28.1. Advanced Process Placement with PBS Professional

When launching a Linux session of Fluent under Altair PBS Professional, the following advanced options for process placement have beta support:

  • -scheduler_ppn=<M>

    This command line option sets the number of cores per chunk to <M>, where the chunk setting is defined as part of the PBS Professional installation. By default, this is populated using the qstat command and should not be required to be set by the user. When using Fluent Launcher, this can be set through the FL_SCHEDULER_PPN environment variable.

  • -scheduler_rpn=<R>

    This command line option sets the number of Fluent parallel processes desired on each chunk to <R>. By default, it is set equal to the FL_SCHEDULER_PPN value after it is set through user input or by the qstat command. This signifies a request for one Fluent parallel process per core. When using Fluent Launcher, this can be set through the FL_SCHEDULER_RPN environment variable.

  • FL_SCHEDULER_OPT=<entry>

    This environment variable is an advanced setting that allows you to manually provide the complete -l entry. This can be set at the command line before launching Fluent or through Fluent Launcher. This variable will take precedence over -scheduler_ppn=<M> and/or -scheduler_rpn=<R>.

The following two examples will launch two Fluent parallel processes on two compute nodes with one Fluent parallel process on each node:

  • fluent 3d -t2 -scheduler=pbs -scheduler_ppn=48 -scheduler_rpn=1

  • export FL_SCHEDULER_OPT="-l select=2:ncpus=48:mpiprocs=1" fluent 3d -t2 -scheduler=pbs

The previous examples are for a cluster with 48 cores per compute nodes.