Index: /branches/DataAnalysis.ComplexityAnalyzer/HeuristicLab.Problems.DataAnalysis.Symbolic.Regression/3.4/HeuristicLab.Problems.DataAnalysis.Symbolic.Regression-3.4.csproj
===================================================================
--- /branches/DataAnalysis.ComplexityAnalyzer/HeuristicLab.Problems.DataAnalysis.Symbolic.Regression/3.4/HeuristicLab.Problems.DataAnalysis.Symbolic.Regression-3.4.csproj	(revision 11406)
+++ /branches/DataAnalysis.ComplexityAnalyzer/HeuristicLab.Problems.DataAnalysis.Symbolic.Regression/3.4/HeuristicLab.Problems.DataAnalysis.Symbolic.Regression-3.4.csproj	(revision 11407)
@@ -185,4 +185,5 @@
   </ItemGroup>
   <ItemGroup>
+    <Compile Include="MultiObjective\SymbolicRegressionMultiObjectivePearsonRSquaredNestedTreeSizeEvaluator.cs" />
     <Compile Include="MultiObjective\SymbolicRegressionMultiObjectivePearsonRSquaredTreeComplexityEvaluator.cs" />
     <Compile Include="MultiObjective\SymbolicRegressionMultiObjectiveValidationBestSolutionAnalyzer.cs" />
Index: /branches/DataAnalysis.ComplexityAnalyzer/HeuristicLab.Problems.DataAnalysis.Symbolic.Regression/3.4/MultiObjective/SymbolicRegressionMultiObjectivePearsonRSquaredNestedTreeSizeEvaluator.cs
===================================================================
--- /branches/DataAnalysis.ComplexityAnalyzer/HeuristicLab.Problems.DataAnalysis.Symbolic.Regression/3.4/MultiObjective/SymbolicRegressionMultiObjectivePearsonRSquaredNestedTreeSizeEvaluator.cs	(revision 11407)
+++ /branches/DataAnalysis.ComplexityAnalyzer/HeuristicLab.Problems.DataAnalysis.Symbolic.Regression/3.4/MultiObjective/SymbolicRegressionMultiObjectivePearsonRSquaredNestedTreeSizeEvaluator.cs	(revision 11407)
@@ -0,0 +1,74 @@
+﻿#region License Information
+/* HeuristicLab
+ * Copyright (C) 2002-2014 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 <http://www.gnu.org/licenses/>.
+ */
+#endregion
+
+using System.Collections.Generic;
+using System.Linq;
+using HeuristicLab.Common;
+using HeuristicLab.Core;
+using HeuristicLab.Data;
+using HeuristicLab.Encodings.SymbolicExpressionTreeEncoding;
+using HeuristicLab.Persistence.Default.CompositeSerializers.Storable;
+
+namespace HeuristicLab.Problems.DataAnalysis.Symbolic.Regression {
+  [Item("Pearson R² & Nested Tree size Evaluator", "Calculates the Pearson R² and the nested tree size of a symbolic regression solution.")]
+  [StorableClass]
+  public class SymbolicRegressionMultiObjectivePearsonRSquaredNestedTreeSizeEvaluator : SymbolicRegressionMultiObjectiveEvaluator {
+    [StorableConstructor]
+    protected SymbolicRegressionMultiObjectivePearsonRSquaredNestedTreeSizeEvaluator(bool deserializing) : base(deserializing) { }
+    protected SymbolicRegressionMultiObjectivePearsonRSquaredNestedTreeSizeEvaluator(SymbolicRegressionMultiObjectivePearsonRSquaredNestedTreeSizeEvaluator original, Cloner cloner)
+      : base(original, cloner) {
+    }
+    public override IDeepCloneable Clone(Cloner cloner) {
+      return new SymbolicRegressionMultiObjectivePearsonRSquaredNestedTreeSizeEvaluator(this, cloner);
+    }
+
+    public SymbolicRegressionMultiObjectivePearsonRSquaredNestedTreeSizeEvaluator() : base() { }
+
+    public override IEnumerable<bool> Maximization { get { return new bool[2] { true, false }; } }
+
+    public override IOperation InstrumentedApply() {
+      IEnumerable<int> rows = GenerateRowsToEvaluate();
+      var solution = SymbolicExpressionTreeParameter.ActualValue;
+      double[] qualities = Calculate(SymbolicDataAnalysisTreeInterpreterParameter.ActualValue, solution, EstimationLimitsParameter.ActualValue.Lower, EstimationLimitsParameter.ActualValue.Upper, ProblemDataParameter.ActualValue, rows, ApplyLinearScalingParameter.ActualValue.Value);
+      QualitiesParameter.ActualValue = new DoubleArray(qualities);
+      return base.InstrumentedApply();
+    }
+
+    public static double[] Calculate(ISymbolicDataAnalysisExpressionTreeInterpreter interpreter, ISymbolicExpressionTree solution, double lowerEstimationLimit, double upperEstimationLimit, IRegressionProblemData problemData, IEnumerable<int> rows, bool applyLinearScaling) {
+      double r2 = SymbolicRegressionSingleObjectivePearsonRSquaredEvaluator.Calculate(interpreter, solution, lowerEstimationLimit, upperEstimationLimit, problemData, rows, applyLinearScaling);
+      return new double[2] { r2, solution.IterateNodesPostfix().Sum(n => n.GetLength()) };
+    }
+
+    public override double[] Evaluate(IExecutionContext context, ISymbolicExpressionTree tree, IRegressionProblemData problemData, IEnumerable<int> rows) {
+      SymbolicDataAnalysisTreeInterpreterParameter.ExecutionContext = context;
+      EstimationLimitsParameter.ExecutionContext = context;
+      ApplyLinearScalingParameter.ExecutionContext = context;
+
+      double[] quality = Calculate(SymbolicDataAnalysisTreeInterpreterParameter.ActualValue, tree, EstimationLimitsParameter.ActualValue.Lower, EstimationLimitsParameter.ActualValue.Upper, problemData, rows, ApplyLinearScalingParameter.ActualValue.Value);
+
+      SymbolicDataAnalysisTreeInterpreterParameter.ExecutionContext = null;
+      EstimationLimitsParameter.ExecutionContext = null;
+      ApplyLinearScalingParameter.ExecutionContext = null;
+
+      return quality;
+    }
+  }
+}
Index: /branches/DataAnalysis.ComplexityAnalyzer/HeuristicLab.Problems.DataAnalysis.Symbolic/3.4/Analyzers/SymbolicDataAnalysisModelComplexityAnalyzer.cs
===================================================================
--- /branches/DataAnalysis.ComplexityAnalyzer/HeuristicLab.Problems.DataAnalysis.Symbolic/3.4/Analyzers/SymbolicDataAnalysisModelComplexityAnalyzer.cs	(revision 11406)
+++ /branches/DataAnalysis.ComplexityAnalyzer/HeuristicLab.Problems.DataAnalysis.Symbolic/3.4/Analyzers/SymbolicDataAnalysisModelComplexityAnalyzer.cs	(revision 11407)
@@ -59,5 +59,5 @@
             double complexity = 1;
             for (int i = 0; i < node.SubtreeCount; i++) {
-              complexity *= CalculateComplexity(node.GetSubtree(i)) * 2;
+              complexity *= CalculateComplexity(node.GetSubtree(i));
             }
             return complexity;
Index: /branches/DataAnalysis.ComplexityAnalyzer/HeuristicLab.Problems.DataAnalysis.Symbolic/3.4/Analyzers/SymbolicDataAnalysisMultiObjectiveTrainingBestSolutionAnalyzer.cs
===================================================================
--- /branches/DataAnalysis.ComplexityAnalyzer/HeuristicLab.Problems.DataAnalysis.Symbolic/3.4/Analyzers/SymbolicDataAnalysisMultiObjectiveTrainingBestSolutionAnalyzer.cs	(revision 11406)
+++ /branches/DataAnalysis.ComplexityAnalyzer/HeuristicLab.Problems.DataAnalysis.Symbolic/3.4/Analyzers/SymbolicDataAnalysisMultiObjectiveTrainingBestSolutionAnalyzer.cs	(revision 11407)
@@ -133,4 +133,5 @@
 
       var nonDominatedSolutions = nonDominatedInvididuals.Select(x => new { Solution = CreateSolution(x.Tree, x.Qualities), Qualities = x.Qualities }).ToList();
+      nonDominatedSolutions.ForEach(s => s.Solution.Name = string.Join(",", s.Qualities.Select(q => q.ToString())));
 
       #region update Pareto-optimal solution archive
Index: /branches/DataAnalysis.ComplexityAnalyzer/HeuristicLab.Problems.DataAnalysis.Symbolic/3.4/SymbolicDataAnalysisExpressionTreeSimplificationOperator.cs
===================================================================
--- /branches/DataAnalysis.ComplexityAnalyzer/HeuristicLab.Problems.DataAnalysis.Symbolic/3.4/SymbolicDataAnalysisExpressionTreeSimplificationOperator.cs	(revision 11407)
+++ /branches/DataAnalysis.ComplexityAnalyzer/HeuristicLab.Problems.DataAnalysis.Symbolic/3.4/SymbolicDataAnalysisExpressionTreeSimplificationOperator.cs	(revision 11407)
@@ -0,0 +1,60 @@
+﻿#region License Information
+/* HeuristicLab
+ * Copyright (C) 2002-2014 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 <http://www.gnu.org/licenses/>.
+ */
+#endregion
+
+using HeuristicLab.Common;
+using HeuristicLab.Core;
+using HeuristicLab.Encodings.SymbolicExpressionTreeEncoding;
+using HeuristicLab.Operators;
+using HeuristicLab.Parameters;
+using HeuristicLab.Persistence.Default.CompositeSerializers.Storable;
+
+namespace HeuristicLab.Problems.DataAnalysis.Symbolic {
+  public class SymbolicDataAnalysisExpressionTreeSimplificationOperator : SingleSuccessorOperator {
+    private const string SymbolicExpressionTreeParameterName = "SymbolicExpressionTree";
+
+    public ILookupParameter<ISymbolicExpressionTree> SymbolicExpressionTreeParameter {
+      get { return (ILookupParameter<ISymbolicExpressionTree>)Parameters[SymbolicExpressionTreeParameterName]; }
+    }
+
+    private readonly SymbolicDataAnalysisExpressionTreeSimplifier simplifier = new SymbolicDataAnalysisExpressionTreeSimplifier();
+
+    [StorableConstructor]
+    protected SymbolicDataAnalysisExpressionTreeSimplificationOperator(bool deserializing) : base(deserializing) { }
+    protected SymbolicDataAnalysisExpressionTreeSimplificationOperator(SymbolicDataAnalysisExpressionTreeSimplificationOperator original, Cloner cloner)
+      : base(original, cloner) { }
+    public override IDeepCloneable Clone(Cloner cloner) {
+      return new SymbolicDataAnalysisExpressionTreeSimplificationOperator(this, cloner);
+    }
+
+    public SymbolicDataAnalysisExpressionTreeSimplificationOperator() {
+      Parameters.Add(new LookupParameter<ISymbolicExpressionTree>(SymbolicExpressionTreeParameterName, "The symbolic expression tree to be simplified."));
+    }
+
+    public override IOperation Apply() {
+      var tree = SymbolicExpressionTreeParameter.ActualValue;
+      var simplifiedTree = simplifier.Simplify(tree);
+      simplifiedTree = simplifier.Simplify(simplifiedTree);
+      SymbolicExpressionTreeParameter.ActualValue = simplifiedTree;
+
+      return base.Apply();
+    }
+  }
+}
