This page documents the basics of how to write job scripts for the HPC clusters. Cluster-specific details are kept in separate sub pages for each cluster.
Job Script Basics
To run a job on the cluster involves creating a shell script called
a job script. The job script is a plain-text file containing any
number of commands, including your main computational task, i.e., it
may copy or rename files, cd into the proper directory, etc., all
before doing the "real" work. The lines in the script file are the
commands to be executed, in the given order. Lines starting with a
# are ignored as comments, except lines that start with
which are not executed, but contain special instructions to the queue
If you are not familiar with shell scripts, they are simply a set of commands that you could have typed at the command line. You can find more information about shell scripts here: Introduction to Bash shell scripts.
A job script consists of a couple of parts, in this order:
- The first line, which is always
- Paremeters to the queue system
- Commands to set up the execution environment
- The actual commands you want to be run
Parameters to the queue system may be specified on the
command line and/or in
#SBATCH lines in the job script. There can
be as many
#SBATCH lines as you want, and you can combine several
parameters on the same line. If a parameter is specified both on the
command line and in the job script, the parameter specified on the
command line takes precedence. The
#SBATCH lines must precede any
commands in the script.
Which parameters are allowed or required depends the job type and cluster, but two parameters must be present in (almost) any job:
--account, which specifies the project the job will run in. Required by all jobs.
--walltime, which specifies how long a job should be allowed to run. If it has not finished within that time, it will be cancelled. Required by all jobs except optimist jobs, where it is forbidden.
The other parameters will be described in the sub pages for each cluster.
It is recommended to start the commands to set up the environment with
set -o errexit # Exit the script on any error set -o nounset # Treat any unset variables as an error module --quiet purge # Reset the modules to the system default
and will most likely include one or more
module load SomeProgram/SomeVersion
to set up environment variables like
$PATH to get access to the
specified programs. It is recommended to specify the explicit version
module load command. We also recommend adding a
module list # For easier debugging
module load commands. See Software Module
Scheme for more information about software
All in all, a generic job script might look like this:
# Job name: #SBATCH --job-name=YourJobname # # Project: #SBATCH --account=nnXXXXk # # Wall time limit: #SBATCH --walltime=DD-HH:MM:SS # # Other parameters: #SBATCH ... ## Set up job environment: set -o errexit # Exit the script on any error set -o nounset # Treat any unset variables as an error module --quiet purge # Reset the modules to the system default module load SomeProgram/SomeVersion module list ## Do some work: YourCommands
Download the script: generic_job.sh (you might have
to right-click and select
Save Link As... or similar).
Wall Time Limit
The wall time limit (
--walltime) is required for all jobs except
optimist jobs. Optimist jobs don't have any fixed wall time
--walltime is not allowed for them.
The most used formats for the walltime specification is
HH:MM:SS, where DD is days, HH hours, MM minutes and SS
seconds. For instance:
3-12:00:00: 3.5 days
7:30:00: 7.5 hours
We recommend you to be as precise as you can when specifying the wall time limit as it will inflict on how fast your jobs will start to run: It is easier for a short job to get started between two larger, higher priority jobs (so-called backfilling). On the other hand, if the job has not finished before the wall time limit, it will be cancelled, so too long is better than too short due to lost work!
- Environment variables available in job scripts
- Job work directory
- Array jobs
- Running Job Steps in Parallel
- Porting Job Scripts from PBS/Torque
- Running MPI Jobs
1. Technically, any script language that uses
#as a comment character can be used, but the recommended, and the only one supported by the Metacenter, is bash. ↩