Elitism in GA: Should I Let Selected Elites Become Parents?

Question

I am a little confused by the concept of elitism in the genetic algorithm (and other evolutionary algorithms). When I reserve and then copy 1 (or more) elite people to the next generation,

• Should I consider the elite decision in the parental selection of the current generation (creating a new population)?
• Or should I use others (distracting the elite) to create a new population and simply copy the elites directly to the next generation?

If the latter, what is elitism? Is it just to not lose the best solution? Because in this scheme it will not help convergence at all.

for example, here under the crossover / mutation part it is indicated that elites are not involved.

(Of course, the same question may be asked regarding the survivor’s choice.)

Answer 1

Elitism only means that the most suitable group of people is guaranteed a place in the next generation - usually without mutation. They should continue to be elected as parents, in addition to being nominated.

This article takes a somewhat strange approach to elitism. He suggests duplicating the most suitable person - this person receives two reserved slots in the next generation. One of these slots is mutated, the other is not. This means that in the next generation, at least one of these slots will return the general population as a parent, and possibly two if both are overtaken.

This seems like a viable approach. In any case, by choosing the elite as parents, simultaneously perpetuating them or copying the elites, and then mutating one, the elites must nevertheless be closely attached to the population as a whole so that they can share their useful genes.

@ Peladao's response and comments are also absolutely spontaneous - especially about the need to maintain diversity and avoid premature convergence, and elites should only represent a small fraction of the population.

Answer 2

I see no reason why the elites could not be used as parents, except perhaps for a small loss in diversity. (Therefore, the number of elites should be small compared to the population).

Since elites are the best people, they are valuable candidates for creating new people using a crossover if the elites themselves are also copied (unchanged) to the new population.

Maintaining sufficient diversity and avoiding premature convergence is always important, also when elites are not used as parents.

Answer 3

There are various methodologies used to implement elitism, as evidenced by other valid answers.
As a rule, for elitism, simply copy N individuals into a new generation without applying any changes. However, these people can be selected by suitability rating (true elitism), ensuring that records are truly “saved”, or they can be selected by proportional selection (as indicated in Mitchell T.’s book “Machine Science”). The latter is the same as in the choice of roulette, but note that in this case individuals are not used to create new offspring, but are directly copied in the new population (survivors!). When the choice of elitism is proportional, we get a good compromise between a lack of diversity and a premature excessive situation.

Applying real elitism and avoiding using the "elite" as parents will be counterproductive, especially given the reality of the crossover operation.

Answer 4

Briefly highlights about the use of the elite:

• The number of elites in the population should not exceed 10% of the total population to maintain diversity.
• From this it can be said that 5% can be a direct part of the next generation, and the rest should go through crossover and mutation with other non-elite groups of the population.