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//******************************************************************************
//
// File: PiSeq.c
//
// This C source file is copyright (C) 2008 by Alan Kaminsky. All rights
// reserved. For further information, contact the author, Alan Kaminsky, at
// ark@cs.rit.edu.
//
// This C 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.
//
//******************************************************************************
#include <stdlib.h>
#include <stdio.h>
#include <sys/time.h>
#include <mpi.h>
#include "Random.h"
/**
* 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: 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 11-Aug-2008
*/
// Program shared variables.
// World communicator.
static MPI_Comm world;
static int size;
static int rank;
// Command line arguments.
static long long int seed;
static long long int N;
// Pseudorandom number generator.
static Random prng;
// Number of points within the unit circle.
static long long int count;
// Hidden operations.
/**
* Print a usage message and exit.
*/
static void usage(void)
{
fprintf (stderr, "Usage: PiSeq <seed> <N>\n");
fprintf (stderr, "<seed> = Random seed\n");
fprintf (stderr, "<N> = Number of random points\n");
exit (1);
}
/**
* Returns the current wall clock time in milliseconds.
* Java equivalent: java.lang.System.currentTimeMillis()
*/
static long long int currentTimeMillis(void)
{
struct timeval tv;
long long int result;
gettimeofday (&tv, NULL);
result = tv.tv_sec;
result *= 1000;
result += tv.tv_usec / 1000;
return result;
}
// Main program.
/**
* Main program.
*/
int main
(int argc,
char **argv)
{
long long int time, i;
double x, y;
// Start timing.
time = -currentTimeMillis();
// Initialize MPI middleware.
MPI_Init (&argc, &argv);
world = MPI_COMM_WORLD;
MPI_Comm_size (world, &size);
MPI_Comm_rank (world, &rank);
// Validate command line arguments.
if (argc != 3) usage();
sscanf (argv[1], "%lld", &seed);
sscanf (argv[2], "%lld", &N);
// Set up PRNG.
setSeed (&prng, seed);
// Generate n random points in the unit square, count how many are in
// the unit circle.
count = 0;
for (i = 0; i < N; ++ i)
{
x = nextDouble (&prng);
y = nextDouble (&prng);
if (x*x + y*y <= 1.0) ++ count;
}
// Stop timing.
time += currentTimeMillis();
// Print results.
printf ("pi = 4 * %lld / %lld = %.20f\n", count, N, 4.0 * count / N);
printf ("%lld msec\n", time);
// Finalize MPI middleware.
MPI_Finalize();
}
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