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    * Licensed to the Apache Software Foundation (ASF) under one or more
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    * 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.math4.legacy.genetics;
  
  import java.util.List;
  
  import org.apache.commons.math4.legacy.exception.DimensionMismatchException;
  import org.apache.commons.math4.legacy.exception.MathIllegalArgumentException;
  import org.apache.commons.math4.legacy.exception.NumberIsTooLargeException;
  import org.junit.Assert;
  import org.junit.Test;
  
  public class NPointCrossoverTest {
  
      @Test(expected = DimensionMismatchException.class)
      public void testCrossoverDimensionMismatchException() {
          final Integer[] p1 = new Integer[] {1,0,1,0,0,1,0,1,1};
          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 NPointCrossover<>(1);
          cp.crossover(p1c,p2c);
      }
  
      @Test(expected = NumberIsTooLargeException.class)
      public void testNumberIsTooLargeException() {
          final Integer[] p1 = new Integer[] {1,0,1,0,0,1,0,1,1};
          final Integer[] p2 = new Integer[] {0,1,1,0,1,0,1,1,1};
  
          final BinaryChromosome p1c = new DummyBinaryChromosome(p1);
          final BinaryChromosome p2c = new DummyBinaryChromosome(p2);
  
          final CrossoverPolicy cp = new NPointCrossover<>(15);
          cp.crossover(p1c,p2c);
      }
  
      @Test(expected = MathIllegalArgumentException.class)
      public void testCrossoverInvalidFixedLengthChromosomeFirst() {
          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() {
              @Override
              public double fitness() {
                  // Not important
                  return 0;
              }
          };
  
          final CrossoverPolicy cp = new NPointCrossover<>(1);
          cp.crossover(p1c,p2c);
      }
  
      @Test(expected = MathIllegalArgumentException.class)
      public void testCrossoverInvalidFixedLengthChromosomeSecond() {
          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() {
              @Override
              public double fitness() {
                  // Not important
                  return 0;
              }
          };
  
          final CrossoverPolicy cp = new NPointCrossover<>(1);
          cp.crossover(p1c,p2c);
      }
  
      @Test
      public void testCrossover() {
          Integer[] p1 = new Integer[] {1,0,1,0,1,0,1,0,1};
          Integer[] p2 = new Integer[] {0,1,0,1,0,1,0,1,0};
  
          BinaryChromosome p1c = new DummyBinaryChromosome(p1);
          BinaryChromosome p2c = new DummyBinaryChromosome(p2);
  
          final int order = 3;
          NPointCrossover<Integer> npc = new NPointCrossover<>(order);
  
          // the two parent chromosomes are different at each position, so it is easy to detect
          // the number of crossovers that happened for each child
          for (int i=0; i<20; i++) {
              ChromosomePair pair = npc.crossover(p1c,p2c);
 
             Integer[] c1 = new Integer[p1.length];
             Integer[] c2 = new Integer[p2.length];
 
             c1 = ((BinaryChromosome) pair.getFirst()).getRepresentation().toArray(c1);
             c2 = ((BinaryChromosome) pair.getSecond()).getRepresentation().toArray(c2);
 
             Assert.assertEquals(order, detectCrossoverPoints(p1c, p2c, (BinaryChromosome) pair.getFirst()));
             Assert.assertEquals(order, detectCrossoverPoints(p2c, p1c, (BinaryChromosome) pair.getSecond()));
         }
     }
 
     private int detectCrossoverPoints(BinaryChromosome p1, BinaryChromosome p2, BinaryChromosome c) {
         int crossovers = 0;
         final int length = p1.getLength();
 
         final List<Integer> p1Rep = p1.getRepresentation();
         final List<Integer> p2Rep = p2.getRepresentation();
         final List<Integer> cRep = c.getRepresentation();
 
         List<Integer> rep = p1Rep;
         for (int i = 0; i < length; i++) {
             if (rep.get(i) != cRep.get(i)) {
                 crossovers++;
                 rep = rep == p1Rep ? p2Rep : p1Rep;
             }
         }
 
         return crossovers;
     }
 }