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Subject: Re: [OMPI devel] Default mapping / binding
From: Ralph Castain (rhc_at_[hidden])
Date: 2013-12-17 18:27:20

So to be clear:

if nothing is specified, we map-by socket and rank-by slot

if map-by <obj> is specified, we will also rank-by <obj> as that seems to be the user expectation (based on feedback on the user/devel lists)

On Dec 17, 2013, at 2:19 PM, Jeff Squyres (jsquyres) <jsquyres_at_[hidden]> wrote:

> I actually asked Ralph to make one more change. The default MCW rank ordering was to match the mapping. So in the np>2 case, on a 2 socket system, we'd order like this:
> -----
> [savbu-usnic-a:01121] MCW rank 0 bound to socket 0[core 0[hwt 0-1]]: [BB/../../../../../../..][../../../../../../../..]
> [savbu-usnic-a:01121] MCW rank 1 bound to socket 1[core 8[hwt 0-1]]: [../../../../../../../..][BB/../../../../../../..]
> [savbu-usnic-a:01121] MCW rank 2 bound to socket 0[core 1[hwt 0-1]]: [../BB/../../../../../..][../../../../../../../..]
> [savbu-usnic-a:01121] MCW rank 3 bound to socket 1[core 9[hwt 0-1]]: [../../../../../../../..][../BB/../../../../../..]
> -----
> I think in this case, we want to order MCW 0,1 on the same socket, and MCW 2,3 on the other socket (vs. MCW 0,2 on one socket and MCW 1,3 on the other socket).
> (of course, this is all *by default*, meaning that you can change it with mpirun CLI options to do whatever you want)
> Speak now if you disagree...
> --
> Jeff Squyres
> jsquyres_at_[hidden]
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