Generalized Mean Pooling

Generalized Mean Pooling (GeM) computes the generalized mean of each channel in a tensor. Formally:

$\textbf{e} = \left[\left(\frac{1}{|\Omega|}\sum\_{u\in{\Omega}}x^{p}\_{cu}\right)^{\frac{1}{p}}\right]\_{c=1,\cdots,C}$

where $p > 0$ is a parameter. Setting this exponent as $p > 1$ increases the contrast of the pooled feature map and focuses on the salient features of the image. GeM is a generalization of the average pooling commonly used in classification networks ($p = 1$) and of spatial max-pooling layer ($p = \infty$).

Source: MultiGrain

Image Source: Eva Mohedano