source: branches/2936_GQAPIntegration/HeuristicLab.Encodings.IntegerVectorEncoding/3.3/Crossovers/RoundedBlendAlphaCrossover.cs @ 16710

Last change on this file since 16710 was 16710, checked in by gkronber, 3 months ago

#2936: merged r15682 & r16117:16658 from trunk/HeuristicLab.Encodings.IntegerVectorEncoding to branch/HeuristicLab.Encodings.IntegerVectorEncoding

File size: 7.4 KB
Line 
1#region License Information
2/* HeuristicLab
3 * Copyright (C) 2002-2019 Heuristic and Evolutionary Algorithms Laboratory (HEAL)
4 *
5 * This file is part of HeuristicLab.
6 *
7 * HeuristicLab is free software: you can redistribute it and/or modify
8 * it under the terms of the GNU General Public License as published by
9 * the Free Software Foundation, either version 3 of the License, or
10 * (at your option) any later version.
11 *
12 * HeuristicLab is distributed in the hope that it will be useful,
13 * but WITHOUT ANY WARRANTY; without even the implied warranty of
14 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
15 * GNU General Public License for more details.
16 *
17 * You should have received a copy of the GNU General Public License
18 * along with HeuristicLab. If not, see <http://www.gnu.org/licenses/>.
19 */
20#endregion
21
22using System;
23using HeuristicLab.Common;
24using HeuristicLab.Core;
25using HeuristicLab.Data;
26using HeuristicLab.Parameters;
27using HEAL.Attic;
28
29namespace HeuristicLab.Encodings.IntegerVectorEncoding {
30  /// <summary>
31  /// Rounded blend alpha crossover for integer vectors (BLX-a). Creates a new offspring by selecting a random value
32  /// from the interval between the two alleles of the parent solutions and rounding the result to the next feasible
33  /// integer. The interval is increased in both directions by the factor alpha.
34  /// </summary>
35  [Item("RoundedBlendAlphaCrossover", "The rounded blend alpha crossover (BLX-a) for integer vectors creates new offspring by sampling a new value in the range [min_i - d * alpha, max_i + d * alpha) at each position i and rounding the result to the next feasible integer. Here min_i and max_i are the smaller and larger value of the two parents at position i and d is max_i - min_i.")]
36  [StorableType("F371B342-7D0C-4ED9-8F3F-A641E82DC8F1")]
37  public class RoundedBlendAlphaCrossover : BoundedIntegerVectorCrossover {
38    /// <summary>
39    /// The alpha parameter specifies how much the interval between the parents should be extended to the left and right.
40    /// The value of this parameter also determines the name of the operator: BLX-0.0 for example means alpha is set to 0.
41    /// When Alpha is 0, then the offspring will only be chosen in between the parents, the bigger alpha is the more it will be possible to choose
42    /// values left and right of the min and max value for each gene.
43    /// </summary>
44    public ValueLookupParameter<DoubleValue> AlphaParameter {
45      get { return (ValueLookupParameter<DoubleValue>)Parameters["Alpha"]; }
46    }
47
48    [StorableConstructor]
49    protected RoundedBlendAlphaCrossover(StorableConstructorFlag _) : base(_) { }
50    protected RoundedBlendAlphaCrossover(RoundedBlendAlphaCrossover original, Cloner cloner) : base(original, cloner) { }
51    /// <summary>
52    /// Initializes a new instance of <see cref="RoundedBlendAlphaCrossover"/> with one parameter (<c>Alpha</c>).
53    /// </summary>
54    public RoundedBlendAlphaCrossover()
55      : base() {
56      Parameters.Add(new ValueLookupParameter<DoubleValue>("Alpha", "The Alpha parameter controls the extension of the range beyond the two parents. It must be >= 0. A value of 0.5 means that half the range is added to both sides of the intervals.", new DoubleValue(0.5)));
57    }
58
59    public override IDeepCloneable Clone(Cloner cloner) {
60      return new RoundedBlendAlphaCrossover(this, cloner);
61    }
62
63    /// <summary>
64    /// Performs the rounded blend alpha crossover (BLX-a) of two integer vectors.<br/>
65    /// It creates new offspring by sampling a new value in the range [min_i - d * alpha, max_i + d * alpha) at each position i
66    /// and rounding the result to the next integer.
67    /// Here min_i and max_i are the smaller and larger value of the two parents at position i and d is max_i - min_i.
68    /// </summary>
69    /// <exception cref="ArgumentException">
70    /// Thrown when <paramref name="parent1"/> and <paramref name="parent2"/> are of different length or<br/>
71    /// when <paramref name="alpha"/> is less than 0.
72    /// </exception>
73    /// <param name="random">The random number generator.</param>
74    /// <param name="parent1">The first parent for the crossover operation.</param>
75    /// <param name="parent2">The second parent for the crossover operation.</param>
76    /// <param name="bounds">The bounds and step size for each dimension (will be cycled in case there are less rows than elements in the parent vectors).</param>
77    /// <param name="alpha">The alpha value for the crossover.</param>
78    /// <returns>The newly created integer vector resulting from the crossover operation.</returns>
79    public static IntegerVector Apply(IRandom random, IntegerVector parent1, IntegerVector parent2, IntMatrix bounds, DoubleValue alpha) {
80      if (parent1.Length != parent2.Length) throw new ArgumentException("RoundedBlendAlphaCrossover: The parents' vectors are of different length.", "parent1");
81      if (alpha.Value < 0) throw new ArgumentException("RoundedBlendAlphaCrossover: Paramter alpha must be greater or equal than 0.", "alpha");
82      if (bounds == null || bounds.Rows < 1 || bounds.Columns < 2) throw new ArgumentException("RoundedBlendAlphaCrossover: Invalid bounds specified.", "bounds");
83
84      int length = parent1.Length;
85      var result = new IntegerVector(length);
86      double max = 0, min = 0, d = 0, resMin = 0, resMax = 0;
87      int minBound, maxBound, step = 1;
88
89      for (int i = 0; i < length; i++) {
90        minBound = bounds[i % bounds.Rows, 0];
91        maxBound = bounds[i % bounds.Rows, 1];
92        if (bounds.Columns > 2) step = bounds[i % bounds.Rows, 2];
93        maxBound = FloorFeasible(minBound, maxBound, step, maxBound - 1);
94
95        max = Math.Max(parent1[i], parent2[i]);
96        min = Math.Min(parent1[i], parent2[i]);
97        d = Math.Abs(max - min);
98        resMin = FloorFeasible(minBound, maxBound, step, min - d * alpha.Value);
99        resMax = CeilingFeasible(minBound, maxBound, step, max + d * alpha.Value);
100
101        result[i] = RoundFeasible(minBound, maxBound, step, resMin + random.NextDouble() * Math.Abs(resMax - resMin));
102      }
103      return result;
104    }
105
106    /// <summary>
107    /// Checks that the number of parents is equal to 2 and forwards the call to <see cref="Apply(IRandom, RealVector, RealVector, DoubleValue)"/>.
108    /// </summary>
109    /// <exception cref="ArgumentException">Thrown when the number of parents is not equal to 2.</exception>
110    /// <exception cref="InvalidOperationException">Thrown when the parameter alpha could not be found.</exception>
111    /// <param name="random">The random number generator to use.</param>
112    /// <param name="parents">The collection of parents (must be of size 2).</param>
113    /// <param name="bounds">The bounds and step size for each dimension (will be cycled in case there are less rows than elements in the parent vectors).</param>
114    /// <returns>The integer vector resulting from the crossover operation.</returns>
115    protected override IntegerVector CrossBounded(IRandom random, ItemArray<IntegerVector> parents, IntMatrix bounds) {
116      if (parents.Length != 2) throw new ArgumentException("RoundedBlendAlphaCrossover: The number of parents is not equal to 2", "parents");
117      if (AlphaParameter.ActualValue == null) throw new InvalidOperationException("RoundedBlendAlphaCrossover: Parameter " + AlphaParameter.ActualName + " could not be found.");
118      return Apply(random, parents[0], parents[1], bounds, AlphaParameter.ActualValue);
119    }
120  }
121}
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