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Subject: Re: [OMPI devel] RTE issue I. Support for non-MPI jobs
From: Jeff Squyres (jsquyres_at_[hidden])
Date: 2007-12-04 10:59:31

On Dec 4, 2007, at 10:11 AM, Ralph H Castain wrote:

> (a) do we want to retain the feature to run non-MPI jobs with mpirun
> as-is
> (and accept the tradeoffs, including the one described below in II)?
> (b) do we provide a flag to mpirun (perhaps adding the distinction
> that
> "orterun" must be used for non-MPI jobs?) to indicate "this is NOT
> an MPI
> job" so we can act accordingly?

Based on talking to Ralph this morning, I'd [cautiously] be in favor
of b) -- have an MCA param / command line switch that allows switching
between jobs that call orte_init and those that do not, along with
setting the default by looking at argv[0] (orterun = does not call
orte_init, mpirun = does call orte_init).

The benefits are what Ralph described: less complex ORTE code and the
potential for optimizations that are difficult if you don't know if
the launched applications are going to call MPI_INIT (orte_init) or not.

But this is definitely a change from past behavior -- so it's worth
community discussion. The real question is: how many OMPI users
actually use mpirun to launch non-MPI jobs?

My $0.02 is that we're focusing ORTE on OMPI these days. So
optimizing more for MPI starting is a Good Thing(tm).

> (c) simply eliminate support for non-MPI jobs?
> (d) other suggestions?

Jeff Squyres
Cisco Systems