Changeset 14873 for branches/HeuristicLab.ExpressionGenerator/HeuristicLab.ExpressionGenerator/3.4/ExpressionTemplate.cs

Timestamp:

04/15/17 08:44:15 (7 years ago)

Author:

gkronber

Message:

#2704: added possibility to automatically adjust constants based on the distributions of evaluated expressions to allow limiting distributions for arguments of functions (e.g. log should have positive args only, exp should have rather small args only)

File:

• branches/HeuristicLab.ExpressionGenerator/HeuristicLab.ExpressionGenerator/3.4/ExpressionTemplate.cs (modified) (4 diffs)

branches/HeuristicLab.ExpressionGenerator/HeuristicLab.ExpressionGenerator/3.4/ExpressionTemplate.cs

@@ -23 +23 @@
 using System.Collections.Generic;
 using System.Linq;
+using HeuristicLab.Common;
 using HeuristicLab.Core;
 using HeuristicLab.Random;
@@ -28 +29 @@
 namespace HeuristicLab.ExpressionGenerator {
   public abstract class ExpressionTemplate {
-    private List<Tuple<Expression, double>> arguments;
-    private readonly Func<IEnumerable<double>, double> transform;
+    protected List<Tuple<Expression, double>> arguments;
+    protected readonly Func<IEnumerable<double>, double> transform;
     public string Label { get; set; }
 
     protected Expression Instantiate(string name, IRandom random, int n, bool sampleWithRepetition = false) {
+      var func = Expression.Function(name, transform, SampleArguments(random, n, sampleWithRepetition));
+      func.Label = Label;
+      return func;
+    }
+
+    protected IEnumerable<Expression> SampleArguments(IRandom random, int n, bool sampleWithRepetition = false) {
       var weights = arguments.Select(x => x.Item2);
       var args = sampleWithRepetition
        ? arguments.SampleProportional(random, n, weights).Select(x => x.Item1)
        : arguments.SampleProportionalWithoutRepetition(random, n, weights).Select(x => x.Item1);
-      var func = Expression.Function(name, transform, args);
-      func.Label = Label;
-      return func;
+      return args;
     }
 
@@ -58 +63 @@
     }
 
-    public void AddArguments(IEnumerable<Expression> expressions, IEnumerable<double> weights) { 
+    public void AddArguments(IEnumerable<Expression> expressions, IEnumerable<double> weights) {
       arguments = arguments ?? new List<Tuple<Expression, double>>();
       arguments.AddRange(expressions.Zip(weights, Tuple.Create));
@@ -87 +92 @@
     }
   }
+
+  public class ScalingTemplate : ExpressionTemplate {
+    private readonly IRandom scaledVariance;
+    // w * expr
+    public ScalingTemplate(IRandom scaledVariance = null) : base(ExpressionGenerator.Product) {
+      this.scaledVariance = scaledVariance;
+    }
+
+    public override Expression Instantiate(string name, IRandom random, bool sampleWithRepetition = false) {
+      var expr = SampleArguments(random, 1, sampleWithRepetition).First();
+
+      // use the evaluator to determine variance of the sampled expression and initialize the constant accordingly to reach the target variance
+      var @const = 1.0;
+      if (scaledVariance != null) {
+        var evaluator = new ExpressionEvaluator();
+        var data = evaluator.GenerateData(expr, 10000);
+        var variance = data[expr].VariancePop();
+        @const = scaledVariance.NextDouble() / variance;
+      }
+
+      var func = Expression.Function(name, transform, new Expression[] { Expression.Constant(name, @const), expr });
+      func.Label = "*";
+      return func;
+    }
+  }
+
+  public class OffsetTemplate : ExpressionTemplate {
+    private readonly IRandom offset;
+    // expr + offset
+    public OffsetTemplate(IRandom offset = null) : base(ExpressionGenerator.Sum) {
+      this.offset = offset;
+    }
+
+    public override Expression Instantiate(string name, IRandom random, bool sampleWithRepetition = false) {
+      var expr = SampleArguments(random, 1, sampleWithRepetition).First();
+
+      // use the evaluator to determine variance of the sampled expression and initialize the constant accordingly to reach the target offset
+      var @const = 0.0;
+      if (offset != null) {
+        var evaluator = new ExpressionEvaluator();
+        var data = evaluator.GenerateData(expr, 10000);
+        var average = data[expr].Average();
+        @const = offset.NextDouble() - average;
+      }
+
+      var func = Expression.Function(name, transform, new Expression[] { Expression.Constant(name, @const), expr });
+      func.Label = "+";
+      return func;
+    }
+  }
+
+  public class RangeTemplate : ExpressionTemplate {
+    private readonly IRandom minValue;
+    private readonly IRandom valueRange;
+    // expr + offset
+    public RangeTemplate(IRandom minValue = null, IRandom valueRange = null) : base(null) {
+      this.minValue = minValue;
+      this.valueRange = valueRange;
+    }
+
+    public override Expression Instantiate(string name, IRandom random, bool sampleWithRepetition = false) {
+      var expr = SampleArguments(random, 1, sampleWithRepetition).First();
+
+      // use the evaluator to determine variance of the sampled expression and initialize the constant accordingly to reach the target offset
+      var mult = 1.0;
+      var add = 0.0;
+
+      if (minValue != null || valueRange != null) {
+        var evaluator = new ExpressionEvaluator();
+        var data = evaluator.GenerateData(expr, 10000);
+        if (valueRange != null) {
+          var targetRange = valueRange.NextDouble();
+          var min = data[expr].Min();
+          var max = data[expr].Max();
+          var range = max - min;
+          mult = targetRange / range;
+          add = -min + min / mult;
+        }
+        if (minValue != null) {
+          var targetMin = minValue.NextDouble();
+          var min = data[expr].Min();
+          add += (targetMin - min) / mult;
+        }
+
+        expr = Expression.Function(name + "-toZero", ExpressionGenerator.Sum, new Expression[] { Expression.Constant("name-add0", add), expr });
+        expr.Label = "+";
+        expr = Expression.Function(name + "-mult", ExpressionGenerator.Product, new Expression[] { Expression.Constant("name-mult", mult), expr });
+        expr.Label = "*";
+      }
+
+      return expr;
+    }
+  }
 }