concave_hull produces segmentation fault with specific combination of points

[raine-fmg]

Expected behavior and actual behavior.

concave_hull is causing a segmentation fault

Steps to reproduce the problem.

from shapely import concave_hull, MultiPoint
import numpy as np

concave_hull(MultiPoint(np.array([[ 584245.72096874, 7549593.72686167],
       [584251.71398371, 7549594.01629478],
       [584242.72446125, 7549593.58214511],
       [584230.73978847, 7549592.9760418 ],
       [584233.73581213, 7549593.13045099],
       [584236.7318358 , 7549593.28486019],
       [584239.72795377, 7549593.43742855],
       [584227.74314188, 7549592.83423486]])))

Operating system

Windows 10 Enterprise 22H2

Shapely version and provenance

shapely==2.0.1 (installed via pip)
numpy==1.24.2

Aditional Info

I recreated in a fresh venv to ensure there were no other complexities associated with my environment. I originally posted the issue here on SO, just in case it was something geometric that I wasn't aware of. It seems to be something to do with collinearity (but I include more notes on removing certain points etc in my SO question).

[jorisvandenbossche]

Thanks for the report!

This seems to be an issue with the current concave_hull implementation when indeed the points are almost "flat". This was reported to upstream GEOS as well a few days ago: libgeos/geos#946 (and added your reproducer as an additional example there).

[jorisvandenbossche]

This will be fixed in GEOS 3.12.1 (when released)

[mwtoews]

Also fixed in GEOS 3.11.4 (when released).