[Debian-med-packaging] Bug#1057983: brian: runtime dependency on cython legitimate

[Étienne Mollier]

Hi Matthias,

Would it be helpful, for the upcoming transition, to demote the
dependency to cython3 to a recommendation?

Matthias Klose, on 2023-12-11:
> Please check that this dependency can be removed. Most likely this
> dependency is generated by pybuild, because the setup.py requires
> Cython in it's 'install_requires' attribute.  Please remove that,
> after checking that it is not a runtime dependency, and also report
> that issue upstream for upcoming releases.
> 
> If the runtime dependency is necessary, please just close this bug
> report.

I suspected that python3-brian is one of the few cases where the
cython3 dependency could be legitimate, so I searched within
upstream examples and found at least one[1] which, when I
attempt to run is without cython3, will output warnings and
informational messages, then crash several steps later, issue
which is fixed when I install cython3 and rerun the script.

[1]: https://brian2.readthedocs.io/en/stable/examples/advanced.compare_GSL_to_conventional.html

Meddling with GSL looks far fetched for this module's usage
though, and most functions have implemented mechanisms to
fallback to numpy when cython3 is not available.  cython3 is
thus not 100% necessary, but it is useful at runtime.  I checked
against the existing autopkgtest, and lacking cython3 has no
influence in that particular context so far.  That being said, a
number of functions benefit from a substancial (as in 170%, but
GSL will bump that to a whooping 3500% depending on the target
CPU) performance boost from running with cython3 available.
(Speaking of GSL, this one depends on make and libgsl-dev, but
they look missing from the runtime dependencies for now; g++ is
part of the suggestions though.)

Have a nice day,  :)
-- 
  .''`.  Étienne Mollier <emollier at debian.org>
 : :' :  gpg: 8f91 b227 c7d6 f2b1 948c  8236 793c f67e 8f0d 11da
 `. `'   sent from /dev/pts/3, please excuse my verbosity
   `-    on air: Matt Stevens - Big Sky
-------------- next part --------------
A non-text attachment was scrubbed...
Name: signature.asc
Type: application/pgp-signature
Size: 833 bytes
Desc: not available
URL: <http://alioth-lists.debian.net/pipermail/debian-med-packaging/attachments/20231214/ee6d20ef/attachment-0001.sig>