torch.Tensor.is_leaf

Tensor.is_leaf

所有具有 requires_grad 且為 False 的 Tensor，依照慣例將會是葉 Tensor。

對於具有 requires_grad 且為 True 的 Tensor，如果它們是由使用者建立的，則它們將會是葉 Tensor。 這表示它們不是運算的結果，因此 grad_fn 為 None。

只有葉 Tensor 會在呼叫 backward() 期間填入其 grad。 若要為非葉 Tensor 填入 grad，您可以使用 retain_grad()。

範例

>>> a = torch.rand(10, requires_grad=True)
>>> a.is_leaf
True
>>> b = torch.rand(10, requires_grad=True).cuda()
>>> b.is_leaf
False
# b was created by the operation that cast a cpu Tensor into a cuda Tensor
>>> c = torch.rand(10, requires_grad=True) + 2
>>> c.is_leaf
False
# c was created by the addition operation
>>> d = torch.rand(10).cuda()
>>> d.is_leaf
True
# d does not require gradients and so has no operation creating it (that is tracked by the autograd engine)
>>> e = torch.rand(10).cuda().requires_grad_()
>>> e.is_leaf
True
# e requires gradients and has no operations creating it
>>> f = torch.rand(10, requires_grad=True, device="cuda")
>>> f.is_leaf
True
# f requires grad, has no operation creating it