[R] ^ operation much slower in R 1.7.1 than in R 1.7.0 ???

[Philippe Grosjean]

I propose to move this thread to R-devel...

Prof. Brian Ripley wrote:
>And are you able to give an explanation?  For example, did you compile
>each under the same compiler system?

I just noticed that behaviour yesterday, and had not much time yet to
investigate it. I compiled 1.7.0 myself (but compared with the binary
provided on CRAN; no changes). I used the 1.7.1 binary provided on CRAN. I
know these binaries are not supported, so we (Windows users) will have to
look at that by ourselve. Indeed yes, I'll first compile 1.7.1 with the same
compiler I used for 1.7.0.

>I doubt if this is worth R-core's time to pursue, so over to interested
>users to find an explanation and fix.

OK. But I was wondering if people at R-core team, especially those who
worked on Windows specific aspects, would have in mind some changes they did
between 1.7.0 and 1.7.1 than can cause this. Since these changes are mainly
corrections of bugs, the list is hopefully not so long... and it could help
a lot to have these hints. Thanks very much.

Best,

Philippe Grosjean

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On Mon, 4 Aug 2003, James MacDonald wrote:

> I get similar results as Philippe on WinXP (1.33 GHz laptop, 512 Mb
> RAM).
>
> R 1.7.1
> 2.86 sec
> 7.82 sec
>
> R 1.7.0
> 0.64 sec
> 1.64 sec
>
> Jim
>
>
>
>
> James W. MacDonald
> Affymetrix and cDNA Microarray Core
> University of Michigan Cancer Center
> 1500 E. Medical Center Drive
> 7410 CCGC
> Ann Arbor MI 48109
> 734-647-5623
>
> >>> Peter Dalgaard BSA <p.dalgaard at biostat.ku.dk> 08/04/03 11:30AM >>>
> "Philippe Grosjean" <phgrosjean at sciviews.org> writes:
>
> > I do not understand what happens here (under Win XP):
> >
> > a <- abs(matrix(rnorm(800*800)/2, ncol=800, nrow=800))
> > system.time(b <- a^1000)[3]
> >
> > took about 1 sec on my computer with R 1.7.0 and it takes now 4.59
> sec with
> > R 1.7.1
> >
> > Similarly,
> >
> > phi <- 1.6180339887498949
> > a <- floor(runif(750000)*1000)
> > system.time(b <- (phi^a - (-phi)^(-a))/sqrt(5))[3]
> >
> > took about 0.9 sec with R 1.7.0, and it takes 11.8 sec (!!!) in R
> 1.7.1.
> >
> > Are there some changes made between 1.7.0 and 1.7.1 that could cause
> such a
> > large difference in time to do such simple computations???
>
> Hmm, on linux, I get approx 0.31 for the first example with 1.7.0,
> 1.7.1, r-patched, and r-devel. Similarly, I get 0.8 for the second ex.
> in all four cases.
>
>

--
Brian D. Ripley,                  ripley at stats.ox.ac.uk
Professor of Applied Statistics,  http://www.stats.ox.ac.uk/~ripley/
University of Oxford,             Tel:  +44 1865 272861 (self)
1 South Parks Road,                     +44 1865 272866 (PA)
Oxford OX1 3TG, UK                Fax:  +44 1865 272595

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