Bug#499565: basic matrix computations give incorrect results

[John Peterkort]

Package: scilab
Version: 4.1.2-6
Severity: normal
File: /usr/bin/scilab

*** Please type your report below this line ***
When using Scilab-4.1.2 in a amd64 system some basic matrix computations give 
incorrect results.  (When doing the same computations in a virtual machine 
running 32 bit Ubuntu 8.04 and scilab-4.1.2 the results are correct.)

~$ uname -a
Linux gig 2.6.26-1-openvz-amd64 #1 SMP Wed Sep 10 16:30:00 UTC 2008 x86_64 GNU/Linux


FIRST EXAMPLE:

-->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.

The result of C=2*R is incorrect. C(1,3) should be 1 not 2, C(1,5) should be 4 
not 2, and C(3,5) should be -4 not -2.

If I enter R directly using the keyboard instead of calculating it as R = 
rref(A), then the calculation C = 2 * R is correct.


SECOND EXAMPLE:

-->s = [1 5 6; 9 7 9; 1 5 4]
  s  =

     1.    5.    6.
     9.    7.    9.
     1.    5.    4.

-->t = inv(s)
  t  =

   - 0.2236842    0.1315789    0.0394737
   - 0.3552632  - 0.0263158    0.5921053
     0.5          0.         - 0.5

-->u = s * t
  u  =

     1.           0.    0.
   - 8.882D-16    2.    8.882D-16
     0.           0.    1.

u should be the 3x3 identity matrix, and so u(2,2) should be 1 not 2.



-- System Information:
Debian Release: lenny/sid
   APT prefers unstable
   APT policy: (500, 'unstable')
Architecture: amd64 (x86_64)

Kernel: Linux 2.6.26-1-openvz-amd64 (SMP w/2 CPU cores)
Locale: LANG=en_US.UTF-8, LC_CTYPE=en_US.UTF-8 (charmap=UTF-8)
Shell: /bin/sh linked to /bin/bash

Versions of packages scilab depends on:
ii  scilab-bin                    4.1.2-6    Matrix-based scientific software p
ii  tk8.4 [wish]                  8.4.19-2   Tk toolkit for Tcl and X11, v8.4 -

Versions of packages scilab recommends:
ii  scilab-doc                    4.1.2-6    Matrix-based scientific software p

Versions of packages scilab suggests:
ii  gfortran                      4:4.3.2-1  The GNU Fortran 95 compiler

-- no debconf information