Message-ID: <32240E1F.1D96@pobox.oleane.com>
Date: Wed, 28 Aug 1996 11:15:11 +0200
From: Francois Charton <deef AT pobox DOT oleane DOT com>
Organization: CCMSA
MIME-Version: 1.0
To: Mark Gilbert <mark DOT gilbert AT pop3 DOT hiway DOT co DOT uk>
CC: djgpp AT delorie DOT com
Subject: Re: DJGPP random blues
References: <01bb942b$d2fb26c0$0100007f AT hiway DOT co DOT uk DOT hiway DOT co DOT uk>
Content-Type: text/plain; charset=us-ascii
Content-Transfer-Encoding: 7bit

Mark Gilbert wrote:
> 
> I can't figure rand() and random() out. They both seem positively un-random
> giving out the same numbers every time.
> 
> Does anyone know of a problem with these functions in DJGPP?
> Does anyone know how to get them working?
>

Are you sure :
1/ that you include the <stdlib.h> header
2/ that before calling rand(), you *first* call the srand() function, 
which initialize rand(), if you don't things like this *will* occur. Not 
that everytime your call srand() with the same parameter, you get the 
same random serie (a useful feature if you need to use the same random 
numbers several times. 

If this does not help, post the piece of code that calls rand() and an 
example of the results you get...

Also, rand() has a bug, (but not the one you describe, at least on my 
machine...) : it is not *very* random, in the sense that the numbers it 
outputs "loop over" every about 30 million iterations. This is no big 
deal if you justwant some "slight" alea, without caring whether this is 
actually random or not. But if you are doing anything involving *real* 
randomness, use random() or, better, a specific routines (places to look 
for this are Numerical Recipes in C, 2nd edition, they have a web page 
with the book online, look it up..., and Knuth's Art of Computer 
Programming, part II).

Regards,
Francois