Markus Metz wrote: > Some more results with Sören's test program on a Intel(R) Core(TM) i5 > CPU M450 @ 2.40GHz (2 real cores, 4 fake cores) with gcc 4.7.2 and > clang 3.3 > > gcc -O3 > v is 2.09131e+13 > > real 2m0.393s > user 1m57.610s > sys 0m0.003s > > gcc -Ofast > v is 2.09131e+13 > > real 0m7.218s > user 0m7.018s > sys 0m0.017s
nice. one thing we need to remember though is that it's not entirely free, one thing -Ofast turns on is -ffast-math, """ This option is not turned on by any -O option besides -Ofast since it can result in incorrect output for programs that depend on an exact implementation of IEEE or ISO rules/specifications for math functions. It may, however, yield faster code for programs that do not require the guarantees of these specifications. """ which may not be fit for our purposes. With the ifort compiler there is '-fp-model precise' which allows only optimizations which don't harm the results. Maybe gcc has something similar. Glad to see -floop-parallelize-all in gcc 4.7, it will help us identify places to focus OpenMP work on. Hamish _______________________________________________ grass-user mailing list grass-user@lists.osgeo.org http://lists.osgeo.org/mailman/listinfo/grass-user