1 Apr
2010
1 Apr
'10
7:23 a.m.
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(a)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"