title: Genetic algorithm selection and crossover questions
body: <p>I have been using my own GA for a while where I use random selection and elitism (top 10% or so) to get 50% of my population. I then do crossover to produce the next 50%, followed by mutation of course. It sounds strange, but it has gotten me far enough in my problem to be satisfied with it for now.</p>
  
  <p>I'd like to start using more elaborate selection methods, specifically ranked selection. I'd also like to employ a crossover probability.</p>
  
  <p>My questions are:</p>
  
  <ol>
  <li>When doing ranked selection, is each individual only allowed to be selected once?</li>
  <li>What typically happens to the parents after crossover? Do they get replaced by children or do they also go onto the next generation?</li>
  </ol>