Pawel, On Aug 31, 2011, at 4:46 PM, pawelm wrote:
> I just found this (performance improvement of the "dist" function when using > openmp): > > .Internal(setMaxNumMathThreads(1)); .Internal(setNumMathThreads(1)); m <- > matrix(rnorm(810000),900,900); system.time(d <- dist(m)) > > user system elapsed > 3.510 0.013 3.524 > > .Internal(setMaxNumMathThreads(5)); .Internal(setNumMathThreads(5)); m <- > matrix(rnorm(810000),900,900); system.time(d <- dist(m)); > > user system elapsed > 3.536 0.007 1.321 > > Works great! Just the question stays if it's a good practice to use > "R_num_math_threads" in external packages? > Normally you don't need to mess with all this and I would recommend not to do so. The R internals use a different strategy since they need to cope with the fall-back case, but packages should not worry about that. The default number of threads is defined by the OMP_NUM_THREADS environment variable and that is the documented way in OpenMP, so my recommendation would be to not mess with num_threads() which is precisely why I did not use it in the example I gave you. That said, R-devel has new facilities for parallelization so things may change in the future. Cheers, Simon ______________________________________________ R-devel@r-project.org mailing list https://stat.ethz.ch/mailman/listinfo/r-devel
