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Subject: Re: [OMPI users] Anyscientific application heavily using MPI_Barrier?
From: Eugene Loh (Eugene.Loh_at_[hidden])
Date: 2009-08-24 18:43:11


Richard Treumann wrote:

Guess I should have kept quiet a bit longer. As I recall we had already seen a counter example to Jeff's stronger statement and that motivated my narrower one.

          If there are no wildcard receives - every MPI_Barrier call is semantically irrelevant.
Do you have a counter example for my more cautious assertion?
No, but my momentary interest included wildcards, and it seemed to me that, as a corollary to your claim, that if there are wildcards, then Barriers could be relevent.  And my example was "proof by demonstration".
( I had already granted that a correct MPI program could be made incorrect with a barrier and the barrier that broke it would have to be considered be "semantically relevant". I would reword the statement with that in mind if I were to offer it up again. )