[torqueusers] MPI jobs not tied to nodes/ppn configuration

Jerry Smith jdsmit at sandia.gov
Thu Oct 15 14:39:33 MDT 2009

This is dependent on how the scheduler is setup  ( if you allow multiple 
jobs on a single node etc ).

But I believe you can use:
qsub -l ncpus=X ...  where X is the total number of cpus you need.


rozelak at volny.cz wrote:
> Hallo,
> I have access to heterogeneous clusters with many multi-core/processor
> nodes, where PBSPro is installed. When I want to start MPI job, I need
> to specify how many nodes, and how many CPUs per node I want. E.g.,
> when I require 32 MPI processes, I need to run it as:
> qsub -l nodes=16:ppn=2 ...
> The problem is, that PBS will wait until there are at lest 16 nodes,
> each with 2 cores free, even if there are more that 32 cores free (e.g.
> 15 nodes with 2 free cores each + 2 and more nodes with one free core,
> giving 32+ free cores available). This can be found for any nodes/ppn
> combination, e.g.:
> qsub -l nodes=32:ppn=1 ...
> will not be started on 31 nodes with 4+ free cores (having 124 cores
> free!). What I need is just to say -- I need XY cores/processors for
> my job in a cluster, and I do not care how many nodes it will be started
> on, while each node may allocate different number of cores.
> So, the question is: is 'torque' able to handle such cases? And how?
> If so, I will talk about it with our clusters admins, as I remember
> that they considered the migration from PBS and they are opened to our(users)
> wishes.
> Thank you very much for your answer,
> Dan T.
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