[Boost-users] Re: ublas and matrix expression

From: Russell Hind (rhind_at_[hidden])
Date: 2004-04-08 08:33:35

Angus Leeming wrote:
> Russell Hind wrote:
> 
>>Thanks, where are these methods defined?  I'm using 1.30.2 and have
>>searched the ublas directory for files with lu_factorize in and
>>can't find it.
> 
> 
> I do not know when these routines arrived, but they are certainly 
> present in boost 1.31. Example usage:
> 

Yep, found lu.hpp in CVS.  This is what I think I have

matrix<double> X;
vector<double> y;

These are known and I have created them.

I'm trying to solve

Xa = y

So should I be doing this?  (I'm getting compile errors with bcc so 
can't check anything at the moment).

permutation_matrix<size_t> pm(X.size1());
lu_factorize(X, pm)
lu_substitute(X, pm, y);

so on the way out of lu_substitute, y will contain the values for a?

Or am I completely on the wrong track?

If not, is there another way of solving this without using lu_*?  the 
initial expression I gave came from re-arranging Xa = y to give it in 
terms of a.  I'm currently stuck with 1.30.2 but would like to be able 
to solve this using boost, rather than having to find another library.

Thanks

Russell