yes i know these things.
i confused in mathematical calucation:
assume we have:
x = torch.tensor([2. , 3. , 5.], requires_grad= True)
y_1 = x.pow(2)
y_2 = x.pow(2).sum()
then:
y_1 = tensor([ 4.,  9., 25.], grad_fn=)
y_2 = tensor(38., grad_fn=)
we know Derivation of x^2 is equal to 2x and gradient of y_1 is be 2x
why we put sum  end of it(y_1==>y_2)??