src/test/java/org/apache/commons/math3/genetics/UniformCrossoverTest.java

/*
 * 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.
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package org.apache.commons.math3.genetics;

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

import org.junit.Assert;

import org.apache.commons.math3.exception.DimensionMismatchException;
import org.apache.commons.math3.exception.MathIllegalArgumentException;
import org.apache.commons.math3.exception.OutOfRangeException;
import org.junit.BeforeClass;
import org.junit.Test;

public class UniformCrossoverTest {
    private static final int LEN = 10000;
    private static final List<Integer> p1 = new ArrayList<Integer>(LEN);
    private static final List<Integer> p2 = new ArrayList<Integer>(LEN);

    @SuppressWarnings("boxing")
    @BeforeClass
    public static void setUpBeforeClass() {
        for (int i = 0; i < LEN; i++) {
            p1.add(0);
            p2.add(1);
        }
    }

    @Test(expected = OutOfRangeException.class)
    public void testRatioTooLow() {
        new UniformCrossover<Integer>(-0.5d);
    }

    @Test(expected = OutOfRangeException.class)
    public void testRatioTooHigh() {
        new UniformCrossover<Integer>(1.5d);
    }

    @Test
    public void testCrossover() {
        // test crossover with different ratios
        performCrossover(0.5);
        performCrossover(0.7);
        performCrossover(0.2);
    }

    private void performCrossover(double ratio) {
        final DummyBinaryChromosome p1c = new DummyBinaryChromosome(p1);
        final DummyBinaryChromosome p2c = new DummyBinaryChromosome(p2);

        final CrossoverPolicy cp = new UniformCrossover<Integer>(ratio);

        // make a number of rounds
        for (int i = 0; i < 20; i++) {
            final ChromosomePair pair = cp.crossover(p1c, p2c);

            final List<Integer> c1 = ((DummyBinaryChromosome) pair.getFirst()).getRepresentation();
            final List<Integer> c2 = ((DummyBinaryChromosome) pair.getSecond()).getRepresentation();

            int from1 = 0;
            int from2 = 0;

            // check first child
            for (int val : c1) {
                if (val == 0) {
                    from1++;
                } else {
                    from2++;
                }
            }

            Assert.assertEquals(1.0 - ratio, (double) from1 / LEN, 0.1);
            Assert.assertEquals(ratio, (double) from2 / LEN, 0.1);

            from1 = 0;
            from2 = 0;

            // check second child
            for (int val : c2) {
                if (val == 0) {
                    from1++;
                } else {
                    from2++;
                }
            }

            Assert.assertEquals(ratio, (double) from1 / LEN, 0.1);
            Assert.assertEquals(1.0 - ratio, (double) from2 / LEN, 0.1);
        }
    }

    @Test(expected = DimensionMismatchException.class)
    public void testCrossoverDimensionMismatchException(){
        @SuppressWarnings("boxing")
        final Integer[] p1 = new Integer[] {1,0,1,0,0,1,0,1,1};
        @SuppressWarnings("boxing")
        final Integer[] p2 = new Integer[] {0,1,1,0,1};

        final BinaryChromosome p1c = new DummyBinaryChromosome(p1);
        final BinaryChromosome p2c = new DummyBinaryChromosome(p2);

        final CrossoverPolicy cp = new UniformCrossover<Integer>(0.5d);
        cp.crossover(p1c, p2c);
    }

    @Test(expected = MathIllegalArgumentException.class)
    public void testCrossoverInvalidFixedLengthChromosomeFirst() {
        @SuppressWarnings("boxing")
        final Integer[] p1 = new Integer[] {1,0,1,0,0,1,0,1,1};
        final BinaryChromosome p1c = new DummyBinaryChromosome(p1);
        final Chromosome p2c = new Chromosome() {
            public double fitness() {
                // Not important
                return 0;
            }
        };

        final CrossoverPolicy cp = new UniformCrossover<Integer>(0.5d);
        cp.crossover(p1c, p2c);
    }

    @Test(expected = MathIllegalArgumentException.class)
    public void testCrossoverInvalidFixedLengthChromosomeSecond() {
        @SuppressWarnings("boxing")
        final Integer[] p1 = new Integer[] {1,0,1,0,0,1,0,1,1};
        final BinaryChromosome p2c = new DummyBinaryChromosome(p1);
        final Chromosome p1c = new Chromosome() {
            public double fitness() {
                // Not important
                return 0;
            }
        };

        final CrossoverPolicy cp = new UniformCrossover<Integer>(0.5d);
        cp.crossover(p1c, p2c);
    }
}