test/loops/NoopLockLoops.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.*;
import java.util.concurrent.locks.*;
import java.util.*;

public final class NoopLockLoops {
    static final ExecutorService pool = Executors.newCachedThreadPool();
    static final LoopHelpers.SimpleRandom rng = new LoopHelpers.SimpleRandom();
    static boolean print = false;
    static int iters = 20000000;

    public static void main(String[] args) throws Exception {
        int maxThreads = 100;
        if (args.length > 0)
            maxThreads = Integer.parseInt(args[0]);

        new ReentrantLockLoop(1).test();
        new ReentrantLockLoop(1).test();
        print = true;

        for (int k = 1, i = 1; i <= maxThreads;) {
            System.out.print("Threads: " + i);
            new ReentrantLockLoop(i).test();
            Thread.sleep(100);
            if (i == k) {
                k = i << 1;
                i = i + (i >>> 1);
            }
            else
                i = k;
        }
        pool.shutdown();
    }

    static final class ReentrantLockLoop implements Runnable {
        private int v = rng.next();
        private volatile int result = 17;
        private final LoopHelpers.BarrierTimer timer = new LoopHelpers.BarrierTimer();
        private final CyclicBarrier barrier;
        private final int nthreads;
        private volatile int readBarrier;
        ReentrantLockLoop(int nthreads) {
            this.nthreads = nthreads;
            barrier = new CyclicBarrier(nthreads+1, timer);
        }

        final void test() throws Exception {
            for (int i = 0; i < nthreads; ++i)
                pool.execute(this);
            barrier.await();
            barrier.await();
            if (print) {
                long time = timer.getTime();
                long tpi = time / ((long) iters * nthreads);
                System.out.print("\t" + LoopHelpers.rightJustify(tpi) + " ns per lock");
                double secs = (double) time / 1000000000.0;
                System.out.println("\t " + secs + "s run time");
            }

            int r = result;
            if (r == 0) // avoid overoptimization
                System.out.println("useless result: " + r);
        }

        public final void run() {
            try {
                barrier.await();
                int sum = v + 1;
                int x = sum + 1;
                int n = iters;
                while (n-- > 0) {
                    synchronized (this) {
                        x = LoopHelpers.compute4(x);
                    }
                    sum += x;
                    if ((x += readBarrier) == 0)
                        ++readBarrier;

                }
                barrier.await();
                result += sum;
            }
            catch (Exception ie) {
                return;
            }
        }
    }

}
Revision:	1.7
Committed:	Thu Dec 18 18:13:06 2014 UTC (9 years, 4 months ago) by jsr166
Branch:	MAIN
Changes since 1.6:	+1 -2 lines
Log Message:	move k = 1 into loop initializer
#	User	Rev	Content
1	dl	1.1	/*
2			* Written by Doug Lea with assistance from members of JCP JSR-166
3	dl	1.2	* Expert Group and released to the public domain, as explained at
4	jsr166	1.6	* http://creativecommons.org/publicdomain/zero/1.0/
5	dl	1.1	*/
6
7			import java.util.concurrent.*;
8			import java.util.concurrent.locks.*;
9			import java.util.*;
10
11			public final class NoopLockLoops {
12			static final ExecutorService pool = Executors.newCachedThreadPool();
13			static final LoopHelpers.SimpleRandom rng = new LoopHelpers.SimpleRandom();
14			static boolean print = false;
15			static int iters = 20000000;
16
17			public static void main(String[] args) throws Exception {
18			int maxThreads = 100;
19	jsr166	1.3	if (args.length > 0)
20	dl	1.1	maxThreads = Integer.parseInt(args[0]);
21
22			new ReentrantLockLoop(1).test();
23			new ReentrantLockLoop(1).test();
24			print = true;
25
26	jsr166	1.7	for (int k = 1, i = 1; i <= maxThreads;) {
27	dl	1.1	System.out.print("Threads: " + i);
28			new ReentrantLockLoop(i).test();
29			Thread.sleep(100);
30			if (i == k) {
31			k = i << 1;
32			i = i + (i >>> 1);
33	jsr166	1.3	}
34			else
35	dl	1.1	i = k;
36			}
37			pool.shutdown();
38			}
39
40			static final class ReentrantLockLoop implements Runnable {
41			private int v = rng.next();
42			private volatile int result = 17;
43			private final LoopHelpers.BarrierTimer timer = new LoopHelpers.BarrierTimer();
44			private final CyclicBarrier barrier;
45			private final int nthreads;
46			private volatile int readBarrier;
47			ReentrantLockLoop(int nthreads) {
48			this.nthreads = nthreads;
49			barrier = new CyclicBarrier(nthreads+1, timer);
50			}
51
52			final void test() throws Exception {
53	jsr166	1.3	for (int i = 0; i < nthreads; ++i)
54	dl	1.1	pool.execute(this);
55			barrier.await();
56			barrier.await();
57			if (print) {
58			long time = timer.getTime();
59	jsr166	1.4	long tpi = time / ((long) iters * nthreads);
60	dl	1.1	System.out.print("\t" + LoopHelpers.rightJustify(tpi) + " ns per lock");
61	jsr166	1.4	double secs = (double) time / 1000000000.0;
62	dl	1.1	System.out.println("\t " + secs + "s run time");
63			}
64
65			int r = result;
66			if (r == 0) // avoid overoptimization
67			System.out.println("useless result: " + r);
68			}
69
70			public final void run() {
71			try {
72	jsr166	1.3	barrier.await();
73	dl	1.1	int sum = v + 1;
74			int x = sum + 1;
75			int n = iters;
76			while (n-- > 0) {
77	jsr166	1.5	synchronized (this) {
78	dl	1.1	x = LoopHelpers.compute4(x);
79			}
80			sum += x;
81			if ((x += readBarrier) == 0)
82			++readBarrier;
83
84			}
85			barrier.await();
86			result += sum;
87			}
88	jsr166	1.3	catch (Exception ie) {
89			return;
90	dl	1.1	}
91			}
92			}
93
94			}