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Subject: Re: [OMPI devel] Barrier Implementation Oddity
From: George Bosilca (bosilca_at_[hidden])
Date: 2013-07-01 08:48:58


Yes, Bruck for barrier is a variant of the dissemination algorithm as described in:
 - Debra Hensgen, Raphael Finkel, and Udi Manbet. Two algorithms for barrier synchronization. International Journal of Parallel Programming, 17(1):1–17, 1988.

  George.

On Jun 29, 2013, at 12:05 , Ronny Brendel <ronnybrendel_at_[hidden]> wrote:

> Hi,
>
> I am digging through openmpi to find out what algorithm the barrier actually uses.
> seems to be bruck/dissemination.
>
> However i stumbled upon something odd.
> in: ompi/mca/coll/tuned/coll_tuned_barrier.c
> function: ompi_coll_tuned_barrier_intra_bruck
>
> I think you intend (by the comments and the function name) to send to the previous node and receive from the next. But actually it looks like you are doing the reverse. (which should then be the dissemination algorithm)
>
> It's no big deal, I'm just a bit confused right now, and wonder if I'm missing something. I hope you can help me understand.
>
> cheers,
> Ronny
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