R-Help (and package author) I'm trying to understand within the context of R what the benefit of using an iterator is. My only goal in using the foreach package is to improve computational speed with some embarrassingly parallel tasks I have to compute.
I took the example found at the link below to provide a reproducible example and ran it in a "conventional" way to iterate in a loop and the timing suggests here (as well as with my actual project) that using an iterator generates the same object, but at a much slower speed. If I can get the same thing faster without using an iterator what would be the potential of its use? https://msdn.microsoft.com/en-us/microsoft-r/foreach > library(doParallel) > cl <- makeCluster(8) > registerDoParallel(cl) > x <- matrix(rnorm(1000000), ncol=1000) > itx <- iter(x, by='row') > system.time(r1 <- foreach(i=itx, .combine=c) %dopar% mean(i)) user system elapsed 0.40 0.08 0.87 > system.time(r2 <- foreach(i= 1:nrow(x), .combine=c) %dopar% mean(x[i,])) user system elapsed 0.41 0.03 0.81 > all.equal(r1,r2) [1] TRUE ______________________________________________ R-help@r-project.org mailing list -- To UNSUBSCRIBE and more, see https://stat.ethz.ch/mailman/listinfo/r-help PLEASE do read the posting guide http://www.R-project.org/posting-guide.html and provide commented, minimal, self-contained, reproducible code.
