
is possible to use different cases in different generations, the same fitness
cases are usually used across all generations. Fitness can be calculated in a
number of ways. Koza (1992) defines four fitness metrics: raw, standard-
ized, adjusted, and normalized fitnesses.
Steps 3 and 4 of the GP process are often carried out in parallel. A
probability is assigned to reproduction, and another to crossover, so that
the two sum to 1. If, for example, the probability of reproduction is 10
percent (a typical value in Koza’s problems), then the probability of
crossover is 90 percent. This means that once fitness calculations have
been made, and it is time to build ...