Cisco’s Jeff Squyres writes that the MPI-3 non-blocking “barrier” collective (MPI_Ibarrier) may seem counter-intuitive, but it is actually very useful. I mean, why would you block while waiting?
Here’s an analogy: a barrier is very much like the start of a meeting. You can’t start the meeting until all the participants of the meeting arrive. And there’s always That Guy who’s 15 minutes late (yeah, we all know That Guy). Think of non-blocking barriers as a notification mechanism that everyone has reached (or passed) a common milestone.
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