[GE users] PE allocation rules

Daniel Templeton Dan.Templeton at Sun.COM
Thu Jul 19 22:19:11 BST 2007

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If you set your allocation rule to "2", you'll get two slots per 
machine, but that's going to try to only put two tasks on each machine, 
and will only overlap task pairs if the load formula dictates it.  What 
you're really asking for is the ability to schedule only even numbers of 
tasks to a host, e.g. "$fill_up:2".  (Note that "$round_robin:2" would 
be the same as the current "2".)  That's not something that Grid Engine 
can do.  We're generally only concerned about mins and maxes.  We 
haven't put much time into multiples (except with array job task ids).  
Sounds like a reasonable RFE, though.


Shannon V. Davidson wrote:
> Here's a simple problem.
>     * I have four 8-CPU hosts.
>     * I run serial jobs and distributed parallel MPI jobs on the hosts
>     * I want to schedule a 10 CPU distributed parallel job.
>     * For efficiency reasons, I need to run no less than 2 MPI tasks
>       (slots) of the job on each host.
> What PE allocation rule can I use?
> If I use $fill_up or $round_robin, I'll likely schedule an odd number 
> of MPI tasks on a host.  If I create several PE's with a specific 
> number for the allocation rule ("mpi2", "mpi4", and "mpi8" PEs with 
> allocation_rules of 2, 4, and 8 respectively), and submit the job with 
> a wildcard PE (-pe "mpi*" 10), the job will sit in the pending queue 
> forever, since none of these individual PEs will support the 
> scheduling of 10 CPUs.
> Am I missing something obvious?
> Perhaps it's possible to force the scheduling of 2 slots per host by 
> using $fill_up with some strange resource definition and request, but 
> I haven't resorted to trying that yet.  Instead, I'm working on an RFE 
> to support a flexible PE allocation rule.
> Shannon

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