[Moabusers] Re: [torqueusers] OpenMP with Torque

[Prakash Velayutham]

On Mar 10, 2008, at 2:48 PM, Garrick Staples wrote:

> On Mon, Mar 10, 2008 at 02:44:26PM -0400, Prakash Velayutham alleged:
>> Hello All,
>>
>> I sent an email on this topic some days ago, but did not get any
>> response. So decided to rephrase my question to see if this invokes
>> any response.
>>
>> When a user requests just 1 CPU for a job (qsub -lnodes=1) and does
>> not specify OMP_NUM_THREADS explicitly, and if the node has 4 CPUs,
>> does the job get restricted to 1 CPU that was allocated to the user  
>> or
>> does it spread to the 4 CPUs (if the other CPUs are not taken by  
>> other
>> jobs)?
>>
>> My scheduler is Moab, so I am copying Moab users list here too.
>
> No, torque doesn't set OMP_NUM_THREADS.  Torque doesn't know  
> anything about
> OpenMP, MPI, or anythen else that jobs do.
>
> -- 
> Garrick Staples, GNU/Linux HPCC SysAdmin
> University of Southern California

But, does the job get restricted to just 1 CPU or does it get outside  
of its allocation during OpenMP calls?

If OMP_NUM_THREADS is required to be set for the restriction to work,  
is there a way I can do it using prolog scripts or some other mechanism.
Currently, when a user requests just 1 CPU and start his OpenMP code,  
the code hikes the load on the machine up to 4 (on a 4 CPU system) and  
no further jobs get allocated on that system because of the high load.

Thanks,
Prakash