source: trunk/sources/HeuristicLab.GP/Recombination/SizeConstrictedGPCrossoverBase.cs @ 1197

Last change on this file since 1197 was 1197, checked in by gkronber, 13 years ago

merged fix for #479 (Crossover operators create trees that are larger than the allowed max size) (r1196) to trunk

File size: 3.2 KB
Line 
1#region License Information
2/* HeuristicLab
3 * Copyright (C) 2002-2008 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 System.Collections.Generic;
24using System.Linq;
25using System.Text;
26using HeuristicLab.Core;
27using HeuristicLab.Operators;
28using HeuristicLab.Random;
29using HeuristicLab.Data;
30using HeuristicLab.Constraints;
31using System.Diagnostics;
32
33namespace HeuristicLab.GP {
34  public abstract class SizeConstrictedGPCrossoverBase : GPCrossoverBase {
35
36    private int MaxRecombinationTries { get { return 20; } }
37
38    public SizeConstrictedGPCrossoverBase()
39      : base() {
40      AddVariableInfo(new VariableInfo("MaxTreeHeight", "The maximal allowed height of the tree", typeof(IntData), VariableKind.In));
41      AddVariableInfo(new VariableInfo("MaxTreeSize", "The maximal allowed size (number of nodes) of the tree", typeof(IntData), VariableKind.In));
42    }
43
44    internal override IFunctionTree Cross(IScope scope, TreeGardener gardener, MersenneTwister random, IFunctionTree tree0, IFunctionTree tree1) {
45      int maxTreeHeight = GetVariableValue<IntData>("MaxTreeHeight", scope, true).Data;
46      int maxTreeSize = GetVariableValue<IntData>("MaxTreeSize", scope, true).Data;
47
48      // when tree0 is terminal then try to cross into tree1, when tree1 is also terminal just return tree0 unchanged.
49      IFunctionTree newTree;
50      int tries = 0;
51      do {
52        if (tree0.SubTrees.Count > 0) {
53          newTree = Cross(gardener, random, (IFunctionTree)tree0.Clone(), (IFunctionTree)tree1.Clone(), maxTreeSize, maxTreeHeight);
54        } else if (tree1.SubTrees.Count > 0) {
55          newTree = Cross(gardener, random, (IFunctionTree)tree1.Clone(), (IFunctionTree)tree0.Clone(), maxTreeSize, maxTreeHeight);
56        } else newTree = tree0;
57        if (tries++ > MaxRecombinationTries)
58          throw new InvalidOperationException("Couldn't recombine parents to create a valid child not larger than " + maxTreeSize + " and not higher than " + maxTreeHeight + ".");
59      } while (newTree.Size > maxTreeSize || newTree.Height > maxTreeHeight);
60      return newTree;
61    }
62
63    internal abstract IFunctionTree Cross(TreeGardener gardener, MersenneTwister random, IFunctionTree tree0, IFunctionTree tree1, int maxTreeSize, int maxTreeHeight);
64
65    private IFunctionTree TakeNextParent(IScope scope) {
66      IFunctionTree parent = GetVariableValue<IFunctionTree>("FunctionTree", scope.SubScopes[0], false);
67      scope.RemoveSubScope(scope.SubScopes[0]);
68      return parent;
69    }
70  }
71}
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