// storage is in lower triangular form, i.e. values[r][c] with c <= r
/// <summary>
/// Initializes a new symmetric matrix.
/// </summary>
/// <param name="dimension">The dimension of the matrix, which must be positive.</param>
public SymmetricMatrix(int dimension)
{
if (dimension < 1)
{
throw new ArgumentOutOfRangeException("dimension");
}
this.dimension = dimension;
values = SymmetricMatrixAlgorithms.InitializeStorage(dimension);
}
/// <summary>
/// Copies the matrix.
/// </summary>
/// <returns>An independent copy of the matrix.</returns>
public SymmetricMatrix Copy()
{
double[][] copy = SymmetricMatrixAlgorithms.InitializeStorage(dimension);
for (int r = 0; r < Dimension; r++)
{
for (int c = 0; c <= r; c++)
{
copy[r][c] = values[r][c];
}
}
return(new SymmetricMatrix(copy, dimension));
}
/// <summary>
/// Negates a symmetric matrix.
/// </summary>
/// <param name="A">The matrix.</param>
/// <returns>The matrix -A.</returns>
public static SymmetricMatrix operator -(SymmetricMatrix A)
{
if (A == null)
{
throw new ArgumentNullException("A");
}
double[][] resultStore = SymmetricMatrixAlgorithms.InitializeStorage(A.dimension);
for (int r = 0; r < A.Dimension; r++)
{
for (int c = 0; c <= r; c++)
{
resultStore[r][c] = -A.values[r][c];
}
}
return(new SymmetricMatrix(resultStore, A.dimension));
}
/// <summary>
/// Multiplies a symmetric matrix by a real factor.
/// </summary>
/// <param name="alpha">The factor.</param>
/// <param name="A">The matrix.</param>
/// <returns>The product of the matrix and the factor.</returns>
public static SymmetricMatrix operator *(double alpha, SymmetricMatrix A)
{
if (A == null)
{
throw new ArgumentNullException(nameof(A));
}
double[][] productStore = SymmetricMatrixAlgorithms.InitializeStorage(A.dimension);
for (int r = 0; r < A.Dimension; r++)
{
for (int c = 0; c <= r; c++)
{
productStore[r][c] = alpha * A.values[r][c];
}
}
return(new SymmetricMatrix(productStore, A.dimension));
}
/// <summary>
/// Subtracts two symmetric matrices.
/// </summary>
/// <param name="A">The first matrix.</param>
/// <param name="B">The second matrix.</param>
/// <returns>The difference <paramref name="A"/> - <paramref name="B"/>.</returns>
public static SymmetricMatrix operator -(SymmetricMatrix A, SymmetricMatrix B)
{
if (A == null)
{
throw new ArgumentNullException("A");
}
if (B == null)
{
throw new ArgumentNullException("B");
}
if (A.dimension != B.dimension)
{
throw new DimensionMismatchException();
}
double[][] differenceStore = SymmetricMatrixAlgorithms.InitializeStorage(A.dimension);
for (int r = 0; r < A.dimension; r++)
{
for (int c = 0; c <= r; c++)
{
differenceStore[r][c] = A.values[r][c] - B.values[r][c];
}
}
return(new SymmetricMatrix(differenceStore, A.dimension));
}
