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source: stable/HeuristicLab.Encodings.SymbolicExpressionTreeEncoding/3.4/Manipulators/ReplaceBranchManipulation.cs @ 14186

Last change on this file since 14186 was 14186, checked in by swagner, 8 years ago

#2526: Updated year of copyrights in license headers

File size: 5.6 KB
Line 
1#region License Information
2/* HeuristicLab
3 * Copyright (C) 2002-2016 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.Collections.Generic;
23using System.Linq;
24using HeuristicLab.Common;
25using HeuristicLab.Core;
26using HeuristicLab.Data;
27using HeuristicLab.Parameters;
28using HeuristicLab.Persistence.Default.CompositeSerializers.Storable;
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#pragma warning disable 612, 618
81        parent = symbolicExpressionTree.Root.IterateNodesPrefix().Skip(1).Where(n => n.SubtreeCount > 0).SelectRandom(random);
82#pragma warning restore 612, 618
83
84        childIndex = random.Next(parent.SubtreeCount);
85        var child = parent.GetSubtree(childIndex);
86        maxLength = maxTreeLength - symbolicExpressionTree.Length + child.GetLength();
87        maxDepth = maxTreeDepth - symbolicExpressionTree.Depth + child.GetDepth();
88
89        allowedSymbols.Clear();
90        foreach (var symbol in parent.Grammar.GetAllowedChildSymbols(parent.Symbol, childIndex)) {
91          // check basic properties that the new symbol must have
92          if (symbol.Name != child.Symbol.Name &&
93            symbol.InitialFrequency > 0 &&
94            parent.Grammar.GetMinimumExpressionDepth(symbol) + 1 <= maxDepth &&
95            parent.Grammar.GetMinimumExpressionLength(symbol) <= maxLength) {
96            allowedSymbols.Add(symbol);
97          }
98        }
99        tries++;
100      } while (tries < MAX_TRIES && allowedSymbols.Count == 0);
101
102      if (tries < MAX_TRIES) {
103        var weights = allowedSymbols.Select(s => s.InitialFrequency).ToList();
104#pragma warning disable 612, 618
105        var seedSymbol = allowedSymbols.SelectRandom(weights, random);
106#pragma warning restore 612, 618
107
108        // replace the old node with the new node
109        var seedNode = seedSymbol.CreateTreeNode();
110        if (seedNode.HasLocalParameters)
111          seedNode.ResetLocalParameters(random);
112
113        parent.RemoveSubtree(childIndex);
114        parent.InsertSubtree(childIndex, seedNode);
115        ProbabilisticTreeCreator.PTC2(random, seedNode, maxLength, maxDepth);
116      }
117    }
118  }
119}
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