/*
  Copyright 2006 by Sean Luke
  Licensed under the Academic Free License version 3.0
  See the file "LICENSE" for more information
*/


package ec.select;
import ec.util.*;
import ec.*;

/* 
 * FitProportionateSelection.java
 * 
 * Created: Thu Feb 10 16:31:24 2000
 * By: Sean Luke
 */

/**
 * Picks individuals in a population in direct proportion to their
 * fitnesses as returned by their fitness() methods.  This is expensive to
 * set up and bring down, so it's not appropriate for steady-state evolution.
 * If you're not familiar with the relative advantages of 
 * selection methods and just want a good one,
 * use TournamentSelection instead.   Not appropriate for
 * multiobjective fitnesses.
 *
 * 

 * Note: Fitnesses must be non-negative.  0 is assumed to be the worst fitness.
 * 

 
Typical Number of Individuals Produced Per produce(...) call

 Always 1.

 
Default Base

 select.fitness-proportionate

 *
 * @author Sean Luke
 * @version 1.0 
 */

public class FitProportionateSelection extends SelectionMethod
    {
    /** Default base */
    public static final String P_FITNESSPROPORTIONATE = "fitness-proportionate";
    /** Normalized, totalized fitnesses for the population */
    public double[] fitnesses;

    public Parameter defaultBase()
        {
        return SelectDefaults.base().push(P_FITNESSPROPORTIONATE);
        }

    // don't need clone etc. 

    public void prepareToProduce(final EvolutionState s,
        final int subpopulation,
        final int thread)
        {
        // load fitnesses
        fitnesses = new double[s.population.subpops[subpopulation].individuals.length];
        for(int x=0;x