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Subject: Re: [OMPI users] job runs with mpirun on a node but not if submitted via Torque.
From: Ralph Castain (rhc_at_[hidden])
Date: 2009-04-01 02:13:26


The difference you are seeing here indicates that the "direct" run is
using the rsh launcher, while the other run is using the Torque
launcher.

So I gather that by "direct" you mean that you don't get an allocation
from Maui before running the job, but for the other you do? Otherwise,
OMPI should detect the that it is running under Torque and
automatically use the Torque launcher unless directed to do otherwise.

The --set-sid option causes the orteds to separate from mpirun's
process group. This was done on the rsh launcher to avoid having
signals directly propagate to local processes so that mpirun could
properly deal with them.

The --no-daemonize option on the Torque launch keeps the daemons in
the PBS job so that Torque can properly terminate them all when you
reach your time limit. We let the rsh-launched daemons daemonize so
that they terminate the ssh session as there are system limits to the
number of ssh sessions you can have concurrently open.

Once the daemon gets running on the node, there isn't anything
different about how it starts a process that depends upon how the
daemon was started. The environment seen by the processes will be the
same either way, with the exception of the process group. Is there
something about that application which is sensitive to the process
group?

If so, what you could do is simply add -mca pls rsh to your command
line when launching it. This will direct OMPI to use the rsh launcher,
which will give you the same behavior as your "direct" scenario (we
will still read the PBS_NODEFILE to get the allocation).

You might also want to upgrade to the 1.3 series - the launch system
there is simpler and scales better. If your application cares about
process group, you might still need to specify the rsh launcher (in
1.3, you would use -mca plm rsh to do this - slight syntax change),
but it would be interesting to see if it has any impact...and would
definitely run better either way.

Ralph

On Mar 31, 2009, at 8:36 PM, Rahul Nabar wrote:

> 2009/3/31 Ralph Castain <rhc_at_[hidden]>:
>> It is very hard to debug the problem with so little information. We
>> regularly run OMPI jobs on Torque without issue.
>
> Another small thing that I noticed. Not sure if it is relevant.
>
> When the job starts running there is an orte process. The args to this
> process are slightly different depending on whether the job was
> submitted with Torque or directly on a node. Could this be an issue?
> Just a thought.
>
> The essential difference seems that the torque run has the
> --no-daemonize option whereas the direct run has a --set-sid option. I
> got these via ps after I submitted an interactive Torque job.
>
> Do these matter at all? Full ps output snippets reproduced below. Some
> other numbers also seem different on closer inspection but that might
> be by design.
>
> ###############via Torque; segfaults. ##################
> rpnabar 11287 0.1 0.0 24680 1828 ? Ss 21:04 0:00 orted
> --no-daemonize --bootproxy 1 --name 0.0.1 --num_procs 2 --vpid_start 0
> --nodename node17 --universe rpnabar_at_node17:default-universe-11286
> --nsreplica "0.0.0;tcp://10.0.0.17:45839" --gprreplica
> "0.0.0;tcp://10.0.0.17:45839"
> ######################################################
>
>
> ##############direct MPI run; this works OK################
> rpnabar 11026 0.0 0.0 24676 1712 ? Ss 20:52 0:00 orted
> --bootproxy 1 --name 0.0.1 --num_procs 2 --vpid_start 0 --nodename
> node17 --universe rpnabar_at_node17:default-universe-11024 --nsreplica
> "0.0.0;tcp://10.0.0.17:34716" --gprreplica
> "0.0.0;tcp://10.0.0.17:34716" --set-sid
> ##########################################################
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