Selon Knut-Frode Dagestad <[email protected]>: > Hi list, > > When warping images with many GCPs, the -tps switch (Thin Plate Spline) > is found to be necessary to get decent accuracy. This makes however > warping very slow. The only method I found to increase speed is the -et > switch, but at cost of spatial accuracy. > > > Below some comments about the other tries which did not help: > > - compiling GDAL with armadillo support had no effect on speed. > Btw, to compile with armadillo I had to manually insert -llapack in the > following line in configure: > if test -z "`${CXX} testarmadillo.cpp -o testarmadillo -larmadillo > 2>&1`" ; then ..... > Perhaps ${LIBS} should be added permanently to this line in trunk? >
Could you file a ticket about that ? > - compiling GDAL with OpenCL had also no effect. At first surprising, > but looking at the opencl warp kernel it seems that it only makes a > difference for other resampling algorithms than nearest neighbour? The OpenCL warper was designed to speed-up computational intensive algorithms, such as lanczos resampling. For nearest resampling, most of the time is spent in I/O, or reprojection. > > - Increasing memory with -wm had no effect Yes, it depends on particular configuration of source and target datasets, particularly if they're tiled or not. Tuning this might be non obvious. > > - Using several threads (-multi -wo NUM_THREADS=ALL_CPUS) actually > increased computing time significantly (my proj version is 4.7.1). As underlined in http://osgeo-org.1560.n6.nabble.com/gdal-dev-NEW-Multi-threaded-warping-td4980252.html , you need proj 4.8.0 for lock-less reprojection. Older versions have a global mutex that will prevent efficient parallism. _______________________________________________ gdal-dev mailing list [email protected] http://lists.osgeo.org/mailman/listinfo/gdal-dev
