[postgis-devel] RE: 40% faster st_distance and returningmeasurepoints :-)

[Nicklas Avén]

Thank you Regina

I've been looking for this hints about how to do, but I guess I have
looked at the wrong places. If there is no guide about how to
participate maybe that's something needed.

Now I have managed to create a function that delivers the lines from
where the distance is calulated.:-)

And the ordinary st_distance works about 40% faster.

Thanks again
Nicklas


lör 2009-03-14 klockan 21:16 -0400 skrev Paragon Corporation:
> Nick,
>  
> Some general tips when suggesting changes.  
>  
> 1) Add an entry to our bug tracker system
> 2) If you are providing code -- attach it to the bug tracker system,
> but we would prefer a patch instead of a full file.
> For windows development, I usually use Tortoise SVN.  It makes it
> wicked easy to create a patch and to work against the latest PostGIS
> subversion trunk and branch.  Presumably this patch you have is
> against trunk since for branch we only accept minor changes and bug
> fixes that do not introduce new functionality.
>  
> Aside from that -- keep up the good work and welcome to the club.
>  
> Thanks,
> Regina
> 
> 
> ______________________________________________________________________
> From: postgis-devel-bounces at postgis.refractions.net
> [mailto:postgis-devel-bounces at postgis.refractions.net] On Behalf Of
> nicklas.aven at jordogskog.no
> Sent: Thursday, March 12, 2009 11:12 AM
> To: postgis-devel at postgis.refractions.net
> Subject: [postgis-devel] RE: 40% faster st_distance and
> returningmeasurepoints :-)
> 
> 
> 
> Hi again
>  
> I found that my modification crashed st_dwithin, but this version I
> think will work.
>  
> /Nicklas
>  
>  
>  
>  
> Datum: 2009-03-11 13:46:35
> Från: nicklas.aven at jordogskog.no
> Till: 
> Ämne: 40% faster st_distance and returning measurepoints :-)
> 
> 
> Hallo
> 
> I'm new to this list and have done my first steps in writing c-code.
> Thanks to the very well-written and readable source-code I think I
> have succeded over my expectations.
> 
> What I have done is rewriting quite great parts of measures.c. My goal
> was to get the points out of st_distance from where the distance was
> calculated. 
> The result was that st_distance worked about 40% faster on my small
> testmaterial. The points I wanted is also there, but I don't know the
> best way to output them.
> 
> The idea I have followed is just to store the shortest distance and
> it's points in a new structure I have called DISTLINE. 
> Then I only do testing if a diastance is closer then the "earlier
> shortest" in "distance2d_pt_pt" so there is no testing in the looping
> of the other relateted functions. 
> 
> I think the progress in speed should make it interesting for
> implementing but someone experienced have to take a serious look at
> it. 
> I also would be greatful if I could get some help with the output of
> my points. they are included in the structure DISTLINE like 
> 
> typedef struct
> {
>   double d;  /*distance*/
>   POINT2D *p1;  /*1st measure point*/
>   POINT2D *p2; /*2nd measure point*/
> } DISTLINE;
> 
> and they will be present when the process returns to function:
> lwgeom_mindistance2d_recursive
> 
> I attach my measure.c, libwgeom.h a small dataset with som roads in
> Norway and my resulting dll
> 
> The test I have done to compare speed is just 
> select a.vegnummer,b.vegnummer, st_distance(a.the_geom,b.the_geom) as
> avstand from distancetest a,distancetest b;
> on the attached dataset.
> My result was:
> 
> original measure.c
> Total query runtime: 3999 ms.
> 400 rows retrieved.
> 
> The new measure.c
> Total query runtime: 2374 ms.
> 400 rows retrieved.
> 
> This increase in speed could be quite important on big "nearest
> neighbour" calculations.
> I also mean som function like st_shortestline(geom1,geom2) would be
> nice and now the points for that line is ready to use.
> Have a nice day
> from a quite proud beginner
> 
> Nicklas Avén
> 
>  
> 
> _______________________________________________
> postgis-devel mailing list
> postgis-devel at postgis.refractions.net
> http://postgis.refractions.net/mailman/listinfo/postgis-devel