#region License Information
/* HeuristicLab
* Copyright (C) 2002-2010 Heuristic and Evolutionary Algorithms Laboratory (HEAL)
*
* This file is part of HeuristicLab.
*
* HeuristicLab is free software: you can redistribute it and/or modify
* it under the terms of the GNU General Public License as published by
* the Free Software Foundation, either version 3 of the License, or
* (at your option) any later version.
*
* HeuristicLab is distributed in the hope that it will be useful,
* but WITHOUT ANY WARRANTY; without even the implied warranty of
* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
* GNU General Public License for more details.
*
* You should have received a copy of the GNU General Public License
* along with HeuristicLab. If not, see .
*/
#endregion
using System;
using HeuristicLab.Core;
using HeuristicLab.Persistence.Default.CompositeSerializers.Storable;
using HeuristicLab.Common;
namespace HeuristicLab.Encodings.PermutationEncoding {
///
/// An operator which performs a variant of the cyclic crossover on two permutations.
///
/// It is implemented as described in Affenzeller, M. et al. 2009. Genetic Algorithms and Genetic Programming - Modern Concepts and Practical Applications. CRC Press. p. 136.
/// The operator first selects a random position in the permutation and from that position copies the first cycle to the offspring.
/// Then all empty positions are filled from the second parent.
///
[Item("CyclicCrossover2", "An operator which performs the cyclic crossover on two permutations. It is implemented as described in Affenzeller, M. et al. 2009. Genetic Algorithms and Genetic Programming - Modern Concepts and Practical Applications. CRC Press. p. 136.")]
[StorableClass]
public class CyclicCrossover2 : PermutationCrossover {
[StorableConstructor]
protected CyclicCrossover2(bool deserializing) : base(deserializing) { }
protected CyclicCrossover2(CyclicCrossover2 original, Cloner cloner) : base(original, cloner) { }
public CyclicCrossover2() : base() { }
public override IDeepCloneable Clone(Cloner cloner) {
return new CyclicCrossover2(this, cloner);
}
///
/// Performs a variant of the cyclic crossover on and .
///
/// Thrown when and are not of equal length.
/// Thrown if the numbers in the permutation elements are not in the range [0;N) with N = length of the permutation.
///
/// Start at a randomly chosen position x in parent1 and transfer it to the child at the same position.
/// Now this position x is no longer available for the node on position x in parent2, so
/// the value of the node at position x in parent2 is searched in parent1 and is then transferred
/// to the child preserving the position. Now this new position y is no longer available for the node in parent2 and so on.
/// This procedure is repeated until it is again at position x, then the cycle is over.
/// All further positions are copied from the second permutation.
///
/// Thrown if the two parents are not of equal length.
/// The random number generator.
/// The parent scope 1 to cross over.
/// The parent scope 2 to cross over.
/// The created cross over permutation as int array.
public static Permutation Apply(IRandom random, Permutation parent1, Permutation parent2) {
if (parent1.Length != parent2.Length) throw new ArgumentException("CyclicCrossover2: The parent permutations are of unequal length.");
int length = parent1.Length;
int[] result = new int[length];
bool[] indexCopied = new bool[length];
int j, number;
j = random.Next(length); // get number to start cycle
while (!indexCopied[j]) { // copy whole cycle to new permutation
result[j] = parent1[j];
number = parent2[j];
indexCopied[j] = true;
j = 0;
while ((j < length) && (parent1[j] != number)) { // search copied number in second permutation
j++;
}
}
for (int i = 0; i < length; i++) { // copy rest of secound permutation to new permutation
if (!indexCopied[i]) {
result[i] = parent2[i];
}
}
return new Permutation(parent1.PermutationType, result);
}
///
/// Checks number of parents and calls .
///
/// Thrown if there are not exactly two parents.
/// A random number generator.
/// An array containing the two permutations that should be crossed.
/// The newly created permutation, resulting from the crossover operation.
protected override Permutation Cross(IRandom random, ItemArray parents) {
if (parents.Length != 2) throw new InvalidOperationException("CyclicCrossover2: The number of parents is not equal to 2.");
return Apply(random, parents[0], parents[1]);
}
}
}