Free cookie consent management tool by TermsFeed Policy Generator

source: branches/DataAnalysis Refactoring/HeuristicLab.Encodings.SymbolicExpressionTreeEncoding/3.4/ArchitectureManipulators/ArgumentCreater.cs @ 5549

Last change on this file since 5549 was 5549, checked in by gkronber, 12 years ago

#1418 unified size/height vs. length/depth terminology and adapted unit tests for symbolic expression tree encoding version 3.4

File size: 11.8 KB
Line 
1#region License Information
2/* HeuristicLab
3 * Copyright (C) 2002-2011 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 HeuristicLab.Common;
26using HeuristicLab.Core;
27using HeuristicLab.Data;
28using HeuristicLab.Persistence.Default.CompositeSerializers.Storable;
29using HeuristicLab.Parameters;
30
31namespace HeuristicLab.Encodings.SymbolicExpressionTreeEncoding {
32  /// <summary>
33  /// Creates a new argument within one function-defining branch of a symbolic expression tree.
34  /// As described in Koza, Bennett, Andre, Keane, Genetic Programming III - Darwinian Invention and Problem Solving, 1999, pp. 106
35  /// </summary>
36  [Item("ArgumentCreater", "Manipulates a symbolic expression by creating a new argument within one function-defining branch. As described in Koza, Bennett, Andre, Keane, Genetic Programming III - Darwinian Invention and Problem Solving, 1999, pp. 106")]
37  [StorableClass]
38  public sealed class ArgumentCreater : SymbolicExpressionTreeArchitectureManipulator, ISymbolicExpressionTreeSizeConstraintOperator {
39    private const string MaximumSymbolicExpressionTreeLengthParameterName = "MaximumSymbolicExpressionTreeLength";
40    private const string MaximumSymbolicExpressionTreeDepthParameterName = "MaximumSymbolicExpressionTreeDepth";
41    #region Parameter Properties
42    public IValueLookupParameter<IntValue> MaximumSymbolicExpressionTreeLengthParameter {
43      get { return (IValueLookupParameter<IntValue>)Parameters[MaximumSymbolicExpressionTreeLengthParameterName]; }
44    }
45    public IValueLookupParameter<IntValue> MaximumSymbolicExpressionTreeDepthParameter {
46      get { return (IValueLookupParameter<IntValue>)Parameters[MaximumSymbolicExpressionTreeDepthParameterName]; }
47    }
48    #endregion
49    #region Properties
50    public IntValue MaximumSymbolicExpressionTreeLength {
51      get { return MaximumSymbolicExpressionTreeLengthParameter.ActualValue; }
52    }
53    public IntValue MaximumSymbolicExpressionTreeDepth {
54      get { return MaximumSymbolicExpressionTreeDepthParameter.ActualValue; }
55    }
56    #endregion
57    [StorableConstructor]
58    private ArgumentCreater(bool deserializing) : base(deserializing) { }
59    private ArgumentCreater(ArgumentCreater original, Cloner cloner) : base(original, cloner) { }
60    public ArgumentCreater()
61      : base() {
62      Parameters.Add(new ValueLookupParameter<IntValue>(MaximumSymbolicExpressionTreeLengthParameterName, "The maximal length (number of nodes) of the symbolic expression tree."));
63      Parameters.Add(new ValueLookupParameter<IntValue>(MaximumSymbolicExpressionTreeDepthParameterName, "The maximal depth of the symbolic expression tree (a tree with one node has depth = 0)."));
64    }
65
66    public override sealed void ModifyArchitecture(
67      IRandom random,
68      ISymbolicExpressionTree symbolicExpressionTree,
69      IntValue maxFunctionDefinitions, IntValue maxFunctionArguments) {
70      CreateNewArgument(random, symbolicExpressionTree, MaximumSymbolicExpressionTreeLength.Value, MaximumSymbolicExpressionTreeDepth.Value, maxFunctionDefinitions.Value, maxFunctionArguments.Value);
71    }
72
73    public override IDeepCloneable Clone(Cloner cloner) {
74      return new ArgumentCreater(this, cloner);
75    }
76
77    public static bool CreateNewArgument(
78      IRandom random,
79      ISymbolicExpressionTree symbolicExpressionTree,
80      int maxTreeLength, int maxTreeDepth,
81      int maxFunctionDefinitions, int maxFunctionArguments) {
82      // work on a copy in case we find out later that the tree would be too big
83      // in this case it's easiest to simply return the original tree.
84      ISymbolicExpressionTree clonedTree = (ISymbolicExpressionTree)symbolicExpressionTree.Clone();
85
86      var functionDefiningBranches = clonedTree.IterateNodesPrefix().OfType<DefunTreeNode>();
87      if (functionDefiningBranches.Count() == 0)
88        // no function defining branch found => abort
89        return false;
90
91      // select a random function defining branch
92      var selectedDefunBranch = functionDefiningBranches.SelectRandom(random);
93      var definedArguments = (from symbol in selectedDefunBranch.Grammar.Symbols.OfType<Argument>()
94                              select symbol.ArgumentIndex).Distinct();
95      if (definedArguments.Count() >= maxFunctionArguments)
96        // max number of arguments reached => abort
97        return false;
98
99      var allowedArgumentIndexes = Enumerable.Range(0, maxFunctionArguments);
100      var newArgumentIndex = allowedArgumentIndexes.Except(definedArguments).First();
101      ArgumentTreeNode newArgumentNode = MakeArgumentNode(newArgumentIndex);
102
103      // this operation potentially creates very big trees so the access to the length property might throw overflow exception
104      try {
105        if (CreateNewArgumentForDefun(random, clonedTree, selectedDefunBranch, newArgumentNode) && clonedTree.Length <= maxTreeLength && clonedTree.Depth <= maxTreeDepth) {
106
107          // size constraints are fulfilled
108          // replace root of original tree with root of manipulated tree
109          symbolicExpressionTree.Root = clonedTree.Root;
110          return true;
111        } else {
112          // keep originalTree
113          return false;
114        }
115      }
116      catch (OverflowException) {
117        // keep original tree
118        return false;
119      }
120    }
121
122    private static bool CreateNewArgumentForDefun(IRandom random, ISymbolicExpressionTree tree, DefunTreeNode defunBranch, ArgumentTreeNode newArgumentNode) {
123      // select a random cut point in the function defining branch
124      // the branch at the cut point is to be replaced by a new argument node
125      var cutPoints = (from node in defunBranch.IterateNodesPrefix()
126                       where node.SubTrees.Count() > 0
127                       from subtree in node.SubTrees
128                       select new { Parent = node, ReplacedChildIndex = node.IndexOfSubTree(subtree), ReplacedChild = subtree }).ToList();
129
130      if (cutPoints.Count() == 0)
131        // no cut point found => abort;
132        return false;
133      var selectedCutPoint = cutPoints[random.Next(cutPoints.Count)];
134      // replace the branch at the cut point with an argument node
135      var replacedBranch = selectedCutPoint.ReplacedChild;
136      selectedCutPoint.Parent.RemoveSubTree(selectedCutPoint.ReplacedChildIndex);
137      selectedCutPoint.Parent.InsertSubTree(selectedCutPoint.ReplacedChildIndex, newArgumentNode);
138
139      // find all old invocations of the selected ADF and attach a cloned version of the replaced branch (with all argument-nodes expanded)
140      // iterate in post-fix order to make sure that the subtrees of n are already adapted when n is processed
141      var invocationNodes = (from node in tree.IterateNodesPostfix().OfType<InvokeFunctionTreeNode>()
142                             where node.Symbol.FunctionName == defunBranch.FunctionName
143                             where node.SubTrees.Count() == defunBranch.NumberOfArguments
144                             select node).ToList();
145      // do this repeatedly until no matching invocations are found     
146      while (invocationNodes.Count > 0) {
147        List<ISymbolicExpressionTreeNode> newlyAddedBranches = new List<ISymbolicExpressionTreeNode>();
148        foreach (var invocationNode in invocationNodes) {
149          // check that the invocation node really has the correct number of arguments
150          if (invocationNode.SubTrees.Count() != defunBranch.NumberOfArguments) throw new InvalidOperationException();
151          // append a new argument branch after expanding all argument nodes
152          var clonedBranch = (ISymbolicExpressionTreeNode)replacedBranch.Clone();
153          clonedBranch = ReplaceArgumentsInBranch(clonedBranch, invocationNode.SubTrees);
154          invocationNode.InsertSubTree(newArgumentNode.Symbol.ArgumentIndex, clonedBranch);
155          newlyAddedBranches.Add(clonedBranch);
156        }
157        // iterate in post-fix order to make sure that the subtrees of n are already adapted when n is processed
158        invocationNodes = (from newlyAddedBranch in newlyAddedBranches
159                           from node in newlyAddedBranch.IterateNodesPostfix().OfType<InvokeFunctionTreeNode>()
160                           where node.Symbol.FunctionName == defunBranch.FunctionName
161                           where node.SubTrees.Count() == defunBranch.NumberOfArguments
162                           select node).ToList();
163      }
164      // increase expected number of arguments of function defining branch
165      // it's possible that the number of actually referenced arguments was reduced (all references were replaced by a single new argument)
166      // but the number of expected arguments is increased anyway
167      defunBranch.NumberOfArguments++;
168      defunBranch.Grammar.AddSymbol(newArgumentNode.Symbol);
169      defunBranch.Grammar.SetMinSubtreeCount(newArgumentNode.Symbol, 0);
170      defunBranch.Grammar.SetMaxSubtreeCount(newArgumentNode.Symbol, 0);
171      // allow the argument as child of any other symbol
172      foreach (var symb in defunBranch.Grammar.Symbols)
173        for (int i = 0; i < defunBranch.Grammar.GetMaxSubtreeCount(symb); i++) {
174          defunBranch.Grammar.SetAllowedChild(symb, newArgumentNode.Symbol, i);
175        }
176      foreach (var subtree in tree.Root.SubTrees) {
177        // when the changed function is known in the branch then update the number of arguments
178        var matchingSymbol = subtree.Grammar.Symbols.OfType<InvokeFunction>().Where(s => s.FunctionName == defunBranch.FunctionName).SingleOrDefault();
179        if (matchingSymbol != null) {
180          subtree.Grammar.SetMinSubtreeCount(matchingSymbol, defunBranch.NumberOfArguments);
181          subtree.Grammar.SetMaxSubtreeCount(matchingSymbol, defunBranch.NumberOfArguments);
182          foreach (var child in subtree.Grammar.GetAllowedSymbols(subtree.Symbol, 0)) {
183            for (int i = 0; i < subtree.Grammar.GetMaxSubtreeCount(matchingSymbol); i++) {
184              subtree.Grammar.SetAllowedChild(matchingSymbol, child, i);
185            }
186          }
187        }
188      }
189
190      return true;
191    }
192
193    private static ISymbolicExpressionTreeNode ReplaceArgumentsInBranch(ISymbolicExpressionTreeNode branch, IEnumerable<ISymbolicExpressionTreeNode> argumentTrees) {
194      ArgumentTreeNode argNode = branch as ArgumentTreeNode;
195      if (argNode != null) {
196        // replace argument nodes by a clone of the original subtree that provided the result for the argument node
197        return (SymbolicExpressionTreeNode)argumentTrees.ElementAt(argNode.Symbol.ArgumentIndex).Clone();
198      } else {
199        // call recursively for all subtree
200        List<ISymbolicExpressionTreeNode> subtrees = new List<ISymbolicExpressionTreeNode>(branch.SubTrees);
201        while (branch.SubTrees.Count() > 0) branch.RemoveSubTree(0);
202        foreach (var subtree in subtrees) {
203          branch.AddSubTree(ReplaceArgumentsInBranch(subtree, argumentTrees));
204        }
205        return branch;
206      }
207    }
208
209    private static ArgumentTreeNode MakeArgumentNode(int argIndex) {
210      var node = (ArgumentTreeNode)(new Argument(argIndex)).CreateTreeNode();
211      return node;
212    }
213  }
214}
Note: See TracBrowser for help on using the repository browser.