From mboxrd@z Thu Jan  1 00:00:00 1970
From: lm@bitmover.com (Larry McVoy)
Date: Wed, 31 Mar 2010 19:01:55 -0700
Subject: [TUHS] Origins of drand48()?
In-Reply-To: <20100401012300.GJ17405@mercury.ccil.org>
References: <20100331222002.GA28694@minnie.tuhs.org>
	<20100401012300.GJ17405@mercury.ccil.org>
Message-ID: <20100401020155.GG18965@bitmover.com>

Hi John.

I suspect it is really ATT source.  There is a lot more of that around
than people admit.

I also suspect it doesn't matter.  Your points about how it works are
part of it, but the bigger part is that Unix, at this point, has very
little IP value.  It's mostly there in Linux et al.

--lm

On Wed, Mar 31, 2010 at 09:23:00PM -0400, John Cowan wrote:
> Warren Toomey scripsit:
> 
> > As far as I can determine, drand48() arrived in SysVR1 and is defined
> > in the first SVID. It doesn't appear in SysIII, nor in the early BSDs.
> > Can anybody shed some light on drand48()? Could it have been written
> > elsewhere and made available e.g on a Usenix tape or comp.sources.*,
> > and included into SysV, or is SysV the origin of the code?
> 
> FWIW, the code appears in OpenSolaris with an AT&T 1988 copyright header.
> It's been generified and given a CDDL license and Sun Microsystems 2008
> copyright header.
> 
> There are a bunch of other copies floating around *without* an AT&T
> copyright, e.g.
> http://cs.nyu.edu/~yap/classes/visual/data/ply/cygwin-version/ply/drand48.c .
> 
> > I'm sure the algorithm comes from elsewhere, e.g. Knuth, but the
> > strong code similarity is a worry.
> 
> It's a linear congruential generator with multiplier 25214903917,
> addend 11, and modulus 2^48, so there's nothing special about that.
> LCGs are indeed discussed in Knuth volume 2.
> 
> -- 
> John Cowan  cowan at ccil.org    http://ccil.org/~cowan
> Big as a house, much bigger than a house, it looked to [Sam], a grey-clad
> moving hill.  Fear and wonder, maybe, enlarged him in the hobbit's eyes,
> but the Mumak of Harad was indeed a beast of vast bulk, and the like of him
> does not walk now in Middle-earth; his kin that live still in latter days are
> but memories of his girth and his majesty.  --"Of Herbs and Stewed Rabbit"
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-- 
---
Larry McVoy                lm at bitmover.com           http://www.bitkeeper.com
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