oriented_envelope divide by zero warning when applied to an axes-aligned rectangle

[DOSull]

Reporting this here so it doesn't fall between the cracks.

I found this on shapely (see shapely/shapely#2215) where it shows up as a warning calling minimum_rotated_rectangle on a rectangle parallel to the axes. As reported there:

Python 3.13.1 | packaged by conda-forge | (main, Jan 13 2025, 09:45:31) [Clang 18.1.8 ] on darwin
Type "help", "copyright", "credits" or "license" for more information.
>>> from shapely.geometry import *
>>> Polygon([Point(-100,-100),Point(-100,100),Point(100,100),Point(100,-100)]).minimum_rotated_rectangle
/opt/miniconda3/envs/shapely/lib/python3.13/site-packages/shapely/constructive.py:996: RuntimeWarning: divide by zero encountered in oriented_envelope
  return lib.oriented_envelope(geometry, **kwargs)
<POLYGON ((-100 -100, -100 100, 100 100, 100 -100, -100 -100))>

Apparently it's an Apple Silicon problem only. It's only a warning, and the reported result appears correct. So not urgent, but kind of annoying!

I thought I'd see if it was happening on the CLI using geosop but that became a bit of a rabbit hole. I assume the function in question is minAreaRectangle. In any case it doesn't run into the problem at the command line:

geosop -a "POLYGON ((-100 -100, -100 100, 100 100, 100 -100, -100 -100))" minAreaRectangle 
POLYGON ((-100 -100, -100 100, 100 100, 100 -100, -100 -100))

Which is curious...

[mwtoews]

Until recently (#1228), geosop didn't catch/show floating point exceptions. But if you are able to build and test from main, try the same command in -v verbose mode to see if it shows any other messages. I didn't see any message from Linux, so it could be tested on Apple Silicon.

The algorithm in question is mostly in https://github.com/libgeos/geos/blob/main/src/algorithm/MinimumAreaRectangle.cpp which doesn't show any obvious source of division. Note that pin-pointing the exact place where a FPE occurs can be time-consuming, as I don't know how to register a trace.

[dr-jts]

Indeed this does show a FPE in geosop on Apple silicon:

geosop -v -a "POLYGON ((-100 -100, -100 100, 100 100, 100 -100, -100 -100))" minAreaRectangle 
Input A: WKT literal
Read 1 geometries, 5 vertices  -- 1,478 usec
[ 1] minAreaRectangle: A[1] Polygon( 5 )  -> Polygon( 5 )  --  519 usec
POLYGON ((-100 -100, -100 100, 100 100, 100 -100, -100 -100))
Operation raised floating-point environment flag(s): FE_DIVBYZERO FE_INVALID
Ran 1 minAreaRectangle ops ( 5 vertices)  -- 519 usec    (GEOS 3.14.0dev)

Now, how to find out where that's occurring...

[DOSull]

If I had to guess I'd say it's somewhere in the convex hull stuff that is invoked? But I am not even not an expert on C++ or GEOS, so I'll leave figuring out where it's happening to the experts!