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Subject: Re: [OMPI users] disabling tcp altogether
From: Jeff Squyres (jsquyres_at_[hidden])
Date: 2008-06-04 13:52:12

On Jun 4, 2008, at 10:39 AM, tayfun sen wrote:

> I would like to run an OpenMPI application on one node and since I
> think
> it would be better performance wise I want it to use shared memory for
> communication and not tcp. Is it possible to use shared memory not
> only
> for MPI communication but also for control messages and other similar
> inner MPI related communication? (so no tcp communication whatsoever
> is
> used).

I'm afraid not -- the only "oob" component ("out of band", meaning
"not user-level MPI communication") that we have written is the TCP
component. We've toyed with the idea of writing others, but have
never done it.

The oob component is mainly used during process startup and shutdown.
So it doesn't really affect your steady-state MPI performance.

> # mpirun --host localhost --mca btl sm,self --mca oob ^tcp -n 2 hello
> [myhost:08491] [NO-NAME] ORTE_ERROR_LOG: Not found in file
> runtime/orte_init_stage1.c at line 182
> --------------------------------------------------------------------------
> It looks like orte_init failed for some reason; your parallel
> process is


This is OMPI's way of telling you that by deselecting the tcp oob, it
can't find any others to use.

Jeff Squyres
Cisco Systems