/*
 * @(#) smt1_2.c - Random generator quality M[] and D[] tester
 * (Task 1_2 at the Special Military Training course).
 * (c) 1996 Ivan Maidanski <ivmai@chat.ru> http://ivmai.chat.ru
 * Freeware program source. All rights reserved.
 **
 * Language: ANSI C
 * Tested with: Borland C++ v3.1
 * Last modified: 1996-12-04 21:35:00 GMT+03:00
 */

#include <stdio.h>
#include <math.h>

#define K 12

int rnd_func(int x)
{
 return (x*5%(1<<K));
}

float exp_rnd_func(float lambda,int *seed)
{
 return (-log((float)(*seed=rnd_func(*seed))/(1<<K))/lambda);
}

int main()
{
 int seed,n,i;
 float x,lambda,mx,dx;
 printf("Input Lambda (Lambda>0):\n");
 scanf("%f",&lambda);
 printf("Input N (amount of generated numbers):\n");
 scanf("%d",&n);
 printf("Input random seed [%d..%d],odd:\n",(1<<(K-2))-1,(1<<K)-1);
 scanf("%d",&seed);
 for (mx=0,dx=0,i=0;i<n;i++)
 {
  x=exp_rnd_func(lambda,&seed);
  mx+=x;
  dx+=x*x;
 }
 mx/=n;
 dx-=mx*mx*n;
 dx/=(n-1);
 printf("\n");
 printf("Theoretic M[x]: %f\n",1/lambda);
 printf("Experimental M[x]: %f\n",mx);
 printf("Theoretic D[x]: %f\n",1/(lambda*lambda));
 printf("Experimental D[x]: %f\n\n",dx);
 return 0;
}