Hi Konrad. As Dirk said, Rcpp makes life easy for the programmer by taking care of some of the background work automatically. So there may be a time vs. speed trade off against bespoke handwritten code. I have a comparison between a few implementations (base, C,Rcpp, Fortran) of a relatively simple function which may interest you [1].
Thanks, Avi [1] https://www.avrahamadler.com/2018/12/23/the-need-for-speed-part-2-c-vs-fortran-vs-c/ Sent from my iPhone > On Aug 10, 2022, at 6:22 PM, Dirk Eddelbuettel <e...@debian.org> wrote: > > > Hi Konrad, > > On 10 August 2022 at 08:22, konrad wrote: > | I have a question regarding the cost of .Call. If I implement the > | rosenbrock function in R and in Rcpp. The R version is substentially > | faster then the C++ version. The Rcpp function is basically an R > | function which calls the C++ function using .Call. Which part of the > | code generates this overhead of the Rcpp function. Is it the .Call > | itself or the conversion of the types from R to Rcpp? Or have I done > | something wrong? > > It's just a not a meaningful benchmark as there are essentially no operations > on the R side either. > > And Rcpp, by making it _convenient_ injects some extra code and tests and > state keeping all of which is documented and for which you have some toggles > to suppress at least parts. > > But in short, it's a non-question. By all means keep exploring Rcpp but you > will need something meatier for it to make sense. You should have no problem > finding examples. > > Cheers, Dirk > > | > | library(Rcpp) > | library(microbenchmark) > | > | > | fr <- function(x) { ## Rosenbrock Banana function > | x1 <- x[1] > | x2 <- x[2] > | 100 * (x2 - x1 * x1)^2 + (1 - x1)^2 > | } > | > | sourceCpp(code = " > | #include <Rcpp.h> > | > | // [[Rcpp::export]] > | double fr_rcpp(Rcpp::NumericVector x) { > | double x1 = x[0]; > | double x2 = x[1]; > | return 100 * (x2 - x1 * x1)*(x2 - x1 * x1) + (1 - x1)*(1 - x1); > | } > | ") > | > | x <- c(1, 2) > | identical(fr(x), fr_rcpp(x)) > | > | r <- microbenchmark(fr(x), fr_rcpp(x)) > | boxplot(r) > | > | > | Thank you very much for your help! > | > | > | All the best, > | > | > | Konrad > | _______________________________________________ > | 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 > -- > dirk.eddelbuettel.com | @eddelbuettel | e...@debian.org > _______________________________________________ > 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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