Thanks Markus for the explanation. I've set PostGIS as my backend. Will revert as I get more into v.net
On 22/04/2013, at 8:20 PM, Markus Metz wrote: > On Mon, Apr 22, 2013 at 11:03 AM, Mark Wynter <m...@dimensionaledge.com> > wrote: >> Thanks Marcus. >> Tried sqlite backend suggestion - no improvement - then read that that >> sqlite is the default backend for grass7. >> I suspect the complexity of the input dataset may be the contributing >> factor. For example, I ran v.clean over the already cleaned OSM dataset >> (2.6M lines), and it took only a few minutes since there were no >> intersections and no duplicates to remove. > > I tested with a OSM road vector with 2.6M lines, the output has 5.3M > lines: lots of intersections and duplicates which were cleaned in less > than 15 minutes. > > I am surprised that you experience slow removal of duplicates, > breaking lines should take much longer. > > About why removing duplicates takes longer at the end: when you have 5 > lines that could be duplicates you could check > > 1 with 2, 3, 4, 5 > 2 with 1, 3, 4, 5 > 3 with 1, 2, 4, 5 > 4 with 1, 2, 3, 5 > 5 with 1, 2, 3, 4 > > or checking each combination only once: > > 1 with 2, 3, 4, 5 > 2 with 3, 4, 5 > 3 with 4, 5 > 4 with 5 > > alternatively > > 2 with 1 > 3 with 1, 2 > 4 with 1, 2, 3 > 5 with 1, 2, 3, 4 > > The current implementation uses the latter. > > Markus M > >> >> >>> Something is wrong there. Your dataset has 971074 roads, I tested with >>> an OSM dataset with 2645287 roads, 2.7 times as many as in your >>> dataset. Cleaning these 2645287 lines took me less than 15 minutes. I >>> suspect a slow database backend (dbf). Try to use sqlite as database >>> backend: >>> >>> db.connect driver=sqlite >>> database=$GISDBASE/$LOCATION_NAME/$MAPSET/sqlite/sqlite.db >>> >>> Do not substitute the variables. >>> >>> HTH, >>> >>> Markus M >> _______________________________________________ grass-user mailing list grass-user@lists.osgeo.org http://lists.osgeo.org/mailman/listinfo/grass-user
