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Subject: Re: [OMPI users] Debugging Runtime/Ethernet Problems
From: Jeff Squyres (jsquyres) (jsquyres_at_[hidden])
Date: 2013-09-20 12:31:19


On Sep 20, 2013, at 12:27 PM, Lloyd Brown <lloyd_brown_at_[hidden]> wrote:

> Interesting. I was taking the approach of "only exclude what you're
> certain you don't want" (the native IB and TCP/IPoIB stuff) since I
> wasn't confident enough in my knowledge of the OpenMPI internals, to
> know what I should explicitly include.
>
> However, taking Jeff's suggestion, this does seem to work, and gives me
> the expected Ethernet performance:
>
> "mpirun --mca btl tcp,sm,self --mca btl_tcp_if_include em1 ./osu_bw"
>
> So, in short, I'm still not sure why my exclude syntax doesn't work.

Check two things:

1. What BTLs are available? Is there some other BTL that may be used instead of openib?

2. (this one is more likely) What IP interfaces are available on all nodes? The most obvious guess here is that you didn't exclude 127.0.0.1/8, and OMPI found this interface on all nodes, and therefore assumed that it was routable/usable on all nodes. Hence, one quick experiment might be to try your exclude syntax again, but *also* exclude 127.0.0.8/8.

-- 
Jeff Squyres
jsquyres_at_[hidden]
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