[torqueusers] Curious question

[Charles Johnson]

On Mar 30, 2010, at 9:40 AM, Ken Nielson wrote:

> Glen Beane wrote:
>>
>>
>> On Tue, Mar 30, 2010 at 10:07 AM, Glen Beane <glen.beane at gmail.com <mailto:glen.beane at gmail.com 
>> >> wrote:
>>
>>
>>
>>    On Tue, Mar 30, 2010 at 9:55 AM, Charles Johnson
>>    <charles.johnson at accre.vanderbilt.edu
>>    <mailto:charles.johnson at accre.vanderbilt.edu>> wrote:
>>
>>        About the nodes file ... I have always been under the
>>        impression that
>>        the nodes file gives an ordering to nodes selected for jobs,  
>> i.e.,
>>        nodes at the top of the list are considered before nodes at  
>> the
>>        bottom. We are currently in a down time for refreshing
>>        hardware, and
>>        the whole cluster is quiescent. As a test of hardware we
>>        submitted a
>>        single job suitable for any one of several hundred nodes at
>>        the top of
>>        the nodes file. The job ran on a node roughly halfway down the
>>        nodes
>>        file. Again, there were no other jobs on the cluster.
>>
>>        I am curious as to why? Any ideas?
>>
>>        We are using torque 2.4.5 and moab 5.3.6
>>
>>
>>
>>    This is really a Moab question since Moab selects the node that
>>    the job will run on, it has nothing to do with the order of the
>>    nodes in the TORQUE node file. I think the default for Moab might
>>    be "last fit", so as it scans the available nodes it will select
>>    the last one it finds that satisfies the requirements for the
>>    job.  There is a "first fit" and "best fit" option if I remember
>>    correctly.
>>
>>    With the fifo scheduler, then yes, I think the job would run on
>>    the first available node in the node list.
>>
>>
>> actually, I was thinking of LASTAVAILABLE, not "last fit", so the  
>> definition would be different than what I stated.  This is the  
>> correct definition: "This algorithm is a best fit in time algorithm  
>> that minimizes the impact of reservation based node-time  
>> fragmentation."  I think this might be the default, but I don't  
>> remember for sure.
>> ------------------------------------------------------------------------
>>
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>>
> If you were to run TORQUE without a scheduler and started the job  
> manually TORQUE will choose the last node in the nodes file to run on.
>
> Ken Nielson
> Adaptive Computing


Thanks to all who replied. Clarity reigns. :)

~Cheers--

Charles
--
Charles Johnson
Advanced Computing Center for Research and Education
Office: 615-343-2776
Cell: 615-478-5743