Fitness function

A fitness function is the objective function of an evolutionary algorithm (EA). Occasionally, a fitness function is also described as part of an objective function or the other way around. As evolutionary algorithms fitness functions have a biological model, biological fitness, indicating the degree of adaptation of an organism to its environment. In evolutionary algorithms describes the fitness of a candidate solution, how well he solves the optimization problem underlying.

A fitness function must not necessarily be able to calculate an absolute value, as it is often sufficient to compare candidates to select the better ones. A relative indication of fitness ( candidate a is better than b ) is sufficient in some cases, such as in tournament selection.

If a solution to several problems sought simultaneously ( multi-objective optimization ) and can not be summarized this, then the fitness function does not return a single value, but a tuple.