> >> >> > since v.what.rast is (for me) extremely slow, I have added > >> >> > cover map support to r.random. > >> >> .. > >> >> > PS: v.what.rast still running on just 300k points while I > >> >> > implemented above :-) Anyone who could make v.what.rast faster? > >> >> > >> >> Maybe it's the qsort(), maybe it's the i,j loop within a loop. > >> > > >> > The loop is certainly inefficient. Rather than shifting the entire > >> > array down every time it finds a duplicate, it should keep separate > >> > source and destination indices, e.g. (untested): > >> > > >> > for (i = j = 0; j < point_cnt; j++) Glynn: > > --- vector/v.what.rast/main.c 17 Oct 2007 14:07:23 -0000 1.26 > > +++ vector/v.what.rast/main.c 21 Oct 2007 17:52:42 -0000 > > ... patch Markus: > Thanks (for your patience): I have made a Spearfish test: > > g.region rast=elevation.10m > r.random elevation.10m vect=elevpnts n=5000 --o > v.db.addcol elevpnts col="height double precision" > > # old > time v.what.rast elevpnts rast=elevation.10m col=height > real 0m25.253s > user 0m24.756s > sys 0m0.308s > > # new > real 0m24.040s > user 0m23.707s > sys 0m0.297s > > Interestingly, timing rather identical (also for 1000). Using the DBF > driver here.
It is as expected, only a small speed up. While the for i,j loop map may have been inefficient, it still was fast enough to only take a second to get though. The bulk of the time was and is being taken up by running db_execute_imediate() for each point later on in the script. (then db_commit_transaction() is run after the loop) To solve this in v.in.garmin and v.in.gpsbabel we wrote all db SET .. to .. statements to a temporary file, then ran db.execute once for the tmp file instead of earlier running db.execute for every point. It is not a direct analogy, but it did made a huge difference there. Or maybe it is the bsearch() for every point in the db_execute_imediate() loop? Hamish __________________________________________________ Do You Yahoo!? Tired of spam? Yahoo! Mail has the best spam protection around http://mail.yahoo.com _______________________________________________ grass-dev mailing list [email protected] http://grass.itc.it/mailman/listinfo/grass-dev
