#region License Information
/* HeuristicLab
* Copyright (C) 2002-2012 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.Collections.Generic;
using System.Linq;
using HeuristicLab.Common;
using HeuristicLab.Core;
using HeuristicLab.Data;
using HeuristicLab.Encodings.SymbolicExpressionTreeEncoding;
using HeuristicLab.Parameters;
using HeuristicLab.Persistence.Default.CompositeSerializers.Storable;
namespace HeuristicLab.Problems.DataAnalysis.Symbolic {
[Item("DepthConstrainedCrossover", "An operator which performs subtree swapping within a specific depth range. The range parameter controls the crossover behavior:\n" +
"- HighLevel (upper 25% of the tree)\n" +
"- Standard (mid 50% of the tree)\n" +
"- LowLevel (lower 25% of the tree)")]
public sealed class SymbolicDataAnalysisExpressionDepthConstrainedCrossover :
SymbolicDataAnalysisExpressionCrossover where T : class, IDataAnalysisProblemData {
private enum Ranges { HighLevel, Standard, LowLevel };
private const string DepthRangeParameterName = "DepthRange";
#region Parameter properties
public ConstrainedValueParameter DepthRangeParameter {
get { return (ConstrainedValueParameter)Parameters[DepthRangeParameterName]; }
}
#endregion
#region Properties
public StringValue DepthRange {
get { return (StringValue)DepthRangeParameter.ActualValue; }
}
#endregion
[StorableConstructor]
private SymbolicDataAnalysisExpressionDepthConstrainedCrossover(bool deserializing) : base(deserializing) { }
private SymbolicDataAnalysisExpressionDepthConstrainedCrossover(SymbolicDataAnalysisExpressionCrossover original, Cloner cloner)
: base(original, cloner) { }
public SymbolicDataAnalysisExpressionDepthConstrainedCrossover()
: base() {
Parameters.Add(new ConstrainedValueParameter(DepthRangeParameterName, "Depth range specifier"));
DepthRangeParameter.ValidValues.Add(new StringValue(Enum.GetName(typeof(Ranges), Ranges.HighLevel)).AsReadOnly());
DepthRangeParameter.ValidValues.Add(new StringValue(Enum.GetName(typeof(Ranges), Ranges.Standard)).AsReadOnly());
DepthRangeParameter.ValidValues.Add(new StringValue(Enum.GetName(typeof(Ranges), Ranges.LowLevel)).AsReadOnly());
name = "DepthConstrainedCrossover";
}
public override IDeepCloneable Clone(Cloner cloner) { return new SymbolicDataAnalysisExpressionDepthConstrainedCrossover(this, cloner); }
public override ISymbolicExpressionTree Crossover(IRandom random, ISymbolicExpressionTree parent0, ISymbolicExpressionTree parent1) {
return Cross(random, parent0, parent1, MaximumSymbolicExpressionTreeDepth.Value, MaximumSymbolicExpressionTreeLength.Value, DepthRange.Value);
}
///
/// Takes two parent individuals P0 and P1.
/// Randomly choose nodes that fall within the specified depth range in both parents.
///
/// Pseudo-random number generator.
/// First parent.
/// Second parent.
/// Maximum allowed length depth.
/// Maximum allowed tree length.
/// Controls the crossover behavior:
/// - HighLevel (upper 25% of the tree),
/// - Standard (mid 50%)
/// - LowLevel (low 25%)
///
public static ISymbolicExpressionTree Cross(IRandom random, ISymbolicExpressionTree parent0, ISymbolicExpressionTree parent1, int maxDepth, int maxLength, string mode) {
int depth = parent0.Root.GetDepth() - 1; // substract 1 because the tree levels are counted from 0
var depthRange = new IntRange();
const int depthOffset = 2; // skip the first 2 levels (root + startNode)
switch ((int)Enum.Parse(typeof(Ranges), mode)) {
case (int)Ranges.HighLevel:
depthRange.Start = depthOffset; // skip the first 2 levels (root + startNode)
depthRange.End = depthRange.Start + (int)Math.Round(depth * 0.25);
break;
case (int)Ranges.Standard:
depthRange.Start = depthOffset + (int)Math.Round(depth * 0.25);
depthRange.End = depthRange.Start + (int)Math.Round(depth * 0.5);
break;
case (int)Ranges.LowLevel:
depthRange.Start = depthOffset + (int)Math.Round(depth * 0.75);
depthRange.End = Math.Max(depthRange.Start, depth);
break;
}
// make sure that the depth range does not exceeded the actual depth of parent0
if (depthRange.Start > depth)
depthRange.Start = depth;
if (depthRange.End < depthRange.Start)
depthRange.End = depthRange.Start;
var crossoverPoints0 = (from node in GetNodesAtDepth(parent0, depthRange) select new CutPoint(node.Parent, node)).ToList();
if (crossoverPoints0.Count == 0)
throw new Exception("No crossover points available in the first parent");
var crossoverPoint0 = crossoverPoints0.SelectRandom(random);
int level = parent0.Root.GetBranchLevel(crossoverPoint0.Child);
int length = parent0.Root.GetLength() - crossoverPoint0.Child.GetLength();
var allowedBranches = (from s in GetNodesAtDepth(parent1, depthRange)
where s.GetDepth() + level <= maxDepth
where s.GetLength() + length <= maxLength
where crossoverPoint0.IsMatchingPointType(s)
select s).ToList();
if (allowedBranches.Count == 0) return parent0;
var selectedBranch = allowedBranches.SelectRandom(random);
Swap(crossoverPoint0, selectedBranch);
return parent0;
}
private static IEnumerable GetNodesAtDepth(ISymbolicExpressionTree tree, IntRange depthRange) {
var treeDepth = tree.Root.GetDepth();
return from node in tree.Root.IterateNodesPostfix()
let depth = treeDepth - node.GetDepth()
where depthRange.Start <= depth
where depth <= depthRange.End
select node;
}
}
}