org.apache.mahout.ga.watchmaker.cd.CDCrossover.java Source code

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Here is the source code for org.apache.mahout.ga.watchmaker.cd.CDCrossover.java

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/**
 * Licensed to the Apache Software Foundation (ASF) under one or more
 * contributor license agreements.  See the NOTICE file distributed with
 * this work for additional information regarding copyright ownership.
 * The ASF licenses this file to You under the Apache License, Version 2.0
 * (the "License"); you may not use this file except in compliance with
 * the License.  You may obtain a copy of the License at
 *
 *     http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */

package org.apache.mahout.ga.watchmaker.cd;

import java.util.List;
import java.util.Random;

import com.google.common.base.Preconditions;
import com.google.common.collect.Lists;
import org.uncommons.maths.random.Probability;
import org.uncommons.watchmaker.framework.operators.AbstractCrossover;

/**
 * Crossover operator.
 */
public class CDCrossover extends AbstractCrossover<CDRule> {

    public CDCrossover(int crossoverPoints) {
        super(crossoverPoints);
    }

    public CDCrossover(int crossoverPoints, Probability crossoverProbability) {
        super(crossoverPoints, crossoverProbability);
    }

    @Override
    protected List<CDRule> mate(CDRule parent1, CDRule parent2, int numberOfCrossoverPoints, Random rng) {
        Preconditions.checkArgument(parent1.getNbConditions() == parent2.getNbConditions(),
                "Cannot perform cross-over with parents of different size.");
        CDRule offspring1 = new CDRule(parent1);
        CDRule offspring2 = new CDRule(parent2);
        // Apply as many cross-overs as required.
        for (int i = 0; i < numberOfCrossoverPoints; i++) {
            // Cross-over index is always greater than zero and less than
            // the length of the parent so that we always pick a point that
            // will result in a meaningful cross-over.
            int crossoverIndex = 1 + rng.nextInt(parent1.getNbConditions() - 1);
            for (int j = 0; j < crossoverIndex; j++) {
                swap(offspring1, offspring2, j);
            }
        }

        List<CDRule> result = Lists.newArrayListWithCapacity(2);
        result.add(offspring1);
        result.add(offspring2);
        return result;
    }

    static void swap(CDRule ind1, CDRule ind2, int index) {

        // swap W
        double dtemp = ind1.getW(index);
        ind1.setW(index, ind2.getW(index));
        ind2.setW(index, dtemp);

        // swap O
        boolean btemp = ind1.getO(index);
        ind1.setO(index, ind2.getO(index));
        ind2.setO(index, btemp);

        // swap V
        dtemp = ind1.getV(index);
        ind1.setV(index, ind2.getV(index));
        ind2.setV(index, dtemp);
    }
}