[scilab-Users] Inexplicable result with scilab 5.0.2 and matrix multiplication

[Sylvestre Ledru]

Hello,

It is most probably a bug in the printing functions... I can reproduce
it with the binary (ie not compiled on my computer) but I can't on my
dev version (compiled with gfortran 4.3.1)
Once, we had a simular bug caused by a bug in gfortran. Maybe it is a
regression.

Thanks for pointing this out.
Sylvestre

Le lundi 13 octobre 2008 à 23:32 +0200, Christoph Dittmann a écrit :
> Hi,
> 
> I've got a problem with scilab 5.0.2. It seems to print certain values 
> wrong. The following example shows the problem:
> -->M = [1,2;3,2]; C = M^(-1)*M
>   C  =
> 
>      2.           1.110D-16
>      1.110D-16    2.
> 
> This is what I get with scilab 5.0.2 on Ubuntu 8.04 (x86) using the 
> precompiled version from http://www.scilab.org/download/ . My problem 
> are the 2's on the diagonal since I've no idea where they come from.
> 
> With scilab 4.1.2, the one from the Ubuntu 8.04 repository, I get what I 
> expect:
> -->M = [1,2;3,2]; C = M^(-1)*M
>   C  =
> 
>      1.           1.110D-16
>      5.551D-17    1.
> 
> 
> Some further calculations with scilab 5.0.2 show that the problem seems 
> to lie in the printing of the result and not its actual numerical value:
> -->x = C(1,1)
>   x  =
> 
>      2.
> -->x * 2
>   ans =
> 
>     2.
> -->x + 0.01
>   ans  =
> 
>      1.01
> 
> 
> Could that be a bug or did I just miss something crucial?
> 
> 
> Thanks,
> Christoph