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Subject: Re: [OMPI devel] Loadbalancing
From: Lenny Verkhovsky (lenny.verkhovsky_at_[hidden])
Date: 2008-04-28 03:42:03


They can also use RankMapping policy for a precise mapping .

On 4/25/08, Jeff Squyres <jsquyres_at_[hidden]> wrote:
>
> Kewl!
>
> I added ticket 1277 so that we are sure to document this for v1.3.
>
>
>
> On Apr 23, 2008, at 11:09 AM, Ralph H Castain wrote:
>
> > I added a new "loadbalance" feature to OMPI today in r18252.
> >
> > Brief summary: adding --loadbalance to the mpirun cmd line will
> > cause the
> > round-robin mapper to balance your specified #procs across the
> > available
> > nodes.
> >
> > More detail:
> > Several users had noted that mapping byslot always caused us to
> > preferentially load the first nodes in an allocation, potentially
> > leaving
> > other nodes unused. If they mapped bynode, of course, this wouldn't
> > happen -
> > but then they were forced to a specific rank-to-node relationship.
> >
> > What they wanted was to have the ranks numbered byslot, but to have
> > the ppn
> > balanced across the entire allocation.
> >
> > This is now supported via the --loadbalance cmd line option. Here is
> > an
> > example of its affect (again, remember that loadbalance only impacts
> > mapping
> > byslot):
> >
> > no-lb lb bynode
> > node0: 0,1,2,3 0,1,2 0,3,6
> > node1: 4,5,6 3,4 1,4
> > node2: 5,6 2,5
> >
> >
> > As you can see, the affect of --loadbalance is to balance the ppn
> > across all
> > the available nodes while retaining byslot rank associations. In
> > this case,
> > instead of leaving one node unused, we take advantage of all available
> > resources.
> >
> > Hope this proves helpful
> > Ralph
> >
> >
> > _______________________________________________
> > devel mailing list
> > devel_at_[hidden]
> > http://www.open-mpi.org/mailman/listinfo.cgi/devel
>
>
>
> --
> Jeff Squyres
> Cisco Systems
>
>
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