// <copyright file="Iterator.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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// 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 System.Collections.Generic;
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using System.Linq;
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namespace IStation.Numerics.LinearAlgebra.Solvers
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{
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/// <summary>
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/// An iterator that is used to check if an iterative calculation should continue or stop.
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/// </summary>
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public sealed class Iterator<T> where T : struct, IEquatable<T>, IFormattable
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{
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/// <summary>
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/// The collection that holds all the stop criteria and the flag indicating if they should be added
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/// to the child iterators.
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/// </summary>
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readonly List<IIterationStopCriterion<T>> _stopCriteria;
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/// <summary>
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/// The status of the iterator.
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/// </summary>
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IterationStatus _status = IterationStatus.Continue;
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/// <summary>
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/// Initializes a new instance of the <see cref="Iterator{T}"/> class with the default stop criteria.
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/// </summary>
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public Iterator()
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{
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_stopCriteria = new List<IIterationStopCriterion<T>>(Matrix<T>.Build.IterativeSolverStopCriteria());
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}
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/// <summary>
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/// Initializes a new instance of the <see cref="Iterator{T}"/> class with the specified stop criteria.
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/// </summary>
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/// <param name="stopCriteria">
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/// The specified stop criteria. Only one stop criterion of each type can be passed in. None
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/// of the stop criteria will be passed on to child iterators.
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/// </param>
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public Iterator(params IIterationStopCriterion<T>[] stopCriteria)
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{
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_stopCriteria = new List<IIterationStopCriterion<T>>(stopCriteria);
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}
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/// <summary>
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/// Initializes a new instance of the <see cref="Iterator{T}"/> class with the specified stop criteria.
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/// </summary>
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/// <param name="stopCriteria">
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/// The specified stop criteria. Only one stop criterion of each type can be passed in. None
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/// of the stop criteria will be passed on to child iterators.
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/// </param>
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public Iterator(IEnumerable<IIterationStopCriterion<T>> stopCriteria)
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{
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_stopCriteria = new List<IIterationStopCriterion<T>>(stopCriteria);
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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 => _status;
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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="Iterator{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 iterators 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 (_stopCriteria.Count == 0)
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{
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throw new ArgumentException("There is no stop criterion in the collection.");
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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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// While we're cancelled we don't call on the stop-criteria.
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if (_status == IterationStatus.Cancelled)
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{
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return _status;
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}
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foreach (var stopCriterion in _stopCriteria)
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{
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var status = stopCriterion.DetermineStatus(iterationNumber, solutionVector, sourceVector, residualVector);
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if (status == IterationStatus.Continue)
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{
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continue;
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}
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_status = status;
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return _status;
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}
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// Got all the way through
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// So we're running because we had vectors passed to us.
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_status = IterationStatus.Continue;
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return _status;
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}
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/// <summary>
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/// Indicates to the iterator that the iterative process has been cancelled.
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/// </summary>
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/// <remarks>
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/// Does not reset the stop-criteria.
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/// </remarks>
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public void Cancel()
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{
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_status = IterationStatus.Cancelled;
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}
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/// <summary>
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/// Resets the <see cref="Iterator{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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foreach (var stopCriterion in _stopCriteria)
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{
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stopCriterion.Reset();
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}
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}
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/// <summary>
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/// Creates a deep clone of the current iterator.
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/// </summary>
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/// <returns>The deep clone of the current iterator.</returns>
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public Iterator<T> Clone()
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{
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return new Iterator<T>(_stopCriteria.Select(sc => sc.Clone()));
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}
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}
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}
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