test/loops/SimpleSpinLockLoops.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.CyclicBarrier;
import java.util.concurrent.ExecutorService;
import java.util.concurrent.Executors;
import java.util.concurrent.atomic.AtomicInteger;

public final class SimpleSpinLockLoops {
    static final ExecutorService pool = Executors.newCachedThreadPool();
    static final LoopHelpers.SimpleRandom rng = new LoopHelpers.SimpleRandom();
    static boolean print = false;
    static int iters = 2000000;

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

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

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

    static final class LockLoop 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;
        private final AtomicInteger spinlock = new AtomicInteger();
        LockLoop(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() {
            final AtomicInteger lock = this.spinlock;
            try {
                barrier.await();
                int sum = v + 1;
                int x = 0;
                int n = iters;
                while (n-- > 0) {
                    do {} while (!lock.compareAndSet(0, 1));
                    int k = (sum & 3);
                    if (k > 0) {
                        x = v;
                        while (k-- > 0)
                            x = LoopHelpers.compute6(x);
                        v = x;
                    }
                    else x = sum + 1;
                    lock.set(0);
                    if ((x += readBarrier) == 0)
                        ++readBarrier;
                    for (int l = x & 1; l > 0; --l)
                        sum += LoopHelpers.compute6(sum);
                }
                barrier.await();
                result += sum;
            }
            catch (Exception ie) {
                return;
            }
        }
    }

}
Revision:	1.10
Committed:	Sat Dec 31 18:54:28 2016 UTC (7 years, 4 months ago) by jsr166
Branch:	MAIN
CVS Tags:	HEAD
Changes since 1.9:	+4 -4 lines
Log Message:	organize imports
#	User	Rev	Content
1	dl	1.1	/*
2			* Written by Doug Lea with assistance from members of JCP JSR-166
3	dl	1.3	* 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	jsr166	1.10	import java.util.concurrent.CyclicBarrier;
8			import java.util.concurrent.ExecutorService;
9			import java.util.concurrent.Executors;
10			import java.util.concurrent.atomic.AtomicInteger;
11	dl	1.1
12			public final class SimpleSpinLockLoops {
13			static final ExecutorService pool = Executors.newCachedThreadPool();
14			static final LoopHelpers.SimpleRandom rng = new LoopHelpers.SimpleRandom();
15			static boolean print = false;
16			static int iters = 2000000;
17
18			public static void main(String[] args) throws Exception {
19			int maxThreads = 100;
20	jsr166	1.4	if (args.length > 0)
21	dl	1.1	maxThreads = Integer.parseInt(args[0]);
22
23			new LockLoop(1).test();
24			new LockLoop(1).test();
25			print = true;
26
27	jsr166	1.7	for (int k = 1, i = 1; i <= maxThreads;) {
28	dl	1.1	System.out.print("Threads: " + i);
29			new LockLoop(i).test();
30			Thread.sleep(100);
31			if (i == k) {
32			k = i << 1;
33			i = i + (i >>> 1);
34	jsr166	1.4	}
35			else
36	dl	1.1	i = k;
37			}
38			pool.shutdown();
39			}
40
41			static final class LockLoop implements Runnable {
42			private int v = rng.next();
43			private volatile int result = 17;
44			private final LoopHelpers.BarrierTimer timer = new LoopHelpers.BarrierTimer();
45			private final CyclicBarrier barrier;
46			private final int nthreads;
47			private volatile int readBarrier;
48			private final AtomicInteger spinlock = new AtomicInteger();
49			LockLoop(int nthreads) {
50			this.nthreads = nthreads;
51			barrier = new CyclicBarrier(nthreads+1, timer);
52			}
53
54			final void test() throws Exception {
55	jsr166	1.4	for (int i = 0; i < nthreads; ++i)
56	dl	1.1	pool.execute(this);
57			barrier.await();
58			barrier.await();
59			if (print) {
60			long time = timer.getTime();
61	jsr166	1.5	long tpi = time / ((long) iters * nthreads);
62	dl	1.1	System.out.print("\t" + LoopHelpers.rightJustify(tpi) + " ns per lock");
63	jsr166	1.5	double secs = (double) time / 1000000000.0;
64	dl	1.1	System.out.println("\t " + secs + "s run time");
65			}
66
67			int r = result;
68			if (r == 0) // avoid overoptimization
69			System.out.println("useless result: " + r);
70			}
71
72			public final void run() {
73			final AtomicInteger lock = this.spinlock;
74			try {
75	jsr166	1.4	barrier.await();
76	dl	1.1	int sum = v + 1;
77			int x = 0;
78			int n = iters;
79			while (n-- > 0) {
80	jsr166	1.9	do {} while (!lock.compareAndSet(0, 1));
81	dl	1.1	int k = (sum & 3);
82			if (k > 0) {
83			x = v;
84			while (k-- > 0)
85	dl	1.2	x = LoopHelpers.compute6(x);
86	dl	1.1	v = x;
87			}
88			else x = sum + 1;
89			lock.set(0);
90			if ((x += readBarrier) == 0)
91			++readBarrier;
92			for (int l = x & 1; l > 0; --l)
93	dl	1.2	sum += LoopHelpers.compute6(sum);
94	jsr166	1.4	}
95	dl	1.1	barrier.await();
96			result += sum;
97			}
98	jsr166	1.4	catch (Exception ie) {
99			return;
100	dl	1.1	}
101			}
102			}
103
104			}