krandom.cpp

cmac实现

// Random number generator from Numerical Recipes in C
// developed by Knuth 

#include "krandom.h"
#include <iostream.h>

int seed;

// knuth's subtractive generator 

long double ran3(int *idum)
{ static int inext, inextp;
  static int ma[56];
  static int iff=0;
  int mj,mk;
  int i, ii, k;
  if (*idum < 0 || iff ==0) {
    iff=1;
    mj=MSEED-(*idum < 0 ? -*idum : *idum);
    mj %= MBIG;
    ma[55]=mj;
    mk=1;
    for (i=1;i<=54;i++) {
      ii=(21*i) % 55;
      ma[ii]=mk;
      mk=mj-mk;
      if (mk < MZ) mk +=MBIG;
      mj=ma[ii];
    }
    for (k=1;k<=4;k++)
      for (i=1;i<=55;i++){
	     ma[i] -= ma[1+(i+30) % 55];
	     if (ma[i] < MZ) ma[i] += MBIG;
	  }
    inext=0;
    inextp=31;
    *idum=1;
    }
    if (++inext == 56) inext=1;
    if (++inextp == 56) inextp=1;
    mj=ma[inext]-ma[inextp];
    if (mj < MZ) mj += MBIG;
    ma[inext]=mj;
    return (mj*FAC);
}

//  return an integer between 0 and Range inclusive  

int choose_random_int_value(int range)
{
  long double rand_value,sum=0.0,interval;
  int i;

  rand_value = ran3(&seed);
  interval = 1.0/(range+1);

  for (i=0; i<=range; i++)
    {
      sum = sum + interval;
      if (rand_value <= sum)
		return (i);
    }
  return(0); // default value returned 
}


long double choose_random_value()
{
	return (ran3(&seed));
}

void initialize_random_number_generator(int val)
{

  seed = val; 

//  cout << "enter large negative integer as seed for random number" << endl; 
//  cin >> seed; 
  
}