# Select Vs Nodes difference

**URL:** <https://community.openpbs.org/t/select-vs-nodes-difference/574>\
**Category:** Users/Site Administrators\
**Created:** [June 13, 2017, 7:32am UTC](https://community.openpbs.org/t/select-vs-nodes-difference/574 "2017-06-13T07:32:39Z")\
**Posts on this page:** 2\
**Page:** 1

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**Author:** ![atulyadavtech](https://yyz2.discourse-cdn.com/flex030/user_avatar/community.openpbs.org/atulyadavtech/32/474_2.png) [@atulyadavtech](https://community.openpbs.org/u/atulyadavtech)\
**Post date:** [June 13, 2017, 7:32am UTC](https://community.openpbs.org/t/select-vs-nodes-difference/574/1 "2017-06-13T07:32:39Z")

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Hi Team,

what is the difference between select and nodes.  
In an HPC environment, when we are using the " select=1:ncpus=2" jobs are entering in queue states And reason is " Not enough free nodes available"  
But, when we replace the resource with “nodes=1:ppn=2” jobs are running fine.

Can you please provide information on this behavior.

Thank You  
Atul Yadav

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**Author:** ![scc](https://yyz2.discourse-cdn.com/flex030/user_avatar/community.openpbs.org/scc/32/234_2.png) [@scc](https://community.openpbs.org/u/scc)\
**Post date:** [June 13, 2017, 1:34pm UTC](https://community.openpbs.org/t/select-vs-nodes-difference/574/2 "2017-06-13T13:34:33Z")

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Hello Atul, those jobs should be almost exactly the same as far as the scheduler is concerned. The -lnodes syntax gets translated by PBS into select (and place) statement equivalent. The job’s schedselect attribute is what the scheduler actually looks at when considering a job to run, and the -lnodes=1:ppn=2" job should have ended up as “schedselect = 1:ncpus=2:mpiprocs=2”. The mpiprocs resource is not actually scheduled upon (it just impacts how the $PBS\_NODEFILE gets written), so it is really should be the same as far as the scheduler is concerned.

The jobs would also differ in their place resource (-lselect would have defaulted to free, -lnodes to scatter), but since these are just single chunk jobs that should not have mattered.

Please share the full “qstat -f” output for one of each kind of the jobs you mention above, with the command run as root on the PBS server host (or as a different PBS manager, since schedselect does not show up to normal users in qstat -f output).

Thanks.