apps/plugins/fft/math.c

   1 #include "math.h"
   2
   3 int64_t fsqrt64(int64_t a, unsigned int fracbits)
   4 {
   5     int64_t b = a/2 + (1 << fracbits); /* initial approximation */
   6     unsigned int n;
   7     const unsigned int iterations = 3; /* very rough approximation */
   8
   9     for (n = 0; n < iterations; ++n)
  10         b = (b + (((int64_t)(a) << fracbits)/b))/2;
  11
  12     return b;
  13 }