From:	eheft AT dnaco DOT net (Eric Heft)
Newsgroups:	comp.os.msdos.djgpp
Subject:	Re: Random generator?
Date:	2 May 1997 20:11:10 GMT
Organization:	The Dayton Network Access Company (DNACo)
Lines:	32
Message-ID:	<5kdhou$o9r$1@pike.dnaco.net>
References:	<2 DOT 2 DOT 32 DOT 19970429193847 DOT 006a0ec4 AT gate72> <33665CFB DOT C26 AT cs DOT com>
NNTP-Posting-Host:	kirk.dnaco.net
To:	djgpp AT delorie DOT com
DJ-Gateway:	from newsgroup comp.os.msdos.djgpp

On getting random numbers :

If you do a histogram of rand() % 100 or random() % 100 you will 
find that its not uniform. If you image that rand return a uniform 
number from 0-31 and you % 10 you map 

[ rand val ] -> (val % 10)
[0,10,20,30] -> 0
[1,11,21,31] -> 1
[2,12,22]    -> 2
[3,13,23]    -> 3
[4,14,24]    -> 4
  . . .         .
[9,19,29]    -> 9


Depending on what your doing it may be close enough not to matter. 

Somthing like this gets rid of this problem. 

int rnd(int lo,int hi)
{
   int rng = hi - lo + 1;
   return ( lo + rng * rand() / MAX_INT );
}


I only spent a couple days trying to find why a modeler I was 
writing always favored low number 8^)

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