Boost logo

Ublas :

Subject: [ublas] Help with lu_factorize
From: Marco Guazzone (marco.guazzone_at_[hidden])
Date: 2009-09-15 11:46:15


I don't understand how the function lu_factorize(A) works (note: only
the version with one parameter, which I think is for LU without
I didn't find any documentation of this function so I've decided to
experiment a bit with it.

I've attached an example.
The input matrix is:
Input matrix

In this example I use both lu_factorize(A) and lu_factorize(A,P)
(i.e.,with the permutation matrix).
The last one works perfectly. After call it, A is what I expected
(also verified with Mathematica and Octave).
LU *with* permutation matrix
        res: 0

The first one instead gives a result that I'm not able to understand.
LU *without* permutation matrix
        res: 0

NOTE: I'm using Boost 1.40 and GCC 4.4.1. I've compiled with:
$ g++ -o lu -Wall -Wextra -pedantic -ansi lu.cpp

Can you give me an help, please?


-- Marco