/// <summary>
/// Calculates the <c>true</c> residual of the matrix equation Ax = b according to: residual = b - Ax
/// </summary>
/// <param name="matrix">Instance of the <see cref="Matrix"/> A.</param>
/// <param name="residual">Residual values in <see cref="Vector"/>.</param>
/// <param name="x">Instance of the <see cref="Vector"/> x.</param>
/// <param name="b">Instance of the <see cref="Vector"/> b.</param>
static void CalculateTrueResidual(Matrix matrix, Vector residual, Vector x, Vector b)
{
// -Ax = residual
matrix.Multiply(x, residual);
residual.Multiply(-1, residual);
// residual + b
residual.Add(b, residual);
}
/// <summary>
/// Calculates the <c>true</c> residual of the matrix equation Ax = b according to: residual = b - Ax
/// </summary>
/// <param name="matrix">Instance of the <see cref="Matrix"/> A.</param>
/// <param name="residual">Residual values in <see cref="Vector"/>.</param>
/// <param name="x">Instance of the <see cref="Vector"/> x.</param>
/// <param name="b">Instance of the <see cref="Vector"/> b.</param>
private static void CalculateTrueResidual(Matrix matrix, Vector residual, Vector x, Vector b)
{
// -Ax = residual
matrix.Multiply(x, residual);
// Do not use residual = residual.Negate() because it creates another object
residual.Multiply(-1, residual);
// residual + b
residual.Add(b, residual);
}