#region License Information
/* HeuristicLab
* Copyright (C) 2002-2010 Heuristic and Evolutionary Algorithms Laboratory (HEAL)
*
* This file is part of HeuristicLab.
*
* HeuristicLab is free software: you can redistribute it and/or modify
* it under the terms of the GNU General Public License as published by
* the Free Software Foundation, either version 3 of the License, or
* (at your option) any later version.
*
* HeuristicLab is distributed in the hope that it will be useful,
* but WITHOUT ANY WARRANTY; without even the implied warranty of
* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
* GNU General Public License for more details.
*
* You should have received a copy of the GNU General Public License
* along with HeuristicLab. If not, see .
*/
#endregion
using System;
using System.Linq;
using HeuristicLab.Common;
using HeuristicLab.Core;
using HeuristicLab.Data;
using HeuristicLab.Operators;
using HeuristicLab.Optimization;
using HeuristicLab.Parameters;
using HeuristicLab.Persistence.Default.CompositeSerializers.Storable;
using HeuristicLab.Encodings.SymbolicExpressionTreeEncoding.Symbols;
using System.Collections.Generic;
using System.Text;
using System.Diagnostics;
namespace HeuristicLab.Encodings.SymbolicExpressionTreeEncoding.ArchitectureManipulators {
///
/// As described in Koza, Bennett, Andre, Keane, Genetic Programming III - Darwinian Invention and Problem Solving, 1999, pp. 112
///
[Item("ArgumentDeleter", "Manipulates a symbolic expression by deleting an argument from an existing function defining branch.")]
[StorableClass]
public sealed class ArgumentDeleter : SymbolicExpressionTreeArchitectureManipulator {
public override sealed void ModifyArchitecture(
IRandom random,
SymbolicExpressionTree symbolicExpressionTree,
ISymbolicExpressionGrammar grammar,
IntValue maxTreeSize, IntValue maxTreeHeight,
IntValue maxFunctionDefiningBranches, IntValue maxFunctionArguments,
out bool success) {
success = DeleteArgument(random, symbolicExpressionTree, grammar, maxTreeSize.Value, maxTreeHeight.Value, maxFunctionDefiningBranches.Value, maxFunctionArguments.Value);
}
public static bool DeleteArgument(
IRandom random,
SymbolicExpressionTree symbolicExpressionTree,
ISymbolicExpressionGrammar grammar,
int maxTreeSize, int maxTreeHeight,
int maxFunctionDefiningBranches, int maxFunctionArguments) {
var functionDefiningBranches = symbolicExpressionTree.IterateNodesPrefix().OfType();
if (functionDefiningBranches.Count() == 0)
// no function defining branch => abort
return false;
var selectedDefunBranch = functionDefiningBranches.SelectRandom(random);
if (selectedDefunBranch.NumberOfArguments <= 1)
// argument deletion by consolidation is not possible => abort
return false;
// the argument to be removed is always the one with the largest index
// (otherwise we would have to decrement the index of the larger argument symbols)
var removedArgument = (from sym in selectedDefunBranch.Grammar.Symbols.OfType()
select sym.ArgumentIndex).Distinct().OrderBy(x => x).Last();
// find invocations of the manipulated funcion and remove the specified argument tree
var invocationNodes = (from node in symbolicExpressionTree.IterateNodesPrefix().OfType()
where node.Symbol.FunctionName == selectedDefunBranch.FunctionName
select node).ToList();
foreach (var invokeNode in invocationNodes) {
invokeNode.RemoveSubTree(removedArgument);
}
DeleteArgumentByConsolidation(random, selectedDefunBranch, removedArgument);
// delete the dynamic argument symbol that matches the argument to be removed
var matchingSymbol = selectedDefunBranch.Grammar.Symbols.OfType().Where(s => s.ArgumentIndex == removedArgument).Single();
selectedDefunBranch.Grammar.RemoveSymbol(matchingSymbol);
selectedDefunBranch.NumberOfArguments--;
// reduce arity in known functions of all root branches
foreach (var subtree in symbolicExpressionTree.Root.SubTrees) {
var matchingInvokeSymbol = subtree.Grammar.Symbols.OfType().Where(s => s.FunctionName == selectedDefunBranch.FunctionName).SingleOrDefault();
if (matchingInvokeSymbol != null) {
subtree.Grammar.SetMinSubtreeCount(matchingInvokeSymbol, selectedDefunBranch.NumberOfArguments);
subtree.Grammar.SetMaxSubtreeCount(matchingInvokeSymbol, selectedDefunBranch.NumberOfArguments);
}
}
return true;
}
private static void DeleteArgumentByConsolidation(IRandom random, DefunTreeNode branch, int removedArgumentIndex) {
// replace references to the deleted argument with random references to existing arguments
var possibleArgumentSymbols = (from sym in branch.Grammar.Symbols.OfType()
where sym.ArgumentIndex != removedArgumentIndex
select sym).ToList();
var argNodes = from node in branch.IterateNodesPrefix().OfType()
where node.Symbol.ArgumentIndex == removedArgumentIndex
select node;
foreach (var argNode in argNodes) {
var replacementSymbol = possibleArgumentSymbols.SelectRandom(random);
argNode.Symbol = replacementSymbol;
}
}
}
}