/*
 * Java program to compute the value of pi using Monte Carlo
 *
 * command-line arguments:  number_of_samples, seed
 */
package csci3366.hw2;

import java.util.Random;

public class MonteCarloPi {

    /* main method */

    public static void main(String[] args) {

        String usageMsg = "arguments are number_of_samples seed";

        /* process command-line arguments */
        if (args.length != 2)  {
            System.err.println(usageMsg);
            System.exit(1);
        }
        int numSamples = 0;
        int seed = 0;
        try {
            numSamples = Integer.parseInt(args[0]);
            seed = Integer.parseInt(args[1]);
        }
        catch (NumberFormatException e) {
            System.err.println(usageMsg);
            System.exit(1);
        }

        /* record start time */
        long startTime = System.currentTimeMillis();

        /* do calculation */ 
        Random randGenerator = new Random(seed);
        int count = 0;
        for (int i = 0; i < numSamples; ++i) {
            double x = randGenerator.nextDouble();
            double y = randGenerator.nextDouble();
            if ((x*x + y*y) <= 1.0)
                ++count;
        }
        double pi = 4.0 * (double) count / (double) numSamples;

        /* record end time and print results */
        long endTime = System.currentTimeMillis();
        System.out.printf("sequential Java program results:\n");
        System.out.printf("number of samples = %d, seed = %d\n", 
                numSamples, seed);
        System.out.printf("estimated pi = %12.10f\n", pi);
        System.out.printf(
                "difference between estimated pi and math.h M_PI = %12.10f\n", 
                Math.abs(pi - Math.PI));
        System.out.printf("time to compute = %g seconds\n", 
                ((double) (endTime - startTime) / 1000.0));
    }
}