Does W&B use the `multiprocessing` library?

Yes, W&B uses the multiprocessing library. As a result, scripts that call W&B directly need to guard their entry point so that child processes don’t re-run the top-level code. The following error message indicates this issue:

An attempt has been made to start a new process before the current process 
has finished its bootstrapping phase.

To resolve this error, add entry point protection with if __name__ == "__main__":. You need this protection when you run W&B directly from the script. It ensures that worker processes spawned by multiprocessing don’t re-run your training code.

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Experiments