testcases/kernel/fs/fs-bench/boxmuler.c

#include <math.h>
#include <stdlib.h>

#define M_2PI (M_PI*2)

int box_muler(int min, int max)
{
  double u1,u2,z;
  int i;
  int ave;
  int range;
  int ZZ;
  if (min >= max) {
    return (-1);
  }
  range = max - min;
  ave = range/2;
  for (i = 0 ; i< 10 ; i++) {
    u1 =  ((double)(random() % 1000000))/ 1000000;
    u2 =  ((double)(random() % 1000000))/ 1000000;
    z = sqrt( -2.0 * log(u1) ) * cos ( M_2PI * u2 );
    ZZ = min + (ave + (z*(ave/4)));
    if (ZZ >= min && ZZ < max) {
        return (ZZ);
    }
  }
  return (-1);
}