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Version: 1.0

Joblib Launcher plugin

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The Joblib Launcher plugin provides a launcher for parallel tasks based on Joblib.Parallel.


pip install hydra-joblib-launcher --upgrade


Once installed, add hydra/launcher=joblib to your command line. Alternatively, override hydra/launcher in your config:

- hydra/launcher: joblib

By default, process-based parallelism using all available CPU cores is used. By overriding the default configuration, it is e.g. possible limit the number of parallel executions.

The JobLibLauncherConf backing the config is defined here:

You can discover the Joblib Launcher parameters with:

$ python hydra/launcher=joblib --cfg hydra -p hydra.launcher
# @package hydra.launcher
_target_: hydra_plugins.hydra_joblib_launcher.joblib_launcher.JoblibLauncher
n_jobs: 10
backend: null
prefer: processes
require: null
verbose: 0
timeout: null
pre_dispatch: 2*n_jobs
batch_size: auto
temp_folder: null
max_nbytes: null
mmap_mode: r

See Joblib.Parallel documentation for full details about the parameters above.

An example application using this launcher is provided in the plugin repository.

Starting the app with python --multirun task=1,2,3,4,5 will launch five parallel executions:

$ python --multirun task=1,2,3,4,5
[HYDRA] Joblib.Parallel(n_jobs=-1,verbose=0,timeout=None,pre_dispatch=2*n_jobs,batch_size=auto,temp_folder=None,max_nbytes=None,mmap_mode=r,backend=loky) is launching 5 jobs
[HYDRA] Launching jobs, sweep output dir : multirun/2020-02-18/10-00-00
[__main__][INFO] - Process ID 14336 executing task 2 ...
[__main__][INFO] - Process ID 14333 executing task 1 ...
[__main__][INFO] - Process ID 14334 executing task 3 ...
[__main__][INFO] - Process ID 14335 executing task 4 ...
[__main__][INFO] - Process ID 14337 executing task 5 ...