1 | #region License Information
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2 | /* HeuristicLab
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3 | * Copyright (C) 2002-2016 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;
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23 | using System.Collections.Generic;
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24 | using System.Linq;
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25 | using HeuristicLab.Common;
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26 | using HeuristicLab.Core;
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27 | using HeuristicLab.Random;
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28 |
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29 | namespace HeuristicLab.ExpressionGenerator {
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30 | public abstract class ExpressionTemplate {
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31 | protected List<Tuple<Expression, double>> arguments;
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32 | protected readonly Func<IEnumerable<double>, double> transform;
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33 | public string Label { get; set; }
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34 |
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35 | protected Expression Instantiate(string name, IRandom random, int n, bool sampleWithRepetition = false) {
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36 | var func = Expression.Function(name, transform, SampleArguments(random, n, sampleWithRepetition));
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37 | func.Label = Label;
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38 | return func;
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39 | }
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40 |
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41 | protected IEnumerable<Expression> SampleArguments(IRandom random, int n, bool sampleWithRepetition = false) {
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42 | var weights = arguments.Select(x => x.Item2);
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43 | var args = sampleWithRepetition
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44 | ? arguments.SampleProportional(random, n, weights).Select(x => x.Item1)
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45 | : arguments.SampleProportionalWithoutRepetition(random, n, weights).Select(x => x.Item1);
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46 | return args;
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47 | }
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48 |
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49 | public abstract Expression Instantiate(string name, IRandom random, bool sampleWithRepetition = false);
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50 |
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51 | protected ExpressionTemplate(Func<IEnumerable<double>, double> transform) {
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52 | this.transform = transform;
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53 | }
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54 |
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55 | public void AddArgument(Expression expression, double weight = 1d) {
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56 | arguments = arguments ?? new List<Tuple<Expression, double>>();
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57 | arguments.Add(Tuple.Create(expression, weight));
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58 | }
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59 |
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60 | public void AddArguments(IEnumerable<Expression> expressions) {
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61 | arguments = arguments ?? new List<Tuple<Expression, double>>();
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62 | arguments.AddRange(expressions.Select(x => Tuple.Create(x, 1d)));
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63 | }
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64 |
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65 | public void AddArguments(IEnumerable<Expression> expressions, IEnumerable<double> weights) {
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66 | arguments = arguments ?? new List<Tuple<Expression, double>>();
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67 | arguments.AddRange(expressions.Zip(weights, Tuple.Create));
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68 | }
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69 | }
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70 |
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71 | public class RandomArityTemplate : ExpressionTemplate {
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72 | private readonly IRandom arityDistribution;
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73 |
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74 | public RandomArityTemplate(Func<IEnumerable<double>, double> transform, IRandom arityDistribution) : base(transform) {
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75 | this.arityDistribution = arityDistribution;
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76 | }
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77 |
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78 | public override Expression Instantiate(string name, IRandom random, bool sampleWithRepetition = false) {
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79 | var arity = (int)Math.Round(arityDistribution.NextDouble());
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80 | return Instantiate(name, random, arity, sampleWithRepetition);
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81 | }
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82 | }
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83 |
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84 | public class FixedArityTemplate : ExpressionTemplate {
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85 | private readonly int arity;
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86 | public FixedArityTemplate(Func<IEnumerable<double>, double> transform, int arity) : base(transform) {
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87 | this.arity = arity;
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88 | }
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89 |
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90 | public override Expression Instantiate(string name, IRandom random, bool sampleWithRepetition = false) {
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91 | return Instantiate(name, random, arity, sampleWithRepetition);
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92 | }
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93 | }
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94 |
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95 | public class ScalingTemplate : ExpressionTemplate {
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96 | private readonly IRandom scaledVariance;
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97 | // w * expr
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98 | public ScalingTemplate(IRandom scaledVariance = null) : base(ExpressionGenerator.Product) {
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99 | this.scaledVariance = scaledVariance;
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100 | }
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101 |
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102 | public override Expression Instantiate(string name, IRandom random, bool sampleWithRepetition = false) {
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103 | var expr = SampleArguments(random, 1, sampleWithRepetition).First();
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104 |
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105 | // use the evaluator to determine variance of the sampled expression and initialize the constant accordingly to reach the target variance
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106 | var @const = 1.0;
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107 | if (scaledVariance != null) {
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108 | var evaluator = new ExpressionEvaluator();
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109 | var data = evaluator.GenerateData(expr, 10000);
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110 | var variance = data[expr].VariancePop();
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111 | @const = scaledVariance.NextDouble() / variance;
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112 | }
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113 |
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114 | var func = Expression.Function(name, transform, new Expression[] { Expression.Constant(name, @const), expr });
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115 | func.Label = "*";
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116 | return func;
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117 | }
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118 | }
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119 |
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120 | public class OffsetTemplate : ExpressionTemplate {
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121 | private readonly IRandom offset;
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122 | // expr + offset
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123 | public OffsetTemplate(IRandom offset = null) : base(ExpressionGenerator.Sum) {
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124 | this.offset = offset;
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125 | }
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126 |
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127 | public override Expression Instantiate(string name, IRandom random, bool sampleWithRepetition = false) {
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128 | var expr = SampleArguments(random, 1, sampleWithRepetition).First();
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129 |
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130 | // use the evaluator to determine variance of the sampled expression and initialize the constant accordingly to reach the target offset
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131 | var @const = 0.0;
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132 | if (offset != null) {
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133 | var evaluator = new ExpressionEvaluator();
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134 | var data = evaluator.GenerateData(expr, 10000);
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135 | var average = data[expr].Average();
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136 | @const = offset.NextDouble() - average;
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137 | }
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138 |
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139 | var func = Expression.Function(name, transform, new Expression[] { Expression.Constant(name, @const), expr });
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140 | func.Label = "+";
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141 | return func;
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142 | }
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143 | }
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144 |
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145 | public class RangeTemplate : ExpressionTemplate {
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146 | private readonly IRandom minValue;
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147 | private readonly IRandom valueRange;
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148 | // expr + offset
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149 | public RangeTemplate(IRandom minValue = null, IRandom valueRange = null) : base(null) {
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150 | this.minValue = minValue;
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151 | this.valueRange = valueRange;
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152 | }
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153 |
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154 | public override Expression Instantiate(string name, IRandom random, bool sampleWithRepetition = false) {
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155 | var expr = SampleArguments(random, 1, sampleWithRepetition).First();
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156 |
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157 | // use the evaluator to determine variance of the sampled expression and initialize the constant accordingly to reach the target offset
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158 | var mult = 1.0;
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159 | var add = 0.0;
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160 |
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161 | if (minValue != null || valueRange != null) {
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162 | var evaluator = new ExpressionEvaluator();
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163 | var data = evaluator.GenerateData(expr, 10000);
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164 | if (valueRange != null) {
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165 | var targetRange = valueRange.NextDouble();
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166 | var min = data[expr].Min();
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167 | var max = data[expr].Max();
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168 | var range = max - min;
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169 | mult = targetRange / range;
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170 | add = -min + min / mult;
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171 | }
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172 | if (minValue != null) {
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173 | var targetMin = minValue.NextDouble();
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174 | var min = data[expr].Min();
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175 | add += (targetMin - min) / mult;
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176 | }
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177 |
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178 | expr = Expression.Function(name + "-toZero", ExpressionGenerator.Sum, new Expression[] { Expression.Constant("name-add0", add), expr });
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179 | expr.Label = "+";
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180 | expr = Expression.Function(name + "-mult", ExpressionGenerator.Product, new Expression[] { Expression.Constant("name-mult", mult), expr });
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181 | expr.Label = "*";
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182 | }
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183 |
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184 | return expr;
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185 | }
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186 | }
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187 | }
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