evokit.tools.diversity package

Module contents

Toolset for diversity maintenance.

evokit.tools.diversity.share_fitness(pop: Population, sigma_share: float, alpha: float, distance_measure: Callable[[Individual, Individual], float]) → None[source]

Perform fitness sharing [1] by adjusting (in-place) the Individual.fitness of each individual in a population.

The fitness is updated according to the following expression:

$x_i\mathrm{.fitness} \leftarrow \frac{x_i\mathrm{.fitness}}{\sum^{|\mathcal{P}|}_{j} {\mathrm{sh}\,(d(x_i,x_j))}}$

where

$\mathrm{sh}\,(k) = \left\{ \begin{array}{ll} 1 - (k / \sigma_{\mathrm{share}})^{\alpha} & \mathrm{if}~k \le \sigma_{\mathrm{share}} \\ 0 & \mathrm{otherwise.} \end{array} \right.$