Why does my process hang when using Hydra with W&B?

If your process hangs when started with Hydra, this is likely caused by a multiprocessing conflict between Hydra and W&B.

To fix this, change W&B’s multiprocessing protocol to "thread". You can do this in one of two ways:

Option 1: Pass a settings parameter to wandb.init():

wandb.init(settings=wandb.Settings(start_method="thread"))

Option 2: Set a global environment variable:

export WANDB_START_METHOD=thread

For more information, see the Hydra integration guide and Distributed training troubleshooting.

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Experiments Run Crashes