Skip to content
Related Articles

Related Articles

Improve Article

Java Program to Implement Park-Miller Random Number Generation Algorithm

  • Last Updated : 15 Dec, 2020

Park–Miller random number generator is also known as Lehmer random number generator. A general formula of a random number generator (RNG) of this type is, Xk+1 = a * xk mod m

Where the modulus m is a prime number or a power of a prime number, the multiplier a is an element of high multiplicative order modulo m, and the seed X0 is coprime to m.  

Attention reader! Don’t stop learning now. Get hold of all the important Java Foundation and Collections concepts with the Fundamentals of Java and Java Collections Course at a student-friendly price and become industry ready. To complete your preparation from learning a language to DS Algo and many more,  please refer Complete Interview Preparation Course.

Algorithm of Park-Miller

1) Declare variables m, a, q, r and r_seed(X0) as constant variables and assign 

m = 2145678965L;
a = 48271L;
q = 44488L;
r = 3399L;
r_seed = 12345678L

Here, the value of constants m and r_seed are chosen in such a way that the GCD(m, r_seed) = 1. The modulus can also be chosen as a prime number, making the choice of a coprime seed trivial (any 0 < X0 < m will do). Here, the values a, q, r are constants.

2) Declare function uniform with double as return-type.

     2.1) Declare variable hi, lo, t.

     2.2) set variables hi, lo, t as following : 

              2.2.1) hi= as seed divided by b

              2.2.2) lo = seed – b * hi

              2.2.3) t = a * lo – c * hi

Where hi and li are the highest and lowest numbers in a range respectively for a random number for particular m and r_seed(X0).

     2.3) check if (t > 0) i.e; generated random number is positive then set  r_seed = t.

     2.4) else set r_seed = t + m. // generated random number is negative

     2.5) return seed from function uniform.

3) In the main method

     3.1) Start a loop from i=0 to 10

             3.1.1)Call the function random and store the results for each iteration.

     3.2)Print the results


Example: The below program Implements Park-Miller Random Number Generation Algorithm.

Note: Each iteration of this code will produce different output.


// Java implementation of Park-Miller algorithm
public class Park_Miller_Random_Numbers {
    // m is coprime to seed r_seed
    static final long m = 2147483647L;
    // constants
    static final long a = 48271L;
    static final long q = 44488L;
    static final long r = 3399L;
    // take a r_seed that is coprime to m
    static long r_seed = 12345678L;
    public static double uniform()
        // highest and lowest for
        // a random number generation
        // range
        long hi = r_seed / q;
        long lo = r_seed - q * hi;
        // calculate random number
        long t = a * lo - r * hi;
        // if positive
        if (t > 0)
            r_seed = t;
            r_seed = t + m;
        return r_seed;
    public static void main(String[] argv)
        double[] A = new double[10];
        for (int i = 0; i < 5; i++)
            A[i] = uniform();
        for (int i = 0; i < 5; i++)
            System.out.print("  " + A[i]);
  1.085252519E9  5.08259731E8  1.352291773E9  1.563240271E9  8.90733155E8

My Personal Notes arrow_drop_up
Recommended Articles
Page :