Thanks for the info Jeff! All of my "test" nodes are temporarily busy, but I should be able to play with this some more tomorrow.

I'll update the post if I have more questions or find any additional tips ;-)


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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