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Subject: Re: [OMPI users] Debugging Runtime/Ethernet Problems
From: Jeff Squyres (jsquyres) (jsquyres_at_[hidden])
Date: 2013-09-20 20:54:16


On Sep 20, 2013, at 1:00 PM, Lloyd Brown <lloyd_brown_at_[hidden]> wrote:

> It is interesting to me, though, that I need to explicitly exclude
> lo/127.0.0.1 in this case, but when I'm on an Ethernet-only node, and I
> just do the plain "mpirun ./appname", I don't have to exclude anything,
> and it figures out to use em1, and not lo.

This is probably a case of Open MPI being "too helpful" / optimizing for the common case: ignoring 127.0.0.1/8.

Specifically:

- btl_tcp_if_include defaults to empty
- btl_tcp_if_exclude defaults to 127.0.0.1/8

Meaning: if you specify nothing, you'll exclude localhost. If you specify an include, it takes precedence over the default exclude. If you specify an exclude, you need to *also* ignore localhost.

-- 
Jeff Squyres
jsquyres_at_[hidden]
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