[geos-devel] Is Overlay-NG active?

[Roger Bivand]

On Thu, 15 Oct 2020, Paul Ramsey wrote:

> The "plan" as I see it is to, for 3.9, actually make NG the default for 
> the standard intersection(), union(), unaryunion(), difference(), 
> symdifference() calls. So the "test" will be "is this GEOS 3.9". I don't 
> want to go forward into the future where a released GEOS has two 
> potential behaviour modes, that way lies madness. We needed to keep a 
> switch in place to allow other development to continue and to compare 
> before/after easily on the working branch (and to allow people like you 
> to test the new without suddenly have everything break on ordinary 
> testing).
>
> Does that make sense?

Yes, it does, thank you.

Best wishes,

Roger

>
> P
>
>> On Oct 15, 2020, at 8:59 AM, Roger Bivand <Roger.Bivand at nhh.no> wrote:
>>
>> 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
>> https://scholar.google.no/citations?user=AWeghB0AAAAJ&hl=en
>> _______________________________________________
>> geos-devel mailing list
>> geos-devel at lists.osgeo.org
>> https://lists.osgeo.org/mailman/listinfo/geos-devel
>
>

-- 
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
https://scholar.google.no/citations?user=AWeghB0AAAAJ&hl=en