[Debian-med-packaging] Bug#1096018: bart-cuda: autopkgtest failure with glibc 2.41 due to increased accuracy of atan2f function

[Aurelien Jarno]

control: severity -1 serious

Hi,

On 2025-02-15 11:06, Aurelien Jarno wrote:
> Source: bart-cuda
> Version: 0.8.00-2
> Severity: important
> Tags: ftbfs patch
> Justification: fails to build from source
> X-Debbugs-Cc: debian-glibc at lists.debian.org
> User: debian-glibc at lists.debian.org
> Usertags: glibc2.41
> 
> Dear maintainer,
> 
> The bart-cuda autopkgtest fails when run against glibc 2.41, which is
> currently in experiemntal. It fails with [1]:
> 
> | 3772s touch tests/test-traj-custom
> | 3772s set -e ; mkdir /tmp/autopkgtest-lxc.oedkyjwg/downtmp/autopkgtest_tmp/tests/tmp/$$/ ; cd /tmp/autopkgtest-lxc.oedkyjwg/downtmp/autopkgtest_tmp/tests/tmp/$$/			;\
> | 3772s /tmp/autopkgtest-lxc.oedkyjwg/downtmp/autopkgtest_tmp//traj -R0. -r -y360 -D t0.ra 				;\
> | 3772s /tmp/autopkgtest-lxc.oedkyjwg/downtmp/autopkgtest_tmp//phantom -k -t t0.ra k0.ra 				;\
> | 3772s /tmp/autopkgtest-lxc.oedkyjwg/downtmp/autopkgtest_tmp//traj -R30. -r -y360 -D t30.ra			;\
> | 3772s /tmp/autopkgtest-lxc.oedkyjwg/downtmp/autopkgtest_tmp//phantom -k -t t30.ra k30.ra 				;\
> | 3772s /tmp/autopkgtest-lxc.oedkyjwg/downtmp/autopkgtest_tmp//estshift 4 k0.ra k30.ra | grep "30.00000" 		;\
> | 3772s rm *.ra ; cd .. ; rmdir /tmp/autopkgtest-lxc.oedkyjwg/downtmp/autopkgtest_tmp/tests/tmp/$$/
> | 3774s make: *** [tests/traj.mk:53: tests/test-traj-rot] Error 1
> 
> Investigation shows that this is due to improved accuracy of the atan2f
> function in glibc 2.41. In details bart-cuda computes
> atan2f(0x1.166202p-4, 0x1.e22c5ap-4) and it expects it to be 30.00000
> when converted from radian to degrees, ie it expects the atan2f function
> to return 0x1.0c1524p-1.
> 
> With glibc 2.41, the atan2f function has been improved [2] and now
> returns instead 0x1.0c1522p-1 which is closer to the real value than
> 0x1.0c1524p-1.  This corresponds to 29.999998 when converted to degrees.
> The patch below fixes the issue by accepting both values.
> 

glibc 2.41 is now in unstable, bumping the severity accordingly.

Regards
Aurelien

-- 
Aurelien Jarno                          GPG: 4096R/1DDD8C9B
aurelien at aurel32.net                     http://aurel32.net