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C++ Program to Implement the linear congruential generator for Pseudo Random Number Generation
The linear congruential generator is a very simple example of a random number generator. It is one of the oldest and best-known pseudorandom number generator algorithms. The function which is used in this method −
Xn+1=(aXn + C) mod m
where X is the sequence of pseudorandom values, and
m,0<m— the “modulus" a,0<a<m — the "multiplier" c,0<c<m — the "increment" X0, 0<x0<m — the "seed" or "start value"
are integer constants that specify the generator.
A benefit of this method is is that with appropriate choice of parameters, the period is known and long.
Algorithm
Begin Declare class mRND Create a function Seed(number) Assign a variable _seed=number Create a constructor mRND Declare _seed(0), a(0), c(0), m(2147483648) Create a function rnd() Return _seed = (a * _seed + c) mod m Declare a, c, m, _seed Done Declare an another subclass MS_RND inheriting from base class mRND Create a constructor Read the variables a, c Create a function rnd() return mRND::rnd() right shift 16 Done Declare an another subclass BSD_RND inheriting from base class mRND Create a constructor Read the variables a, c Create a function rnd() return mRND::rnd() Done For x=0 to 6 Print MS_RAND For x=0 to 6 Print BSD_RAND Done End
Example Code
#include <iostream> using namespace std; class mRND { public: void seed(unsigned int s) { _seed= s; } protected: mRND() : _seed(0), a(0), c(0), m(2147483648) { } int rnd() { return (_seed = (a * _seed + c) % m); } int a, c; unsigned int m, _seed; }; class MS_RND: public mRND { public: MS_RND() { a = 214013; c = 2531011; } int rnd() { return mRND::rnd() >> 16; } }; class BSD_RND: public mRND { public: BSD_RND() { a = 1016404597; c = 12345; } int rnd() { return mRND::rnd(); } }; int main(int argc, char* argv[]) { BSD_RND bsd_rnd; MS_RND ms_rnd; cout << "MS RAND:" << endl << "-----------" << endl; for (int x = 0; x < 6; x++) cout << ms_rnd.rnd() << endl; cout << endl << "BSD RAND:" << endl << "-------------" << endl; for (int x = 0; x < 6; x++) cout << bsd_rnd.rnd() << endl; return 0; }
Output
MS RAND: ------- 38 7719 21238 2437 8855 11797 BSD RAND: -------- 12345 1915290694 1005338679 629284700 741596485 1834373826
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