Messages in this thread |  | | Date | Thu, 4 Oct 2001 17:03:05 -0700 (PDT) | From | Alexei Podtelezhnikov <> | Subject | Re: VM: 2.4.10 vs. 2.4.10-ac2 and qsort() |
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Hi guys,
I've already expressed my concern about using srand(1) in private e-mails. I think it's unscientific to use one particular random sequence. Since no one checked if that matters, I changed srand(1) to srand(time(NULL)) and I'm posting my results. I don't do testing of Alan or Linus's kernels, but use recent Red Hat kernel. I think I've shown that it does matter.
Six quick consecutive runs of modified qs on a small set of 8 million integers (obviously no swap activity):
> time ./a.out 8000000 0 errors. 24.250u 0.310s 0:24.55 100.0% 0+0k 0+0io 116pf+0w 0 errors. 24.290u 0.260s 0:24.55 100.0% 0+0k 0+0io 116pf+0w 0 errors. 24.300u 0.260s 0:24.55 100.0% 0+0k 0+0io 116pf+0w 0 errors. 24.270u 0.300s 0:24.57 100.0% 0+0k 0+0io 116pf+0w 0 errors. 24.290u 0.270s 0:24.56 100.0% 0+0k 0+0io 116pf+0w 0 errors. 24.280u 0.280s 0:24.55 100.0% 0+0k 0+0io 116pf+0w
Apparently, no significant deviations in computing times.
Six runs of modified qs on a large set of 80 million integers (a lot of swapping!)
> time ./a.out 80000000 0 errors. 261.580u 4.250s 11:09.21 39.7% 0+0k 0+0io 17379pf+0w 0 errors. 260.460u 3.660s 9:09.72 48.0% 0+0k 0+0io 13194pf+0w 0 errors. 260.620u 4.510s 10:39.80 41.4% 0+0k 0+0io 16714pf+0w 0 errors. 261.790u 4.150s 10:09.58 43.6% 0+0k 0+0io 16331pf+0w 0 errors. 260.400u 4.140s 9:23.46 46.9% 0+0k 0+0io 13722pf+0w 0 errors. 259.980u 3.940s 9:10.22 47.9% 0+0k 0+0io 14240pf+0w
mean = 9m57s; standard deviation = 50s.
Apparently, the random sequence does matter (to the Rik's algorithm at least since it's in RH kernel).
I wonder how big the deviation is for official and AC trees. Now Lorenzo's results seem inconclusive.
Regards, Alexei
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