`Traceback (most recent call last):


 "/Users/nisml/anaconda3/envs/raytest/lib/python3.7/site-packages/redis/connection.py", line 427, in read_from_socket

bufflen = recv_into(self._sock, self._buffer)


 "/Users/nisml/anaconda3/envs/raytest/lib/python3.7/site-packages/redis/_compat.py", line 75, in recv_into

return sock.recv_into(*args, **kwargs)
ConnectionResetError: [Errno 54] Connection reset by peer

Traceback (most recent call last):


 "/home/ubuntu/gjx/mmdetection/tools/train.py", line 153, in <module>

main()


 "/home/ubuntu/gjx/mmdetection/tools/train.py", line 149, in main

meta=meta)


 "/home/ubuntu/gjx/mmdetection/mmdet/apis/train.py", line 128, in train_detector

runner.run(data_loaders, cfg.workflow, cfg.total_epochs)


 "/home/ubuntu/anaconda3/envs/mmdet21/lib/python3.7/site-packages/mmcv/runner/epoch_based_runner.py", line 122, in run

epoch_runner(data_loaders[i], **kwargs)


 "/home/ubuntu/anaconda3/envs/mmdet21/lib/python3.7/site-packages/mmcv/runner/epoch_based_runner.py", line 43, in train

self.call_hook('after_train_iter')


 "/home/ubuntu/anaconda3/envs/mmdet21/lib/python3.7/site-packages/mmcv/runner/base_runner.py", line 282, in call_hook

getattr(hook, fn_name)(self)


 "/home/ubuntu/anaconda3/envs/mmdet21/lib/python3.7/site-packages/mmcv/runner/hooks/optimizer.py", line 21, in after_train_iter

runner.outputs['loss'].backward()


 "/home/ubuntu/anaconda3/envs/mmdet21/lib/python3.7/site-packages/torch/tensor.py", line 195, in backward

torch.autograd.backward(self, gradient, retain_graph, create_graph)


 "/home/ubuntu/anaconda3/envs/mmdet21/lib/python3.7/site-packages/torch/autograd/__init__.py", line 99, in backward

allow_unreachable=True)
# allow_unreachable flag
RuntimeError: element 0 of tensors does not require grad and does not have a grad_fn
