[Pytorch/Pytorch Lightning] RuntimeError: element 0 of tensors does not require grad and does not have a grad_fn

환경: CentOS Linux release 7.9.2009

 

▶ 에러 메세지

File "~/anaconda3/envs/venv/lib/python3.8/site-packages/pytorch_lightning/core/module.py", line 1419, in backward
loss.backward(*args, **kwargs)

File "~/anaconda3/envs/venv/lib/python3.8/site-packages/torch/_tensor.py", line 363, in backward
torch.autograd.backward(self, gradient, retain_graph, create_graph, inputs=inputs)

 

▶ 문제 원인

loss가 requires_grad = True 설정이 안 되어 있어서 발생

 

▶ 해결 방법

loss.requires_grad_(True)