Hardtanh Activation

Hardtanh is an activation function used for neural networks:

$f\left(x\right) = -1 \text{ if } x < - 1$ $f\left(x\right) = x \text{ if } -1 \leq x \leq 1$ $f\left(x\right) = 1 \text{ if } x > 1$

It is a cheaper and more computationally efficient version of the tanh activation.

Image Source: Zhuan Lan