There is an OpenMP version of r.clump available at http://sil.uc.edu/downloads.html#software
called r.clump4p. The reported performance gain is 450 times over the original r.clump. The performance gain over the original r.clump vanished: r.clump4p with one thread is now about 12x slower than r.clump, and r.clump4p with 4 threads is now about 5x slower than r.clump. Moreover, the results of r.clump4p are wrong, it clumps together areas with different cell values (no multithreading effect). I tested in a region with 650 million cells, both modules produced about 17.6 million clumps. All differences in the resultant clumps were due to errors in r.clump4p. Tests were performed in GRASS 7 where I have optimized r.clump and also added support for diagonal clump tracing. Markus M _______________________________________________ grass-dev mailing list [email protected] http://lists.osgeo.org/mailman/listinfo/grass-dev
