RuntimeError: one of the variables needed for gradient computation has been modified by an inplace o

Bug: 
RuntimeError: one of the variables needed for gradient computation has been modified by an inplace operation: [torch.cuda.LongTensor [4, 512, 512]] is at version 1; expected version 0 instead. Hint: the backtrace further above shows the operation that failed to compute its gradient. The variable in question was changed in there or anywhere later. Good luck!

[W python_anomaly_mode.cpp:104] Warning: Error detected in NllLoss2DBackward0. Traceback of forward call that

RuntimeError: one of the variables needed for gradient computation has been modified by an inplace o最先出现在Python成神之路。