// <copyright file="BfgsMinimizerBase.cs" company="Math.NET">
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// Math.NET Numerics, part of the Math.NET Project
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// http://numerics.mathdotnet.com
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// http://github.com/mathnet/mathnet-numerics
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//
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// Copyright (c) 2009-2017 Math.NET
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//
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// Permission is hereby granted, free of charge, to any person
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// obtaining a copy of this software and associated documentation
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// files (the "Software"), to deal in the Software without
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// restriction, including without limitation the rights to use,
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// copy, modify, merge, publish, distribute, sublicense, and/or sell
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// copies of the Software, and to permit persons to whom the
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// Software is furnished to do so, subject to the following
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// conditions:
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//
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// The above copyright notice and this permission notice shall be
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// included in all copies or substantial portions of the Software.
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//
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// THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND,
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// EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES
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// OF MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND
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// NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT
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// HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY,
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// WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING
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// FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR
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// OTHER DEALINGS IN THE SOFTWARE.
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// </copyright>
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using System;
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using IStation.Numerics.LinearAlgebra;
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using IStation.Numerics.LinearAlgebra.Double;
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namespace IStation.Numerics.Optimization
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{
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public abstract class MinimizerBase
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{
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public double GradientTolerance { get; set; }
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public double ParameterTolerance { get; set; }
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public double FunctionProgressTolerance { get; set; }
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public int MaximumIterations { get; set; }
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protected const double VerySmall = 1e-15;
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/// <summary>
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/// Creates a base class for minimization
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/// </summary>
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/// <param name="gradientTolerance">The gradient tolerance</param>
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/// <param name="parameterTolerance">The parameter tolerance</param>
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/// <param name="functionProgressTolerance">The function progress tolerance</param>
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/// <param name="maximumIterations">The maximum number of iterations</param>
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protected MinimizerBase(double gradientTolerance, double parameterTolerance, double functionProgressTolerance, int maximumIterations)
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{
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GradientTolerance = gradientTolerance;
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ParameterTolerance = parameterTolerance;
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FunctionProgressTolerance = functionProgressTolerance;
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MaximumIterations = maximumIterations;
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}
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protected ExitCondition ExitCriteriaSatisfied(IObjectiveFunctionEvaluation candidatePoint, IObjectiveFunctionEvaluation lastPoint, int iterations)
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{
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Vector<double> relGrad = new DenseVector(candidatePoint.Point.Count);
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double relativeGradient = 0.0;
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double normalizer = Math.Max(Math.Abs(candidatePoint.Value), 1.0);
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for (int ii = 0; ii < relGrad.Count; ++ii)
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{
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double projectedGradient = GetProjectedGradient(candidatePoint, ii);
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double tmp = projectedGradient *
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Math.Max(Math.Abs(candidatePoint.Point[ii]), 1.0) / normalizer;
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relativeGradient = Math.Max(relativeGradient, Math.Abs(tmp));
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}
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if (relativeGradient < GradientTolerance)
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{
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return ExitCondition.RelativeGradient;
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}
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if (lastPoint != null)
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{
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double mostProgress = 0.0;
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for (int ii = 0; ii < candidatePoint.Point.Count; ++ii)
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{
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var tmp = Math.Abs(candidatePoint.Point[ii] - lastPoint.Point[ii]) /
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Math.Max(Math.Abs(lastPoint.Point[ii]), 1.0);
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mostProgress = Math.Max(mostProgress, tmp);
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}
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if (mostProgress < ParameterTolerance)
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{
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return ExitCondition.LackOfProgress;
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}
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double functionChange = candidatePoint.Value - lastPoint.Value;
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if (iterations > 500 && functionChange < 0 && Math.Abs(functionChange) < FunctionProgressTolerance)
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return ExitCondition.LackOfProgress;
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}
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return ExitCondition.None;
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}
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protected virtual double GetProjectedGradient(IObjectiveFunctionEvaluation candidatePoint, int ii)
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{
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return candidatePoint.Gradient[ii];
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}
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protected void ValidateGradientAndObjective(IObjectiveFunctionEvaluation eval)
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{
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foreach (var x in eval.Gradient)
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{
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if (Double.IsNaN(x) || Double.IsInfinity(x))
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throw new EvaluationException("Non-finite gradient returned.", eval);
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}
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if (Double.IsNaN(eval.Value) || Double.IsInfinity(eval.Value))
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throw new EvaluationException("Non-finite objective function returned.", eval);
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}
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}
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}
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