From owner-freebsd-current Sun Feb 2 17:11:22 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 CCB3B37B401 for ; Sun, 2 Feb 2003 17:11:20 -0800 (PST) Received: from stork.mail.pas.earthlink.net (stork.mail.pas.earthlink.net [207.217.120.188]) by mx1.FreeBSD.org (Postfix) with ESMTP id 51C0043F43 for ; Sun, 2 Feb 2003 17:11:20 -0800 (PST) (envelope-from tlambert2@mindspring.com) Received: from pool0402.cvx21-bradley.dialup.earthlink.net ([209.179.193.147] helo=mindspring.com) by stork.mail.pas.earthlink.net with asmtp (SSLv3:RC4-MD5:128) (Exim 3.33 #1) id 18fV8l-0005LR-00; Sun, 02 Feb 2003 17:11:16 -0800 Message-ID: <3E3DC159.CC749944@mindspring.com> Date: Sun, 02 Feb 2003 17:09:45 -0800 From: Terry Lambert X-Mailer: Mozilla 4.79 [en] (Win98; U) X-Accept-Language: en MIME-Version: 1.0 To: Edward Brocklesby Cc: current@FreeBSD.ORG Subject: Re: rand() is broken References: <200302022039.PAA13951@warspite.cnchost.com> <200302022117.49248.ejb@lythe.org.uk> <3E3DB5C4.56A04F70@mindspring.com> <200302030042.06444.ejb@lythe.org.uk> Content-Type: text/plain; charset=us-ascii Content-Transfer-Encoding: 7bit X-ELNK-Trace: b1a02af9316fbb217a47c185c03b154d40683398e744b8a4144d44f298c0a9fc188a6d6d913271cea8438e0f32a48e08350badd9bab72f9c350badd9bab72f9c Sender: owner-freebsd-current@FreeBSD.ORG Precedence: bulk List-ID: List-Archive: (Web Archive) List-Help: (List Instructions) List-Subscribe: List-Unsubscribe: X-Loop: FreeBSD.ORG Edward Brocklesby wrote: > On Monday 03 February 2003 12:20 am, Terry Lambert wrote: > > Edward Brocklesby wrote: > > > Where was it indicated that random() wouldn't change? > > > > Right there in the boot message, and again when you logged in, > > where the system indicated to you that it was a BSD system; > > Sorry, I can't quite work out what you mean by this. Are you saying that it's > assumed random()'s API won't changed because it's guaranteed by BSD? Some behaviours are assumed to remain constant across BSD systems, which give the system it's "BSD flavor". For me, the random number generators have always been one of these. Personally, I'm concened about being able to repeat physics simulations that use drand48(), the code for the pair production coming from out of Berkeley, as well. So long as the algorithm doesn't change, the results obtained in 1982 are going to be repeatable at any point in the future. This is needed, if you intend to be able to build on published work that used a transformation of the raw numbers out of the simulation, and you need the same raw numbers, in order to do it. The experiment, in other words, needs to be repeatable. Basically, for simulations results like this, where the results are pair productions which are then kept or thrown away, based on whether the particular pair production is "possible", given the theorized physics, changing the random number generator is morally equivalent to changing the data from accelerator experiments, after the fact. Lucent just fired a PhD, very loudly and publically, for that type of number-fudging. -- Terry To Unsubscribe: send mail to majordomo@FreeBSD.org with "unsubscribe freebsd-current" in the body of the message