Why does my fitness functions give me just a Pareto Set of 7 when the population is 20?

Hi, I managed to get a Pareto set in every iteration of my genetic algorithm but for some reason it only gives me 7 out of 20 individuals in the Paretos set. Is it ok to give less or it could be something wrong with the fitness function?

Thank you beforehand

Answer 1

[Alan Weiss]

All that means is that of the 20 members of your population, only 7 were on the Pareto front. If you want more members on the front, use a larger population.

Alan Weiss

MATLAB mathematical toolbox documentation

[Luis Ignacio Ruiz]

Thank you for your quick answer, but why does it happen? Is it because the others aren´t good enough or is there another reason?

Thank you again

[Alan Weiss]

It means that the others were not on the Pareto front. If you don't understand how this can happen, read about how the genetic algorithm works to see that, as a population-based algorithm, not all members of a population are optimal, or even close to optimal.

Or maybe you are unsure about what a Pareto front is; if so, it is the set of noninferior solutions at the bottom of the linked page.

Alan Weiss

MATLAB mathematical toolbox documentation