what I understand about NSGA-II procedure from Deb's paper are:
But what I get from Deb's c code implementation and NSGA-II of JMetal framework are:
1. In Deb's c code implementation, selection process used by comparing two individuals dominance, crowding-distance, and random number [0,1] generation. For example: given individual i and j for parent selection. If both of them do not dominate each other, if i distance = j distance, then generate random number between 0 and 1. If the random number
First of all, I need to clear myself that I am not look at Deb's NSGAII C implementation. I am trying to answer your question from algorithmic point of view.
1. Why is it necessary to sort initial population? Because from initial population, the algorithm will produce offsprings. For that the algorithm require selection operator, and for selection, the only requirement is dominance comparison. Therefore, the initial population is required to evaluate not sorting.
2. In selection process, no crowding distance is used. Selection process only consideres constraint violation and dominance relation.
Cheers.
@Md. Shahriar Mahbub, Thanks for your answer.
1. In selection process, crowded-comparison operator (need non-domination rank and crowding distance value) is used, doesn't it? so crowding distance is used. What did you mean "dominance comparison", if it implemented in pseudocode? It is like:
A style:
if(p dominate q) then
select p
endif
if(q dominate p) then
select q
endif
or is like:
B style
if(p_rank < q_rank) then
select p
endif
if(q_rank < p_rank) then
select q
endif
Use A style or B style?
Then which one should be selected if p and q not dominate each other ("dominance comparison" = style A) or p rank = q rank ("dominance comparison" = style B)?
Hi,
The original version of binary tournament selection is similar to your style A. If p and q do not dominate each other and one can selected randomly.
One more thing, the original version of binary tournament do not use ranking or crowding distances.
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