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Subject: Re: [OMPI users] Intercommunicators Collective Communciation
From: Jeff Squyres (jsquyres) (jsquyres_at_[hidden])
Date: 2014-05-09 20:22:46

On May 9, 2014, at 7:56 PM, Spenser Gilliland <spenser_at_[hidden]> wrote:

> I'm having some trouble understanding Intercommunicators with
> Collective Communication. Is there a collective routine to express a
> transfer from all left process to all right processes? or vice versa?

The intercomm collectives are all basically defined as data movement from one group to the other (*and* vice versa), with the obvious exception of Barrier, which has no data movement -- just synchronization.

The key to understand is (aside from barrier):

- collectives with intracomms are data movement in the *same* group
- collectives with intercomms are data movement to the *other* group

Jeff Squyres
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