UL factorization

[U,L]=ul(A) returns a permuted unit upper triangular matrix U and a lower triangular matrix L such t

Description

[U,L]=ul(A) returns a permuted unit upper triangular matrix U and a lower triangular matrix L such that A = U*L. The UL factors can be used for solving linear equations, similarly to the factors of the LU decomposition. The function calls Matlab's built-in lu function, so it works for full or sparse, real or complex, square or (for more recent Matlab versions) rectangular matrices. The m-file is just 4 lines:
function [u,l]=ul(A)
[u,l]=lu(A(end:-1:1,end:-1:1));
u=u(end:-1:1,end:-1:1);
l=l(end:-1:1,end:-1:1);

• MATLAB release: MATLAB 5.2 (R10)

[Tim Davis]

Why is this useful? Why is there no consideration of fill-reducing orderings (the 4-output LU)? Since no fill-reducing orderings are exploited, this function is not useful for large sparse matrices, as the description states.