[torqueusers] Curious question

Ken Nielson knielson at adaptivecomputing.com
Tue Mar 30 08:40:28 MDT 2010

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

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