source: branches/2974_Constants_Optimization/HeuristicLab.Problems.DataAnalysis.Symbolic/3.4/ConstantsOptimization/LMConstantsOptimizer.cs @ 16514

Last change on this file since 16514 was 16514, checked in by mkommend, 2 years ago

#2974: Updated CoOp to handle negative R² values approprietly.

File size: 6.8 KB
Line 
1#region License Information
2/* HeuristicLab
3 * Copyright (C) 2002-2018 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.Encodings.SymbolicExpressionTreeEncoding;
26
27namespace HeuristicLab.Problems.DataAnalysis.Symbolic.ConstantsOptimization {
28  public class LMConstantsOptimizer {
29
30    private LMConstantsOptimizer() { }
31
32    /// <summary>
33    /// Method to determine whether the numeric constants of the tree can be optimized. This depends primarily on the symbols occuring in the tree.
34    /// </summary>
35    /// <param name="tree">The tree that should be analyzed</param>
36    /// <returns>A flag indicating whether the numeric constants of the tree can be optimized</returns>
37    public static bool CanOptimizeConstants(ISymbolicExpressionTree tree) {
38      return AutoDiffConverter.IsCompatible(tree);
39    }
40
41    /// <summary>
42    /// Optimizes the numeric constants in a symbolic expression tree in place.
43    /// </summary>
44    /// <param name="tree">The tree for which the constants should be optimized</param>
45    /// <param name="dataset">The dataset containing the data.</param>
46    /// <param name="targetVariable">The target variable name.</param>
47    /// <param name="rows">The rows for which the data should be extracted.</param>
48    /// <param name="applyLinearScaling">A flag to determine whether linear scaling should be applied during the optimization</param>
49    /// <param name="maxIterations">The maximum number of iterations of the Levenberg-Marquard algorithm.</param>
50    /// <returns></returns>
51    public static double OptimizeConstants(ISymbolicExpressionTree tree,
52      IDataset dataset, string targetVariable, IEnumerable<int> rows,
53      bool applyLinearScaling, int maxIterations = 10) {
54      if (tree == null) throw new ArgumentNullException("tree");
55      if (dataset == null) throw new ArgumentNullException("dataset");
56      if (!dataset.ContainsVariable(targetVariable)) throw new ArgumentException("The dataset does not contain the provided target variable.");
57
58      var allVariables = Util.ExtractVariables(tree);
59      var numericNodes = Util.ExtractNumericNodes(tree);
60
61      AutoDiff.IParametricCompiledTerm term;
62      if (!AutoDiffConverter.TryConvertToAutoDiff(tree, applyLinearScaling, numericNodes, allVariables, out term))
63        throw new NotSupportedException("Could not convert symbolic expression tree to an AutoDiff term due to not supported symbols used in the tree.");
64
65      //Variables of the symbolic expression tree correspond to parameters in the term
66      //Hence if no parameters are present no variables occur in the tree and the R² = 0
67      if (term.Parameters.Count == 0) return 0.0;
68
69      var initialConstants = Util.ExtractConstants(numericNodes, applyLinearScaling);
70      double[] constants;
71      double[,] x = Util.ExtractData(dataset, allVariables, rows);
72      double[] y = dataset.GetDoubleValues(targetVariable, rows).ToArray();
73
74      var result = OptimizeConstants(term, initialConstants, x, y, maxIterations, out constants);
75      if (result > 0.0 && constants.Length != 0)
76        Util.UpdateConstants(numericNodes, constants);
77
78      return result;
79    }
80
81    /// <summary>
82    /// Optimizes the numeric coefficents of an AutoDiff Term using the Levenberg-Marquard algorithm.
83    /// </summary>
84    /// <param name="term">The AutoDiff term for which the numeric coefficients should be optimized.</param>
85    /// <param name="initialConstants">The starting values for the numeric coefficients.</param>
86    /// <param name="x">The input data for the optimization.</param>
87    /// <param name="y">The target values for the optimization.</param>
88    /// <param name="maxIterations">The maximum number of iterations of the Levenberg-Marquard</param>
89    /// <param name="constants">The opitmized constants.</param>
90    /// <param name="LM_IterationCallback">An optional callback for detailed analysis that is called in each algorithm iteration.</param>
91    /// <returns>The R² of the term evaluated on the input data x and the target data y using the optimized constants</returns>
92    public static double OptimizeConstants(AutoDiff.IParametricCompiledTerm term, double[] initialConstants, double[,] x, double[] y,
93      int maxIterations, out double[] constants, Action<double[], double, object> LM_IterationCallback = null) {
94
95      if (term.Parameters.Count == 0) {
96        constants = new double[0];
97        return 0.0;
98      }
99
100      var optimizedConstants = (double[])initialConstants.Clone();
101      int numberOfRows = x.GetLength(0);
102      int numberOfColumns = x.GetLength(1);
103      int numberOfConstants = optimizedConstants.Length;
104
105      alglib.lsfitstate state;
106      alglib.lsfitreport rep;
107      alglib.ndimensional_rep xrep = (p, f, obj) => LM_IterationCallback(p, f, obj);
108      int retVal;
109
110      try {
111        alglib.lsfitcreatefg(x, y, optimizedConstants, numberOfRows, numberOfColumns, numberOfConstants, cheapfg: false, state: out state);
112        alglib.lsfitsetcond(state, 0.0, 0.0, maxIterations);
113        alglib.lsfitsetxrep(state, LM_IterationCallback != null);
114        alglib.lsfitfit(state, Evaluate, EvaluateGradient, xrep, term);
115        alglib.lsfitresults(state, out retVal, out optimizedConstants, out rep);
116      } catch (ArithmeticException) {
117        constants = new double[0];
118        return double.NaN;
119      } catch (alglib.alglibexception) {
120        constants = new double[0];
121        return double.NaN;
122      }
123
124      constants = optimizedConstants;
125      return rep.r2;
126    }
127
128
129    private static void Evaluate(double[] c, double[] x, ref double fx, object o) {
130      AutoDiff.IParametricCompiledTerm term = (AutoDiff.IParametricCompiledTerm)o;
131      fx = term.Evaluate(c, x);
132    }
133
134    private static void EvaluateGradient(double[] c, double[] x, ref double fx, double[] grad, object o) {
135      AutoDiff.IParametricCompiledTerm term = (AutoDiff.IParametricCompiledTerm)o;
136      Tuple<double[], double> result = term.Differentiate(c, x);
137      fx = result.Item2;
138      Array.Copy(result.Item1, grad, grad.Length);
139    }
140  }
141}
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