Groups > comp.lang.c > #19070

Re: Odd benchmark behavior

From	Nils M Holm <news2009@t3x.org>
Newsgroups	comp.lang.c
Subject	Re: Odd benchmark behavior
Date	2012-03-27 11:59 +0000
Organization	TARFU
Message-ID	<9tdodjF8lkU1@mid.individual.net> (permalink)
References	<9talg3F84gU1@mid.individual.net> <jkptnr$j8a$1@dont-email.me> <9td4i1FvsgU1@mid.individual.net> <jks2ke$42b$1@dont-email.me>

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BartC <bc@freeuk.com> wrote:
> I don't think your program actually used that much memory (only 80KB or so). 
> Have a look at the NSIEVE benchmark:
> 
> http://shootout.alioth.debian.org/gp4/benchmark.php?test=nsieve&lang=gcc

I think it is not a matter of the amount of memory being allocated,
but a matter of the amount of memory actually being accessed. The
algorithm used in the shootout accesses memory N+p(N) times, where
N is the upper limit of the range to check and N is the number of
primes in that range. My algorithm accesses memory at least N^2/2
times, so the difference is about the same as O(n) vs O(n^2), i.e.
my program does a lot more memory access in the same amount of
memory.

-- 
Nils M Holm  < n m h @ t 3 x . o r g >  www.t3x.org

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Odd benchmark behavior Nils M Holm <news2009@t3x.org> - 2012-03-26 07:51 +0000
  Re: Odd benchmark behavior "io_x" <a@b.c.invalid> - 2012-03-26 11:26 +0200
    Re: Odd benchmark behavior "BartC" <bc@freeuk.com> - 2012-03-26 10:40 +0100
      Re: Odd benchmark behavior gwowen <gwowen@gmail.com> - 2012-03-26 03:37 -0700
      Re: Odd benchmark behavior "io_x" <a@b.c.invalid> - 2012-03-26 14:13 +0200
    Re: Odd benchmark behavior "io_x" <a@b.c.invalid> - 2012-03-26 11:55 +0200
      Re: Odd benchmark behavior "io_x" <a@b.c.invalid> - 2012-03-27 09:17 +0200
        Re: Odd benchmark behavior "io_x" <a@b.c.invalid> - 2012-03-27 09:20 +0200
          Re: Odd benchmark behavior "Scott Fluhrer" <sfluhrer@ix.netcom.com> - 2012-03-27 13:39 -0400
          Re: Odd benchmark behavior pete <pfiland@mindspring.com> - 2012-03-27 21:49 -0500
            Re: Odd benchmark behavior "io_x" <a@b.c.invalid> - 2012-04-05 12:18 +0200
              Re: Odd benchmark behavior pete <pfiland@mindspring.com> - 2012-04-05 06:48 -0400
                Re: Odd benchmark behavior "io_x" <a@b.c.invalid> - 2012-04-05 14:12 +0200
                Re: Odd benchmark behavior pete <pfiland@mindspring.com> - 2012-04-05 09:03 -0400
                Re: Odd benchmark behavior "io_x" <a@b.c.invalid> - 2012-04-05 16:18 +0200
                Re: Odd benchmark behavior "io_x" <a@b.c.invalid> - 2012-04-07 13:26 +0200
                Re: Odd benchmark behavior "io_x" <a@b.c.invalid> - 2012-04-06 09:31 +0200
        Re: Odd benchmark behavior "io_x" <a@b.c.invalid> - 2012-03-27 19:01 +0200
  Re: Odd benchmark behavior "BartC" <bc@freeuk.com> - 2012-03-26 10:36 +0100
    Re: Odd benchmark behavior Nils M Holm <news2009@t3x.org> - 2012-03-26 10:02 +0000
  Re: Odd benchmark behavior Ian Collins <ian-news@hotmail.com> - 2012-03-26 22:58 +1300
  Re: Odd benchmark behavior "BartC" <bc@freeuk.com> - 2012-03-26 15:16 +0100
    Re: Odd benchmark behavior Nils M Holm <news2009@t3x.org> - 2012-03-27 06:20 +0000
      Re: Odd benchmark behavior "BartC" <bc@freeuk.com> - 2012-03-27 10:13 +0100
        Re: Odd benchmark behavior Nils M Holm <news2009@t3x.org> - 2012-03-27 11:59 +0000

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