1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
|
//******************************************************************************
//
// File: PiSmp3.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 "Random.h"
/**
* PiSmp3 is an SMP parallel 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: PiSmp3 <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 in parallel in multiple processors. The program
* uses class edu.rit.util.Random for its pseudorandom number generator. The
* program measures the computation's running time.
*
* @author Alan Kaminsky
* @version 11-Aug-2008
*/
// Program shared variables.
// 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: PiSmp3 <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();
// Validate command line arguments.
if (argc != 3) usage();
sscanf (argv[1], "%lld", &seed);
sscanf (argv[2], "%lld", &N);
#pragma omp parallel private(prng,x,y) reduction(+:count)
{
// Set up PRNG.
setSeed (&prng, seed);
// Generate n random points in the unit square, count how many are
// in the unit circle.
count = 0;
#pragma omp for schedule(static)
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);
}
|
