LSF: Queue Change Questions and Answers

Will the ptile resource parameter still work with exclusive use of nodes?

Yes. You can use ptile in the same manner as you did with the old queues. If you specify ptile less than 8, then the remaining cores on the node will be idle. Some users prefer to run using less than 8 processes per node for memory or performance reasons.

What if I want to submit a parallel job using less than 8 cores?

You can use the serial queues! These will share nodes with other serial and parallel jobs small enough to fit on a single node. Applications that use OpenMP or Pthreads can also now use the serial queues.

Exclusive use of nodes doesn’t seem like it increases utilization, does it?

Actually, it does help increase utilization by allowing the LSF scheduler to properly “backfill” shorter running parallel jobs and allow large parallel jobs to get scheduled in a reasonable amount of time. In addition, many users running parallel jobs use ptile=8 anyway. Exclusive use of nodes prevents a problem job from landing on the node and crashing another job while also allowing consistent run times for parallel jobs.