[geos-devel] Is Overlay-NG active?

[Regina Obe]

Roger,

I'll let Paul answer the question of when we can expect a 3.9 as he probably has a better idea than anyone else.
All I know is the plan is we'll be releasing GEOS 3.9 and PostGIS 3.1 around the same time since there is some functionality in PostGIS 3.1 that leverages GEOS 3.9 if it is compiled with GEOS 3.9.

As far as testing, on the PostGIS side to make the old Geos and new Geos agree, I've been applying ST_Normalize

Which looks to come from Geos CAPI - GEOSNormalize

Can you use that to deal with the  failures you are running into?  That should make the wkt of both GEOS old and new agree.

Thanks,
Regina

> -----Original Message-----
> From: geos-devel [mailto:geos-devel-bounces at lists.osgeo.org] On Behalf Of
> Paul Ramsey
> Sent: Thursday, October 15, 2020 12:39 PM
> To: Roger.Bivand at nhh.no; GEOS Development List <geos-
> devel at lists.osgeo.org>
> Subject: Re: [geos-devel] Is Overlay-NG active?
> 
> 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?
> 
> 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
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