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)
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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^)