Re: [Condor-users] Multi-Threaded Jobs on Condor

[Cecile Garros <cecile@xxxxxxxxxxxxxxxxx>]

Si,

We faced the same problem recently. It seems one solution is to set more 
job slots than the actual number of CPU. For your dual-core boxes you 
would have:

  * 2 slots of type 1, with type 1: cpus=1, ram=50%
  * 1 additional slot of type 2, with type 2: cpus=2, ram=100%

To make this possible you have to "lie" to Condor and to add the 
following attributes in your local configuration file:

  * NUM_CPUS=4
  * MEMORY=2*ActualMemory

Then you have to specify that a job should not start on a type1 slot if 
a type 2 slot is in use and vice versa.

Finally you can tag your multi-threaded jobs to run on type 2 slots. 
Ordinary jobs should run on type 1 slots as a default.

A good summary about what has been done on that- with interesting links 
as well- is here:
https://lists.cs.wisc.edu/archive/condor-users/2007-June/msg00295.shtml

Hope this helps,
-Cecile


> > We have a small cluster of dual processor nodes. We want to be able
> > to submit jobs which contain a multi-threaded code through Condor.
> >
> > Ideally, we want the job to claim both processors on the node - if we
> > use slots then the allocate can claim two slots on different nodes.
> >
> > Is there anyway to specify this in the parallel job submission file
> > so that both 'slots' on the same node are claimed correctly?
> >     
>
> Si,
>
> Right now there's no way to accomplish this without preemption (or
> suspension). That is, you can't have Condor hold a slot free while the
> other slot is running a non-parallel job so a parallel job in the queue
> gets the whole machine.
>
> What you can do is set up a machine so when a job tagged as being
> "parallel" wants the machine it a) always runs in slot 1; and b) always
> preempts the running job in slot2; and c) always sets the START
> expression for slot2 to false when it's on the machine.
>
> It's not an ideal solution but it's the only way to achieve this right
> now. You could use suspension if you're not on Windows instead of
> preemption for the job in slot2 which makes things a little better. Or
> checkpointing so you don't loose forward progress from the job in slot2.
>
> If you search the archives you'll find a thread about setting up
> complicated inter-slot start expressions that have jobs suspending and
> preempting jobs in other slots. I can't remember the title now. Sorry.
> :( Maybe one of the Condor guys can jump in with a pointer to the
> complicated setup. It was a university who was doing it, they gave a
> talk at Condor Week a few years ago about it.
>
> - Ian
>
>
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--
Cecile GARROS

Solution Consultant
Software Development Division
mailto:cecile@xxxxxxxxxxxxxxxxx

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