I just tried the same using in DB storage. I found that the more or less monotonic linear relationship with tile size (as was shown on my original weblog post) apparently still holds for in db rasters (which I used in the original post). The overlay also remains much slower than R. (see the figure in the recompiled doc in which I just removed the -R flag )
https://dl.dropboxusercontent.com/u/2703650/Courses/geostats/SpeedTestPointOverlay2.html If these findings are generally robust I suppose that I should try to find some time to compile them properly in order to add a comment and some figures to the weblog. Duncan On Fri, Sep 20, 2013 at 12:16 AM, Duncan Golicher <[email protected]>wrote: > Hi Bborie, > > OK, I might well have been thinking on old lines. So I tested again > against the R extract function with the same data (this time on my slow > laptop) > > https://dl.dropboxusercontent.com/u/2703650/SpeedTestPointOverlay.html > > You are quite right! With a tile size of 200 to 300 or so PostGIS now does > beat the extract function in the raster package (although still slower with > suboptimal tile sizes). This was certainly not the case when I tested a > year ago (when all runs were several orders of magnitude slower unless tile > size was very small, in which case load time was prohibitive). ST_VALUE is > now performing very differently (postgis2.2dev compiled from source). More > good news! > > Duncan > > > On Thu, Sep 19, 2013 at 9:18 PM, Bborie Park <[email protected]> wrote: > >> >> Note that the point on raster overlay can be beaten easily for speed by >>> the extract function in the R raster package. However the polygon overlays >>> are now very fast and compare well with any alternative way of getting the >>> result. Using PLR to run R functions within PostGIS is great if you want >>> medians, quartiles etc or any other derived property. >>> >>> >> I wonder what is going on to make the point on raster overlay in PostGIS >> slower than in R. I'd have expected the numbers to be about the same as >> that operation is conceptually very simple. >> >> -bborie >> >> >> _______________________________________________ >> postgis-users mailing list >> [email protected] >> http://lists.osgeo.org/cgi-bin/mailman/listinfo/postgis-users >> > > > > -- > Dr Duncan Golicher > Investigador Titular, > El Colegio de la Frontera Sur, Chiapas,Mexico > Mexico tel +52 1 967 137 94 20 > Skype name duncangolicher > > Publications: http://www.mendeley.com/profiles/duncan-golicher > > Senior lecturer, Bournemouth University, UK > Centre for Conservation Ecology & Environmental Change > School of Applied Sciences > Christchurch House rm C218a > Bournemouth University > Fern Barrow > Poole (Dorset) BH12 5BB UK > Tel. +44 (0)1202 961682 > > For list of publications see Researcher ID: > http://www.researcherid.com/rid/B-4240-2009 > > [email protected] > [email protected] > > Researcher ID: > http://www.researcherid.com/rid/B-4240-2009 > -- Dr Duncan Golicher Investigador Titular, El Colegio de la Frontera Sur, Chiapas,Mexico Mexico tel +52 1 967 137 94 20 Skype name duncangolicher Publications: http://www.mendeley.com/profiles/duncan-golicher Senior lecturer, Bournemouth University, UK Centre for Conservation Ecology & Environmental Change School of Applied Sciences Christchurch House rm C218a Bournemouth University Fern Barrow Poole (Dorset) BH12 5BB UK Tel. +44 (0)1202 961682 For list of publications see Researcher ID: http://www.researcherid.com/rid/B-4240-2009 [email protected] [email protected] Researcher ID: http://www.researcherid.com/rid/B-4240-2009
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