/// <summary>
/// Generate a fill-reducing ordering using the CCOLAMD algorithm.
/// </summary>
/// <param name="A">The matrix.</param>
/// <param name="constraints">Constraint set of A (of size ncol).</param>
/// <returns>The permutation vector or NULL, if an error occurred.</returns>
public static int[] Generate <T>(CompressedColumnStorage <T> A, int[] constraints)
where T : struct, IEquatable <T>, IFormattable
{
int rows = A.RowCount;
int cols = A.ColumnCount;
var p = new int[cols + 1];
A.ColumnPointers.CopyTo(p, 0);
var amd = new COLAMD();
var info = amd.Order(rows, cols, A.RowIndices, p, constraints);
if (info.Status < COLAMD_OK)
{
// error
return(null);
}
return(p);
}
/// <summary>
///
/// </summary>
/// <param name="n">Number of rows and columns in the symmetrix matrix A.</param>
/// <param name="A">Row indices of A (of size nnz).</param>
/// <param name="p">Column pointers of A (of size n+1).</param>
/// <param name="perm">The permutation vector (of size n+1).</param>
/// <param name="cmember">Constraint set of A (of size n).</param>
/// <param name="stype">0: use both parts, >0: upper, <0: lower.</param>
/// <returns></returns>
/// <remarks>
/// The array <paramref name="perm"/> is used as a workspace during the ordering,
/// which is why it must be of length n+1, not just n.
///
/// If <paramref name="stype"/> < 0, then only the strictly lower triangular
/// part of A is accessed. The upper triangular part is assumed to be the transpose
/// of the lower triangular part. This is the same as SYMAMD, which did not have
/// an stype parameter.
///
/// If <paramref name="stype"/> > 0, only the strictly upper triangular part
/// of A is accessed. The lower triangular part is assumed to be the transpose
/// of the upper triangular part.
///
/// If <paramref name="stype"/> == 0, then the nonzero pattern of A+A' is ordered.
/// </remarks>
public COLAMD.Info Order(int n, int[] A, int[] p, int[] perm, int[] cmember, int stype)
{
var amd = new COLAMD();
return(amd.SymOrder(n, A, p, perm, GetControl(), cmember, stype));
}
/// <summary>
///
/// </summary>
/// <param name="n">Number of rows and columns in the symmetrix matrix A.</param>
/// <param name="A">Row indices of A (of size nnz).</param>
/// <param name="p">Column pointers of A (of size n+1).</param>
/// <param name="perm">The permutation vector (of size n+1).</param>
/// <returns></returns>
/// <remarks>
/// The array <paramref name="perm"/> is used as a workspace during the ordering,
/// which is why it must be of length n+1, not just n.
/// </remarks>
public COLAMD.Info Order(int n, int[] A, int[] p, int[] perm)
{
var amd = new COLAMD();
return(amd.SymOrder(n, A, p, perm, GetControl()));
}
