/****************************************************************
Copyright (C) :    University of Michigan
Project:           NERS 544 - Class example
File:              lcrng32.cpp
Purpose:           An example of a linear congruential
                   random number generator in 32 bits
Compiler:          g++ -ansi -pedantic -Wconversion
                   Use -O2 as well
Programmer:        Alex Bielajew
Revision Date:     09/12/2016

Conversion to a double would be via the following statement below lines  :

double r = 0.5 + in*2.328306436538696e-10;

****************************************************************/

#include <iostream>
#include <iomanip>

using namespace std;

int rand(int in, int iOffset) {return 69069*in + iOffset;}
// The magic multiplier 69069 is cited by Marsaglia as the "best" for 32 bits 

int main(void)
{  cout << "Starting seed = ";
   int iFirst;
   cin >> iFirst;
   if (iFirst%2 == 0)
   {  cout << "*** Starting seed must be an odd number. Exiting! ***\n";
      return 1;
   }
   cout << "Offset = ";
   int iOffset;
   cin >> iOffset;
   if (iOffset%2 == 0)
   {  cout << "*** Offset must be an odd number. Exiting! ***\n";
      return 2;
   }

   cout << "Starting seed: " << iFirst << "   Offset:" << iOffset << "\n\n\n\n";

   int in = iFirst; in = rand(in, iOffset); // Next in series to start
   double r = 0.5 + in*2.328306436538696e-10;
   cout << in << ":" << setprecision(16) << r << endl;
   
   unsigned int i = 0;
 
   while(in != iFirst)
   {  i = i + 1;
      in = rand(in, iOffset); // Update
      double r = 0.5 + in*2.328306436538696e-10;
      if (i < 10) cout << in << ":" << setprecision(16) << r << endl;
      int N = 10000000;
      if (i%N == 0) cout << "." << flush;
   } // Exits when repeats
   
   if (i < 2000000000)
      cout << "\n# loops = " << i + 1 <<  "\n\n";
   else
      cout << "\n# loops = " << i << " + 1 = " << i + 1 << "\n\n";
   
   for (int i = 1; i <= 10; i = i + 1) 
   {  in = rand(in, iOffset);
      double r = 0.5 + in*2.328306436538696e-10;
      cout << in << ":" << setprecision(16) << r << endl;
   }

   return 0;
}