[torqueusers] PBS nodes problem

Greg Wimpey gwimpey at mines.edu
Tue Oct 19 12:05:55 MDT 2004


If I recall, Maui's interpretation of nodes/ppn is "weak".  That is, it
will just multiply them together and allocate the job across whatever
CPUs are available.  Or have I misunderstood the docs?  Of course, this
only applies if you are using Maui as a scheduler.

I would assume that the nodes/ppn/ncpus syntax is a historical legacy of
PBS.  One has to be careful about changing these things so as not to
break existing installations.

On Mon, 2004-10-18 at 14:57, Curtis W. Hillegas wrote:
> The -lnodes=#:ppn=# syntax works very well for dedicated clusters where 
> jobs can be specifically allocated to maximize performance, etc.  But in 
> shared clusters this causes confusion, especially for newer users.  Many 
> users in a shared cluster would rather have their job start earlier with 
> a mix of one, two, or however many processors per node rather than wait 
> until there is an ideal block of free nodes available.  Of course the 
> scheduler can be configured to fill in the processors more the way users 
> would like it, but the concept is sometimes confusing to the end user. 
> Why was the choice made not to allow the user to say "I want n 
> processors allocated however you can fit them on the nodes that 
> currently have unallocated processors?"
> 
> Regards,
> Curt
> 
> Danny Sternkopf wrote:
> > Hi,
> > 
> > ncpus should be used for big SMP machines only. 
> > It specifies the number of cpus for one single node.
> > 
> > If you have one or two processors machines in 
> > cluster then you have to specify the number of nodes.
> > --> 'lnodes:<number of nodes>:<number of cpus per node>
> >     For example: -lnodes=15:ppn=2 will request 30 CPUs
> >                  on Dual machines.
> > 
> > Best regards,
> > 
> > Danny
> > 
> > On Sun, Oct 17, 2004 at 01:39:19AM +0800, torqueusers at supercluster.org wrote:
> > 
> >>Hi,
> >>
> >>Is't compulsory to put "#PBS -l nodes" in the job script? Can I just
> >>use "#PBS -l ncpus"  in my script to submit job? My script failed to
> >>work when I submit without declared no. of nodes? Pls help... Thank
> >>You.
> >>
> >>
> >>Regards,
> >>Josh
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> >>torqueusers at supercluster.org
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> > 
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