#region License Information
/* HeuristicLab
* Copyright (C) 2002-2013 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.Common;
using HeuristicLab.Core;
using HeuristicLab.Data;
using HeuristicLab.Parameters;
using HeuristicLab.Persistence.Default.CompositeSerializers.Storable;
namespace HeuristicLab.Encodings.RealVectorEncoding {
///
/// The uniform all positions arithmetic crossover constructs an offspring by calculating x = alpha * p1 + (1-alpha) * p2 for every position x in the vector.
///
///
/// By setting alpha = 0.5 it is the same as the , but only on two parents.
/// It is implemented as described in Michalewicz, Z. 1999. Genetic Algorithms + Data Structures = Evolution Programs. Third, Revised and Extended Edition, Spring-Verlag Berlin Heidelberg.
///
[Item("UniformAllPositionsArithmeticCrossover", "The uniform all positions arithmetic crossover constructs an offspring by calculating x = alpha * p1 + (1-alpha) * p2 for every position x in the vector. Note that for alpha = 0.5 it is the same as the AverageCrossover (except that the AverageCrossover is defined for more than 2 parents). It is implemented as described in Michalewicz, Z. 1999. Genetic Algorithms + Data Structures = Evolution Programs. Third, Revised and Extended Edition, Spring-Verlag Berlin Heidelberg.")]
[StorableClass]
public class UniformAllPositionsArithmeticCrossover : RealVectorCrossover {
///
/// The alpha parameter needs to be in the interval [0;1] and specifies how close the resulting offspring should be either to parent1 (alpha -> 0) or parent2 (alpha -> 1).
///
public ValueLookupParameter AlphaParameter {
get { return (ValueLookupParameter)Parameters["Alpha"]; }
}
[StorableConstructor]
protected UniformAllPositionsArithmeticCrossover(bool deserializing) : base(deserializing) { }
protected UniformAllPositionsArithmeticCrossover(UniformAllPositionsArithmeticCrossover original, Cloner cloner) : base(original, cloner) { }
///
/// Initializes a new instance with one parameter (Alpha).
///
public UniformAllPositionsArithmeticCrossover()
: base() {
Parameters.Add(new ValueLookupParameter("Alpha", "The alpha value in the range [0;1]", new DoubleValue(0.33)));
}
public override IDeepCloneable Clone(Cloner cloner) {
return new UniformAllPositionsArithmeticCrossover(this, cloner);
}
///
/// Performs the arithmetic crossover on all positions by calculating x = alpha * p1 + (1 - alpha) * p2.
///
/// Thrown when the parent vectors are of different length or alpha is outside the range [0;1].
/// The random number generator.
/// The first parent vector.
/// The second parent vector.
/// The alpha parameter ().
/// The vector resulting from the crossover.
public static RealVector Apply(IRandom random, RealVector parent1, RealVector parent2, DoubleValue alpha) {
int length = parent1.Length;
if (length != parent2.Length) throw new ArgumentException("UniformAllPositionsArithmeticCrossover: The parent vectors are of different length.", "parent1");
if (alpha.Value < 0 || alpha.Value > 1) throw new ArgumentException("UniformAllPositionsArithmeticCrossover: Parameter alpha must be in the range [0;1]", "alpha");
RealVector result = new RealVector(length);
for (int i = 0; i < length; i++) {
result[i] = alpha.Value * parent1[i] + (1 - alpha.Value) * parent2[i];
}
return result;
}
///
/// Checks that there are exactly 2 parents, that the alpha parameter is not null and fowards the call to .
///
/// Thrown when there are not exactly two parents.
/// Thrown when the alpha parmeter could not be found.
/// The random number generator.
/// The collection of parents (must be of size 2).
/// The vector resulting from the crossover.
protected override RealVector Cross(IRandom random, ItemArray parents) {
if (parents.Length != 2) throw new ArgumentException("UniformAllPositionsArithmeticCrossover: There must be exactly two parents.", "parents");
if (AlphaParameter.ActualValue == null) throw new InvalidOperationException("UniformAllPositionsArithmeticCrossover: Parameter " + AlphaParameter.ActualName + " could not be found.");
return Apply(random, parents[0], parents[1], AlphaParameter.ActualValue);
}
}
}