How to compute the derivative of the neural network?

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Filipe_ew - 2021-06-28T11:30:39+00:00
Question: How to compute the derivative of the neural network?

Hi, Once you have trained a neural network, is it possible to obtain a derivative of it? I have a neural network "net" in a structure. I would like to know if there is a routine that will provide the derivatives of net (derivative of its outputs with respect to its inputs).   It is probably not difficult, for a feedforward model, there is just matrix multiplications and sigmoid functions, but it would be nice to have a routine that will do that directly on "net".

Expert Answer

Profile picture of John Williams John Williams answered . 2025-11-20

Differentiate to obtain dyi/dxn
y = b2 + LW*h
h = tanh(b1+IW*x)
or, with tensor notation(i.e., summation over repeated indices),
yi = b2i + Lwij*hj
hj = tanh(b1j + IWjk*xk)
Now just use the chain rule.
Hope this helps.


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