Fast integer distance formula

On Wed, 04 Oct 2006 16:04:49 GMT, ---@--- (Robert Scott) wrote:

>I have an approximation for the Pythagorean distance formula (magnitude of
>vector [x,y]) using integer arithmetic that I would like to improve.  Currently
>I am using this:
>
  (snipped)
>
>The improvement I am looking for is in accuracy.  I would like to try for a
>4-fold improvement in accuracy (.5%) without substantially increasing the
>running time of what I have now.  Does anyone know of a better approximation
>that is almost as fast?
>
>Robert Scott
>Ypsilanti, Michigan

Hi Robert,

0.5% max error is a tough goal to achieve.
(I don't speak "C", so I'm not able understand your 
code.)
  Have ya' had a look at:

   "A Root of Less Evil", IEEE Signal Processing 
    Magazine, DSP Tips & Tricks column, Vol. 22, 
    No. 2, March 2005.

There's a scheme in that article that yields 
1% max error in magnitude approximation.

Good Luck,
[-Rick-]
Ypsilanti, huh?  Have they fixed the 
roads in Michigan yet?