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source: branches/ALPS/HeuristicLab.Encodings.SymbolicExpressionTreeEncoding/3.4/Manipulators/ReplaceBranchManipulation.cs @ 12018

Last change on this file since 12018 was 12018, checked in by pfleck, 9 years ago

#2269

  • merged trunk after 3.3.11 release
  • updated copyright and plugin version in ALPS plugin
  • removed old ALPS samples based on an userdefined alg
File size: 5.5 KB
Line 
1#region License Information
2/* HeuristicLab
3 * Copyright (C) 2002-2015 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.Linq;
23using HeuristicLab.Common;
24using HeuristicLab.Core;
25using HeuristicLab.Data;
26using HeuristicLab.Parameters;
27using HeuristicLab.Persistence.Default.CompositeSerializers.Storable;
28using System.Collections.Generic;
29
30namespace HeuristicLab.Encodings.SymbolicExpressionTreeEncoding {
31  [StorableClass]
32  [Item("ReplaceBranchManipulation", "Selects a branch of the tree randomly and replaces it with a newly initialized branch (using PTC2).")]
33  public sealed class ReplaceBranchManipulation : SymbolicExpressionTreeManipulator, ISymbolicExpressionTreeSizeConstraintOperator {
34    private const int MAX_TRIES = 100;
35    private const string MaximumSymbolicExpressionTreeLengthParameterName = "MaximumSymbolicExpressionTreeLength";
36    private const string MaximumSymbolicExpressionTreeDepthParameterName = "MaximumSymbolicExpressionTreeDepth";
37    #region Parameter Properties
38    public IValueLookupParameter<IntValue> MaximumSymbolicExpressionTreeLengthParameter {
39      get { return (IValueLookupParameter<IntValue>)Parameters[MaximumSymbolicExpressionTreeLengthParameterName]; }
40    }
41    public IValueLookupParameter<IntValue> MaximumSymbolicExpressionTreeDepthParameter {
42      get { return (IValueLookupParameter<IntValue>)Parameters[MaximumSymbolicExpressionTreeDepthParameterName]; }
43    }
44    #endregion
45    #region Properties
46    public IntValue MaximumSymbolicExpressionTreeLength {
47      get { return MaximumSymbolicExpressionTreeLengthParameter.ActualValue; }
48    }
49    public IntValue MaximumSymbolicExpressionTreeDepth {
50      get { return MaximumSymbolicExpressionTreeDepthParameter.ActualValue; }
51    }
52    #endregion
53
54    [StorableConstructor]
55    private ReplaceBranchManipulation(bool deserializing) : base(deserializing) { }
56    private ReplaceBranchManipulation(ReplaceBranchManipulation original, Cloner cloner) : base(original, cloner) { }
57    public ReplaceBranchManipulation()
58      : base() {
59      Parameters.Add(new ValueLookupParameter<IntValue>(MaximumSymbolicExpressionTreeLengthParameterName, "The maximal length (number of nodes) of the symbolic expression tree."));
60      Parameters.Add(new ValueLookupParameter<IntValue>(MaximumSymbolicExpressionTreeDepthParameterName, "The maximal depth of the symbolic expression tree (a tree with one node has depth = 0)."));
61    }
62
63    public override IDeepCloneable Clone(Cloner cloner) {
64      return new ReplaceBranchManipulation(this, cloner);
65    }
66
67    protected override void Manipulate(IRandom random, ISymbolicExpressionTree symbolicExpressionTree) {
68      ReplaceRandomBranch(random, symbolicExpressionTree, MaximumSymbolicExpressionTreeLength.Value, MaximumSymbolicExpressionTreeDepth.Value);
69    }
70
71    public static void ReplaceRandomBranch(IRandom random, ISymbolicExpressionTree symbolicExpressionTree, int maxTreeLength, int maxTreeDepth) {
72      var allowedSymbols = new List<ISymbol>();
73      ISymbolicExpressionTreeNode parent;
74      int childIndex;
75      int maxLength;
76      int maxDepth;
77      // repeat until a fitting parent and child are found (MAX_TRIES times)
78      int tries = 0;
79      do {
80        parent = symbolicExpressionTree.Root.IterateNodesPrefix().Skip(1).Where(n => n.SubtreeCount > 0).SelectRandom(random);
81        childIndex = random.Next(parent.SubtreeCount);
82        var child = parent.GetSubtree(childIndex);
83        maxLength = maxTreeLength - symbolicExpressionTree.Length + child.GetLength();
84        maxDepth = maxTreeDepth - symbolicExpressionTree.Depth + child.GetDepth();
85
86        allowedSymbols.Clear();
87        foreach (var symbol in parent.Grammar.GetAllowedChildSymbols(parent.Symbol, childIndex)) {
88          // check basic properties that the new symbol must have
89          if (symbol.Name != child.Symbol.Name &&
90            symbol.InitialFrequency > 0 &&
91            parent.Grammar.GetMinimumExpressionDepth(symbol) + 1 <= maxDepth &&
92            parent.Grammar.GetMinimumExpressionLength(symbol) <= maxLength) {
93            allowedSymbols.Add(symbol);
94          }
95        }
96        tries++;
97      } while (tries < MAX_TRIES && allowedSymbols.Count == 0);
98
99      if (tries < MAX_TRIES) {
100        var weights = allowedSymbols.Select(s => s.InitialFrequency).ToList();
101        var seedSymbol = allowedSymbols.SelectRandom(weights, random);
102        // replace the old node with the new node
103        var seedNode = seedSymbol.CreateTreeNode();
104        if (seedNode.HasLocalParameters)
105          seedNode.ResetLocalParameters(random);
106
107        parent.RemoveSubtree(childIndex);
108        parent.InsertSubtree(childIndex, seedNode);
109        ProbabilisticTreeCreator.PTC2(random, seedNode, maxLength, maxDepth);
110      }
111    }
112  }
113}
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