[geos-devel] QD (Quad-Double) Approach to Robustness

[Martin Davis]

Not sure - I'll try it soon.

Martin Davis, Senior Technical Architect
Vivid Solutions Inc.      www.vividsolutions.com
Suite #1A-2328 Government Street Victoria, B.C. V8T 5G5
Phone: (250) 385 6040 - Local 308 Fax: (250) 385 6046


> -----Original Message-----
> From: geos-devel-bounces at geos.refractions.net 
> [mailto:geos-devel-bounces at geos.refractions.net] On Behalf Of 
> strk at refractions.net
> Sent: June 14, 2006 11:56 AM
> To: GEOS Development List
> Subject: Re: [geos-devel] QD (Quad-Double) Approach to Robustness
> 
> 
> On Wed, Jun 14, 2006 at 11:40:00AM -0700, Martin Davis wrote:
> > > > In any case, I'm not sure that JTS uses FP equals for
> > > anything other
> > > > than checking whether two points are *exactly* the 
> same.  So this
> > > > should be portable, I assume.
> > 
> > I think you're misreading what I said.  I meant that JTS 
> uses == (via
> > equals2D) to test whether the *value* of two coordinates is exactly 
> > the same.  Pointers don't enter into it.
> > 
> > You absolutely should NOT try to replace those equality tests with 
> > "approximately equals".  Approx equals may have a place in 
> some of the 
> > algorithms, but this needs to be carefully evaluated on a 
> case-by-case 
> > basis.
> 
> Ok, so back to original problem: do you obtain a successful 
> result with JTS against the XML test I attached ? GEOS is 
> successfull or not depending on wheter or not Coordinate copy 
> constructor and/or assignment operator is inlined.
> 
> --strk;
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