3.6.7章节运行train_ch3函数报错

[cdrj]

bug描述 num_epochs, lr = 5, 0.1 d2l.train_ch3(net, train_iter, test_iter, cross_entropy, num_epochs, batch_size, [W, b], lr)

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RuntimeError Traceback (most recent call last)

in 2 3 ----> 4 d2l.train_ch3(net, train_iter, test_iter, cross_entropy, num_epochs, batch_size, [W, b], lr) ~\动手深度学习\d2lzh_pytorch\utils.py in train_ch3(net, train_iter, test_iter, loss, num_epochs, batch_size, params, lr, optimizer) 132 param.grad.data.zero_() 133 --> 134 l.backward() 135 if optimizer is None: 136 sgd(params, lr, batch_size) C:\ProgramData\Anaconda3\envs\pytorch\lib\site-packages\torch\tensor.py in backward(self, gradient, retain_graph, create_graph) 193 products. Defaults to ``False``. 194 """ --> 195 torch.autograd.backward(self, gradient, retain_graph, create_graph) 196 197 def register_hook(self, hook): C:\ProgramData\Anaconda3\envs\pytorch\lib\site-packages\torch\autograd\__init__.py in backward(tensors, grad_tensors, retain_graph, create_graph, grad_variables) 97 Variable._execution_engine.run_backward( 98 tensors, grad_tensors, retain_graph, create_graph, ---> 99 allow_unreachable=True) # allow_unreachable flag 100 101 RuntimeError: element 0 of tensors does not require grad and does not have a grad_fn **版本信息** pytorch: torchvision:1.4.0 torchtext: ...