text: Title: cuda requirement
  Body: Is it possible to run this on a (recent) Mac, which does not support CUDA? I would have guessed setting --GPU 0 would not attempt to call CUDA, but it fails. 
  
  ```
  File "/Users/../Desktop/bopbtl/venv/lib/python3.7/site-packages/torch/cuda/__init__.py", line 61, in _check_driver
      raise AssertionError("Torch not compiled with CUDA enabled")
  AssertionError: Torch not compiled with CUDA enabled
  ```