//******************************************************************************
//
// File:    PiSeq.java
// Package: edu.rit.clu.monte
// Unit:    Class edu.rit.clu.monte.PiSeq
//
// This Java source file is copyright (C) 2007 by Alan Kaminsky. All rights
// reserved. For further information, contact the author, Alan Kaminsky, at
// ark@cs.rit.edu.
//
// This Java source file is part of the Parallel Java Library ("PJ"). PJ is free
// software; you can redistribute it and/or modify it under the terms of the GNU
// General Public License as published by the Free Software Foundation; either
// version 3 of the License, or (at your option) any later version.
//
// PJ is distributed in the hope that it will be useful, but WITHOUT ANY
// WARRANTY; without even the implied warranty of MERCHANTABILITY or FITNESS FOR
// A PARTICULAR PURPOSE. See the GNU General Public License for more details.
//
// A copy of the GNU General Public License is provided in the file gpl.txt. You
// may also obtain a copy of the GNU General Public License on the World Wide
// Web at http://www.gnu.org/licenses/gpl.html.
//
//******************************************************************************

package edu.rit.clu.monte;

import edu.rit.pj.Comm;

import edu.rit.util.Random;

/**
 * Class PiSeq is a sequential program that calculates an approximate value for
 * π using a Monte Carlo technique. The program generates a number of random
 * points in the unit square (0,0) to (1,1) and counts how many of them lie
 * within a circle of radius 1 centered at the origin. The fraction of the
 * points within the circle is approximately π/4.
 * <P>
 * Usage: java edu.rit.clu.monte.PiSeq <I>seed</I> <I>N</I>
 * <BR><I>seed</I> = Random seed
 * <BR><I>N</I> = Number of random points
 * <P>
 * The computation is performed sequentially in a single processor. The program
 * uses class edu.rit.util.Random for its pseudorandom number generator. The
 * program measures the computation's running time. This establishes a benchmark
 * for measuring the computation's running time on a parallel processor.
 *
 * @author  Alan Kaminsky
 * @version 31-Jan-2007
 */
public class PiSeq
    {

// Prevent construction.

    private PiSeq()
        {
        }

// Program shared variables.

    // Command line arguments.
    static long seed;
    static long N;

    // Pseudorandom number generator.
    static Random prng;

    // Number of points within the unit circle.
    static long count;

// Main program.

    /**
     * Main program.
     */
    public static void main
        (String[] args)
        throws Exception
        {
        // Start timing.
        long time = -System.currentTimeMillis();

        // Initialize middleware.
        Comm.init (args);

        // Validate command line arguments.
        if (args.length != 2) usage();
        seed = Long.parseLong (args[0]);
        N = Long.parseLong (args[1]);

        // Set up PRNG.
        prng = Random.getInstance (seed);

        // Generate n random points in the unit square, count how many are in
        // the unit circle.
        count = 0L;
        for (long i = 0L; i < N; ++ i)
            {
            double x = prng.nextDouble();
            double y = prng.nextDouble();
            if (x*x + y*y <= 1.0) ++ count;
            }

        // Stop timing.
        time += System.currentTimeMillis();

        // Print results.
        System.out.println (time + " msec total");
        System.out.println
            ("pi = 4 * " + count + " / " + N + " = " +
             (4.0 * count / N));
        }

// Hidden operations.

    /**
     * Print a usage message and exit.
     */
    private static void usage()
        {
        System.err.println ("Usage: java edu.rit.clu.monte.PiSeq <seed> <N>");
        System.err.println ("<seed> = Random seed");
        System.err.println ("<N> = Number of random points");
        System.exit (1);
        }

    }