From owner-freebsd-current  Sun Feb  2 16:17:43 2003
Delivered-To: freebsd-current@freebsd.org
Received: from mx1.FreeBSD.org (mx1.freebsd.org [216.136.204.125])
	by hub.freebsd.org (Postfix) with ESMTP id E485137B401
	for <current@FreeBSD.ORG>; Sun,  2 Feb 2003 16:17:41 -0800 (PST)
Received: from devonshire.cnchost.com (devonshire.concentric.net [207.155.248.12])
	by mx1.FreeBSD.org (Postfix) with ESMTP id 74E4D43E4A
	for <current@FreeBSD.ORG>; Sun,  2 Feb 2003 16:17:41 -0800 (PST)
	(envelope-from bakul@bitblocks.com)
Received: from bitblocks.com (adsl-209-204-185-216.sonic.net [209.204.185.216])
	by devonshire.cnchost.com
	id TAA02092; Sun, 2 Feb 2003 19:17:32 -0500 (EST)
	[ConcentricHost SMTP Relay 1.15]
Message-ID: <200302030017.TAA02092@devonshire.cnchost.com>
Cc: Steve Kargl <sgk@troutmask.apl.washington.edu>,
	Mark Murray <mark@grondar.org>, current@FreeBSD.ORG,
	"Andrey A. Chernov" <ache@nagual.pp.ru>
Subject: Re: rand() is broken 
In-reply-to: Your message of "Sun, 02 Feb 2003 15:14:53 PST."
             <200302022314.SAA14785@illustrious.cnchost.com> 
Date: Sun, 02 Feb 2003 16:17:32 -0800
From: Bakul Shah <bakul@bitblocks.com>
Sender: owner-freebsd-current@FreeBSD.ORG
Precedence: bulk
List-ID: <freebsd-current.FreeBSD.ORG>
List-Archive: <http://docs.freebsd.org/mail/> (Web Archive)
List-Help: <mailto:majordomo@FreeBSD.ORG?subject=help> (List Instructions)
List-Subscribe: <mailto:majordomo@FreeBSD.ORG?subject=subscribe%20freebsd-current>
List-Unsubscribe: <mailto:majordomo@FreeBSD.ORG?subject=unsubscribe%20freebsd-current>
X-Loop: FreeBSD.ORG

> Interesting....  The SunOS output exactly matches random(3)
> behavior from 4.3BSD!  In fact random() remained the same for
> 4.3BSD-Reno, -Tahoe, 4.4BSD-Alpha and Net2.
> 
> 4.2BSD random() behavior is different from all of the above.
> There was real bug-fix between 4.2BSD and 4.3BSD.
> 
> I don't know when the FreeBSD/Redhat change was made or if it
> broke any statistical properties.

FYI:
The FreeBSD change was made in -r1.4 of random.c by Andrey in
Oct 1996.  The previous version of random.c behaves exactly
the same as the one in  4.3BSD, SunOS and AIX.  I am sorry I
was too busy with other things then and missed this change.

Andrey refers to an OCT 1988 CACM paper by Park & Miller
"Random number generators: good ones are hard to find" as a
justification for this change.

Also FYI: NetBSD random(3) matches the 4.3BSD random().
Haven't checked OpenBSD.

To Unsubscribe: send mail to majordomo@FreeBSD.org
with "unsubscribe freebsd-current" in the body of the message