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From: mark@mips.COM (Mark G. Johnson)
Newsgroups: comp.sys.dec
Subject: Re: Random numbers on PDP-11
Keywords: PDP-11 random numbers
Message-ID: <39908@mips.mips.COM>
Date: 5 Jul 90 14:22:04 GMT
References: <19191@orstcs.CS.ORST.EDU> <1739@mountn.dec.com> <19207@orstcs.CS.ORST.EDU>
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In article <19207@orstcs.CS.ORST.EDU> kohler@jacobs.CS.ORST.EDU (kurt kohler) writes:
>Thanks for the reply, but I guess I should have been more explicit. What
>I wanted was a function that could be evaluated with the 16 bit arithmetic
>on the PDP-11. Actually since all that is required is a 32 bit multiply
>I could use it I suppose, it would just be more straight forward to
>have 16 bit constants and a 16 bit result.


Vol. 2 of Cookbook de la Knuth, 2nd edition, section 3.6, suggests some
properties that your multiplier, modulus, and addend should have.
The following choices have some of his suggested properties; read Knuth
and see if you agree.

         X(0)    :=  31416
         X(n+1)  :=  [ (33573 * X(n)) + 4511 ] mod 65536

note: 2^16 = 65536, so the method above is suited for use on a binary
                    computer with 16-bit wordlength.
-- 
 -- Mark Johnson	
 	MIPS Computer Systems, 930 E. Arques M/S 2-02, Sunnyvale, CA 94086
	(408) 524-8308    mark@mips.com  {or ...!decwrl!mips!mark}