Version: Next


Sometimes you want to run a parameter sweep. A parameter sweep is a method of evaluating a function (or a program) with a pre-determined set of parameters. The examples below will clarify what this means.

To run a parameter sweep, use the --multirun (-m) flag and pass a comma separated list for each dimension you want to sweep.

To run your program with the 3 different schemas in schema config group:

$ python -m schema=warehouse,support,school

Here is sweep over the db types (mysql,postgresql) and the schemas (warehouse,support,school). Output does not contain the configuration prints.

$ python schema=warehouse,support,school db=mysql,postgresql -m
[2019-10-01 14:44:16,254] - Launching 6 jobs locally
[2019-10-01 14:44:16,254] - Sweep output dir : multirun/2019-10-01/14-44-16
[2019-10-01 14:44:16,254] - #0 : schema=warehouse db=mysql
[2019-10-01 14:44:16,321] - #1 : schema=warehouse db=postgresql
[2019-10-01 14:44:16,390] - #2 : schema=support db=mysql
[2019-10-01 14:44:16,458] - #3 : schema=support db=postgresql
[2019-10-01 14:44:16,527] - #4 : schema=school db=mysql
[2019-10-01 14:44:16,602] - #5 : schema=school db=postgresql

Hydra supports other kind of sweeps, for example a range sweep: x=range(1,10) or a glob: support=glob(*).
See the Extended Override syntax for details.


The sweeping logic is implemented by a simple sweeper that is built into Hydra. Additional sweepers are available as plugins. For example, the Ax Sweeper can automatically find the best parameter combination!


A Launcher is what runs your job, Hydra comes with a simple launcher that runs the jobs locally and serially. However, other launchers are available as plugins. For example - The JobLib Launcher can execute the different parameter combinations in parallel on your local machine using multi-processing.

There are plans to add additional Launchers, such as a Launcher that launches your application code on AWS.

Last updated on by Rosario Scalise