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The filenames, paths, email addresses, and some values below are things you will probably need to change. In some cases, values/names have been used to demonstrate possibilities that you could employ (in a slightly different way). Apart from the -l options, no option should appear on multiple lines.

While defaults exist for many options, HPC staff ask researchers to specify CPU core, memory, and walltime requirements as accurately as possible.

A -W option can be used for more complicated tasks such as job dependencies, stage-in and stage-out. Researchers may wish to consult with HPC staff with regard to use of the -W options. A man qsub will provide more information and more options than provided above.

Users interested in protecting there job runs with checkpointing should realize that this feature comes at a cost (I/O operations). Checkpoint restart of a job (using BLCR) will not work for all job types. HPC staff advise use to test this feature on a typical job first before using it on other similar jobs. Generally speaking, checkpointing will only be a real benefit to jobs that run for over a week.

The variables listed in the table below are commonly used within a PBS script file.

Note: On multi-core systems, a node (line in PBS_NODEFILE) will identify the hostname and a CPU core.

This example runs PAUP on the input file input.nex that resides in the current working directory. A file (here we'll name it pbsjob) is created with the contents:

#!/bin/bash
#PBS -c s
#PBS -j oe
#PBS -m ae
#PBS -N jobname
#PBS -l pmem=5gb
#PBS -l walltime=500:00:00
#PBS -M your.name@jcu.edu.au

ncpu=`wc -l $PBS_NODEFILE | awk '{print $1}'`
echo "------------------------------------------------------"
echo " This job is allocated "$ncpu" CPU cores on "
cat $PBS_NODEFILE | uniq
echo "------------------------------------------------------"
echo "PBS: Submitted to $PBS_QUEUE@$PBS_O_HOST"
echo "PBS: Working directory is $PBS_O_WORKDIR"
echo "PBS: Job identifier is $PBS_JOBID"
echo "PBS: Job name is $PBS_JOBNAME"
echo "------------------------------------------------------"
 
cd $PBS_O_WORKDIR
source /etc/profile.d/modules.sh
module load paup
paup -n input.nex

To submit the job for execution on a HPRC compute node simply enter the command:

qsub pbsjob

If you know this job will require more than 4GB but less than 8GB of RAM, you could use the command:

qsub -l nodes=1:ppn=2 pbsjob

If you know this job will require more than 8GB but less than 16GB of RAM, you could use the command:

qsub -l nodes=1:ppn=8 pbsjob

The reason for the special cases (latter two) is to guarantee memory resources for your job. If memory on a node is overallocated, swap will be used. Job(s) that are actively using swap (disk) to simulate memory could take more than 1000 times longer to finish than a job running on dedicated memory. In most cases, this will mean your job will never finish.

Using Job Arrays

Users with a knowledge of shell scripting (e.g., bash) may choose to take advantage of job arrays. This feature significantly reduces load on our Torque/Maui server (compared to lots of individual job submissions). The example below (assume the file name is pbsjob), will only be useful as a guide

#!/bin/bash
#PBS -c s
#PBS -j oe
#PBS -m ae
#PBS -N jobarray
#PBS -M your.name@jcu.edu.au
#PBS -l pmem=2gb
#PBS -l walltime=9:00:00

cd $PBS_O_WORKDIR
source /etc/profile.d/modules.sh
module load matlab
matlab -r myjob$PBS_ARRAYID

Issuing the command

qsub -S /bin/bash -t 1-8 pbsjob

will see 8 jobs run under one major identifier. To view status of individual jobs in the array. The above example is identical (in terms of what jobs would be executed) to the one in the "Do It Yourself" section below.

Chances are you may need more advanced features of the scripting language than what is shown above. HPRC staff will endeavour to provide assistance with job arrays, if requested.

Do It Yourself

There are several legitimate reasons for wanting to run multiple single processor jobs in parallel within a single PBS script. For example, you may want to run 8 MATLAB jobs which require a toolbox that only has 4 licensed users. Only 1 MATLAB license is checked out if all 8 jobs are run on the same system. An example PBS script to do this task would look like

#!/bin/bash
#PBS -c s
#PBS -j oe
#PBS -m ae
#PBS -N jobname
#PBS -M your.name@jcu.edu.au
#PBS -l walltime=1000:00:00
#PBS -l nodes=1:ppn=8
#PBS -l pmem=32gb

ncpu=`wc -l $PBS_NODEFILE`
echo "------------------------------------------------------"
echo " This job is allocated "$ncpu" CPU cores on "
cat $PBS_NODEFILE | uniq
echo "------------------------------------------------------"
echo "PBS: Submitted to $PBS_QUEUE@$PBS_O_HOST"
echo "PBS: Working directory is $PBS_O_WORKDIR"
echo "PBS: Job identifier is $PBS_JOBID"
echo "PBS: Job name is $PBS_JOBNAME"
echo "------------------------------------------------------"

cd $PBS_O_WORKDIR
source /etc/profile.d/modules.sh
module load matlab
matlab -r myjob1 &
matlab -r myjob2 &
matlab -r myjob3 &
matlab -r myjob4 &
matlab -r myjob5 &
matlab -r myjob6 &
matlab -r myjob7 &
matlab -r myjob8 &
wait    # Wait for background jobs to finish.

To submit the job for execution on a HPRC compute node simply enter the command:

qsub pbsjob

Note: The echo commands in the PBS script example above are informational only.

A standard compute node in the JCU HPC cluster has approximately 2.5GB of memory per CPU core.  The following table contains a number of examples of PBS options/directives that should be used for the given memory requirement of the job in question.

Note that the above table only contains a discrete number of examples.  Big memory nodes have approximately 5GB of memory per CPU core.  The bigmem queue should be used when you require more than 63GB of memory for your job.

Note:  Multi-processor jobs may have core counts that don't match the memory request.  For example, it is entirely possible that an MPI job that consumes 8 CPU cores only requires 2GB of memory.