Bug#1037242: liblapacke: dsyev() only returns upper/lower triangle of eigenvector matrix

[Sébastien Villemot]

Dear David,

Le vendredi 09 juin 2023 à 10:16 +0000, David Houseman a écrit :
> Package: liblapacke
> Version: 3.9.0-3
> Severity: important
> X-Debbugs-Cc: david at grey-house.net
> 
> 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.

[…]

> 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.

Thanks for your report.

I confirm that the bug is present in Debian “Bullseye” 11, and that it
is fixed in the recently Debian “Bookworm” 12.

I am going to fix it in bullseye (see #1038943 for the details).

Cheers,

-- 
⢀⣴⠾⠻⢶⣦⠀  Sébastien Villemot
⣾⠁⢠⠒⠀⣿⡁  Debian Developer
⢿⡄⠘⠷⠚⠋⠀  https://sebastien.villemot.name
⠈⠳⣄⠀⠀⠀⠀  https://www.debian.org

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