[boost] uBLAS: problem with sparse_vector

From: Marc Duflot (m.duflot_at_[hidden])
Date: 2002-06-27 09:17:52

There is a bug in uBLAS that is illustrated with the following code:

#include <iostream>
#include <boost/numeric/ublas/vector_sp.h>
#include <boost/numeric/ublas/io.h>

int main () {
    numerics::sparse_vector<double> v (3);
    v(1) = v(0) = 42;
    std::cout << v << std::endl;
}

The output of the program is (with g++ 2.95.2 and g++ 3.0.4 on Linux)
[3](42,0,0)

The element v(1) is 0 instead of 42. The bug comes from the fact that v(1) is 
evaluated before v(0) = 42. The bug is not present with the Intel compiler on 
the same platform.

Note: there is the same problem with Loki::AssocVector.

I think that this feature must be documented (or corrected if it is possible) 
before uBLAS is accepted into boost.

Sorry if it is indeed documented somewhere or if it is a known bug.

-- 
Marc Duflot
http://vesta.ltas.ulg.ac.be/~duflot/