[SciPy-Dev] Moving slow parts of find_peaks to Cython

[Lars G.]

Hello,

I'm currently working on 3 PRs that move slow parts in `find_peaks`,
`peak_prominences` and `peak_widths` to Cython.

* ENH: Speed-up peak distance filtering with Cython
  https://github.com/scipy/scipy/pull/8523
* ENH: Cythonize peak_prominences
  https://github.com/scipy/scipy/pull/8541
* ENH: Cythonize peak_widths
  https://github.com/scipy/scipy/pull/8594

I quite happy with the first two PRs and think they have left the "work
in progress" state and are ready for some final polishing. I might still
tweak the third one here or there but nothing too drastic.

Because these 3 modify the same files I'd propose to merge in the given
order (if desired) so that I can rebase and resolve the arising merge
conflicts.

If any of you guys with more experience in Cython have tips to improve
the performance even further I'd be especially happy to learn. :D
As always, thank you for your time and feedback.

Best regards,
Lars