S is a sigmoidal function,
A_i is a matrix, and
x is an input vector, and
S is applied element-wise to its matrix argument, a specific type of artificial neural network can be described as
S(A_2 (S(A_1 (S(A_0 x)))))
Out for an arbitrary number of
A terms. The
A matrices are not necessarily square, but of course their dimensions match up so the output of one matrix vector multiplication and be the input of the next.
Sometimes, it is desirable to know which input vector maximizes a specific element of the output vector. How can I find an
x which approximately maximizes a particular element in the output vector?