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Subject: Re: [OMPI users] OpenMPI Hangs, No Error
From: Jeff Squyres (jsquyres_at_[hidden])
Date: 2010-07-07 07:35:08

On Jul 6, 2010, at 6:36 PM, Reuti wrote:

> But just for curiosity: at one point Open MPI chooses the ports. At
> that point it might possible to implement to start two SSH tunnels per
> slave node to have both directions and the daemons have to contact
> then "localhost" on a specific port which will be tunneled to each
> slave. In principle it should work I think, but it's just not
> implemented for now.

Agreed. Patches would be welcome! :-)

> Maybe it could be an addition to Open MPI for security concerned
> usage. I wonder about the speed impact, when compression is switched
> on per se in SSH in such a setup in case you transfer large amounts of
> data via Open MPI.

For control data (i.e., control messages passed during MPI startup, shutdown, etc.), the impact may not matter much. For MPI data (i.e., having something like an "ssh" BTL), I could imagine quite a bit of slowdown. But then again, it depends on what your goals are -- if your local policies demand ssh or nothing, having "slow" MPI might be better than nothing.

Jeff Squyres
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