mathnet-numerics/src/Numerics/LinearAlgebra/Complex32/Solvers/Preconditioners/UnitPreconditioner.cs

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using System;
using MathNet.Numerics.LinearAlgebra.Solvers;
using MathNet.Numerics.Properties;

namespace MathNet.Numerics.LinearAlgebra.Complex32.Solvers.Preconditioners
{
    using Numerics;

    /// <summary>
    /// A unit preconditioner. This preconditioner does not actually do anything
    /// it is only used when running an <see cref="IIterativeSolver{T}"/> without
    /// a preconditioner.
    /// </summary>
    internal sealed class UnitPreconditioner : IPreConditioner
    {
        /// <summary>
        /// The coefficient matrix on which this preconditioner operates.
        /// Is used to check dimensions on the different vectors that are processed.
        /// </summary>
        private int _size;
        
        /// <summary>
        /// Initializes the preconditioner and loads the internal data structures.
        /// </summary>
        /// <param name="matrix">
        /// The matrix upon which the preconditioner is based.
        /// </param>
        /// <exception cref="ArgumentNullException">If <paramref name="matrix"/> is <see langword="null"/>. </exception>
        /// <exception cref="ArgumentException">If <paramref name="matrix"/> is not a square matrix.</exception>
        public void Initialize(Matrix<Complex32> matrix)
        {
            if (matrix == null)
            {
                throw new ArgumentNullException("matrix");
            }

            if (matrix.RowCount != matrix.ColumnCount)
            {
                throw new ArgumentException(Resources.ArgumentMatrixSquare, "matrix");
            }

            _size = matrix.RowCount;
        }

        /// <summary>
        /// Approximates the solution to the matrix equation <b>Ax = b</b>.
        /// </summary>
        /// <param name="rhs">The right hand side vector.</param>
        /// <param name="lhs">The left hand side vector. Also known as the result vector.</param>
        /// <exception cref="ArgumentNullException">If <paramref name="rhs"/> is <see langword="null"/>.</exception>
        /// <exception cref="ArgumentNullException">If <paramref name="lhs"/> is <see langword="null"/>. </exception>
        /// <exception cref="ArgumentException">
        ///   <para>
        ///     If <paramref name="rhs"/> and <paramref name="lhs"/> do not have the same size.
        ///   </para>
        ///   <para>
        ///     - or -
        ///   </para>
        ///   <para>
        ///     If the size of <paramref name="rhs"/> is different the number of rows of the coefficient matrix.
        ///   </para>
        /// </exception>
        public void Approximate(Vector<Complex32> rhs, Vector<Complex32> lhs)
        {
            if (rhs == null)
            {
                throw new ArgumentNullException("rhs");
            }

            if (lhs == null)
            {
                throw new ArgumentNullException("lhs");
            }

            if ((lhs.Count != rhs.Count) || (lhs.Count != _size))
            {
                throw new ArgumentException(Resources.ArgumentVectorsSameLength);
            }

            rhs.CopyTo(lhs);
        }

        /// <summary>
        /// Approximates the solution to the matrix equation <b>Ax = b</b>.
        /// </summary>
        /// <param name="rhs">The right hand side vector.</param>
        /// <returns>The left hand side vector.</returns>
        /// <exception cref="ArgumentNullException">If <paramref name="rhs"/> is <see langword="null"/>. </exception>
        /// <exception cref="ArgumentException">
        /// If the size of <paramref name="rhs"/> is different the number of rows of the coefficient matrix.
        /// </exception>
        public Vector<Complex32> Approximate(Vector<Complex32> rhs)
        {
            if (rhs == null)
            {
                throw new ArgumentNullException("rhs");
            }

            if (rhs.Count != _size)
            {
                throw new ArgumentException(Resources.ArgumentMatrixDimensions);
            }

            var result = new DenseVector(rhs.Count);
            Approximate(rhs, result);
            return result;
        }
    }
}