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Subject: Re: [OMPI users] Question on MPI_Ssend
From: Jeff Squyres (jsquyres_at_[hidden])
Date: 2011-09-13 07:16:03

On Sep 13, 2011, at 5:02 AM, devendra rai wrote:

> I am using MPI_Ssend and a corresponding a MPI_Recv. I notice that whenever MPI_Recv starts waiting firs, and then MPI_Ssend is posted, the MPI calls just block. This, of course results in non-coherent application behavior.

I'm not sure what you mean by "non-coherent application behavior."

Note that MPI_SSEND is a synchronous send, which, by definition, means that it won't complete until the matching receive has been posted. In practice, this usually means that the receiver has started to receive (and sent an ACK back to the sender).

If you want non-blocking behavior, you might want to investigate MPI_ISEND and MPI_IRECV.

Jeff Squyres
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