Perhaps you guys should try to benchmark that test on an nVidia GPU? ;-)
Best regards, Marc On Thu, 2006-01-26 at 15:55 +0100, Uwe Ligges wrote: > Philippe Grosjean wrote: > > > Excellent, but... > > > > > x <- rnorm(1000000) > > > y <- rnorm(1000000) > > > system.time(x%*%y) > > [1] 0.03 0.00 0.03 NA NA > > > system.time(sum(x*y)) > > [1] 0.05 0.00 0.04 NA NA > > > system.time(crossprod(x, y)) > > [1] 0 0 0 NA NA > > > > So, to paraphrase a well-known contributor on this mailing list: > > "Excellent! So, what did you decided to do during the next 30 > > milliseconds you will save by using crossprod() instead of x%*%y? > > (joke) > > > > Best, > > > > Philippe Grosjean > > > > P.S.: Uwe, perhaps you should consider buying a faster computer, isn't > > it? :-() > > Well, I use R, you know. It is even fast enough for my 5 year old > laptop. For your super computer, please replace 1e6 by 1e8 in the > example above. ;-) > > Uwe > > > > Uwe Ligges wrote: > > > >> [EMAIL PROTECTED] wrote: > >> > >> > >>> Hi, > >>> > >>> x and y are (numeric) vectors. I wonder if one of the following is more > >>> efficient than the other: > >>> > >>> x%*%y > >>> > >>> or > >>> > >>> sum(x*y) > >>> ? > >> > >> > >> > >> I'd try > >> > >> x <- rnorm(1000000) > >> y <- rnorm(1000000) > >> system.time(x%*%y) > >> system.time(sum(x*y)) > >> > >> and finally (hint, hint!): > >> > >> system.time(crossprod(x, y)) > >> > >> Uwe Ligges > >> > >> > >> > >>> Thanks, > >>> Dimitri Szerman > >>> ______________________________________________ R-help@stat.math.ethz.ch mailing list https://stat.ethz.ch/mailman/listinfo/r-help PLEASE do read the posting guide! http://www.R-project.org/posting-guide.html