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.


Hard override for the number of cpus used in the PBS submit. This is useful when the number of CPUs used in the mpirun command is not the same as the number of cpus required. For example, when running an OpenMP only model like qgcm, set ncpus=1, and then set ncpureq to the number of threads required to run the model.


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: 192GiB 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.

Set platform specific defaults. Available sub options:

Override default memory per node. Used when memory not specified to calculate memory request


Override default ncpus per node. Used to calculate ncpus to fully utilise nodes regardless of requested number of cpus


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.


Request a non-default amount of storage that is local to the compute. See NCI jobfs documentation and the CLEX blog for details.


On the NCI system gadi all storage mount points must be specified, except /home and /scratch/$PROJECT. By default payu will scan all relevant configuration paths and manifests for filepaths that are stored on mounts that begin with /scratch or /g/data, and add the correct storage flags to the qsub submission. In cases where payu cannot determine all the required storage points automatically they can be specified using the storage option. Each key is a storage mount point descriptor, and contains an array of project code values:

            - x00
            - a15
            - zz3


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: /scratch/${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: /scratch/v45/core_input/iaf/

or a list of input directories:

   - year_100_restarts
   - core_inputs
   - /scratch/v45/core_input/iaf/

If there are 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 laboratory’s 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. This rate can be either an integer or date-based. For the default rate of 5, we keep the restart files for every fifth run (restart000, restart005, restart010, etc.). To save all restart files, set restart_freq: 1.

If restart_history is not configured, 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 restart000, restart005, restart010, and restart011. Restarts 11 through 14 are not deleted until restart015 has been saved.

To use a date-based restart frequency, specify a number with a time unit. The supported time units are YS - year-start, MS - month-start, W - week, D - day, H - hour, T - minute and S - second. For example, restart_freq: 10YS would save earliest restart of the year, 10 years from the last permanently archived restart’s datetime.

Please note that currently, only ACCESS-OM2, MOM5 and MOM6 models support date-based restart frequency, as it depends on the payu model driver being able to parse restarts files for a datetime.


Specifies how many of the most recent restart files to retain regardless of restart_freq.

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: /scratch/${PROJECT}/${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.


The experiment name used for archival. This will override the experiment name generated using metadata and existing archives (see Metadata and Related Experiments).


payu automatically generates and updates manifest files. See Manifests section for details.


These options allow fine-grained control of manifest checking to enable reproducible experiments. The default value is the value of the global reproduce flag, which is set using a command line argument and defaults to False. These options override the global reproduce flag. If set to True payu will refuse to run if the hashes in the relevant manifest do not match.

exe (Default: global reproduce flag)

Enforce executable reproducibility. If set to True will refuse to run if hashes do not match.

input (Default: global reproduce flag)

Enforce input file reproducibility. If set to True will refuse to run if hashes do no match. Will not search for any new files.

restart (Default: global reproduce flag)

Enforce restart file reproducibility.

scaninputs (Default: True)

Scan input directories for new files. Set to False when reproduce input is True.

If a manifest file is complete and it is desirable to not add spurious files to the manifest but allow existing files to change, setting this option to False would allow that behaviour.

ignore (Default: .*):

List of glob patterns which match files to ignore when scanning input directories. This is an array, so multiple patterns can be specified on multiple lines. The default is .* which ignores all hidden files on a POSIX filesystem.


Collation scheduling can be configured independently of model runs. Not all models support, or indeed require, collation. Collation is currently supported for MITgcm and any of the FMS based models (MOM, GOLD, SIS).

The collate process joins a number of smaller files which contain different parts of the model grid together into target output files.

Parallelisation of collation is supported for FMS based models using threaded multiprocessing. Collation time can be reduced if there are multiple target collate files. The magnitude of the collation time reduction depends a great deal on the time taken to collate each target file, the number of such files, and the number of cpus used. It is difficult to say a priori what settings are optimal: some experimentation may be necessary.

There is also experimental support for MPI parallelisation when using mppnccombine-fast

Collate options are specified as sub-options within a separate collate namespace:

enable (Default: True)

Flag to enable/disable collation

queue (Default: copyq)

PBS queue used for collation jobs.


Time required for output collation.

mem (Default: 2GB)

Memory required for output collation.

FMS based model only options:


Number of cpus used for collation.


Ignore these target files during collation. This can either be a single filename or a list of filenames.


Specify the flags passed to the collation program. Defaults depend on value of mpi flag


Binary executable for the collate program. This can be either a filename in the laboratory’s bin directory, or an absolute filepath.

restart (Defaut: False)

Collate restart files from previous run.


Use mpi parallelism and mppnccombine-fast.


When mpi is True attempt to generate an equivalent glob string for the list of files being collated to avoid issues with limits on the number of arguments for an command being run using MPI

threads (Default: 1)

When mpi is True it is also possible to still use multiple threads by specifying this option. The number of cpus used for each collation thread is then ncpus / nthreads


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.

See above for specific collate options.


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 archive.


User-defined command to be called after model archival, but prior to any postprocessing operations, such as payu collate.


User-defined command to be called if model does not run correctly and returns an error code. Useful for automatic error postmortem.


User-defined command to be called at the start of the sync pbs job. This is useful for any post-processing before syncing files to a remote archive.


This is an older, less user-friendly, method to submit a script after payu has completed all steps that might alter the output directory. e.g. collation. Unlike the userscripts, it does not support user commands. These scripts are always re-submitted via qsub.


Sync archive to a remote directory using rsync. Make sure that the configured path to sync output to, i.e. path, is the correct location before enabling automatic syncing or before running payu sync.

If postscript is also configured, the latest output and restart files will not be automatically synced after a run.

enable (Default: False):

Controls whether or not a sync job is submitted either after the archive or collation job, if collation is enabled.

queue (Default: copyq)

PBS queue used to submit the sync job.

walltime (Default: 10:00:00)

Time required to run the job.

mem (Default: 2GB)

Memory required for the job.

ncpus (Default: 1)

Number of ncpus required for the job.


Destination path to sync archive outputs to. This must be a unique absolute path for your experiment, otherwise, outputs will be overwritten.

restarts (Default: False)

Sync permanently archived restarts, which are determined by restart_freq.

rsync_flags (Default: -vrltoD --safe-links)

Additional flags to add to rsync commands used for syncing files.


Patterns to exclude from rsync commands. This is equivalent to rsync’s --exclude PATTERN. This can be a single pattern or a list of patterns. If a pattern includes any special characters, e.g. .*+?|[]{}(), it will need to be quoted. For example:

   - 'iceh.????-??-??.nc'
   - '*-IN-PROGRESS'
exclude_uncollated (Default: True if collation is enabled)

Flag to exclude uncollated files from being synced. This is equivalent to adding --exclude *.nc.*.


List of glob patterns which match extra paths to sync to remote archive. This can be a single pattern or a list of patterns. Note that these paths will be protected against any local delete options.

remove_local_files (Default: False)

Remove local files once they are successfully synced to the remote archive. Files in protected paths will not be deleted. Protected paths include the extra_paths (if defined), last output, the last saved restart (determined by restart_freq), and any subsequent restarts.

remove_local_dirs (Default: False)

Remove local directories once a directory has been successfully synced. This will delete any files in local directories that were excluded from syncing. Similarly to remove_local_files, protected paths will not be deleted.

runlog (Default: True)

Create or update a bare git repository clone of the run history, called git-runlog, in the remote archive directory.

Experiment Tracking


Automatically commits changes to configuration files and manifests in the control directory when the model runs. This creates a git runlog of the history of the experiment.

enable (Default: True) Flag to enable/disable runlog.


Generates and updates metadata files and unique experiment IDs (UUIDs). For more details, see Metadata and Related Experiments.

enable (Default: True)

Flag to enable/disable creating/updating metadata files and UUIDs. If set to False, the experiment name used for archival is either the control directory name or the configured experiment name.

model (Default: The configured model value)

Model name used when generating metadata for new experiments.



Specify the full path to a restart directory from which to start the run. This is known as a “warm start”. This option has no effect if there is an existing restart directory in archive, and so does not have to be removed for subsequent submissions.

debug (Default: False)

Enable the debugger for any mpirun jobs. Equivalent to mpirun --debug. At NCI this defaults to a Totalview session. This will probably only work for interactive sessions.


Override default MPI module and add MPI command line arguments.

runcmd (Default: mpirun)

Specify command to invoke MPI executables.


Set path for environment module to find and load MPI module.


Override default MPI module version. Default is determined dynamically by inspecting the model executables.


Set command line arguments (flags) 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
mpirun (Deprecated)

Replicates mpi flags above.


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 compute nodes.


Define the maximum number of runs per PBS job submit. The default is 1. The actual number of runs per PBS submit will be the minimum of runspersub and the total number of runs set with the -n command-line flag.


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


Specify lists of environment modules and/or directories to load/use at the start of the PBS job, for example:

      - /path/to/module/directory
      - netcdf-c-4.9.0
      - parallel-netcdf-1.12.3
      - xerces-c-3.2.3

This is seldom needed, because payu is good at automatically determining the environment modules required by model executables. If the modules require module use in order to be found, this command can also be run prior to payu run instead of listing the directory under the use option, e.g.:

module use /path/to/module/directory
payu run