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Groups > comp.lang.c > #139107

Re: Multi-channel rand()

From Keith Thompson <kst-u@mib.org>
Newsgroups comp.lang.c
Subject Re: Multi-channel rand()
Date 2018-12-26 15:32 -0800
Organization None to speak of
Message-ID <lnmuorc19x.fsf@kst-u.example.com> (permalink)
References (1 earlier) <bpNUD.21754$X_3.4267@fx01.am4> <c720a209-9a04-47ab-b9e1-29b1b570231a@googlegroups.com> <6yOUD.36923$Bu5.21082@fx19.iad> <q00el7$k2q$1@dont-email.me> <yDPUD.74886$qN7.68567@fx12.iad>

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Richard Damon <Richard@Damon-Family.org> writes:
[...]
> In many implementations, rand() IS based on the sample code from K&R,
> which is very old, very simple, and not very good. The fix isn't to add
> ad hoc randomizer fixes like you were suggesting, but to use a better
> random number generator, and a source of those algorithms was given earlier.
[...]

Some rand() implementations are even worse than the sample code
from K&R.  In the NetBSD implementation, the low order bit of the
value returned by rand() alternates 0 and 1, the low order 2 bits
repeat with a cycle of length 4. etc.  The K&R implementation
doesn't do that.

https://github.com/Keith-S-Thompson/crude_rand_test

-- 
Keith Thompson (The_Other_Keith) kst@mib.org  <http://www.ghoti.net/~kst>
Will write code for food.
"We must do something.  This is something.  Therefore, we must do this."
    -- Antony Jay and Jonathan Lynn, "Yes Minister"

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Thread

Multi-channel rand() "Rick C. Hodgin" <rick.c.hodgin@gmail.com> - 2018-12-24 19:54 -0500
  Re: Multi-channel rand() "Chris M. Thomasson" <invalid_chris_thomasson@invalid.invalid> - 2018-12-24 19:38 -0800
  Re: Multi-channel rand() nobody@example.org (Scott) - 2018-12-25 04:05 +0000
    Re: Multi-channel rand() "Rick C. Hodgin" <rick.c.hodgin@gmail.com> - 2018-12-24 23:57 -0500
      Re: Multi-channel rand() Mr Flibble <flibbleREMOVETHISBIT@i42.co.uk> - 2018-12-25 09:22 +0000
        Professional coders??? (Was: Multi-channel rand()) gazelle@shell.xmission.com (Kenny McCormack) - 2018-12-25 10:09 +0000
        Re: Multi-channel rand() "Rick C. Hodgin" <rick.c.hodgin@gmail.com> - 2018-12-25 07:59 -0500
          Re: Multi-channel rand() Mr Flibble <flibbleREMOVETHISBIT@i42.co.uk> - 2018-12-25 21:59 +0000
            Re: Multi-channel rand() nobody@example.org (Scott) - 2018-12-26 02:43 +0000
      Re: Multi-channel rand() rbowman <bowman@montana.com> - 2018-12-25 10:15 -0700
        Re: Multi-channel rand() Keith Thompson <kst-u@mib.org> - 2018-12-25 10:14 -0800
  Re: Multi-channel rand() Anton Shepelev <anton.txt@g{oogle}mail.com> - 2018-12-25 13:35 +0300
    Re: Multi-channel rand() fir <profesor.fir@gmail.com> - 2018-12-25 02:56 -0800
    Re: Multi-channel rand() "Rick C. Hodgin" <rick.c.hodgin@gmail.com> - 2018-12-25 08:02 -0500
  Re: Multi-channel rand() Bart <bc@freeuk.com> - 2018-12-25 11:52 +0000
    Re: Multi-channel rand() Anton Shepelev <anton.txt@g{oogle}mail.com> - 2018-12-25 14:58 +0300
    Re: Multi-channel rand() Richard Damon <Richard@Damon-Family.org> - 2018-12-25 06:59 -0500
      Re: Multi-channel rand() "Rick C. Hodgin" <rick.c.hodgin@gmail.com> - 2018-12-25 08:05 -0500
    Re: Multi-channel rand() "Rick C. Hodgin" <rick.c.hodgin@gmail.com> - 2018-12-25 08:04 -0500
  Re: Multi-channel rand() Bart <bc@freeuk.com> - 2018-12-26 15:48 +0000
    Re: Multi-channel rand() "Rick C. Hodgin" <rick.c.hodgin@gmail.com> - 2018-12-26 07:58 -0800
      Re: Multi-channel rand() Richard Damon <Richard@Damon-Family.org> - 2018-12-26 12:06 -0500
        Re: Multi-channel rand() "Rick C. Hodgin" <rick.c.hodgin@gmail.com> - 2018-12-26 12:45 -0500
          Re: Multi-channel rand() Richard Damon <Richard@Damon-Family.org> - 2018-12-26 13:20 -0500
            Re: Multi-channel rand() "Rick C. Hodgin" <rick.c.hodgin@gmail.com> - 2018-12-26 10:30 -0800
              Re: Multi-channel rand() "Chris M. Thomasson" <invalid_chris_thomasson@invalid.invalid> - 2018-12-26 11:35 -0800
                Re: Multi-channel rand() "Rick C. Hodgin" <rick.c.hodgin@gmail.com> - 2018-12-26 14:52 -0500
              Re: Multi-channel rand() Richard Damon <Richard@Damon-Family.org> - 2018-12-26 16:31 -0500
                Re: Multi-channel rand() "Rick C. Hodgin" <rick.c.hodgin@gmail.com> - 2018-12-26 22:28 -0500
                Re: Multi-channel rand() "Chris M. Thomasson" <invalid_chris_thomasson@invalid.invalid> - 2018-12-30 20:42 -0800
            Re: Multi-channel rand() Keith Thompson <kst-u@mib.org> - 2018-12-26 15:32 -0800
          Re: Multi-channel rand() Bart <bc@freeuk.com> - 2018-12-26 19:38 +0000
            Re: Multi-channel rand() Keith Thompson <kst-u@mib.org> - 2018-12-26 15:35 -0800
        Re: Multi-channel rand() "Rick C. Hodgin" <rick.c.hodgin@gmail.com> - 2018-12-26 12:59 -0500
          Re: Multi-channel rand() Richard Damon <Richard@Damon-Family.org> - 2018-12-26 16:05 -0500
        Re: Multi-channel rand() "Rick C. Hodgin" <rick.c.hodgin@gmail.com> - 2018-12-26 13:08 -0500
          Re: Multi-channel rand() Richard Damon <Richard@Damon-Family.org> - 2018-12-26 15:50 -0500
      Re: Multi-channel rand() Bart <bc@freeuk.com> - 2018-12-26 17:42 +0000
        Re: Multi-channel rand() "Rick C. Hodgin" <rick.c.hodgin@gmail.com> - 2018-12-26 12:48 -0500
        Re: Multi-channel rand() Richard Damon <Richard@Damon-Family.org> - 2018-12-26 12:58 -0500
          Re: Multi-channel rand() Bart <bc@freeuk.com> - 2018-12-26 19:03 +0000
            Re: Multi-channel rand() "Rick C. Hodgin" <rick.c.hodgin@gmail.com> - 2018-12-26 14:45 -0500
              Re: Multi-channel rand() Bart <bc@freeuk.com> - 2018-12-26 20:46 +0000
                Re: Multi-channel rand() "Rick C. Hodgin" <rick.c.hodgin@gmail.com> - 2018-12-26 16:25 -0500
                Re: Multi-channel rand() Richard Damon <Richard@Damon-Family.org> - 2018-12-26 17:13 -0500
                Re: Multi-channel rand() "Rick C. Hodgin" <rick.c.hodgin@gmail.com> - 2018-12-26 22:23 -0500
                Re: Multi-channel rand() Bart <bc@freeuk.com> - 2018-12-26 23:39 +0000
                Re: Multi-channel rand() Richard Damon <Richard@Damon-Family.org> - 2018-12-26 17:36 -0500
            Re: Multi-channel rand() Richard Damon <Richard@Damon-Family.org> - 2018-12-26 16:27 -0500
    Re: Multi-channel rand() rbowman <bowman@montana.com> - 2018-12-26 19:19 -0700
      Re: Multi-channel rand() Richard Damon <Richard@Damon-Family.org> - 2018-12-26 22:17 -0500
      Re: Multi-channel rand() James Kuyper <jameskuyper@alumni.caltech.edu> - 2018-12-26 19:32 -0800
      Re: Multi-channel rand() Keith Thompson <kst-u@mib.org> - 2018-12-26 19:34 -0800
        Re: Multi-channel rand() Bart <bc@freeuk.com> - 2018-12-27 11:29 +0000
          Re: Multi-channel rand() James Kuyper <jameskuyper@alumni.caltech.edu> - 2018-12-27 05:27 -0800
            Re: Multi-channel rand() "Rick C. Hodgin" <rick.c.hodgin@gmail.com> - 2018-12-27 09:41 -0500
              Re: Multi-channel rand() "Rick C. Hodgin" <rick.c.hodgin@gmail.com> - 2018-12-27 09:42 -0500
                Re: Multi-channel rand() James Kuyper <jameskuyper@alumni.caltech.edu> - 2018-12-27 07:01 -0800
                Re: Multi-channel rand() "Rick C. Hodgin" <rick.c.hodgin@gmail.com> - 2018-12-27 10:28 -0500
                Re: Multi-channel rand() Richard Damon <Richard@Damon-Family.org> - 2018-12-27 10:48 -0500
                Re: Multi-channel rand() "Rick C. Hodgin" <rick.c.hodgin@gmail.com> - 2018-12-27 11:08 -0500
                Re: Multi-channel rand() "Chris M. Thomasson" <invalid_chris_thomasson@invalid.invalid> - 2018-12-27 13:49 -0800
                Re: Multi-channel rand() "Rick C. Hodgin" <rick.c.hodgin@gmail.com> - 2018-12-27 17:18 -0500
                Re: Multi-channel rand() "Chris M. Thomasson" <invalid_chris_thomasson@invalid.invalid> - 2018-12-29 13:59 -0800
                Re: Multi-channel rand() "Chris M. Thomasson" <invalid_chris_thomasson@invalid.invalid> - 2018-12-30 14:01 -0800
                Re: Multi-channel rand() Bart <bc@freeuk.com> - 2018-12-30 22:07 +0000
                Re: Multi-channel rand() "Rick C. Hodgin" <rick.c.hodgin@gmail.com> - 2018-12-30 17:20 -0500
                Re: Multi-channel rand() Richard Damon <Richard@Damon-Family.org> - 2018-12-27 17:47 -0500
                Re: Multi-channel rand() "Chris M. Thomasson" <invalid_chris_thomasson@invalid.invalid> - 2018-12-30 20:45 -0800
                Re: Multi-channel rand() James Kuyper <jameskuyper@alumni.caltech.edu> - 2018-12-27 08:22 -0800
                Re: Multi-channel rand() "Rick C. Hodgin" <rick.c.hodgin@gmail.com> - 2018-12-27 11:40 -0500
                Re: Multi-channel rand() James Kuyper <jameskuyper@alumni.caltech.edu> - 2018-12-27 09:21 -0800
                Re: Multi-channel rand() "Rick C. Hodgin" <rick.c.hodgin@gmail.com> - 2018-12-27 12:45 -0500
                Re: Multi-channel rand() James Kuyper <jameskuyper@alumni.caltech.edu> - 2018-12-27 10:57 -0800
                Re: Multi-channel rand() "Rick C. Hodgin" <rick.c.hodgin@gmail.com> - 2018-12-27 14:35 -0500
                Re: Multi-channel rand() Tim Rentsch <txr@alumni.caltech.edu> - 2018-12-28 09:25 -0800
                Re: Multi-channel rand() Tim Rentsch <txr@alumni.caltech.edu> - 2018-12-28 09:55 -0800
                Re: Multi-channel rand() Keith Thompson <kst-u@mib.org> - 2018-12-28 12:36 -0800
                Re: Multi-channel rand() Robert Wessel <robertwessel2@yahoo.com> - 2018-12-27 20:34 -0600
              Re: Multi-channel rand() Richard Damon <Richard@Damon-Family.org> - 2018-12-27 10:37 -0500
            Re: Multi-channel rand() Bart <bc@freeuk.com> - 2018-12-27 14:46 +0000
              Re: Multi-channel rand() James Kuyper <jameskuyper@alumni.caltech.edu> - 2018-12-27 07:05 -0800
                Re: Multi-channel rand() Keith Thompson <kst-u@mib.org> - 2018-12-27 11:28 -0800
                Re: Multi-channel rand() James Kuyper <jameskuyper@alumni.caltech.edu> - 2018-12-27 12:07 -0800
                Re: Multi-channel rand() Keith Thompson <kst-u@mib.org> - 2018-12-27 12:47 -0800
                Re: Multi-channel rand() James Kuyper <jameskuyper@alumni.caltech.edu> - 2018-12-27 14:47 -0800
  Re: Multi-channel rand() "Chris M. Thomasson" <invalid_chris_thomasson@invalid.invalid> - 2018-12-26 11:58 -0800

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