Backward issue

[PengKunPROO]

Hi, I use my own dataset, and it has only two images, When the program iterated over 700 times, I occured this error! Could u know how to solve this? Thanks! //error info// Traceback (most recent call last): File "train.py", line 407, in trainer.train() File "train.py", line 206, in train output = self.train_step(i_iter, bar) File "train.py", line 118, in train_step loss.backward() File "/home/ubuntu/miniconda3/envs/3dgs_custom/lib/python3.8/site-packages/torch/_tensor.py", line 487, in backward torch.autograd.backward( File "/home/ubuntu/miniconda3/envs/3dgs_custom/lib/python3.8/site-packages/torch/autograd/init.py", line 200, in backward Variable._execution_engine.run_backward( # Calls into the C++ engine to run the backward pass RuntimeError: element 0 of tensors does not require grad and does not have a grad_fn