boxmuler.c revision df3eb16e38c6a163b0a7367c885679eed6140964 
1#include <math.h>
2#include <stdlib.h>
3
4#define M_2PI (M_PI*2)
5
6int box_muler(int min, int max)
7{
8  double u1,u2,z;
9  int i;
10  int ave;
11  int range;
12  int ZZ;
13  if (min >= max ) {
14    return (-1);
15  }
16  range = max - min;
17  ave = range/2;
18  for (i = 0 ; i< 10 ; i++ ) {
19    u1 =  ((double)(random() % 1000000))/ 1000000;
20    u2 =  ((double)(random() % 1000000))/ 1000000;
21    z = sqrt( -2.0 * log(u1) ) * cos ( M_2PI * u2 );
22    ZZ = min + (ave + (z*(ave/4)));
23    if (ZZ >= min && ZZ < max ) {
24        return (ZZ);
25    }
26  }
27  return (-1);
28}
29