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Subject: Re: [OMPI users] Multicast?
From: Jeff Squyres (jsquyres_at_[hidden])
Date: 2008-12-10 10:13:03

On Dec 9, 2008, at 9:49 PM, Brock Palen wrote:

> Is OpenMPI using Multicast for things like MPI_Bcast() ?

Not today. There have been some experiments with it, but nothing yet.

> Some simple tests of really old versions (1.0.2) showed binary tree
> type performance, while latter versions gave me the same run time no
> matter how many CPU's I used.
> Thus this lead me to believe that something like multicast is in
> use. Is it?

That's an interesting result. It should depend on factors such as the
number of MPI processes you use, the size of the message, the layout
on the hosts/network, etc.

Jeff Squyres
Cisco Systems