1 | #region License Information
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2 | /* HeuristicLab
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3 | * Copyright (C) 2002-2015 Heuristic and Evolutionary Algorithms Laboratory (HEAL)
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4 | *
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5 | * This file is part of HeuristicLab.
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6 | *
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7 | * HeuristicLab is free software: you can redistribute it and/or modify
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8 | * it under the terms of the GNU General Public License as published by
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9 | * the Free Software Foundation, either version 3 of the License, or
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10 | * (at your option) any later version.
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11 | *
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12 | * HeuristicLab is distributed in the hope that it will be useful,
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13 | * but WITHOUT ANY WARRANTY; without even the implied warranty of
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14 | * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
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15 | * GNU General Public License for more details.
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16 | *
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17 | * You should have received a copy of the GNU General Public License
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18 | * along with HeuristicLab. If not, see <http://www.gnu.org/licenses/>.
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19 | */
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20 | #endregion
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21 |
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22 | using System.Linq;
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23 | using HeuristicLab.Common;
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24 | using HeuristicLab.Core;
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25 | using HeuristicLab.Data;
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26 | using HeuristicLab.Persistence.Default.CompositeSerializers.Storable;
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27 | using HeuristicLab.Random;
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28 |
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29 | namespace HeuristicLab.Encodings.SymbolicExpressionTreeEncoding {
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30 | /// <summary>
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31 | /// As described in Koza, Bennett, Andre, Keane, Genetic Programming III - Darwinian Invention and Problem Solving, 1999, pp. 112
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32 | /// </summary>
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33 | [Item("ArgumentDeleter", "Manipulates a symbolic expression by deleting an argument from an existing function defining branch. As described in Koza, Bennett, Andre, Keane, Genetic Programming III - Darwinian Invention and Problem Solving, 1999, pp. 112")]
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34 | [StorableType("8B477E92-C6E9-4E7F-B5FC-6214C3585150")]
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35 | public sealed class ArgumentDeleter : SymbolicExpressionTreeArchitectureManipulator {
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36 | [StorableConstructor]
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37 | private ArgumentDeleter(bool deserializing) : base(deserializing) { }
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38 | private ArgumentDeleter(ArgumentDeleter original, Cloner cloner) : base(original, cloner) { }
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39 | public ArgumentDeleter() : base() { }
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40 |
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41 | public override sealed void ModifyArchitecture(
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42 | IRandom random,
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43 | ISymbolicExpressionTree symbolicExpressionTree,
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44 | IntValue maxFunctionDefinitions, IntValue maxFunctionArguments) {
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45 | DeleteArgument(random, symbolicExpressionTree, maxFunctionDefinitions.Value, maxFunctionArguments.Value);
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46 | }
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47 |
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48 | public override IDeepCloneable Clone(Cloner cloner) {
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49 | return new ArgumentDeleter(this, cloner);
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50 | }
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51 |
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52 | public static bool DeleteArgument(
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53 | IRandom random,
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54 | ISymbolicExpressionTree symbolicExpressionTree,
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55 | int maxFunctionDefinitions, int maxFunctionArguments) {
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56 |
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57 | var functionDefiningBranches = symbolicExpressionTree.IterateNodesPrefix().OfType<DefunTreeNode>().ToList();
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58 | if (!functionDefiningBranches.Any())
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59 | // no function defining branch => abort
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60 | return false;
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61 |
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62 | var selectedDefunBranch = functionDefiningBranches.SampleRandom(random);
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63 | if (selectedDefunBranch.NumberOfArguments <= 1)
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64 | // argument deletion by consolidation is not possible => abort
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65 | return false;
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66 | // the argument to be removed is always the one with the largest index
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67 | // (otherwise we would have to decrement the index of the larger argument symbols)
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68 | var removedArgument = (from sym in selectedDefunBranch.Grammar.Symbols.OfType<Argument>()
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69 | select sym.ArgumentIndex).Distinct().OrderBy(x => x).Last();
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70 | // find invocations of the manipulated funcion and remove the specified argument tree
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71 | var invocationNodes = (from node in symbolicExpressionTree.IterateNodesPrefix().OfType<InvokeFunctionTreeNode>()
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72 | where node.Symbol.FunctionName == selectedDefunBranch.FunctionName
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73 | select node).ToList();
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74 | foreach (var invokeNode in invocationNodes) {
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75 | invokeNode.RemoveSubtree(removedArgument);
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76 | }
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77 |
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78 | DeleteArgumentByConsolidation(random, selectedDefunBranch, removedArgument);
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79 |
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80 | // delete the dynamic argument symbol that matches the argument to be removed
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81 | var matchingSymbol = selectedDefunBranch.Grammar.Symbols.OfType<Argument>().Single(s => s.ArgumentIndex == removedArgument);
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82 | selectedDefunBranch.Grammar.RemoveSymbol(matchingSymbol);
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83 | selectedDefunBranch.NumberOfArguments--;
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84 | // reduce arity in known functions of all root branches
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85 | foreach (var subtree in symbolicExpressionTree.Root.Subtrees) {
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86 | var matchingInvokeSymbol = subtree.Grammar.Symbols.OfType<InvokeFunction>().SingleOrDefault(s => s.FunctionName == selectedDefunBranch.FunctionName);
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87 | if (matchingInvokeSymbol != null) {
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88 | subtree.Grammar.SetSubtreeCount(matchingInvokeSymbol, selectedDefunBranch.NumberOfArguments, selectedDefunBranch.NumberOfArguments);
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89 | }
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90 | }
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91 | return true;
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92 | }
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93 |
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94 | private static void DeleteArgumentByConsolidation(IRandom random, DefunTreeNode branch, int removedArgumentIndex) {
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95 | // replace references to the deleted argument with random references to existing arguments
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96 | var possibleArgumentSymbols = (from sym in branch.Grammar.Symbols.OfType<Argument>()
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97 | where sym.ArgumentIndex != removedArgumentIndex
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98 | select sym).ToList();
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99 | var argNodes = from node in branch.IterateNodesPrefix().OfType<ArgumentTreeNode>()
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100 | where node.Symbol.ArgumentIndex == removedArgumentIndex
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101 | select node;
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102 | foreach (var argNode in argNodes) {
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103 | var replacementSymbol = possibleArgumentSymbols.SampleRandom(random);
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104 | argNode.Symbol = replacementSymbol;
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105 | }
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106 | }
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107 | }
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108 | }
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