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; 
    } 
 
 
}