From: p DOT steiner AT t-online DOT de (Peter Steiner)
Newsgroups: comp.os.msdos.djgpp
Subject: Re: Newbie Question: Random Numbers
Date: 7 Aug 1997 13:58:55 GMT
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References: <01bc9a61$57701640$204678c7 AT warren1> <33E839E3 DOT 38A0E28D AT alcyone DOT com> <5sbqs9$jrj AT freenet-news DOT carleton DOT ca>
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On 7 Aug 1997 06:44:25 GMT, Paul Derbyshire <ao950 AT FreeNet DOT Carleton DOT CA> wrote:
>
>Erik Max Francis (max AT alcyone DOT com) writes:
>> Warren Smith wrote:
>> 
>>> How can I get a truly random number (w/o the same sequence of numbers
>>> appearing over and over)?
>> 
>> This is fundamentally impossible with a computer without some strange
>> peripherals, because computers are designed to be deterministic.
>> 
>> There are many, many books written about "pseudorandom numbers," as
>> they'er called.  There's a whole chapter (chapter 7) in _Numerical
>> recipes_, for instance, devoted to this subject.
>
>A URL would be nice. (Preferably for the main page, chapter 7 is probably
>easily tracked down from there.) Just the name of a site or document by
>itself isn't helpful, because it has to be put into a search engine which
>will find ten thousand irrelevant sites. Mostly commercial sites. I think
>that most of the search engines accept money under the table from big
>companies to make their sites pop up at the top of every search someone
>does that is in any way slightly connected to their products. :P

Look in the Linux sources in  drivers/char/random.c  That's a really strong
random number generator.

For quick 16-bit pseudo random numbers try:

int rand = rand_seed;

int random(void) {
   rand=rand * 58321 + 11113;
   return (rand >> 16);
}

I use this to generate nice white noise. It has a wonderful spectrum.
You can use different prime-numbers in the function and improve it by 
switching to long long but this requires full 32-Bit primes.
The rand_seed may be generated using time and date. And then no sequence
will appear over and over.

Bye,

Peter Steiner
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