[postgis-devel] Lame attempt at cascade union in sql

[Martin Davis]

Athlon 63 3500+
2 GB RAM (not that that makes a difference).

Obe, Regina wrote:
> Yap Kevin gave me his sample dataset and that's what I've been using to
> compare his results with mine. What is the processor on your box?  I
> gather Kevin and I must be running something similar since our timings
> seem about the same.
>
> -----Original Message-----
> From: postgis-devel-bounces at postgis.refractions.net
> [mailto:postgis-devel-bounces at postgis.refractions.net] On Behalf Of
> Martin Davis
> Sent: Friday, August 08, 2008 11:52 AM
> To: PostGIS Development Discussion
> Subject: Re: [postgis-devel] Lame attempt at cascade union in sql
>
> Regina, I'm not sure what I can really test for you - I don't have 
> PostGIS on my box, so it's difficult to replicate these tests.  And 
> subsetting the geometries in JTS isn't going to give the same result 
> set, due to the clustering.  Or am I missing something?  Is your sample 
> dataset the same one that Kevin & I are using?
>
> Anyway, don't feel too bad - I think there's a fundamental performance 
> difference between the basic union function in JTS and in GEOS.  Java is
>
> much more efficient at memory allocation than C++ is (at least, using 
> std C++ memory operations).  So barring a stroke of genius in GEOS-land 
> I think JTS is alway going to out-perform.
>
> Also, despite my earlier sarcastic remark about processor speed, this 
> *is* going to make a difference - perhaps by 2-3x?  (Although I don't 
> have a screaming fast box by any means...)
>
> M
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-- 
Martin Davis
Senior Technical Architect
Refractions Research, Inc.
(250) 383-3022