The problem disappears when I run the code on Linux.  It fails in the above fashion on Windows 10.  I’ll take a look through

  
      
      github.com
  
  
    

pytorch/pytorch

s

  Tensors and Dynamic neural networks in Python with strong GPU acceleration

  
  
    
    
  
  


I’m guessing that PyTorch Windows support is, uh, less enthusiastic than Linux.