Cedric, This was addressed about 2 weeks ago on the list, please read the archives. Basic point, Rcpp/sugar will not be faster than basic functions in R. Do something more complicated to see improvements. I would suggest something that involves lots of copies and edits, that will mess with R's memory management but be much more efficient in compiled code.
-Andrew On Tue, Jan 4, 2011 at 8:14 AM, Cedric Ginestet <c.gineste...@googlemail.com > wrote: > Happy new year to everyone, > > I have made a very straightforward comparison of the performance of > standard R, Rcpp function and sugar, and found that the latter produces the > poorest performance. Let me know what you think and how I could improve such > performance assessment. > > ################################################### > Summing1 <- cxxfunction(signature(x="numeric"), ' > NumericVector xV(x); > double out = sum(xV); > return wrap(out); > ',plugin="Rcpp") > Summing2 <- cxxfunction(signature(x="numeric"), ' > NumericVector xV(x); > double out = 0.0; > for(int i=0; i<xV.size(); i++) out += xV[i]; > return wrap(out); > ',plugin="Rcpp") > ################################################### > # Results. > n <- 1000000; x <- rnorm(n) > Summing1(x); Summing2(x); sum(x) > ####################### > gives: > [1] -396.6129 > [1] -396.6129 > [1] -396.6129 > > ################################################### > # Time. > system.time(Summing1(x)); # Sugar > system.time(Summing2(x)); # Rcpp > system.time(sum(x)); # R-base > ################### > > system.time(Summing1(x)); > user system elapsed > 0.016 0.000 0.016 > > system.time(Summing2(x)); > user system elapsed > 0.008 0.000 0.011 > > system.time(sum(x)); > user system elapsed > 0.000 0.000 0.003 > > > Sugar appears to be the slowest! What about Rcpp basic loop? Why isn't as > fast as the standard sum() in R-base? > Cheers, > Cedric > > -- > Cedric Ginestet > Centre for Neuroimaging Sciences (L3.04) > NIHR Biomedical Research Centre > Institute of Psychiatry, Box P089 > Kings College London > De Crespigny Park > London > SE5 8AF > > > _______________________________________________ > Rcpp-devel mailing list > Rcpp-devel@lists.r-forge.r-project.org > https://lists.r-forge.r-project.org/cgi-bin/mailman/listinfo/rcpp-devel > >
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