can't optimize a non-leaf Tensor

[damiansmazurek]

Hi
Recently, when running your code on GPU I have error: can't optimize a non-leaf Tensor
Tested on local machine, GCP Compute engine with PyTorch and Cuda.

[mazzzystar]

Bug fixed, thanks for pointing out.
The problem is that we can not set requires_grad=True before .cuda() for PyTorch>0.4.0.
Details can be found in this commit