possion.cpp

这是泊松分布

#include<stdio.h>
#include<math.h>
#define  lambda 1
#define MAX 1000
#define znew (z=36969*(z&65535)+(z>>16))
#define wnew (w=18000*(w&65535)+(w>>16))
#define MWC ((znew<<16)+wnew)
#define SHR3 (jsr^=(jsr<<17),jsr^=(jsr>>13),jsr^=(jsr<<15))
#define CONG (jcong=69069*jcong+1234567)
#define KISS ((MWC^CONG)+SHR3)
#define UNI (KISS*2.328306e-10)

double r[MAX];

typedef unsigned long UL;
static UL z=362436069,w=521288629,jsr=123456789,jcong=380116160;
void settable(UL i1,UL i2,UL i3,UL i4)
{ int i;
  z=i1;
  w=i2;
  jsr=i3;
  jcong=i4;
}
void randnum(void)
{
 int i=0;
 double k;
 settable(12345,65435,34221,12345) ;
 for(i=0;i<MAX;i++)
 {
 k=UNI;
 r[i]=k;
 }
}
//产生第i个possion分布的随机数
int possion(double r[],int i)
{
 double a,b,u;
 int j,x;
 a=exp(-lambda);
 b=1.0;
 j=0;
 while(b>=a)
 {
  u=r[i];
  b=b*u;
  j++;
  }
 x=j-1;
 return x;
}
void main()
{
 int i,x;
 FILE *out;
 if((out=fopen("POSSIONUM.DAT","w"))==NULL)
 {
 printf("cannot open file\n");
 return;
 }
 randnum();
 for(i=0;i<MAX;i++)
  {x=possion(r,i) ;
   printf("%10d\n",x);
   fprintf(out,"%10d\n",x);
  }
 fclose(out);
}