Hey Jeff,

Finally got my test nodes back and was looking at the info you sent. On the SLURM page, it states the following:

*Open MPI* <http://www.open-mpi.org/> relies upon SLURM to allocate resources for the job and then mpirun to initiate the tasks. When using salloc command, mpirun's -nolocal option is recommended. For example:

$ salloc -n4 sh    # allocates 4 processors and spawns shell for job
mpirun -np 4 -nolocal a.out
exit          # exits shell spawned by initial salloc command

You are saying that I need to use the slurm salloc, then pass SLURM a script? Or could I just add it all into the script? Fro eaample:

#!/bin/sh
salloc -n4
mpirun my_mpi_application

Then, run with srun -b myscript.sh


Jeff F. Pummill
Senior Linux Cluster Administrator
University of Arkansas
Fayetteville, Arkansas 72701
(479) 575 - 4590
http://hpc.uark.edu

"A supercomputer is a device for turning compute-bound
problems into I/O-bound problems." -Seymour Cray


Jeff Squyres wrote:
Ick; I'm surprised that we don't have this info on the FAQ. I'll try to rectify that shortly.

How are you launching your jobs through SLURM? OMPI currently does not support the "srun -n X my_mpi_application" model for launching MPI jobs. You must either use the -A option to srun (i.e., get an interactive SLURM allocation) or use the -b option (submit a script that runs on the first node in the allocation). Your script can be quite short:

#!/bin/sh
mpirun my_mpi_application

Note that OMPI will automatically figure out how many cpu's are in your SLURM allocation, so you don't need to specify "-np X". Hence, you can run the same script without modification no matter how many cpus/nodes you get from SLURM.

It's on the long-term plan to get "srun -n X my_mpi_application" model to work; it just hasn't bubbled up high enough in the priority stack yet... :-\


On Jun 20, 2007, at 1:59 PM, Jeff Pummill wrote:

Just started working with OpenMPI / SLURM combo this morning. I can successfully launch this job from the command line and it runs to completion, but when launching from SLURM they hang.

They appear to just sit with no load apparent on the compute nodes even though SLURM indicates they are running...

[jpummil@trillion ~]$ sinfo -l
Wed Jun 20 12:32:29 2007
PARTITION AVAIL TIMELIMIT JOB_SIZE ROOT SHARE GROUPS NODES STATE NODELIST debug* up infinite 1-infinite no no all 8 allocated compute-1-[1-8] debug* up infinite 1-infinite no no all 1 idle compute-1-0

[jpummil@trillion ~]$ squeue -l
Wed Jun 20 12:32:20 2007
JOBID PARTITION NAME USER STATE TIME TIMELIMIT NODES NODELIST(REASON) 79 debug mpirun jpummil RUNNING 5:27 UNLIMITED 2 compute-1-[1-2] 78 debug mpirun jpummil RUNNING 5:58 UNLIMITED 2 compute-1-[3-4] 77 debug mpirun jpummil RUNNING 7:00 UNLIMITED 2 compute-1-[5-6] 74 debug mpirun jpummil RUNNING 11:39 UNLIMITED 2 compute-1-[7-8]

Are there any known issues of this nature involving OpenMPI and SLURM?

Thanks!

Jeff F. Pummill

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