/// <summary>
/// Computes an LU factorization of an N-square matrix A using partial pivoting with row interchanges.
/// </summary>
/// <param name="A"></param>
/// <param name="X"></param>
/// <param name="P"></param>
/// <typeparam name="M"></typeparam>
/// <typeparam name="N"></typeparam>
public static ref BlockMatrix <N, double> getrf <N>(BlockMatrix <N, double> A, Span <int> P, ref BlockMatrix <N, double> X)
where N : ITypeNat, new()
{
var n = nati <N>();
var lda = n;
A.CopyTo(ref X);
var exit = LAPACK.LAPACKE_dgetrf(RowMajor, n, n, ref head(X), lda, ref head(P));
checkx(exit);
return(ref X);
}