It is the_vectorized_ performance differences that may be in part explained by compiler settings. The interpreter overhead (not just loops) is not.
luke On Mon, 5 Jan 2009, Denney, William S. wrote:
Hello, I don't think that the large disparity in loop performance between Matlab, R, and Octave is explained by compilation time performance settings. For Octave, it is well known that loops perform poorly relative to Matlab (though many other operations perform better). The reason is that Matlab has the just in time (JIT) compiler, and it is responsible for almost all of the loop speed advantage. Have a good day, Bill -----Original Message----- From: John C Nash [mailto:nas...@uottawa.ca] Sent: Sunday, January 04, 2009 1:51 PM To: r-help@r-project.org Subject: [R] R/octave/matlab etc. I'd echo a lot of what has been said about this by the folk who have been making R work so well. One of the main difficulties is that the environment of computations affects relative performance. e.g., what settings did a distro package builder choose. I note that my 3 GHz Dual Core machine running Ubuntu 8.04 gets octave 3.0.0 octave:6> tic; a = a + 1; toc Elapsed time is 0.120027 seconds. octave:16> tic; for i=1:1e7; a(i) = a(i) + 1; end; toc; Elapsed time is 238.311 seconds. R2.8.1 > a <- rep(1,10000000) > system.time(a <- a + 1) user system elapsed 0.080 0.064 0.146 > system.time(for (i in 1:10000000) {a[i] <- a[i] + 1}) user system elapsed 68.092 0.160 68.745 > R looks pretty good in this comparison. I suspect Ubuntu has a rather low optimization level or similar for octave. As Jean G. has indicated, tests may measure the wrong sorts of things. Nonetheless, there is a value -- they can help us check that builds have been done with the right setup. And if we get very disparate performance on machines of supposedly similar capability, we may need to look into the awful details. JN Notice: This e-mail message, together with any attachme...{{dropped:12}} ______________________________________________ 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.
-- Luke Tierney Chair, Statistics and Actuarial Science Ralph E. Wareham Professor of Mathematical Sciences University of Iowa Phone: 319-335-3386 Department of Statistics and Fax: 319-335-3017 Actuarial Science 241 Schaeffer Hall email: l...@stat.uiowa.edu Iowa City, IA 52242 WWW: http://www.stat.uiowa.edu ______________________________________________ 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.
