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From: Jeff Squyres (jsquyres_at_[hidden])
Date: 2007-01-29 20:38:40

On Jan 19, 2007, at 5:21 PM, Evan Smyth wrote:

> I had been using MPICH and its serv_p4 daemon to speed startup times.
> I've decided to try OpenMPI (primarily for the fault-tolerance
> features)
> and would like to know what the equivalent of the serv_p4 daemon is.

We don't yet have one. "Persistent" daemon operations is planned and
somewhat functional, but I wouldn't call it robust yet.

Ralph will likely correct some inaccuracies in the above statement. :-)

> It appears as though the orted daemon may be what I am after but I
> don't
> quite understand it. I used to run serv_p4 with a specific port number
> and then pass a -p4ssport <portnumber> flag to mpirun. The daemon
> would
> remain running on each node and each new mpirun job would simply
> communicate directly through a port with the already running
> instance of
> the daemon on that machine and would save the mpirun from having to
> launch an rsh. This was great for reducing startup and run times
> due to
> rsh issues. The orted daemon does support a -persistent flag which
> seems
> relevant, but I cannot find a real usage example.
> I expect that most of the readers will find this to be a trivial
> problem
> but I'm hoping someone can give me an openmpi equivalent usage
> example.

We usually rely on resource managers (e.g., slurm and the like) for
fast statrtup, which is why persistent daemon-based operation wasn't
high on the priority list.

LAM, for example, has a persistent daemon mode which works quite
nicely. But LAM lacks many of the advanced features in OMPI's MPI

Jeff Squyres
Server Virtualization Business Unit
Cisco Systems