package ac.essex.ecj.fitness;

/**
 * @author Olly Oechsle, University of Essex, Date: 18-Aug-2006
 * @version 1.0
 */
public class FitnessCalculator {

    public static float ALPHA = 1;
    public static float BETA = 1;

    public static float getKozaFitness(int TP, int FP, int totalTruePixels) {

        // use our biased formula to calculate the fitness
        return  (ALPHA * (float) TP) / ((ALPHA * totalTruePixels) + (BETA * (float) FP));

    }


    public static float createKozaFitness(float fitness) {
        // dont allow fitness to be 0 - otherwise we get divide by 0 errors
        if (fitness < 0.00000000001f) fitness = 0.00000000001f;

        // invert fitness - Koza Fitness assumes low numbers to be the best
        // this way when we return 0, we know it is the absolute best and we
        // can stop now.
        return 1.0f / fitness;
    }


}