Re: random number generator

Article View: att.lang.c++

Article #9

From: Emmanuel Delahaye
Date: Sun, 01 Jun 2003 14:09

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In 'comp.lang.c', Pete Becker <petebecker@acm.org> wrote:

>> > 1st number genereated: 2
>> > 2nd number generated: 6
>> > 3rd number generated: 2 (WRONG!!! bad "period" as they say I think)
>> 
>> If you don't like your built-in pseudo-random generator (srand() once,
>> rand() many times), you can implement your own. Search "Mersenne
>> Twister" on Google. 
> 
> Won't help. A random number generator that doesn't repeat values isn't
> random.

AFAIK, there is no 'random' generator here. Just PRNG (pseudo-random 
generator). Do you mean that inside it's period, a PRNG must have 
repetitions? In that case, it means that some values are missing. Always. Not 
very good, IMO.

Lets try with a 2^3 sequence (0-7).

0 1 2 3 4 5 7: balanced but predictable
2 5 1 4 0 1 2: unbalanced (missing values: 3, 7)
1 0 3 4 2 5 7: the kind of sequence I expect.

-- 
-ed- emdel at noos.fr
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From: Emmanuel Delahaye <emdelNOSPAM@noos.fr>
Newsgroups: att.lang.c++,comp.lang.c,comp.lang.c++
Subject: Re: random number generator
Date: 1 Jun 2003 14:09:57 GMT
Organization: World Company
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