source: java/ecj/cecj/sampling/RandomSamplingMethod.java @ 44

package cecj.sampling;

import java.util.ArrayList;
import java.util.List;

import ec.EvolutionState;
import ec.Individual;
import ec.util.Parameter;

/**
 * A random sampling method samples randomly with repetitions given individuals collection. It can
 * be used for so called "k-random opponents" evaluation scheme.
 * 
 * @author Marcin Szubert
 * 
 */
public class RandomSamplingMethod extends SamplingMethod {

        private static final String P_SAMPLE_SIZE = "sample-size";

        private int sampleSize;

        public void setup(EvolutionState state, Parameter base) {
                Parameter sampleSizeParameter = base.push(P_SAMPLE_SIZE);
                sampleSize = state.parameters.getIntWithDefault(sampleSizeParameter, null, 1);
        }

        @Override
        public List<Individual> sample(EvolutionState state, List<Individual> source) {
                List<Individual> result = new ArrayList<Individual>(sampleSize);
                if (!source.isEmpty()) {
                        for (int i = 0; i < sampleSize; i++) {
                                result.add(source.get(state.random[0].nextInt(source.size())));
                        }
                }

                return result;
        }
}