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Subject: Re: [OMPI devel] Orte collectives
From: Ralph H Castain (rhc_at_[hidden])
Date: 2008-01-29 14:27:49


Depends upon which one you are using. For example, allgather operates across
the entire job, so all procs in that jobid have to invoke it. On the other
hand, allgather_list only operates across the procs specified in the list,
so only they need to invoke it.

Xcast sends a message to all procs in the job, but none of those procs needs
to invoke anything - we just deliver the message to the specified RML tag on
each proc. Of course, we assume that there is a recv (typically
non-blocking) posted on that tag (or that it will be posted eventually). If
not, then the message will just sit in the local oob waiting to be delivered
- no harm done, it just gets ignored.

Hope that helps. Let me know if you need some variant as I am adding (not
reducing or changing) grpcomm capabilities on the tmp branch.

Ralph

On 1/29/08 12:19 PM, "Richard Graham" <rlgraham_at_[hidden]> wrote:

> Are the group operations in ORTE (I assume this is what the grpcomm
> component does) available to subsets of a job, or do all procs in the
> orte_jobid_t need to invoke this ?
>
> Thanks,
> Rich
>
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