Path: chuka.playstation.co.uk!news
From: Craig Graham <c_graham@hinge.mistral.co.uk>
Newsgroups: scee.yaroze.freetalk.english
Subject: Re: Square Root
Date: Fri, 21 Aug 1998 18:25:08 +0100
Organization: PlayStation Net Yaroze (SCEE)
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References: <35DD914A.BBA25235@ndirect.co.uk> <35DD9B1E.3FEAA1E5@scee.sony.co.uk>
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Alternatively, if all you want is the length of a vector,
the manhattan distance approximation:

inline short manhatan_distance(register unsigned short a,
        register unsigned short b,
        register unsigned short c)
{
 register short t;

 if(a<b)    // a is > b
 {
  t=a;
  a=b;
  b=t;
 }

 if(b<c)    // b is > c
 {
  t=b;
  b=c;
  c=t;
 }

 if(a<b)    // a is > b
 {
  t=a;
  a=b;
  b=t;
 }

// t=a + (b>>2) + (c>>2);    // faster lower accuracy
 t=a + ((11*b)>>5) + (c>>2);    // slower, more accurate

 return t;
}