praktikum-holons/src/algorithms/geneticAlgorithm/Components/Selections/TournamentSelectionStrategy.java

package algorithms.geneticAlgorithm.Components.Selections;

import java.util.ArrayList;
import java.util.Random;

import algorithms.geneticAlgorithm.Components.GAIndividual;
import algorithms.geneticAlgorithm.Components.GASelectionStrategy;

public class TournamentSelectionStrategy<I extends GAIndividual> implements GASelectionStrategy<I> {

	public class Range{
		
		public double min;
		public double max;
		public Range(double min, double max){
			this.min = min;
			this.max = max;
		}
	}
	
	private ArrayList<I> currentPop;
	public int tournamentSize;
	private Random rng; 
	private ArrayList<Range> tournamentWheel;
	public ArrayList<I> competitors;
	public double selectProb;
	private double maxRange;
	
	
	public TournamentSelectionStrategy(){
		currentPop = new ArrayList<I>();
		tournamentSize = 1;
		rng = new Random();
		selectProb = 1;
	}
	
	public TournamentSelectionStrategy(int tSize, double selectProb){
		currentPop = new ArrayList<I>();
		rng = new Random();
		tournamentSize = tSize;
		this.selectProb = selectProb;
	}
	
	@Override
	public void setCurrentPopulation(ArrayList<I> population) {
		currentPop = population;
	}
	
	public void setTournamentSize(int size){
		tournamentSize = size;
	}

	@Override
	public ArrayList<I> selectIndividuals() {
		ArrayList<I> parents = new ArrayList<I>();
		parents.add(selectSingleIndividual());
		parents.add(selectSingleIndividual());
		return parents;
	}
	
	public I selectSingleIndividual(){
		tournamentSelection();
		initWheel();
		double index = rng.nextDouble() * maxRange;
		for(int i = 0; i < tournamentWheel.size(); i++){
			if(index >= tournamentWheel.get(i).min && index <= tournamentWheel.get(i).max){
				return competitors.get(i);
			}
		}
		return competitors.get(rng.nextInt(competitors.size()));
	}
	
	public void tournamentSelection(){
		competitors = new ArrayList<I>();
		for(int i = 0; i < tournamentSize; i++){
			I candidate = chooseCandidate();
			int size = competitors.size();
			for(int j = 0; j <= size; j++){
				if(j != size){
					if(competitors.get(j).getFittness() < candidate.getFittness()){
						competitors.add(j, candidate);
						break;
					}
				}else{
					competitors.add(candidate);
				}
			}
		}		
	}
	
	public I chooseCandidate(){
		int index = rng.nextInt(currentPop.size());
		I candidate = currentPop.get(index);
		return candidate;
	}
	
	public void initWheel(){
		tournamentWheel = new ArrayList<Range>();
		int power = 0;
		maxRange = 0;
		for(int i = 0; i < tournamentSize; i++){
			double currentProb = selectProb * Math.pow((1- selectProb), power);
			Range range = new Range(maxRange, maxRange + currentProb);
			tournamentWheel.add(range);
			maxRange += currentProb;
			power++;
		}
	}

}