Re: Divide by three?

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#21515

From: Bill Kinnersley
Date: Fri, 02 Jun 1989 02:01

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[In "Divide by three?" shs@uts.amdahl.com (Steve Schoettler) said:]
:
: Here's a puzzle:
: 	What's the fastest way to divide an 11 bit number by three,
: 	on a processor that doesn't have any multiply or divide instructions?
:

How about using the identity

   1/3 = 1/4 + (1/4)^2 + (1/4)^3 + ...

In other words,

   term = number
   ans = 0
   for i=1 to 6
      term = term/4
      ans = ans + term



-- 
--Bill Kinnersley
  Physics Department   Montana State University    Bozeman, MT 59717
  INTERNET: iphwk@terra.oscs.montana.edu      BITNET: IPHWK@MTSUNIX1
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Path: arc1-ca.pugleaf.net!utzoo!attcan!uunet!lll-winken!ncis.tis.llnl.gov!helios.ee.lbl.gov!pasteur!ucbvax!decwrl!terra.oscs.montana.edu!iphwk
From: iphwk@terra.oscs.montana.edu (Bill Kinnersley)
Newsgroups: comp.arch
Subject: Re: Divide by three?
Message-ID: <8906020201.AA10938@terra.oscs.montana.edu>
Date: 2 Jun 89 02:01:39 GMT
Organization: Digital Equipment Corporation
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