test/loops/Fib.java

/*
 * Written by Doug Lea with assistance from members of JCP JSR-166
 * Expert Group and released to the public domain, as explained at
 * http://creativecommons.org/publicdomain/zero/1.0/
 */

import java.util.concurrent.*;

/**
 * Recursive task-based version of Fibonacci. Computes:
 * <pre>
 * Computes fibonacci(n) = fibonacci(n-1) + fibonacci(n-2);  for n> 1
 *          fibonacci(0) = 0;
 *          fibonacci(1) = 1.
 * </pre>
 */
public final class Fib extends RecursiveAction {

    // Performance-tuning constant:
    static int sequentialThreshold;

    static long lastStealCount;

    public static void main(String[] args) throws Exception {
        int procs = 0;
        int num = 45;
        sequentialThreshold = 2;
        try {
            if (args.length > 0)
                procs = Integer.parseInt(args[0]);
            if (args.length > 1)
                num = Integer.parseInt(args[1]);
            if (args.length > 2)
                sequentialThreshold = Integer.parseInt(args[2]);
        }
        catch (Exception e) {
            System.out.println("Usage: java Fib <threads> <number> [<sequentialThreshold>]");
            return;
        }

        for (int reps = 0; reps < 2; ++reps) {
            ForkJoinPool g = (procs == 0) ? ForkJoinPool.commonPool() :
                new ForkJoinPool(procs);
            lastStealCount = g.getStealCount();
            for (int i = 0; i < 20; ++i) {
                test(g, num);
                //                if (i == 0)
                //                    Thread.sleep(100);
            }
            System.out.println(g);
            if (g != ForkJoinPool.commonPool())
                g.shutdown();
            Thread.sleep(500);
        }
    }

    /** for time conversion */
    static final long NPS = (1000L * 1000 * 1000);

    static void test(ForkJoinPool g, int num) throws Exception {
        int ps = g.getParallelism();
        long start = System.nanoTime();
        Fib f = new Fib(num);
        g.invoke(f);
        long time = System.nanoTime() - start;
        double secs = ((double)time) / NPS;
        long result = f.getAnswer();
        System.out.print("Fib " + num + " = " + result);
        System.out.printf("\tTime: %7.3f", secs);

        long sc = g.getStealCount();
        long ns = sc - lastStealCount;
        lastStealCount = sc;
        System.out.printf(" Steals/t: %5d", ns/ps);
        System.out.printf(" Workers: %5d", g.getPoolSize());
        System.out.println();
    }

    // Initialized with argument; replaced with result
    int number;

    Fib(int n) { number = n; }

    int getAnswer() {
        return number;
    }

    public final void compute() {
        int n = number;
        if (n > 1) {
            if (n <= sequentialThreshold)
                number = seqFib(n);
            else {
                Fib f1 = new Fib(n - 1);
                Fib f2 = new Fib(n - 2);
                invokeAll(f1, f2);
                number = f1.number + f2.number;
            }
        }
    }

    // Sequential version for arguments less than threshold
    static final int seqFib(int n) { // unroll left only
        int r = 1;
        do {
            int m = n - 2;
            r += m <= 1 ? m : seqFib(m);
        } while (--n > 1);
        return r;
    }
    
}
Revision:	1.8
Committed:	Sat Sep 12 18:52:19 2015 UTC (8 years, 7 months ago) by dl
Branch:	MAIN
Changes since 1.7:	+4 -8 lines
Log Message:	Use commonPool
#	User	Rev	Content
1	dl	1.1	/*
2			* Written by Doug Lea with assistance from members of JCP JSR-166
3			* Expert Group and released to the public domain, as explained at
4	jsr166	1.5	* http://creativecommons.org/publicdomain/zero/1.0/
5	dl	1.1	*/
6
7			import java.util.concurrent.*;
8
9			/**
10			* Recursive task-based version of Fibonacci. Computes:
11			* <pre>
12			* Computes fibonacci(n) = fibonacci(n-1) + fibonacci(n-2); for n> 1
13	jsr166	1.2	* fibonacci(0) = 0;
14			* fibonacci(1) = 1.
15	dl	1.1	* </pre>
16	jsr166	1.3	*/
17	dl	1.1	public final class Fib extends RecursiveAction {
18
19			// Performance-tuning constant:
20			static int sequentialThreshold;
21
22			static long lastStealCount;
23	jsr166	1.2
24	dl	1.1	public static void main(String[] args) throws Exception {
25			int procs = 0;
26			int num = 45;
27			sequentialThreshold = 2;
28			try {
29			if (args.length > 0)
30			procs = Integer.parseInt(args[0]);
31			if (args.length > 1)
32			num = Integer.parseInt(args[1]);
33	jsr166	1.2	if (args.length > 2)
34	dl	1.1	sequentialThreshold = Integer.parseInt(args[2]);
35			}
36			catch (Exception e) {
37			System.out.println("Usage: java Fib <threads> <number> [<sequentialThreshold>]");
38			return;
39			}
40
41			for (int reps = 0; reps < 2; ++reps) {
42	dl	1.8	ForkJoinPool g = (procs == 0) ? ForkJoinPool.commonPool() :
43	dl	1.1	new ForkJoinPool(procs);
44			lastStealCount = g.getStealCount();
45			for (int i = 0; i < 20; ++i) {
46			test(g, num);
47			// if (i == 0)
48			// Thread.sleep(100);
49			}
50			System.out.println(g);
51	dl	1.8	if (g != ForkJoinPool.commonPool())
52			g.shutdown();
53	dl	1.1	Thread.sleep(500);
54			}
55			}
56
57			/** for time conversion */
58			static final long NPS = (1000L * 1000 * 1000);
59
60			static void test(ForkJoinPool g, int num) throws Exception {
61			int ps = g.getParallelism();
62			long start = System.nanoTime();
63			Fib f = new Fib(num);
64			g.invoke(f);
65			long time = System.nanoTime() - start;
66			double secs = ((double)time) / NPS;
67			long result = f.getAnswer();
68			System.out.print("Fib " + num + " = " + result);
69			System.out.printf("\tTime: %7.3f", secs);
70	jsr166	1.2
71	dl	1.1	long sc = g.getStealCount();
72			long ns = sc - lastStealCount;
73			lastStealCount = sc;
74			System.out.printf(" Steals/t: %5d", ns/ps);
75			System.out.printf(" Workers: %5d", g.getPoolSize());
76			System.out.println();
77			}
78
79			// Initialized with argument; replaced with result
80			int number;
81
82			Fib(int n) { number = n; }
83
84			int getAnswer() {
85			return number;
86			}
87
88			public final void compute() {
89			int n = number;
90			if (n > 1) {
91			if (n <= sequentialThreshold)
92			number = seqFib(n);
93			else {
94			Fib f1 = new Fib(n - 1);
95			Fib f2 = new Fib(n - 2);
96	jsr166	1.2	invokeAll(f1, f2);
97	dl	1.1	number = f1.number + f2.number;
98			}
99			}
100			}
101
102			// Sequential version for arguments less than threshold
103			static final int seqFib(int n) { // unroll left only
104			int r = 1;
105			do {
106			int m = n - 2;
107			r += m <= 1 ? m : seqFib(m);
108			} while (--n > 1);
109			return r;
110			}
111	dl	1.8
112	dl	1.1	}