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Hydra is an open-source Python framework that simplifies the development of research and other complex applications. The key feature is the ability to dynamically create a hierarchical configuration by composition and override it through config files and the command line.

You can continue to use Hydra for configuration management while taking advantage of the power of W&B.

Track metrics

Track your metrics as normal with wandb.init and wandb.log . Here, wandb.entity and wandb.project are defined within a hydra configuration file.

import wandb

@hydra.main(config_path="configs/", config_name="defaults")
def run_experiment(cfg):
run = wandb.init(entity=cfg.wandb.entity, project=cfg.wandb.project)
wandb.log({"loss": loss})

Track Hyperparameters

Hydra uses omegaconf as the default way to interface with configuration dictionaries. OmegaConf's dictionary are not a subclass of primitive dictionaries so directly passing Hydra's Config to wandb.config leads to unexpected results on the dashboard. It's necessary to convert omegaconf.DictConfig to the primitive dict type before passing to wandb.config.

@hydra.main(config_path="configs/", config_name="defaults")
def run_experiment(cfg):
wandb.config = omegaconf.OmegaConf.to_container(
cfg, resolve=True, throw_on_missing=True
wandb.init(entity=cfg.wandb.entity, project=cfg.wandb.project)
wandb.log({"loss": loss})
model = Model(**wandb.config.model.configs)

Troubleshooting Multiprocessing

If your process hangs when started, this may be caused by this known issue. To solve this, try to changing wandb's multiprocessing protocol either by adding an extra settings parameter to `wandb.init` as:


or by setting a global environment variable from your shell:

$ export WANDB_START_METHOD=thread

Optimize Hyperparameters

W&B Sweeps is a highly scalable hyperparameter search platform, which provides interesting insights and visualization about W&B experiments with minimal requirements code real-estate. Sweeps integrates seamlessly with Hydra projects with no-coding requirements. The only thing needed is a configuration file describing the various parameters to sweep over as normal.

A simple example sweep.yaml file would be:

method: bayes
goal: maximize
name: test/accuracy
values: [mnist, cifar10]

- ${env}
- python
- ${program}
- ${args_no_hyphens}

Invoke the sweep with:

wandb sweep sweep.yaml\ \ Once you call this, W&B automatically creates a sweep inside your project and returns a wandb agent command for you to run on each machine you want to run your sweep.

Passing parameters not present in Hydra defaults

Hydra supports passing extra parameters through the command line which aren't present in the default configuration file, by using a + before command. For example, you can pass an extra parameter with some value by simply calling:

$ python +experiment=some_experiment

You cannot sweep over such + configurations similar to what one does while configuring Hydra Experiments. To work around this, you can initialize the experiment parameter with a default empty file and use W&B Sweep to override those empty configs on each call. For more information, read this W&B Report.

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