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Path: utzoo!censor!geac!torsqnt!news-server.csri.toronto.edu!mailrus!wuarchive!zaphod.mps.ohio-state.edu!usc!apple!ucscb.ucsc.edu!alexr
From: alexr@ucscb.ucsc.edu (Alexander M. Rosenberg)
Newsgroups: comp.sys.mac,comp.sys.mac.programmer,comp.sys.mac.misc,comp.sys.mac.system
Subject: Re: Random number Generator wanted.
Message-ID: <8999@goofy.Apple.COM>
Date: 5 Jul 90 22:14:02 GMT
Sender: usenet@Apple.COM
Organization: Hacker's Anonymous
Lines: 36
References:<152@asacsg.mh.nl> <1990Jun29.020739.9146@Neon.Stanford.EDU> <1990Jun30.170949.1426@Neon.Stanford.EDU>

In article <1990Jun30.170949.1426@Neon.Stanford.EDU> 
kaufman@Neon.Stanford.EDU (Marc T. Kaufman) writes:
> I thank Sak for this info.  I am not sure just which Macs this applies 
to --
> probably the ci and fx, certainly not the SE.  Can someone from Apple 
tell us
> when the algorithm changed, and is it part of a system patch so all Macs 
can
> benefit from it?
> 
> Marc Kaufman (kaufman@Neon.stanford.edu)

Sak is incorrect. While he may note that the algorithm is the same (I'm 
not sure), it is definately not probable for him to have matched up 10000 
numbers.

Apple's random number generator uses the tick count as a seed upon each 
InitGraf (I may be wrong here, but I'm sure that it is time derived.) I do 
know that the mouse driver has always kept track of the time at which a 
click occurs, and takes the difference in time between that click and the 
previous one, and adds this number to the current randSeed. This is where 
an additional level of randomness is provided. (Humans tend to be more 
"random" than computers do, eh?)

This is why you may have seen results that didn't follow a pattern.
(It is possible that in 32-bit QuickDraw they changed the algorithm, but I 
seriously doubt it.)

(ignore any paths found here, they are incorrect. I can be reached at
Alex_Rosenberg.INTEGRATION@gateway.qm.apple.com)
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