torch.Tensor 的“data.max”是多少？

Question

I have been browsing the documentation of torch.Tensor, but I have not been able to find this (just similar things).

If a_tensor is a torch.Tensor , what is a_tensor.data.max ? What type, etc.?

In particular, I am reading a_tensor.data.max(1)[1] and a_tensor.data.max(1)[1][i].cpu().numpy() .

Answer 1

When accessing .data you are accessing the underlying data of the tensor. The returned object is a Torch.*Tensor as well, however, it won't be linked to any computational graph.

Take this example:

>>> x = torch.rand(4, requires_grad=True)
>>> y = x**2

>>> y
tensor([0.5272, 0.3162, 0.1374, 0.3004], grad_fn=<PowBackward0>)

While y.data is somewhat detached from graph (no grad_fn function), yet it is not a copy of y as y.detach() would return:

>>> y.data
tensor([0.5272, 0.3162, 0.1374, 0.3004]

Therefore, if you modify y.data 's components you end modifying y itself:

>>> y.data[0] = 1

>>> y
tensor([1.0000, 0.3162, 0.1374, 0.3004], grad_fn=<PowBackward0>)

Notice how the grad_fn didn't change there. If you had done y[0] = 1 , grad_fn would have been updated to <CopySlices> . This shows that modify your tensor's data through .data is not accounted for in terms of gradient, ie , you won't be able to backpropagate these operations. It is required to work with y - not y.data - when planning to use Autograd.

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So, to give an answer to your question: a_tensor.data is a torch.*Tensor , same type as a_tensor , and a_tensor.data.max is a function bound to that tensor.

Answer 2

a_Tensor.data is of type torch.Tensor as well.

You can find the details related to Tensor.max() fromhere .