/// <summary>
/// Setup the pivot strategy.
/// </summary>
/// <param name="matrix">The matrix.</param>
/// <param name="rhs">The right-hand side vector.</param>
/// <param name="eliminationStep">The current elimination step.</param>
/// <param name="max">The maximum row/column index.</param>
/// <exception cref="ArgumentNullException">
/// Thrown if <paramref name="matrix"/> or <paramref name="rhs"/> is <c>null</c>.
/// </exception>
public void Setup(ISparseMatrix <T> matrix, ISparseVector <T> rhs, int eliminationStep, int max)
{
matrix.ThrowIfNull(nameof(matrix));
rhs.ThrowIfNull(nameof(rhs));
// Initialize Markowitz row, column and product vectors if necessary
if (_markowitzRow == null || _markowitzRow.Length != matrix.Size + 1)
{
Initialize(matrix);
}
Count(matrix, rhs, eliminationStep, max);
Products(eliminationStep, max);
}
/// <summary>
/// Move the pivot to the diagonal for this elimination step.
/// </summary>
/// <param name="matrix">The matrix.</param>
/// <param name="rhs">The right-hand side vector.</param>
/// <param name="pivot">The pivot element.</param>
/// <param name="eliminationStep">The elimination step.</param>
/// <remarks>
/// This is done by swapping the rows and columns of the diagonal and that of the pivot.
/// </remarks>
/// <exception cref="ArgumentNullException">
/// Thrown if <paramref name="matrix"/>, <paramref name="rhs"/> or <paramref name="pivot"/> is <c>null</c>.
/// </exception>
public void MovePivot(ISparseMatrix <T> matrix, ISparseVector <T> rhs, ISparseMatrixElement <T> pivot, int eliminationStep)
{
matrix.ThrowIfNull(nameof(matrix));
rhs.ThrowIfNull(nameof(rhs));
pivot.ThrowIfNull(nameof(pivot));
// If we haven't setup, just skip
if (_markowitzProduct == null)
{
return;
}
int oldProduct;
var row = pivot.Row;
var col = pivot.Column;
// If the pivot is a singleton, then we just consumed it
if (_markowitzProduct[row] == 0 || _markowitzProduct[col] == 0)
{
Singletons--;
}
// Exchange rows
if (row != eliminationStep)
{
// Swap row Markowitz numbers
var tmp = _markowitzRow[row];
_markowitzRow[row] = _markowitzRow[eliminationStep];
_markowitzRow[eliminationStep] = tmp;
// Update the Markowitz product
oldProduct = _markowitzProduct[row];
_markowitzProduct[row] = _markowitzRow[row] * _markowitzColumn[row];
if (oldProduct == 0)
{
if (_markowitzProduct[row] != 0)
{
Singletons--;
}
}
else
{
if (_markowitzProduct[row] == 0)
{
Singletons++;
}
}
}
// Exchange columns
if (col != eliminationStep)
{
// Swap column Markowitz numbers
var tmp = _markowitzColumn[col];
_markowitzColumn[col] = _markowitzColumn[eliminationStep];
_markowitzColumn[eliminationStep] = tmp;
// Update the Markowitz product
oldProduct = _markowitzProduct[col];
_markowitzProduct[col] = _markowitzRow[col] * _markowitzColumn[col];
if (oldProduct == 0)
{
if (_markowitzProduct[col] != 0)
{
Singletons--;
}
}
else
{
if (_markowitzProduct[col] == 0)
{
Singletons++;
}
}
}
// Also update the moved pivot
oldProduct = _markowitzProduct[eliminationStep];
_markowitzProduct[eliminationStep] = _markowitzRow[eliminationStep] * _markowitzColumn[eliminationStep];
if (oldProduct == 0)
{
if (_markowitzProduct[eliminationStep] != 0)
{
Singletons--;
}
}
else
{
if (_markowitzProduct[eliminationStep] == 0)
{
Singletons++;
}
}
}