001    /*
002     * Copyright 2011 Christian Kumpe http://kumpe.de/christian/java
003     *
004     * Licensed under the Apache License, Version 2.0 (the "License");
005     * you may not use this file except in compliance with the License.
006     * You may obtain a copy of the License at
007     *
008     *     http://www.apache.org/licenses/LICENSE-2.0
009     *
010     * Unless required by applicable law or agreed to in writing, software
011     * distributed under the License is distributed on an "AS IS" BASIS,
012     * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
013     * See the License for the specific language governing permissions and
014     * limitations under the License.
015     */
016    package de.kumpe.hadooptimizer.examples.tutorial;
017    
018    import org.apache.commons.math.random.RandomGenerator;
019    
020    import de.kumpe.hadooptimizer.Mutator;
021    import de.kumpe.hadooptimizer.NeedsRandomGenerator;
022    
023    public class GaussianMutator implements Mutator<Double>, NeedsRandomGenerator {
024            private static final long serialVersionUID = 1L;
025    
026            private RandomGenerator randomGenerator;
027            private double variance;
028    
029            public GaussianMutator(final double variance) {
030                    this.variance = variance;
031            }
032    
033            @Override
034            public void setRandomGenerator(final RandomGenerator randomGenerator) {
035                    this.randomGenerator = randomGenerator;
036            }
037    
038            @Override
039            public Double mutate(final Double individual) {
040                    return individual + nextGaussian();
041            }
042    
043            private double nextGaussian() {
044                    return randomGenerator.nextGaussian() * Math.sqrt(variance);
045            }
046    }