// <copyright file="UnitPreconditioner.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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// Software is furnished to do so, subject to the following
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// </copyright>
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using System;
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namespace IStation.Numerics.LinearAlgebra.Solvers
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{
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/// <summary>
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/// A unit preconditioner. This preconditioner does not actually do anything
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/// it is only used when running an <see cref="IIterativeSolver{T}"/> without
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/// a preconditioner.
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/// </summary>
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public sealed class UnitPreconditioner<T> : IPreconditioner<T> where T : struct, IEquatable<T>, IFormattable
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{
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/// <summary>
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/// The coefficient matrix on which this preconditioner operates.
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/// Is used to check dimensions on the different vectors that are processed.
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/// </summary>
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int _size;
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/// <summary>
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/// Initializes the preconditioner and loads the internal data structures.
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/// </summary>
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/// <param name="matrix">
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/// The matrix upon which the preconditioner is based.
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/// </param>
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/// <exception cref="ArgumentException">If <paramref name="matrix"/> is not a square matrix.</exception>
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public void Initialize(Matrix<T> matrix)
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{
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if (matrix.RowCount != matrix.ColumnCount)
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{
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throw new ArgumentException("Matrix must be square.", nameof(matrix));
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}
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_size = matrix.RowCount;
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}
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/// <summary>
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/// Approximates the solution to the matrix equation <b>Ax = b</b>.
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/// </summary>
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/// <param name="rhs">The right hand side vector.</param>
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/// <param name="lhs">The left hand side vector. Also known as the result vector.</param>
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/// <exception cref="ArgumentException">
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/// <para>
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/// If <paramref name="rhs"/> and <paramref name="lhs"/> do not have the same size.
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/// </para>
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/// <para>
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/// - or -
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/// </para>
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/// <para>
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/// If the size of <paramref name="rhs"/> is different the number of rows of the coefficient matrix.
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/// </para>
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/// </exception>
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public void Approximate(Vector<T> rhs, Vector<T> lhs)
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{
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if ((lhs.Count != rhs.Count) || (lhs.Count != _size))
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{
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throw new ArgumentException("All vectors must have the same dimensionality.");
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}
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rhs.CopyTo(lhs);
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}
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}
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}
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