[postgis-devel] Another Data Point

[Martin Davis]

Go for it, Regina!  The glove is dropped...

Although I suspect this test may simply be running into the slower 
memory performance due to any or all of Postgres, C, GEOS compared to 
good ol' Java...  Hard to beat that tuned JVM memory manager!

Obe, Regina wrote:
> Ah I think JTS was able to do this in about 40-50 seconds.  And my
> version was able to beat out Kevin's nested by a small margin.  I'll
> retest on mine.
>
> So I think we still need work here.
>
> I'm curious what would happen if I combined the algorithm I wrote with
> the new ST_Union how things would fair.  In theory it should fair the
> same, but I'm not really using Martin's cascaded union algorithm to the
> letter.
>
>
> -----Original Message-----
> From: postgis-devel-bounces at postgis.refractions.net
> [mailto:postgis-devel-bounces at postgis.refractions.net] On Behalf Of Paul
> Ramsey
> Sent: Wednesday, January 21, 2009 12:50 AM
> To: PostGIS Development Discussion
> Cc: lee.keel at uai.com
> Subject: [postgis-devel] Another Data Point
>
> Using the original sample set from Lee Keel,
>
> With the old style ST_Union, 3 hours, 27 minutes:
>
> uniontest=# select st_area(st_union(the_geom)) from sample_poly;
>       st_area
> --------------------
>  0.0324039850011104
> (1 row)
>
> Time: 12419261.819 ms
>
>
> With the new cascaded ST_Union, 4 minutes, 30 seconds, or 46 times
> faster.
>
> uniontest=# select st_area(st_union_fast(the_geom)) from sample_poly;
>       st_area
> --------------------
>  0.0324039850054305
> (1 row)
>
> Time: 271618.181 ms
>
>
> That's one nasty data set.
>
> P.
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-- 
Martin Davis
Senior Technical Architect
Refractions Research, Inc.
(250) 383-3022