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source: branches/GrammaticalEvolution/HeuristicLab.Problems.GrammaticalEvolution/Mappers/BreathFirstMapper.cs @ 10410

Last change on this file since 10410 was 10328, checked in by sawinkle, 11 years ago

#2109:

  • Added method comments + refactoring.
  • Implemented RandomMapper.
  • Changed InitialTreeLength (genotype length) of Symbolic Regression problem from 25 to 30, equally to the Artificial Ant problem with also 30.
File size: 5.3 KB
Line 
1#region License Information
2/* HeuristicLab
3 * Copyright (C) 2002-2013 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 HeuristicLab.Common;
25using HeuristicLab.Core;
26using HeuristicLab.Data;
27using HeuristicLab.Encodings.IntegerVectorEncoding;
28using HeuristicLab.Encodings.SymbolicExpressionTreeEncoding;
29using HeuristicLab.Persistence.Default.CompositeSerializers.Storable;
30
31namespace HeuristicLab.Problems.GrammaticalEvolution {
32  /// <summary>
33  /// BreathFirstMapper
34  /// </summary>
35  [Item("BreathFirstMapper", "Resolves the non-terminal symbols of the resulting phenotypic syntax tree in a breath-first manner.")]
36  [StorableClass]
37  public class BreathFirstMapper : GenotypeToPhenotypeMapper {
38
39    [StorableConstructor]
40    protected BreathFirstMapper(bool deserializing) : base(deserializing) { }
41    protected BreathFirstMapper(BreathFirstMapper original, Cloner cloner) : base(original, cloner) { }
42    public BreathFirstMapper() : base() { }
43
44    public override IDeepCloneable Clone(Cloner cloner) {
45      return new BreathFirstMapper(this, cloner);
46    }
47
48
49    /// <summary>
50    /// Maps a genotype (an integer vector) to a phenotype (a symbolic expression tree).
51    /// Breath-first approach.
52    /// </summary>
53    /// <param name="random">random number generator</param>
54    /// <param name="bounds">only used for PIGEMapper (ignore here)</param>
55    /// <param name="length">only used for PIGEMapper (ignore here)</param>
56    /// <param name="grammar">grammar definition</param>
57    /// <param name="genotype">integer vector, which should be mapped to a tree</param>
58    /// <returns>phenotype (a symbolic expression tree)</returns>
59    public override SymbolicExpressionTree Map(IRandom random, IntMatrix bounds, int length,
60                                               ISymbolicExpressionGrammar grammar,
61                                               IntegerVector genotype) {
62
63      SymbolicExpressionTree tree = new SymbolicExpressionTree();
64      var rootNode = (SymbolicExpressionTreeTopLevelNode)grammar.ProgramRootSymbol.CreateTreeNode();
65      var startNode = (SymbolicExpressionTreeTopLevelNode)grammar.StartSymbol.CreateTreeNode();
66      rootNode.AddSubtree(startNode);
67      tree.Root = rootNode;
68
69      MapBreathFirstIteratively(startNode, genotype, grammar,
70                                genotype.Length, random);
71
72      return tree;
73    }
74
75    /// <summary>
76    /// Genotype-to-Phenotype mapper (iterative breath-first approach, by using a queue -> FIFO).
77    /// </summary>
78    /// <param name="startNode">first node of the tree with arity 1</param>
79    /// <param name="genotype">integer vector, which should be mapped to a tree</param>
80    /// <param name="grammar">grammar to determine the allowed child symbols for each node</param>
81    /// <param name="maxSubtreeCount">maximum allowed subtrees (= number of used genomes)</param>
82    /// <param name="random">random number generator</param>
83    private void MapBreathFirstIteratively(ISymbolicExpressionTreeNode startNode,
84                                          IntegerVector genotype,
85                                          ISymbolicExpressionGrammar grammar,
86                                          int maxSubtreeCount, IRandom random) {
87
88      Queue<Tuple<ISymbolicExpressionTreeNode, int>> queue
89        = new Queue<Tuple<ISymbolicExpressionTreeNode, int>>(); // tuples of <node, arity>
90
91      int genotypeIndex = 0;
92      queue.Enqueue(new Tuple<ISymbolicExpressionTreeNode, int>(startNode, 1));
93
94      while (queue.Count > 0) {
95
96        Tuple<ISymbolicExpressionTreeNode, int> current = queue.Dequeue();
97
98        // foreach subtree of the current node, create a new node and enqueue it, if it is no terminal node
99        for (int i = 0; i < current.Item2; ++i) {
100
101          if (genotypeIndex >= maxSubtreeCount) {
102            // if all genomes were used, only add terminal nodes to the remaining subtrees
103            current.Item1.AddSubtree(GetRandomTerminalNode(current.Item1, grammar, random));
104          } else {
105            var newNode = GetNewChildNode(current.Item1, genotype, grammar, genotypeIndex, random);
106            int arity = SampleArity(random, newNode, grammar);
107
108            current.Item1.AddSubtree(newNode);
109            genotypeIndex++;
110            if (arity > 0) {
111              // new node has subtrees so enqueue the node
112              queue.Enqueue(new Tuple<ISymbolicExpressionTreeNode, int>(newNode, arity));
113            }
114          }
115        }
116      }
117    }
118  }
119}
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