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Newsgroups: comp.arch.arithmetic
Date: Sat, 11 Oct 2014 06:05:59 -0700 (PDT)
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Subject: Re: New appromixation for integer division by 63 or 127
From: nikolaos.kavvadias@gmail.com
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Xref: csiph.com comp.arch.arithmetic:77

I have updated my claims for the algorithm. It works for all tested constant divisors (n=2 to n=16), and given the following assumption:

the range for x is [0,2^(2*n)-2], i.e. for n = 6, the range indeed is 
0:4094. 

And a test program: 

[code] 
#include <stdio.h> 
#include <stdlib.h> 
#include <math.h> 

/* main: 
 */ 
int main(void) 
{ 
  int qapprox, qexact; 
  int i, j, k; 

  for (i = 2; i < 8; i++) { 
    for (j = 1; j < (1<<i)*(1<<i)-1; j++) { 
      k = (1<<i) - 1; 
      qapprox = (((j>>i)+j+((1<<i)+1))>>i)-1; 
      qexact  = j / k; 
      if (qapprox != qexact) { 
        fprintf(stderr, "qapprox = (%d/%d) = %d\tqexact = (%d/%d) = %d\n", 
          j, k, qapprox, j, k, qexact); 
      } 
    } 
  } 
  return 0; 
} 
[/code]