RuntimeError: multiprocessing freeze_support

Symptom

When running a script that calls register() or other functions using scheduler="processes", you encounter:

RuntimeError:
    An attempt has been made to start a new process before the
    current process has finished its bootstrapping phase.
    ...
        if __name__ == '__main__':
            freeze_support()
            ...

Cause

On macOS and Windows, Python uses the spawn multiprocessing start method by default. When spawning worker processes, Python re-imports your script as __main__, which re-executes all top-level code — including the register() call itself — before the worker is ready.

Fix

Wrap all executable code in your script with the if __name__ == '__main__': guard:

from multiview_stitcher import registration, fusion

# Setup (safe at module level)
msims = [...]

if __name__ == '__main__':
    params = registration.register(msims, ...)
    fused = fusion.fuse(...)