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<P><FONT SIZE=2>Paul,<BR>
I wouldn't proclaim victory on that alone. <BR>
<BR>
Do another test. 20 seconds sounds a little too short. <BR>
I'm not saying it isn't right and my memory may be wrong on the JTS result too.<BR>
Besides JTS would have to collect geometries as well I imagine so you can't simply throw that out and proclaim victory.<BR>
<BR>
<BR>
Test out<BR>
<BR>
SELECT geometrytype(st_unite_garray(ARRAY(SELECT the_geom FROM sample_poly)))<BR>
<BR>
Though that wouldn't be quite a true test either. But somewhere between the<BR>
two would be the answer.<BR>
<BR>
<BR>
-----Original Message-----<BR>
From: postgis-devel-bounces@postgis.refractions.net on behalf of Paul Ramsey<BR>
Sent: Wed 1/21/2009 1:58 PM<BR>
To: PostGIS Development Discussion<BR>
Subject: Re: [postgis-devel] Another Data Point<BR>
<BR>
Well, just running this:<BR>
<BR>
uniontest=# select geometrytype(collect(the_geom)) from sample_poly;<BR>
geometrytype<BR>
--------------------<BR>
GEOMETRYCOLLECTION<BR>
(1 row)<BR>
<BR>
Time: 261624.195 ms<BR>
<BR>
takes 251 of the 271 seconds the union operation took... the<BR>
implication is that the GEOS portion of the work is on the order of 10<BR>
seconds.<BR>
<BR>
P.<BR>
<BR>
On Wed, Jan 21, 2009 at 10:10 AM, Martin Davis <mbdavis@refractions.net> wrote:<BR>
> Could be... It would be interesting to see whether GEOS is faster than<BR>
> JTS. Needs a test environment able to run both pieces of code on the same<BR>
> hardware.<BR>
><BR>
> Paul Ramsey wrote:<BR>
>><BR>
>> I got another run in, right near the end, and it showed that<BR>
>> GEOSUnionCascaded took only about 50% of the time in that slice. There<BR>
>> was still more memcpy'ing first. I bet GEOSUnionCascaded on its own<BR>
>> would be as fast as JTS (or faster?).<BR>
>><BR>
>> P.<BR>
>><BR>
>> On Wed, Jan 21, 2009 at 9:05 AM, Paul Ramsey <pramsey@cleverelephant.ca><BR>
>> wrote:<BR>
>><BR>
>>><BR>
>>> Interesting! The Shark only samples for about 20 seconds, so I only<BR>
>>> got the first 10% or so of the run, and the biggest user in that time<BR>
>>> period memcpy'ing in LWGEOM_accum (postgis) and<BR>
>>> advance_transition_function (pgsql). So we are spending a non-trivial<BR>
>>> amount of time just accumulating the input...<BR>
>>><BR>
>>> P<BR>
>>><BR>
>>> On Wed, Jan 21, 2009 at 9:00 AM, Paul Ramsey <pramsey@cleverelephant.ca><BR>
>>> wrote:<BR>
>>><BR>
>>>><BR>
>>>> The glove is dropped indeed... why speculate when I have the Shark...<BR>
>>>> time to see where our time goes...<BR>
>>>><BR>
>>>> P<BR>
>>>><BR>
>>>> On Wed, Jan 21, 2009 at 8:55 AM, Martin Davis <mbdavis@refractions.net><BR>
>>>> wrote:<BR>
>>>><BR>
>>>>><BR>
>>>>> Go for it, Regina! The glove is dropped...<BR>
>>>>><BR>
>>>>> Although I suspect this test may simply be running into the slower<BR>
>>>>> memory<BR>
>>>>> performance due to any or all of Postgres, C, GEOS compared to good ol'<BR>
>>>>> Java... Hard to beat that tuned JVM memory manager!<BR>
>>>>><BR>
>>>>> Obe, Regina wrote:<BR>
>>>>><BR>
>>>>>><BR>
>>>>>> Ah I think JTS was able to do this in about 40-50 seconds. And my<BR>
>>>>>> version was able to beat out Kevin's nested by a small margin. I'll<BR>
>>>>>> retest on mine.<BR>
>>>>>><BR>
>>>>>> So I think we still need work here.<BR>
>>>>>><BR>
>>>>>> I'm curious what would happen if I combined the algorithm I wrote with<BR>
>>>>>> the new ST_Union how things would fair. In theory it should fair the<BR>
>>>>>> same, but I'm not really using Martin's cascaded union algorithm to<BR>
>>>>>> the<BR>
>>>>>> letter.<BR>
>>>>>><BR>
>>>>>><BR>
>>>>>> -----Original Message-----<BR>
>>>>>> From: postgis-devel-bounces@postgis.refractions.net<BR>
>>>>>> [<A HREF="mailto:postgis-devel-bounces@postgis.refractions.net">mailto:postgis-devel-bounces@postgis.refractions.net</A>] On Behalf Of<BR>
>>>>>> Paul<BR>
>>>>>> Ramsey<BR>
>>>>>> Sent: Wednesday, January 21, 2009 12:50 AM<BR>
>>>>>> To: PostGIS Development Discussion<BR>
>>>>>> Cc: lee.keel@uai.com<BR>
>>>>>> Subject: [postgis-devel] Another Data Point<BR>
>>>>>><BR>
>>>>>> Using the original sample set from Lee Keel,<BR>
>>>>>><BR>
>>>>>> With the old style ST_Union, 3 hours, 27 minutes:<BR>
>>>>>><BR>
>>>>>> uniontest=# select st_area(st_union(the_geom)) from sample_poly;<BR>
>>>>>> st_area<BR>
>>>>>> --------------------<BR>
>>>>>> 0.0324039850011104<BR>
>>>>>> (1 row)<BR>
>>>>>><BR>
>>>>>> Time: 12419261.819 ms<BR>
>>>>>><BR>
>>>>>><BR>
>>>>>> With the new cascaded ST_Union, 4 minutes, 30 seconds, or 46 times<BR>
>>>>>> faster.<BR>
>>>>>><BR>
>>>>>> uniontest=# select st_area(st_union_fast(the_geom)) from sample_poly;<BR>
>>>>>> st_area<BR>
>>>>>> --------------------<BR>
>>>>>> 0.0324039850054305<BR>
>>>>>> (1 row)<BR>
>>>>>><BR>
>>>>>> Time: 271618.181 ms<BR>
>>>>>><BR>
>>>>>><BR>
>>>>>> That's one nasty data set.<BR>
>>>>>><BR>
>>>>>> P.<BR>
>>>>>> _______________________________________________<BR>
>>>>>> postgis-devel mailing list<BR>
>>>>>> postgis-devel@postgis.refractions.net<BR>
>>>>>> <A HREF="http://postgis.refractions.net/mailman/listinfo/postgis-devel">http://postgis.refractions.net/mailman/listinfo/postgis-devel</A><BR>
>>>>>> -----------------------------------------<BR>
>>>>>> The substance of this message, including any attachments, may be<BR>
>>>>>> confidential, legally privileged and/or exempt from disclosure<BR>
>>>>>> pursuant to Massachusetts law. It is intended<BR>
>>>>>> solely for the addressee. If you received this in error, please<BR>
>>>>>> contact the sender and delete the material from any computer.<BR>
>>>>>> _______________________________________________<BR>
>>>>>> postgis-devel mailing list<BR>
>>>>>> postgis-devel@postgis.refractions.net<BR>
>>>>>> <A HREF="http://postgis.refractions.net/mailman/listinfo/postgis-devel">http://postgis.refractions.net/mailman/listinfo/postgis-devel</A><BR>
>>>>>><BR>
>>>>>><BR>
>>>>>><BR>
>>>>><BR>
>>>>> --<BR>
>>>>> Martin Davis<BR>
>>>>> Senior Technical Architect<BR>
>>>>> Refractions Research, Inc.<BR>
>>>>> (250) 383-3022<BR>
>>>>><BR>
>>>>> _______________________________________________<BR>
>>>>> postgis-devel mailing list<BR>
>>>>> postgis-devel@postgis.refractions.net<BR>
>>>>> <A HREF="http://postgis.refractions.net/mailman/listinfo/postgis-devel">http://postgis.refractions.net/mailman/listinfo/postgis-devel</A><BR>
>>>>><BR>
>>>>><BR>
>><BR>
>> _______________________________________________<BR>
>> postgis-devel mailing list<BR>
>> postgis-devel@postgis.refractions.net<BR>
>> <A HREF="http://postgis.refractions.net/mailman/listinfo/postgis-devel">http://postgis.refractions.net/mailman/listinfo/postgis-devel</A><BR>
>><BR>
>><BR>
><BR>
> --<BR>
> Martin Davis<BR>
> Senior Technical Architect<BR>
> Refractions Research, Inc.<BR>
> (250) 383-3022<BR>
><BR>
> _______________________________________________<BR>
> postgis-devel mailing list<BR>
> postgis-devel@postgis.refractions.net<BR>
> <A HREF="http://postgis.refractions.net/mailman/listinfo/postgis-devel">http://postgis.refractions.net/mailman/listinfo/postgis-devel</A><BR>
><BR>
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