[torqueusers] Resources_List.ncpus & resources_assigned.ncpus meaning

Emir Imamagic eimamagi at srce.hr
Fri Sep 2 04:46:35 MDT 2005


Hi,

thank you for the answer. After doing bunch of tests, I anticipated such 
response. Resource_List.ncpus job property is indeed inherited from 
queue default resource configuration.

I've noticed that Maui reports correct number of tasks. However, in my 
case I need to retrieve information directly from Torque without 
assumption that Maui is used as scheduler (hm, I should have emphasized 
this in first mail).

Anyways, thank you for clearing this issue. I will simply ignore ncpus 
property and use nodes to get precise information.

Best regards,
emir

Garrick Staples wrote:
> On Mon, Aug 29, 2005 at 12:31:23AM +0200, Emir Imamagic alleged:
> 
>>Hi,
>>
>>I'm using Maui 3.2.6p13 and torque_1.2.0p4 on dual processor cluster. I've 
>>tried to find exact meaning of ncpus field but didn't find consistent 
>>definiton.
>>
>>Does it mean:
>>- total amount of cpus allocated to a job, or
>>- amount of cpus allocated to a job on a single node?
> 
> 
> I went searching the code and found it closer to the later.  First, it
> means absolutely nothing to TORQUE; it is just a value that is passed
> along to the scheduler.  Second, in maui it defines the size of a
> "task".
> 
> A "task" in maui is smallest indivisible set of resources that are
> assigned to jobs.  So asking for "ncpus=4" means you want 1 chunk of 4
> processors.  Since tasks are indivisible, it means that all cpus must be
> on the same node.
> 
> 
> 
>>Furthermore, test in practice shown that none of these definition are 
>>correct. I adjusted nodes $PBS_HOME/server_priv/nodes so the nodes have 4 
>>cpus, and submitted two jobs:
>>- first demanding nodes=1:ppn=3, and
>>- second demanding nodes=1:ppn=2.
>>
>>Command qstat -f reported for both of them:
>>...
>>Resource_List.ncpus = 1
>>Resource_List.nodect = 1
> 
> 
> I think ncpus is being inherited from your queue config in this case?
> 
> Keep in mind that Resource_List is initially populated by pbs_server by
> combining the job request and the queue config.  Then maui may or may
> not adjust the individual values.
> 
> It is probably more useful to look at 'checkjob'.  For example,
> requesting 'ncpus=2' gives me:
> 
> Dedicated Resources Per Task: PROCS: 2
> NodeCount: 1
> 
> 
> 
>>Command qstat -fQ reported that 2 cpus are occupied by the jobs in that 
>>queue:
>>...
>>resources_assigned.ncpus = 2
>>resources_assigned.nodect = 2
>>...
> 
> 
> That's for the queue, not for individual jobs.  And again, I think you
> are only getting seeing ncpus because you have
> resources_{assigned,max,min}.ncpus in the queue.
> 
> 
> 
> 
>>I also tried setting ncpus explicity and the the values reported 
>>correctly, but I only got one cpu allocated (in PBS_NODEFILE). 
>>Furthermore, I found in previous mails, that this is not a preffered way 
>>of allocating nodes for clusters and that one should use -l nodes=*:ppn=* 
>>instead.
> 
> 
> Correct, any value for ncpus > 1 gives you 1 "thing".
> 
> 
> 
>>Is this normal behaviour?
>>
>>If yes, is there some way to get number of cpus allocated to the jobs in 
>>a queue (beside from calling qstat -f and parsing nodes=*:ppn=* and 
>>queue=* for each job)?
> 
> 
> Not that I can find.
> 
> 
> 
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