Your message dated Wed, 26 Jul 2023 21:17:24 +0000
with message-id <[email protected]>
and subject line Bug#1037242: fixed in lapack 3.9.0-3+deb11u1
has caused the Debian Bug report #1037242,
regarding liblapacke: dsyev() only returns upper/lower triangle of eigenvector
matrix
to be marked as done.
This means that you claim that the problem has been dealt with.
If this is not the case it is now your responsibility to reopen the
Bug report if necessary, and/or fix the problem forthwith.
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--
1037242: https://bugs.debian.org/cgi-bin/bugreport.cgi?bug=1037242
Debian Bug Tracking System
Contact [email protected] with problems
--- Begin Message ---
Package: liblapacke
Version: 3.9.0-3
Severity: important
X-Debbugs-Cc: [email protected]
Hello,
Given a symmetric matrix, LAPACKE dsyev() should return in place the matrix of
eigenvectors
(when JOBZ = 'V'). The eigenvector matrix is not symmetric (it is orthogonal).
However,
it appears that dsyev() only returns the upper/lower triangle of the
eigenvector matrix,
which is not enough to easily construct the full eigenvector matrix.
Example (compile with gcc main.c -llapacke):
#include "stdio.h"
#include "lapacke.h"
int main()
{
const int N = 2;
double a[2*2] = { 1.0, 0.5, 0.5, 1.0 };
double s[2];
printf( "input:\n" );
printf( "%f %f\n", a[0], a[1] );
printf( "%f %f\n", a[2], a[3] );
LAPACKE_dsyev( LAPACK_ROW_MAJOR, 'V', 'U', N, a, N, s );
printf( "output:\n" );
printf( "%f %f\n", a[0], a[1] );
printf( "%f %f\n", a[2], a[3] );
return 0;
}
Output:
input:
1.000000 0.500000
0.500000 1.000000
output:
-0.707107 0.707107
0.500000 0.707107
Problem:
The 0.5 in the output lower triangle should be 0.707107.
There is the opposite problem if UPLO = 'L'.
This problem applies to symmetric matrices of all sizes.
I reported this problem to the library authors at
https://github.com/Reference-LAPACK/lapack/issues/850
and they have indicated that this problem is fixed upstream.
This is a fairly critical problem that would silently lead
to quite wrong answers for certain mathematical techniques
possibly including symmetric matrix inversion and/or
multilinear regression. I think it would be better to have
it fixed but I have no idea how difficult it would be to
patch debian stable. I will try the new debian testing and
see whether it is also affected.
Thank you very much,
David Houseman
-- System Information:
Debian Release: 11.7
APT prefers stable-updates
APT policy: (500, 'stable-updates'), (500, 'stable-security'), (500, 'stable')
Architecture: amd64 (x86_64)
Kernel: Linux 5.10.0-21-amd64 (SMP w/4 CPU threads)
Locale: LANG=C, LC_CTYPE=C.UTF-8 (charmap=UTF-8), LANGUAGE not set
Shell: /bin/sh linked to /usr/bin/dash
Init: systemd (via /run/systemd/system)
LSM: AppArmor: enabled
Versions of packages liblapacke depends on:
ii libblas3 [libblas.so.3] 3.9.0-3
ii libc6 2.31-13+deb11u6
ii liblapack3 [liblapack.so.3] 3.9.0-3
ii libopenblas0-pthread [liblapack.so.3] 0.3.13+ds-3
ii libtmglib3 3.9.0-3
liblapacke recommends no packages.
liblapacke suggests no packages.
-- no debconf information
--- End Message ---
--- Begin Message ---
Source: lapack
Source-Version: 3.9.0-3+deb11u1
Done: Sébastien Villemot <[email protected]>
We believe that the bug you reported is fixed in the latest version of
lapack, which is due to be installed in the Debian FTP archive.
A summary of the changes between this version and the previous one is
attached.
Thank you for reporting the bug, which will now be closed. If you
have further comments please address them to [email protected],
and the maintainer will reopen the bug report if appropriate.
Debian distribution maintenance software
pp.
Sébastien Villemot <[email protected]> (supplier of updated lapack package)
(This message was generated automatically at their request; if you
believe that there is a problem with it please contact the archive
administrators by mailing [email protected])
-----BEGIN PGP SIGNED MESSAGE-----
Hash: SHA512
Format: 1.8
Date: Fri, 23 Jun 2023 14:53:50 +0200
Source: lapack
Architecture: source
Version: 3.9.0-3+deb11u1
Distribution: bullseye
Urgency: medium
Maintainer: Debian Science Team
<[email protected]>
Changed-By: Sébastien Villemot <[email protected]>
Closes: 1037242
Changes:
lapack (3.9.0-3+deb11u1) bullseye; urgency=medium
.
* lapacke-syev-heev.patch: new patch, fixes eigenvector matrix in
LAPACKE’s interface to symmetric eigenvalue problem (syev and heev
functions) (Closes: #1037242)
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