[geos-devel] Question about Geometry and GeometryFactoryrelationship...

[strk at refractions.net]

On Wed, May 11, 2005 at 12:21:05PM -0500, Steve Lime wrote:
> Hi Martin: Thanks for the clarification, something to think about
> anyway. In lieu of a code change at the moment I'll couple the two
> myself. GEOS Geometry's are buried behind MapServer shapes so the
> developer/user doesn't see 'em. With MapServer there no logical
> candidate structure/object to attach the factory to without explicitly
> creating something new and GEOS specfic. I'd rather not go there.
> 
> Is the factory object relatively lightweight so that constantly
> instatiating new objects doesn't hurt performance?

This must be profiled to tell.

The default constructor for a GeometryFactory:

GeometryFactory::GeometryFactory() {
        precisionModel=new PrecisionModel();
        SRID=0;
        coordinateListFactory=DefaultCoordinateSequenceFactory::instance();
}

The default constructor for a PrecisionModel:

PrecisionModel::PrecisionModel(){
        modelType=FLOATING;
        scale=1.0;
}

So it takes 2 ints, 1 double and 2 pointers of size + 3 function 
calls (own and PM ctors and ::instance).

Would it be ok for threading if GEOS provides a
defaultGeometryFactory ?

--strk;

> 
> Steve
> 
> >>> mbdavis at VividSolutions.com 5/11/2005 12:02:18 PM >>>
> Geometrys need some metadata to allow methods to execute.  This
> currently includes things like PrecisionModel and SRID (and may grow
> to
> include more things in the future).  Rather than duplicate these for
> every geometry, the GF is referenced by the geometry and shared with
> any
> created geometrys.  This works well in the Java world.  
> 
> In the C++ world if this is a problem I guess each Geometry could own
> its own copy of the GF.  This would require a code change to make
> Geometrys copy the GF for created Geometrys, rather than keep a
> reference to it.
> 
> 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 
> > Steve Lime
> > Sent: May 11, 2005 9:52 AM
> > To: geos-devel at geos.refractions.net 
> > Subject: [geos-devel] Question about Geometry and 
> > GeometryFactoryrelationship...
> > 
> > 
> > Hi All: I'm running into trouble making a clean integration 
> > of GEOS into MapServer. Problem is that GeometryFactory 
> > objects must persist while any Geometry objects spawned from 
> > that factory are in us. This makes it necessary to either use 
> > a global factory which is problematic with theading, or 
> > somehow couple the two so that they are created, persist and 
> > are deleted together. I'm curious why Geometry's cannot 
> > stand-alone? Perhaps I'm missing something obvious in my 
> > implementation.
> > 
> > Steve
> > 
> > Stephen Lime
> > Data & Applications Manager
> > 
> > Minnesota DNR
> > 500 Lafayette Road
> > St. Paul, MN 55155
> > 651-297-2937
> > _______________________________________________
> > geos-devel mailing list
> > geos-devel at geos.refractions.net 
> > http://geos.refractions.net/mailman/listinfo/geos-devel 
> > 
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