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

[Peter Dalgaard BSA]

"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.

-- 
   O__  ---- Peter Dalgaard             Blegdamsvej 3  
  c/ /'_ --- Dept. of Biostatistics     2200 Cph. N   
 (*) \(*) -- University of Copenhagen   Denmark      Ph: (+45) 35327918
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