Thanks, I didn't realize cpu time includes gc time. and yes its dual core
On Wed, May 16, 2012 at 4:31 PM, Eli Barzilay <e...@barzilay.org> wrote: > A few minutes ago, Harry Spier wrote: >> I've just started using the "time" function to check the timings of >> some functions in my program. I'm testing the timings of two >> functions, each of these functions takes a list of lists and >> transforms it into another list of lists. The size of each list of >> lists is in the order of about 1000 x 1000. >> >> Each time I used it in DRacket I got very different results. So I >> did this test. I put three calls to the two functions right after >> each other in the program as follows. >> [...] >> >> and got these results >> >> cpu time: 7176 real time: 6620 gc time: 4537 >> cpu time: 2262 real time: 2289 gc time: 437 >> >> cpu time: 5600 real time: 5257 gc time: 2949 >> cpu time: 3728 real time: 3516 gc time: 1748 >> >> cpu time: 4040 real time: 3673 gc time: 1388 >> cpu time: 2418 real time: 2311 gc time: 422 >> >> Its in DrRacket on a dual core pentium under windows. >> >> Why the widely divergent timings > > They're not that far off -- if you subtract the gc time. In general, > for such timing it's best to run the code several times, possibly with > calling `collect-garbage' between calls. > > >> and why is CPU time in general more than real-time? > > (This looks weird, maybe you're using multiple cores?) > > -- > ((lambda (x) (x x)) (lambda (x) (x x))) Eli Barzilay: > http://barzilay.org/ Maze is Life! ____________________ Racket Users list: http://lists.racket-lang.org/users
