Le jeudi 28 octobre 2010 21:39:51, Buchheit, Maximilian a écrit : > When you use "gdalwarp -tps" what is the practical limit to the number of > GCPs useable in the thin plate spline algorithm before the program bogs > down. I would like to use it with over 1600 spline knots spread over the > image. Currently on a X86_64 smp linux system with 4 cores and 8 cpus and > "-multi" turned on, 1600 knots takes about 30 min. As far as I can > gather from experimenting with the # of knots, most of this time is spent > with either solving for the spline weights or generating the spline > kernel.
-multi can use currently only 2 threads : one for I/O, another one for computation. So more than 2 cores won't help. > > Who can shed some light on what is going on under the hood here? Is the > spline kernel being calculated on-the-fly for every pixel in the image? > What method of solving for the weights is being used, and can it handle > very large sparse matrices? Code lies in http://trac.osgeo.org/gdal/browser/trunk/gdal/alg/thinplatespline.cpp As far as I know, only the get_point() method is called when reprojection is needed so I think it is linear in the number of nodes. Cannot help more on that. Perhaps retry with less nodes > > Thanks, > Max > > ------------------ > Max Buchheit > Canada Centre for Remote Sensing / Centre Canadien de Télédétection > Earth Sciences Sector / Secteur des Sciences de la Terre > Natural Resources Canada / Ressources Naturelles Canada > 4th Floor, 588 Booth Street / 4-ieme étage, 588 rue Booth > Ottawa, Ontario, K1A 0Y7 > Phone: (613) 943-7444/ Email: mbuchhei at nrcan.gc.ca _______________________________________________ gdal-dev mailing list gdal-dev@lists.osgeo.org http://lists.osgeo.org/mailman/listinfo/gdal-dev