Probably the easiest way to think about it is that most of the extra time is the overhead of calling a function. So counting the number of calls to R functions is going to tell you how much overhead there is. (Remember that functions call other functions.)
On 26/06/2011 08:21, Jeff Newmiller wrote:
For the same reason the Cray XMP was fast at numerical computations... a loop written in a low level language can be optimized to work faster than one written in a higher level language. The XMP optimized loops into hardware, but R just optimizes them in C code, exposed to the R programmer as vector operations. --------------------------------------------------------------------------- Jeff Newmiller The ..... ..... Go Live... DCN:<jdnew...@dcn.davis.ca.us> Basics: ##.#. ##.#. Live Go... Live: OO#.. Dead: OO#.. Playing Research Engineer (Solar/Batteries O.O#. #.O#. with /Software/Embedded Controllers) .OO#. .OO#. rocks...1k --------------------------------------------------------------------------- Sent from my phone. Please excuse my brevity. Alexander Engelhardt<a...@chaotic-neutral.de> wrote: Hey, I just read another post about calling R from C. Someone on stackoverflow (DWin makes me suspect its David W.?) referenced this: http://www.math.univ-montp2.fr/~pudlo/R_files/call_R.pdf Which made me think: Why is a loop in R bad, but in C not? And where exactly does looping cost the most? I wrote a piece of code for my bachelor's thesis where I loop from 1 to 500, and estimate a boosted model in every iteration. The procedure takes 2-6 minutes. In this example the loop (instead of some kind of apply()) shouldn't cost too much time, right? I suspect it's way worse if someone would loop from 1 to 10000 and perform only a small task (a mean(), for example) in each loop. Can someone confirm this? Regards, Alex _____________________________________________ R-help@r-project.org mailing list 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. [[alternative HTML version deleted]] ______________________________________________ R-help@r-project.org mailing list 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.
-- Patrick Burns pbu...@pburns.seanet.com twitter: @portfolioprobe http://www.portfolioprobe.com/blog http://www.burns-stat.com (home of 'Some hints for the R beginner' and 'The R Inferno') ______________________________________________ R-help@r-project.org mailing list 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.
