source: java/ecj/cecj/fitness/CompetitiveFitnessSharing.java @ 90

package cecj.fitness;

import java.util.Arrays;
import java.util.List;

import cecj.interaction.InteractionResult;

import ec.EvolutionState;
import ec.Individual;
import ec.simple.SimpleFitness;

public class CompetitiveFitnessSharing implements FitnessAggregateMethod {

        private float[] fitnesses;

        public void prepareToAggregate(EvolutionState state, int subpop) {
                fitnesses = new float[state.population.subpops[subpop].individuals.length];
                Arrays.fill(fitnesses, 0.0f);
        }
        
        public void addToAggregate(EvolutionState state, int subpop,
                        List<List<InteractionResult>> results, int weight) {

                Individual[] inds = state.population.subpops[subpop].individuals;
                if (results.size() != inds.length) {
                        throw new IllegalArgumentException(
                                "Results list's size must be equal to subpopulation size.");
                }

                int numOpponents = results.get(0).size();
                float[] opponentSum = new float[numOpponents];
                for (int opponent = 0; opponent < numOpponents; opponent++) {
                        for (int ind = 0; ind < inds.length; ind++) {
                                opponentSum[opponent] += results.get(ind).get(opponent).getNumericValue();
                        }
                }

                for (int ind = 0; ind < inds.length; ind++) {
                        float indFitness = 0;
                        for (int opponent = 0; opponent < numOpponents; opponent++) {
                                if (opponentSum[opponent] == 0) {
                                        continue;
                                }
                                
                                indFitness += results.get(ind).get(opponent).getNumericValue()
                                                / opponentSum[opponent];
                        }

                        fitnesses[ind] += indFitness * weight;
                        ((SimpleFitness) (inds[ind].fitness)).setFitness(state, indFitness, false);
                }
        }
        
        public void assignFitness(EvolutionState state, int subpop) {
                Individual[] inds = state.population.subpops[subpop].individuals;
                for (int ind = 0; ind < inds.length; ind++) {
                        ((SimpleFitness) inds[ind].fitness).setFitness(state, fitnesses[ind], false);
                }
        }
}