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Subject: Re: [OMPI users] is there an equiv of iprove for bcast?
From: Jeff Squyres (jsquyres_at_[hidden])
Date: 2011-05-09 09:27:14

On May 3, 2011, at 8:20 PM, Randolph Pullen wrote:

> Sorry, I meant to say:
> - on each node there is 1 listener and 1 worker.
> - all workers act together when any of the listeners send them a request.
> - currently I must use an extra clearinghouse process to receive from any of the listeners and bcast to workers, this is unfortunate because of the potential scaling issues
> I think you have answered this in that I must wait for MPI-3's non-blocking collectives.

Yes and no. If each worker starts N non-blocking broadcasts just to be able to test for completion of any of them, you might end up consuming a bunch of resources for them (I'm *anticipating* that pending non-blocking collective requests maybe more heavyweight than pending non-blocking point-to-point requests).

But then again, if N is small, it might not matter.

> Can anyone suggest another way? I don't like the serial clearinghouse approach.

If you only have a few workers and/or the broadcast message is small and/or the broadcasts aren't frequent, then MPI's built-in broadcast algorithms might not offer much more optimization than doing your own with point-to-point mechanisms. I don't usually recommend this, but it may be possible for your case.

Jeff Squyres
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