src/math/sqrt_data.h

   1 #ifndef _SQRT_DATA_H
   2 #define _SQRT_DATA_H
   3
   4 #include <features.h>
   5 #include <stdint.h>
   6
   7 /* if x in [1,2): i = (int)(64*x);
   8    if x in [2,4): i = (int)(32*x-64);
   9    __rsqrt_tab[i]*2^-16 is estimating 1/sqrt(x) with small relative error:
  10    |__rsqrt_tab[i]*0x1p-16*sqrt(x) - 1| < -0x1.fdp-9 < 2^-8 */
  11 extern hidden const uint16_t __rsqrt_tab[128];
  12
  13 #endif