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. . . . (define page-as-binary-matrix (time (image-file->binary-matrix path-to-image-of-page))) (define black-pixel-matrix (time (create-matrix-of-black-pixel-ranges page-as-binary-matrix))) (define page-as-binary-matrix1 (time (image-file->binary-matrix path-to-image-of-page))) (define black-pixel-matrix1 (time (create-matrix-of-black-pixel-ranges page-as-binary-matrix))) (define page-as-binary-matrix2 (time (image-file->binary-matrix path-to-image-of-page))) (define black-pixel-matrix2 (time (create-matrix-of-black-pixel-ranges page-as-binary-matrix))) 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 and why is CPU time in general more than real-time? Thanks, Harry ____________________ Racket Users list: http://lists.racket-lang.org/users
