[geos-devel] Is Overlay-NG active?

[Roger Bivand]

Can I ask whether there is, or could be, a function exposed in the C_API, 
or a header variable say in geoc_c.h, showing whether the running GEOS is 
using Overlay-NG or not?

After help from the list, I've now run checks on R packages either 
themselves linking to GEOS, or using functions from packages which do link 
to GEOS. A half-dozen or so fail on unit tests, typically because the 
ordering  of coordinates varies (say same polygon, but starting at  a 
different place), or the ordering of sub-geometries (say slivers from a 
Union operation) varies from before Overlay-NG. The objects are the same 
(for given precision), but unit tests in packages compare the WKT of the 
output geometry with the expected WKT (often generated from output before 
Overlay-NG).

So if we could provide a way for the unit tests to compare correctly 
branching on Overlay-NG or not, the package maintainers could avoid 
having to scramble when platforms and R packages linking to GEOS begin to 
appear.

Another question raised by package maintainers - do we know when 3.9.0 may 
be expected, and will it have Overlay-NG? However, providing them with an 
easy way to ask the GEOS runtime if it is Overlay-NG or not will relieve 
the pressure.

Anyway, the failure count is very low, a half-dozen from hundreds is fine 
(and if they didn't write tests, that isn't our problem...).

Roger

-- 
Roger Bivand
Department of Economics, Norwegian School of Economics,
Helleveien 30, N-5045 Bergen, Norway.
voice: +47 55 95 93 55; e-mail: Roger.Bivand at nhh.no
https://orcid.org/0000-0003-2392-6140
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