[Pkg-octave-devel] Bug#570231: octave3.2: Errors in working with complex matrices on i386

[Steven De Herdt]

Package: octave3.2
Version: 3.2.4-1
Severity: normal

While working with complex matrices, I noticed strange things going on.
Some searching showed that there is definitely something wrong:

octave3.2:2> a=orth(randn(3));
octave3.2:3> a'*a
ans =

   1.0000e+00  -1.0742e-16   2.2264e-16
  -1.0742e-16   1.0000e+00  -3.1537e-17
   2.2264e-16  -3.1537e-17   1.0000e+00

octave3.2:4> b=orth(randn(3)+J*randn(3));
octave3.2:5> b'*b
ans =

   1.06482 + 0.00000i   0.10484 + 0.51574i   0.14882 + 0.71172i
   0.10484 - 0.51574i   0.90395 + 0.00000i  -0.07914 + 0.08895i
   0.14882 - 0.71172i  -0.07914 - 0.08895i   1.06476 + 0.00000i 

The result is Hermitian, but not quite unitary.
This also happens on octave3.0, but not on amd64 (either version).

A look through Octave's own bug reports produces e.g. 
http://old.nabble.com/wrong-output-for-complex-scalar-product-to26766409.html and
http://old.nabble.com/Wrong-results-for-svd-on-complex-numbers-to27079479.html ,
so this kind of problem is not unheard of.

Depending on one's needs, this may be an 'important' bug.


-- System Information:
Debian Release: squeeze/sid
  APT prefers testing
  APT policy: (990, 'testing')
Architecture: i386 (i686)

Kernel: Linux 2.6.32-trunk-686 (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 octave3.2 depends on:
ii  libamd2.2.0      1:3.4.0-1               approximate minimum degree orderin
ii  libarpack2       2.1+parpack96.dfsg-2+b1 Fortran77 subroutines to solve lar
ii  libatlas3gf-base 3.6.0-24                Automatically Tuned Linear Algebra
ii  libatlas3gf-sse2 3.6.0-24                Automatically Tuned Linear Algebra
ii  libblas3gf [libb 1.2-2                   Basic Linear Algebra Subroutines 3
ii  libbz2-1.0       1.0.5-4                 high-quality block-sorting file co
ii  libc6            2.10.2-2                GNU C Library: Shared libraries
ii  libcamd2.2.0     1:3.4.0-1               symmetric approximate minimum degr
ii  libccolamd2.7.1  1:3.4.0-1               constrained column approximate lib
ii  libcholmod1.7.1  1:3.4.0-1               sparse Cholesky factorization libr
ii  libcolamd2.7.1   1:3.4.0-1               column approximate minimum degree 
ii  libcurl3-gnutls  7.19.7-1                Multi-protocol file transfer libra
ii  libcxsparse2.2.3 1:3.4.0-1               concise sparse matrix library (com
ii  libfftw3-3       3.2.2-1                 library for computing Fast Fourier
ii  libfltk1.1       1.1.10-2                Fast Light Toolkit - shared librar
ii  libfreetype6     2.3.11-1                FreeType 2 font engine, shared lib
ii  libftgl2         2.1.3~rc5-3             library to render text in OpenGL u
ii  libgcc1          1:4.4.2-9               GCC support library
ii  libgfortran3     4.4.2-9                 Runtime library for GNU Fortran ap
ii  libgl1-mesa-glx  7.6.1-1                 A free implementation of the OpenG
ii  libglpk0         4.38-1                  linear programming kit with intege
ii  libglu1-mesa [li 7.6.1-1                 The OpenGL utility library (GLU)
ii  libgomp1         4.4.2-9                 GCC OpenMP (GOMP) support library
ii  libgraphicsmagic 1.3.8-1                 format-independent image processin
ii  libgraphicsmagic 1.3.8-1                 format-independent image processin
ii  libhdf5-serial-1 1.8.4-5                 Hierarchical Data Format 5 (HDF5) 
ii  libice6          2:1.0.6-1               X11 Inter-Client Exchange library
ii  libjasper1       1.900.1-6.1             The JasPer JPEG-2000 runtime libra
ii  libjpeg62        6b-15                   The Independent JPEG Group's JPEG 
ii  liblapack3gf [li 3.2.1-2                 library of linear algebra routines
ii  liblcms1         1.18.dfsg-1.2+b1        Color management library
ii  libltdl7         2.2.6b-2                A system independent dlopen wrappe
ii  libncurses5      5.7+20090803-2          shared libraries for terminal hand
ii  libpcre3         7.8-3                   Perl 5 Compatible Regular Expressi
ii  libpng12-0       1.2.42-1                PNG library - runtime
ii  libqhull5        2009.1-1                calculate convex hulls and related
ii  libqrupdate1     1.0.1-1                 Fast updates of QR and Cholesky de
ii  libreadline6     6.1-1                   GNU readline and history libraries
ii  libsm6           2:1.1.1-1               X11 Session Management library
ii  libstdc++6       4.4.2-9                 The GNU Standard C++ Library v3
ii  libtiff4         3.9.2-2                 Tag Image File Format (TIFF) libra
ii  libumfpack5.4.0  1:3.4.0-1               sparse LU factorization library
ii  libwmf0.2-7      0.2.8.4-6.1             Windows metafile conversion librar
ii  libx11-6         2:1.3.3-1               X11 client-side library
ii  libxext6         2:1.1.1-2               X11 miscellaneous extension librar
ii  libxml2          2.7.6.dfsg-2+b1         GNOME XML library
ii  octave3.2-common 3.2.4-1                 architecture-independent files for
ii  texinfo          4.13a.dfsg.1-5          Documentation system for on-line i
ii  zlib1g           1:1.2.3.4.dfsg-3        compression library - runtime

Versions of packages octave3.2 recommends:
ii  gnuplot                       4.2.6-1    A command-line driven interactive 
ii  libatlas3gf-base              3.6.0-24   Automatically Tuned Linear Algebra

Versions of packages octave3.2 suggests:
ii  octave3.2-doc                 3.2.3-1    PDF documentation on the GNU Octav
pn  octave3.2-emacsen             <none>     (no description available)
pn  octave3.2-headers             <none>     (no description available)
ii  octave3.2-htmldoc             3.2.3-1    HTML documentation on the GNU Octa
pn  octave3.2-info                <none>     (no description available)

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