// <copyright file="FailureStopCriterion.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) 2009-2014 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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// 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 System.Diagnostics;
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namespace IStation.Numerics.LinearAlgebra.Solvers
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{
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/// <summary>
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/// Defines an <see cref="IIterationStopCriterion{T}"/> that monitors residuals for NaN's.
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/// </summary>
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public sealed class FailureStopCriterion<T> : IIterationStopCriterion<T> where T : struct, IEquatable<T>, IFormattable
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{
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/// <summary>
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/// The status of the calculation
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/// </summary>
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IterationStatus _status = IterationStatus.Continue;
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/// <summary>
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/// The iteration number of the last iteration.
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/// </summary>
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int _lastIteration = -1;
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/// <summary>
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/// Determines the status of the iterative calculation based on the stop criteria stored
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/// by the current <see cref="IIterationStopCriterion{T}"/>. Result is set into <c>Status</c> field.
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/// </summary>
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/// <param name="iterationNumber">The number of iterations that have passed so far.</param>
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/// <param name="solutionVector">The vector containing the current solution values.</param>
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/// <param name="sourceVector">The right hand side vector.</param>
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/// <param name="residualVector">The vector containing the current residual vectors.</param>
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/// <remarks>
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/// The individual stop criteria may internally track the progress of the calculation based
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/// on the invocation of this method. Therefore this method should only be called if the
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/// calculation has moved forwards at least one step.
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/// </remarks>
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public IterationStatus DetermineStatus(int iterationNumber, Vector<T> solutionVector, Vector<T> sourceVector, Vector<T> residualVector)
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{
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if (iterationNumber < 0)
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{
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throw new ArgumentOutOfRangeException(nameof(iterationNumber));
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}
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if (solutionVector.Count != residualVector.Count)
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{
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throw new ArgumentException("The array arguments must have the same length.");
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}
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if (_lastIteration >= iterationNumber)
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{
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// We have already stored the actual last iteration number
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// For now do nothing. We only care about the next step.
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return _status;
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}
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// Store the infinity norms of both the solution and residual vectors
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double residualNorm = residualVector.InfinityNorm();
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double solutionNorm = solutionVector.InfinityNorm();
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_status = double.IsNaN(solutionNorm) || double.IsNaN(residualNorm) ? IterationStatus.Failure : IterationStatus.Continue;
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_lastIteration = iterationNumber;
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return _status;
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}
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/// <summary>
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/// Gets the current calculation status.
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/// </summary>
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public IterationStatus Status
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{
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[DebuggerStepThrough]
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get => _status;
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}
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/// <summary>
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/// Resets the <see cref="IIterationStopCriterion{T}"/> to the pre-calculation state.
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/// </summary>
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public void Reset()
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{
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_status = IterationStatus.Continue;
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_lastIteration = -1;
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}
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/// <summary>
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/// Clones the current <see cref="FailureStopCriterion{T}"/> and its settings.
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/// </summary>
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/// <returns>A new instance of the <see cref="FailureStopCriterion{T}"/> class.</returns>
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public IIterationStopCriterion<T> Clone()
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{
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return new FailureStopCriterion<T>();
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}
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}
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}
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