Bug#499565: basic matrix computations give incorrect results

[Sylvestre Ledru]

> -->A = [ 1 2 0 0 1; 2 0 1 0 2; 3 2 1 -1 4]
>   A  =
> 
>      1.    2.    0.    0.    1.
>      2.    0.    1.    0.    2.
>      3.    2.    1.  - 1.    4.
> 
> -->R = rref(A)
>   R  =
> 
>      1.    0.    0.5     0.    2.
>      0.    1.  - 0.25    0.    2.776D-17
>      0.    0.    0.      1.  - 2.
> 
> -->C = 2 * R
>   C  =
> 
>      2.    0.    2.     0.    2.
>      0.    2.  - 0.5    0.    5.551D-17
>      0.    0.    0.     2.  - 2.
> 
> -->C(1,3)-1
>   ans  =
> 
>    - 1.110D-16

I confirm that it is a bug caused by gfortran which I reported upstream:
http://gcc.gnu.org/bugzilla/show_bug.cgi?id=37863
It is fixed and will be available in the next version of gfortran.

A workaround has been added in Scilab 5.0.3 which will be soon available upstream and in Debian.
(once jeuclid made it thought new).

Sylvestre