// This computes reciprocal estimate from table with interpolation.
#include <stdio.h>
#include <stdlib.h>
typedef struct{short r; short d;} en;
static en T[32];
int main(){int er=0;
  for(int j=32; j<64; ++j)
    T[j-32] = (en){(1<<20)/((j<<5)+1), (1<<21)/(j*j+1)};
  for(int j=0; j<32; ++j) printf("%02x %4x %4x\n", j, T[j].r, T[j].d);
if(1) for(int j=1024; j<2048; ++j){en r = T[(j-1024)>>5];
   int w = r.r - (((j&31)*r.d)>>11), g = (1<<20)/(j+1);
   {int ae = abs(g-w); er = er<ae?ae:er;}
   printf("%5x %8x %8x %8x %8x\n", j, r.r, r.d, w, g);}
 printf("mer = %d\n", er);
return 0;}
// mer = 1
// off both ways.