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
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
|
//******************************************************************************
//
// File: PiClu.java
// Package: edu.rit.clu.monte
// Unit: Class edu.rit.clu.monte.PiClu
//
// 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.
//
// Linking this library statically or dynamically with other modules is making a
// combined work based on this library. Thus, the terms and conditions of the
// GNU General Public License cover the whole combination.
//
// As a special exception, the copyright holders of this library give you
// permission to link this library with independent modules to produce an
// executable, regardless of the license terms of these independent modules, and
// to copy and distribute the resulting executable under terms of your choice,
// provided that you also meet, for each linked independent module, the terms
// and conditions of the license of that module. An independent module is a
// module which is not derived from or based on this library. If you modify this
// library, you may extend this exception to your version of the library, but
// you are not obligated to do so. If you do not wish to do so, delete this
// exception statement from your version.
//
// 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.mp.buf.LongItemBuf;
import edu.rit.pj.Comm;
import edu.rit.pj.reduction.LongOp;
import edu.rit.util.LongRange;
import edu.rit.util.Random;
/**
* Class PiClu is a cluster 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: java -Dpj.np=<I>K</I> edu.rit.clu.monte.PiClu <I>seed</I> <I>N</I>
* <BR><I>K</I> = Number of parallel processes
* <BR><I>seed</I> = Random seed
* <BR><I>N</I> = Number of random points
* <P>
* The computation is performed in parallel in multiple threads. The program
* uses class edu.rit.util.Random for its pseudorandom number generator. To
* improve performance, each process has its own pseudorandom number generator,
* and the program uses the reduction pattern to determine the count. The
* program uses the "sequence splitting" technique with the pseudorandom number
* generators to yield results identical to the sequential version. The program
* measures the computation's running time.
*
* @author Alan Kaminsky
* @version 27-Jun-2007
*/
public class PiClu
{
// Prevent construction.
private PiClu()
{
}
// Program shared variables.
// World communicator.
static Comm world;
static int size;
static int rank;
// 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);
world = Comm.world();
size = world.size();
rank = world.rank();
// Validate command line arguments.
if (args.length != 2) usage();
seed = Long.parseLong (args[0]);
N = Long.parseLong (args[1]);
// Determine range of iterations for this thread.
LongRange range = new LongRange (0, N-1) .subrange (size, rank);
long my_N = range.length();
// Set up PRNG and skip ahead over the random numbers the lower-ranked
// processes will generate.
prng = Random.getInstance (seed);
prng.skip (2 * range.lb());
// Generate random points in the unit square, count how many are in the
// unit circle.
count = 0L;
for (long i = 0L; i < my_N; ++ i)
{
double x = prng.nextDouble();
double y = prng.nextDouble();
if (x*x + y*y <= 1.0) ++ count;
}
// Reduce all processes' counts together into process 0.
LongItemBuf buf = new LongItemBuf();
buf.item = count;
world.reduce (0, buf, LongOp.SUM);
count = buf.item;
// Stop timing.
time += System.currentTimeMillis();
// Print results.
System.out.println (time + " msec total " + rank);
if (rank == 0)
{
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 -Dpj.np=<K> edu.rit.clu.monte.PiClu <seed> <N>");
System.err.println ("<K> = Number of parallel processes");
System.err.println ("<seed> = Random seed");
System.err.println ("<N> = Number of random points");
System.exit (1);
}
}
|
