[geos-devel] 3.1.0rc2

[Obe, Regina]

This is just an observation.  I've seen a lot of these type failures in my garden tests and just ignored them.

This for example happens often if you in PostGIS create a MULTIPOLYGON by collecting valid polygons that happen to intersect in some way 
and then pass this to ST_Union. Those are invalid anyway so of course its not that big of a surprise they fail.

I'm just wandering if maybe as part of intermediary process, the union algorithm is creating such invalid multipolygons

-----Original Message-----
From: geos-devel-bounces at lists.osgeo.org on behalf of Hartmut Kaiser
Sent: Fri 1/30/2009 6:35 PM
To: 'GEOS Development List'
Subject: RE: [geos-devel] 3.1.0rc2
 
 The union bug seems to be longstanding. The old process also failed.
 It is a mystery to me why we can't produce pairwise failures though.

 It might be, that you're seeing an error from unioning geometries being
 intermediary results from preceding union operations. The cascaded union
algorithm doesn't 'grow' the result sequentially, but builds several
sub-geometries based on proximity criteria of the initial geometries and
'grows' those. As a result the sequence of pair-wise union operations is
completely different from the naïve union algorithm.

Regards Hartmut

> 
> P
> 
> On 30-Jan-09, at 1:52 PM, Sean Gillies <sgillies at frii.com> wrote:
> 
> > Fine here. That cascaded union problem remains.
> >
> > On Jan 30, 2009, at 1:18 PM, Paul Ramsey wrote:
> >
> >> I've placed RC2 on the download site, with Matz changes and the
> >> removal of stoopid debugging noise in the last one.
> >>
> >> http://download.osgeo.org/geos/geos-3.1.0rc2.tar.bz2
> >>
> >> PSC, if you don't howl about this one, I'm going to make the link
> >> public on Monday morning.
> >>
> >> --
> >> Paul Ramsey
> >> OpenGeo - http://opengeo.org
> >> PostGIS is Love.
> >>
> >> _______________________________________________
> >> geos-devel mailing list
> >> geos-devel at lists.osgeo.org
> >> http://lists.osgeo.org/mailman/listinfo/geos-devel
> >
> >
> >
> > --
> > Sean Gillies
> > sean.gillies at gmail.com
> > http://sgillies.net
> >
> > _______________________________________________
> > geos-devel mailing list
> > geos-devel at lists.osgeo.org
> > http://lists.osgeo.org/mailman/listinfo/geos-devel
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