Don't forget matching. The model depends on a relation between send and receive. This is the fundamental reason for potential difference in overlap. If you talk implementation, which we technically shouldn't for this argument, eventually the fact that a matching receiver is required for a send does impact over multiple sends. the one-sided model a->b is independent of b. the two sided model a<->b because of its dependance implies validity -- you can hide the cost of validity but can't eliminate it. Vinod.

From: [email protected] To: [email protected] Date: Mon, 27 Apr 2009 06:48:57 -0600 Subject: Re: [Mpi-forum] MPI One-Sided Communication

...

On the Earth Simulator, there are/were several application codes which are using one-sided communication (instead of 2-sided). They used one-sided communication especially to overlap communication and computation. When I remember correctly, at least one of this applications won a Gordon Bell Award of SC.

The ambiguity of the progress rule notwithstanding, there is no particular reason that one-sided should give you better overlap than two-sided. If this is the reason that people use one-sided, maybe we should revisit the progress rule ;-)

Keith

_______________________________________________ mpi-forum mailing list [email protected] http://lists.mpi-forum.org/mailman/listinfo.cgi/mpi-forum