Configuring your experiment

This section outlines the configuration of an individual experiment, which is stored in the config.yaml file.

Configuration files are written in the YAML file format. YAML allows us to store and configure both individual fields as well as higher data structures, such as lists and dictionaries. Data can also be encapsulated in larger structures. This is indicated by whitespace in the file, which is significant in YAML.

Configuration Settings


These settings are primarily used by the PBS scheduler.

queue (Default: normal)
The PBS queue to submit your job. Equivalent to qsub -q QUEUE.
project (Default: $PROJECT)
The project from which to submit the model (and deduct CPU hours). Equivalent to qsub -P PROJECT. The default value is the current $PROJECT environment variable. Note that project is used as part of the default configuration for various laboratory filepaths.
jobname (Default: Control directory name)
The name of the job as it appears in the PBS queue. If no name is provided, then it uses the name of the experiment’s control directory.

The number of CPUs used during model simulation. Usually equivalent to qsub -l ncpus=N. This is the number passed on to mpirun during model execution.

Although it usually matches the CPU request, the actual request may be larger if npernode is being used.


The number of CPUs used per node. This settings is passed on to mpirun during model execution. In most cases, this is converted into an equivalent npersocket configuration.

This setting may be needed in cases where a node is unable to efficiently use all of its CPUs, such as performance issues related to NUMA.

mem (Default: 31GiB per node)

Amount of memory required for the job. Equivalent to qsub -l mem=MEM. The default value requests (almost) all of the nodes’ memory for jobs using multiple nodes.

In general, it is good practice to keep this number as low as possible.


The amount of time required to run an individual job, specified as hh:mm:ss. Equivalent to qsub -l walltime=TIME.

Jobs with shorter walltimes will generally be prioritised ahead of jobs with longer walltimes.

Job priority setting. Equivalent to qsub -p PRIORITY.
umask (Default: 027)

Default permission mask (“umask”) for new files created during model execution. Nonzero values will disable specific permissions, following standard octal notation.

The first digit should be a zero when using standard octal format.

This is a generic configuration marker for any unsupported qsub flags. This setting is applied to any qsub calls.


Collation scheduling can be configured independently of model runs. Currently, all collation jobs are single CPU jobs and are not parallelised.

collate_queue (Default: copyq)
PBS queue used for collation jobs.
Time required for output collation.
Memory required for output collation.
Ignore these files during collation. This can either be a single filename or a list of filenames. Only FMS models (MOM, GOLD) support this setting.
Specify the flags passed to the collation program. Only FMS models (MOM, GOLD) support this setting.


These settings are part of general model execution, including OpenMPI configuration.

model (Default: Parent directory of control directory)

The model (or coupled model configuration) used in the experiment. This model name must be one of the supported models shown in payu list.

If no model name is provided, then it will attempt to infer the model based on the parent directory of the experiment. For example, if we run our experiment in ~/mom/bowl1, then mom will be used as the model type. However, it is generally better to specify the model type.

shortpath (Default: /short/${PROJECT})
The top-level directory for general scratch space, where laboratories and model output are stored. Users who run from multiple projects will generally want to set this explicitly.

Listing of the directories containing model input fields, linked to the experiment during setup. This can either be the name of a directory in the laboratory’s input directory:

input: core_inputs

the absolute path of an external directory:

input: /short/v45/core_input/iaf/

or a list of input directories:

   - year_100_restarts
   - core_inputs

If there are multiple files in each directory with the same name, then the earlier directory of the list takes precedence.

Binary executable for the model. This can either be a filename in the laboratorys bin directory, or an absolute filepath. Various model drivers typically define their own default executable names.

If one is running a coupled model containing several submodels, then each model is configured individually within a submodel namespace, such as in the example below for the ACCESS driver:

model: access
      model: matm
      exe: matm_MPI1_nt62.exe
      input: iaf_matm_simon
      ncpus: 1
      model: mom
      exe: fms_MOM_ACCESS_kate.x
      input: iaf_mom
      ncpus: 120
      model: cice
      exe: cice_MPI1_6p.exe
      input: iaf_cice
      ncpus: 6
      model: oasis
      input: iaf_oasis
      ncpus: 0
restart_freq (Default: 5)

Specifies the rate of saved restart files. For the default rate of 5, we keep the restart files for every fifth run (restart004, restart009, restart014, etc.).

Intermediate restarts are not deleted until a permanently archived restart has been produced. For example, if we have just completed run 11, then we keep restart004, restart009, restart010, and restart011. Restarts 10 through 13 are not deleted until restart014 has been saved.

restart_freq: 1 saves all restart files.

The following model-based tags are typically not configured

user (Default: ${USER})
The username used to construct the laboratory paths. It is generally recommended that laboratories be stored under username, so this setting is usually not necessary (nor recommended).
laboratory (Default: /short/${PROJECT}/${USER}/${MODEL})
The top-level directory for the model laboratory, where the codebase, model executables, input fields, running jobs, and archived output are stored.
control (Default: current directory)
The control path for the experiment. The default setting is the path of the current working directory.
experiment (Default: current directory)
The experiment name used for archival. The default setting uses the control directory name.


collate (Default: True)

Controls whether or not a collation job is submitted after model execution.

This is typically True, although individual model drivers will often set the default value to False if collation is unnecessary.


Namelist to include separate userscripts or subcommands at various stages of a payu submission. Inputs can be either script names ( or individual subcommands (echo "some_data" > input.nml, qsub

Specific scripts are defined below:

User-defined command to be called after experiment initialization, but before model setup.
User-defined command to be called after model setup, but prior to model execution.
User-defined command to be called after model execution but prior to model output archivel.
User-defined command to be called after model archival, but prior to any postprocessing operations, such as payu collate.
This is an older, less user-friendly, method to submit a script after payu collate has completed. Unlike the userscripts, it does not support user commands. These scripts are always re-submitted via qsub.


debug (Default: False)
Enable the debugger for any mpirun jobs. Equivalent to mpirun --debug. On raijin, this defaults to a Totalview session. This will probably only work for interactive sessions.

Append any unsupported mpirun arguments to the mpirun call of the model. This setting supports both single lines and a list of input arguments. Example shown below:

   - -mca mpi_preconnect_mpi 1   # Enable preconnecting
   - -mca mtl ^mxm               # Disable MXM acceleration
   - -mca coll ^fca              # Disable FCA acceleration

Enable any environment variables required by mpirun during execution, such as OMPI_MCA_coll. The following example below disables “matching transport layer” and “collective algorithm” components:

   OMPI_MCA_coll: ''
   OMPI_MCA_mtl: ''

Set the stacksize for each process in kiB. unlimited is also a valid setting (and typically required for many models).

Note: unlimited works without any issues, but explicit stacksize values may not be correctly communicated across raijin nodes.

Ignore any restart files and repeat the initial run upon resubmission. This is generally only used for testing purposes, such as bit reproducibility.

Deprecated settings

This is used to extract an individual year out of a larger multi-year forcing field in the MOM ocean model. However, there is currently no performance improvement when using this setting, so it is not recommended and is scheduled for deletion.