Minimum local

Définition

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Français

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Anglais

local minimum

The function

φ(x) = 1/(1 + exp(–x))

which, when graphed, looks rather like a smoothed version of the step function

step(x) = 0 if x < 0, = 1 if x ≥ 0

It is used to transform the total net input of an artificial neuron in some implementations of backprop-trained networks.

A related function, also sometimes used in backprop-trained networks, is 2φ(x)–1, which can also be expressed as tanh(x/2). tanh(x/2) is, of course, a smoothed version of the step function which jumps from –1 to 1 at x = 0, i.e. the function which = –1 if x < 0, and = 1 if x ≥ 0.

Source : UNWS machine learning dictionary ]