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Optimization: Simple to use FindMinimum facade; static impl rename

pull/511/head
Christoph Ruegg 9 years ago
parent
commit
b9b0686a75
  1. 149
      src/Numerics/FindMinimum.cs
  2. 1
      src/Numerics/Numerics.csproj
  3. 25
      src/Numerics/Optimization/GoldenSectionMinimizer.cs
  4. 10
      src/Numerics/Optimization/NelderMeadSimplex.cs
  5. 4
      src/Numerics/Optimization/NewtonMinimizer.cs
  6. 2
      src/UnitTests/OptimizationTests/GoldenSectionMinimizerTests.cs
  7. 2
      src/UnitTests/OptimizationTests/NelderMeadSimplexTests.cs
  8. 2
      src/UnitTests/OptimizationTests/NewtonMinimizerTests.cs

149
src/Numerics/FindMinimum.cs

@ -0,0 +1,149 @@
// <copyright file="FindMinimum.cs" company="Math.NET">
// Math.NET Numerics, part of the Math.NET Project
// http://numerics.mathdotnet.com
// http://github.com/mathnet/mathnet-numerics
//
// Copyright (c) 2009-2017 Math.NET
//
// Permission is hereby granted, free of charge, to any person
// obtaining a copy of this software and associated documentation
// files (the "Software"), to deal in the Software without
// restriction, including without limitation the rights to use,
// copy, modify, merge, publish, distribute, sublicense, and/or sell
// copies of the Software, and to permit persons to whom the
// Software is furnished to do so, subject to the following
// conditions:
//
// The above copyright notice and this permission notice shall be
// included in all copies or substantial portions of the Software.
//
// THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND,
// EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES
// OF MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND
// NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT
// HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY,
// WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING
// FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR
// OTHER DEALINGS IN THE SOFTWARE.
// </copyright>
using System;
using MathNet.Numerics.LinearAlgebra;
using MathNet.Numerics.Optimization;
using MathNet.Numerics.Optimization.ObjectiveFunctions;
namespace MathNet.Numerics
{
public static class FindMinimum
{
/// <summary>
/// Find value x that minimizes the scalar function f(x), constrained within bounds, using the Golden Section algorithm.
/// For more options and diagnostics consider to use <see cref="GoldenSectionMinimizer"/> directly.
/// </summary>
public static double OfScalarFunctionConstrained(Func<double, double> function, double lowerBound, double upperBound, double tolerance=1e-5, int maxIterations=1000)
{
var objective = new SimpleObjectiveFunction1D(function);
var algorithm = new GoldenSectionMinimizer(tolerance, maxIterations);
var result = algorithm.FindMinimum(objective, lowerBound, upperBound);
return result.MinimizingPoint;
}
/// <summary>
/// Find vector x that minimizes the function f(x) using the Nelder-Mead Simplex algorithm.
/// For more options and diagnostics consider to use <see cref="NelderMeadSimplex"/> directly.
/// </summary>
public static Vector<double> OfFunction(Func<Vector<double>, double> function, Vector<double> initialGuess, double tolerance=1e-8, int maxIterations=1000)
{
var objective = ObjectiveFunction.Value(function);
var algorithm = new NelderMeadSimplex(tolerance, maxIterations);
var result = algorithm.FindMinimum(objective, initialGuess);
return result.MinimizingPoint;
}
/// <summary>
/// Find vector x that minimizes the function f(x), constrained within bounds, using the Broyden–Fletcher–Goldfarb–Shanno Bounded (BFGS-B) algorithm.
/// The missing gradient is evaluated numerically (forward difference).
/// For more options and diagnostics consider to use <see cref="BfgsBMinimizer"/> directly.
/// </summary>
public static Vector<double> OfFunctionConstrained(Func<Vector<double>, double> function, Vector<double> lowerBound, Vector<double> upperBound, Vector<double> initialGuess, double gradientTolerance=1e-5, double parameterTolerance=1e-5, double functionProgressTolerance=1e-5, int maxIterations=1000)
{
var objective = ObjectiveFunction.Value(function);
var objectiveWithGradient = new ForwardDifferenceGradientObjectiveFunction(objective, lowerBound, upperBound);
var algorithm = new BfgsBMinimizer(gradientTolerance, parameterTolerance, functionProgressTolerance, maxIterations);
var result = algorithm.FindMinimum(objectiveWithGradient, lowerBound, upperBound, initialGuess);
return result.MinimizingPoint;
}
/// <summary>
/// Find vector x that minimizes the function f(x) using the Broyden–Fletcher–Goldfarb–Shanno (BFGS) algorithm.
/// For more options and diagnostics consider to use <see cref="BfgsMinimizer"/> directly.
/// </summary>
public static Vector<double> OfFunctionGradient(Func<Vector<double>, double> function, Func<Vector<double>, Vector<double>> gradient, Vector<double> initialGuess, double gradientTolerance=1e-5, double parameterTolerance=1e-5, double functionProgressTolerance=1e-5, int maxIterations=1000)
{
var objective = ObjectiveFunction.Gradient(function, gradient);
var algorithm = new BfgsMinimizer(gradientTolerance, parameterTolerance, functionProgressTolerance, maxIterations);
var result = algorithm.FindMinimum(objective, initialGuess);
return result.MinimizingPoint;
}
/// <summary>
/// Find vector x that minimizes the function f(x) using the Broyden–Fletcher–Goldfarb–Shanno (BFGS) algorithm.
/// For more options and diagnostics consider to use <see cref="BfgsMinimizer"/> directly.
/// </summary>
public static Vector<double> OfFunctionGradient(Func<Vector<double>, Tuple<double, Vector<double>>> functionGradient, Vector<double> initialGuess, double gradientTolerance=1e-5, double parameterTolerance=1e-5, double functionProgressTolerance=1e-5, int maxIterations=1000)
{
var objective = ObjectiveFunction.Gradient(functionGradient);
var algorithm = new BfgsMinimizer(gradientTolerance, parameterTolerance, functionProgressTolerance, maxIterations);
var result = algorithm.FindMinimum(objective, initialGuess);
return result.MinimizingPoint;
}
/// <summary>
/// Find vector x that minimizes the function f(x), constrained within bounds, using the Broyden–Fletcher–Goldfarb–Shanno Bounded (BFGS-B) algorithm.
/// For more options and diagnostics consider to use <see cref="BfgsBMinimizer"/> directly.
/// </summary>
public static Vector<double> OfFunctionGradientConstrained(Func<Vector<double>, double> function, Func<Vector<double>, Vector<double>> gradient, Vector<double> lowerBound, Vector<double> upperBound, Vector<double> initialGuess, double gradientTolerance=1e-5, double parameterTolerance=1e-5, double functionProgressTolerance=1e-5, int maxIterations=1000)
{
var objective = ObjectiveFunction.Gradient(function, gradient);
var algorithm = new BfgsBMinimizer(gradientTolerance, parameterTolerance, functionProgressTolerance, maxIterations);
var result = algorithm.FindMinimum(objective, lowerBound, upperBound, initialGuess);
return result.MinimizingPoint;
}
/// <summary>
/// Find vector x that minimizes the function f(x), constrained within bounds, using the Broyden–Fletcher–Goldfarb–Shanno Bounded (BFGS-B) algorithm.
/// For more options and diagnostics consider to use <see cref="BfgsBMinimizer"/> directly.
/// </summary>
public static Vector<double> OfFunctionGradientConstrained(Func<Vector<double>, Tuple<double, Vector<double>>> functionGradient, Vector<double> lowerBound, Vector<double> upperBound, Vector<double> initialGuess, double gradientTolerance=1e-5, double parameterTolerance=1e-5, double functionProgressTolerance=1e-5, int maxIterations=1000)
{
var objective = ObjectiveFunction.Gradient(functionGradient);
var algorithm = new BfgsBMinimizer(gradientTolerance, parameterTolerance, functionProgressTolerance, maxIterations);
var result = algorithm.FindMinimum(objective, lowerBound, upperBound, initialGuess);
return result.MinimizingPoint;
}
/// <summary>
/// Find vector x that minimizes the function f(x) using the Newton algorithm.
/// For more options and diagnostics consider to use <see cref="NewtonMinimizer"/> directly.
/// </summary>
public static Vector<double> OfFunctionGradientHessian(Func<Vector<double>, double> function, Func<Vector<double>, Vector<double>> gradient, Func<Vector<double>, Matrix<double>> hessian, Vector<double> initialGuess, double tolerance=1e-8, int maxIterations=1000)
{
var objective = ObjectiveFunction.GradientHessian(function, gradient, hessian);
var algorithm = new NewtonMinimizer(tolerance, maxIterations);
var result = algorithm.FindMinimum(objective, initialGuess);
return result.MinimizingPoint;
}
/// <summary>
/// Find vector x that minimizes the function f(x) using the Newton algorithm.
/// For more options and diagnostics consider to use <see cref="NewtonMinimizer"/> directly.
/// </summary>
public static Vector<double> OfFunctionGradientHessian(Func<Vector<double>, Tuple<double, Vector<double>, Matrix<double>>> functionGradientHessian, Vector<double> initialGuess, double tolerance=1e-8, int maxIterations=1000)
{
var objective = ObjectiveFunction.GradientHessian(functionGradientHessian);
var algorithm = new NewtonMinimizer(tolerance, maxIterations);
var result = algorithm.FindMinimum(objective, initialGuess);
return result.MinimizingPoint;
}
}
}

1
src/Numerics/Numerics.csproj

@ -92,6 +92,7 @@
<Compile Include="Distributions\BetaScaled.cs" />
<Compile Include="Distributions\Triangular.cs" />
<Compile Include="Euclid.cs" />
<Compile Include="FindMinimum.cs" />
<Compile Include="Generate.cs" />
<Compile Include="GoodnessOfFit.cs" />
<Compile Include="IntegralTransforms\Fourier.cs" />

25
src/Numerics/Optimization/GoldenSectionMinimizer.cs

@ -49,9 +49,16 @@ namespace MathNet.Numerics.Optimization
}
public MinimizationResult1D FindMinimum(IObjectiveFunction1D objective, double lowerBound, double upperBound)
{
return Minimum(objective, lowerBound, upperBound, XTolerance, MaximumIterations, MaximumExpansionSteps, LowerExpansionFactor, UpperExpansionFactor);
}
public static MinimizationResult1D Minimum(IObjectiveFunction1D objective, double lowerBound, double upperBound, double xTolerance = 1e-5, int maxIterations = 1000, int maxExpansionSteps = 10, double lowerExpansionFactor = 2.0, double upperExpansionFactor = 2.0)
{
if (upperBound <= lowerBound)
{
throw new OptimizationException("Lower bound must be lower than upper bound.");
}
double middlePointX = lowerBound + (upperBound - lowerBound)/(1 + Constants.GoldenRatio);
IEvaluation1D lower = objective.Evaluate(lowerBound);
@ -63,17 +70,17 @@ namespace MathNet.Numerics.Optimization
ValueChecker(upper.Value, upperBound);
int expansion_steps = 0;
while ((expansion_steps < this.MaximumExpansionSteps) && (upper.Value < middle.Value || lower.Value < middle.Value))
while ((expansion_steps < maxExpansionSteps) && (upper.Value < middle.Value || lower.Value < middle.Value))
{
if (lower.Value < middle.Value)
{
lowerBound = 0.5*(upperBound + lowerBound) - this.LowerExpansionFactor*0.5*(upperBound - lowerBound);
lowerBound = 0.5*(upperBound + lowerBound) - lowerExpansionFactor*0.5*(upperBound - lowerBound);
lower = objective.Evaluate(lowerBound);
}
if (upper.Value < middle.Value)
{
upperBound = 0.5*(upperBound + lowerBound) + this.UpperExpansionFactor*0.5*(upperBound - lowerBound);
upperBound = 0.5*(upperBound + lowerBound) + upperExpansionFactor*0.5*(upperBound - lowerBound);
upper = objective.Evaluate(upperBound);
}
@ -84,10 +91,12 @@ namespace MathNet.Numerics.Optimization
}
if (upper.Value < middle.Value || lower.Value < middle.Value)
{
throw new OptimizationException("Lower and upper bounds do not necessarily bound a minimum.");
}
int iterations = 0;
while (Math.Abs(upper.Point - lower.Point) > XTolerance && iterations < MaximumIterations)
while (Math.Abs(upper.Point - lower.Point) > xTolerance && iterations < maxIterations)
{
double testX = lower.Point + (upper.Point - middle.Point);
var test = objective.Evaluate(testX);
@ -121,16 +130,20 @@ namespace MathNet.Numerics.Optimization
iterations += 1;
}
if (iterations == MaximumIterations)
if (iterations == maxIterations)
{
throw new MaximumIterationsException("Max iterations reached.");
}
return new MinimizationResult1D(middle, iterations, ExitCondition.BoundTolerance);
}
void ValueChecker(double value, double point)
static void ValueChecker(double value, double point)
{
if (Double.IsNaN(value) || Double.IsInfinity(value))
{
throw new Exception("Objective function returned non-finite value.");
}
}
}
}

10
src/Numerics/Optimization/NelderMeadSimplex.cs

@ -64,7 +64,7 @@ namespace MathNet.Numerics.Optimization
/// <returns>The minimum point</returns>
public MinimizationResult FindMinimum(IObjectiveFunction objectiveFunction, Vector<double> initialGuess)
{
return FindMinimum(objectiveFunction, initialGuess, ConvergenceTolerance, MaximumIterations);
return Minimum(objectiveFunction, initialGuess, ConvergenceTolerance, MaximumIterations);
}
/// <summary>
@ -76,7 +76,7 @@ namespace MathNet.Numerics.Optimization
/// <returns>The minimum point</returns>
public MinimizationResult FindMinimum(IObjectiveFunction objectiveFunction, Vector<double> initialGuess, Vector<double> initalPertubation)
{
return FindMinimum(objectiveFunction, initialGuess, initalPertubation, ConvergenceTolerance, MaximumIterations);
return Minimum(objectiveFunction, initialGuess, initalPertubation, ConvergenceTolerance, MaximumIterations);
}
/// <summary>
@ -87,14 +87,14 @@ namespace MathNet.Numerics.Optimization
/// <param name="objectiveFunction">The objective function, no gradient or hessian needed</param>
/// <param name="initialGuess">The intial guess</param>
/// <returns>The minimum point</returns>
public static MinimizationResult FindMinimum(IObjectiveFunction objectiveFunction, Vector<double> initialGuess, double convergenceTolerance, int maximumIterations=1000)
public static MinimizationResult Minimum(IObjectiveFunction objectiveFunction, Vector<double> initialGuess, double convergenceTolerance, int maximumIterations=1000)
{
var initalPertubation = new LinearAlgebra.Double.DenseVector(initialGuess.Count);
for (int i = 0; i < initialGuess.Count; i++)
{
initalPertubation[i] = initialGuess[i] == 0.0 ? 0.00025 : initialGuess[i] * 0.05;
}
return FindMinimum(objectiveFunction, initialGuess, initalPertubation, convergenceTolerance, maximumIterations);
return Minimum(objectiveFunction, initialGuess, initalPertubation, convergenceTolerance, maximumIterations);
}
/// <summary>
@ -104,7 +104,7 @@ namespace MathNet.Numerics.Optimization
/// <param name="initialGuess">The intial guess</param>
/// <param name="initalPertubation">The inital pertubation</param>
/// <returns>The minimum point</returns>
public static MinimizationResult FindMinimum(IObjectiveFunction objectiveFunction, Vector<double> initialGuess, Vector<double> initalPertubation, double convergenceTolerance, int maximumIterations=1000)
public static MinimizationResult Minimum(IObjectiveFunction objectiveFunction, Vector<double> initialGuess, Vector<double> initalPertubation, double convergenceTolerance, int maximumIterations=1000)
{
// confirm that we are in a position to commence
if (objectiveFunction == null)

4
src/Numerics/Optimization/NewtonMinimizer.cs

@ -48,10 +48,10 @@ namespace MathNet.Numerics.Optimization
public MinimizationResult FindMinimum(IObjectiveFunction objective, Vector<double> initialGuess)
{
return FindMinimum(objective, initialGuess, GradientTolerance, MaximumIterations, UseLineSearch);
return Minimum(objective, initialGuess, GradientTolerance, MaximumIterations, UseLineSearch);
}
public static MinimizationResult FindMinimum(IObjectiveFunction objective, Vector<double> initialGuess, double gradientTolerance, int maxIterations=1000, bool useLineSearch = false)
public static MinimizationResult Minimum(IObjectiveFunction objective, Vector<double> initialGuess, double gradientTolerance, int maxIterations=1000, bool useLineSearch = false)
{
if (!objective.IsGradientSupported)
{

2
src/UnitTests/OptimizationTests/GoldenSectionMinimizerTests.cs

@ -42,7 +42,7 @@ namespace MathNet.Numerics.UnitTests.OptimizationTests
var algorithm = new GoldenSectionMinimizer(1e-5, 1000);
var f1 = new Func<double, double>(x => (x - 3)*(x - 3));
var obj = new SimpleObjectiveFunction1D(f1);
var r1 = algorithm.FindMinimum(obj, -100, 100);
var r1 = GoldenSectionMinimizer.Minimum(obj, -100, 100);
Assert.That(Math.Abs(r1.MinimizingPoint - 3.0), Is.LessThan(1e-4));
}

2
src/UnitTests/OptimizationTests/NelderMeadSimplexTests.cs

@ -112,7 +112,7 @@ namespace MathNet.Numerics.UnitTests.OptimizationTests
{
var obj = new MghObjectiveFunction(test_case.Function, true, true);
var result = NelderMeadSimplex.FindMinimum(obj, test_case.InitialGuess, 1e-8, 1000);
var result = NelderMeadSimplex.Minimum(obj, test_case.InitialGuess, 1e-8, 1000);
if (test_case.MinimizingPoint != null)
{

2
src/UnitTests/OptimizationTests/NewtonMinimizerTests.cs

@ -199,7 +199,7 @@ namespace MathNet.Numerics.UnitTests.OptimizationTests
{
var obj = new MghObjectiveFunction(test_case.Function, true, true);
var result = NewtonMinimizer.FindMinimum(obj, test_case.InitialGuess, 1e-8, 1000, useLineSearch: false);
var result = NewtonMinimizer.Minimum(obj, test_case.InitialGuess, 1e-8, 1000, useLineSearch: false);
if (test_case.MinimizingPoint != null)
{

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