receive anything, so I have to set REQUEST = MPI_REQUEST_NULL in order to avoid errors.
Really, Really thanks you are wonderful, again thanks On 30 September 2015 at 22:56, Jeff Squyres (jsquyres) <jsquy...@cisco.com> wrote: > MPI_REQUEST_NULL Diego
