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!
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