test/loops/ContextSwitchTest.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/licenses/publicdomain
 */

import java.util.concurrent.*;
import java.util.concurrent.locks.*;
import java.util.concurrent.atomic.*;
import java.util.*;

public final class ContextSwitchTest {
    final static int iters = 1000000;
    static AtomicReference turn = new AtomicReference();
    public static void main(String[] args) throws Exception {
        test();
        test();
        test();
    }

    static void test() throws Exception {
        MyThread a = new MyThread();
        MyThread b = new MyThread();
        a.other = b;
        b.other = a;
        turn.set(a);
        long startTime = System.nanoTime();
        a.start();
        b.start();
        a.join();
        b.join();
        long endTime = System.nanoTime();
        int np = a.nparks + b.nparks;
        System.out.println("Average time: " + 
                           ((endTime - startTime) / np) +
                           "ns");
    }

    static final class MyThread extends Thread {
        volatile Thread other;
        volatile int nparks;

        public void run() {
            final AtomicReference t = turn;
            final Thread other = this.other;
            if (turn == null || other == null) 
                throw new NullPointerException();
            int p = 0;
            for (int i = 0; i < iters; ++i) {
                while (!t.compareAndSet(other, this)) {
                    LockSupport.park();
                    ++p;
                }
                LockSupport.unpark(other);
            }
            LockSupport.unpark(other);
            nparks = p;
            System.out.println("parks: " + p);
            
        }
    }
}


Revision:	1.3
Committed:	Thu Sep 15 16:55:40 2005 UTC (18 years, 8 months ago) by dl
Branch:	MAIN
Changes since 1.2:	+14 -11 lines
Log Message:	Misc minor test improvements
#	User	Rev	Content
1	dl	1.2	/*
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			* http://creativecommons.org/licenses/publicdomain
5			*/
6
7	dl	1.1	import java.util.concurrent.*;
8			import java.util.concurrent.locks.*;
9			import java.util.concurrent.atomic.*;
10			import java.util.*;
11
12			public final class ContextSwitchTest {
13			final static int iters = 1000000;
14			static AtomicReference turn = new AtomicReference();
15			public static void main(String[] args) throws Exception {
16	dl	1.3	test();
17			test();
18			test();
19			}
20
21			static void test() throws Exception {
22	dl	1.1	MyThread a = new MyThread();
23			MyThread b = new MyThread();
24			a.other = b;
25			b.other = a;
26			turn.set(a);
27			long startTime = System.nanoTime();
28			a.start();
29			b.start();
30			a.join();
31			b.join();
32			long endTime = System.nanoTime();
33			int np = a.nparks + b.nparks;
34	dl	1.3	System.out.println("Average time: " +
35			((endTime - startTime) / np) +
36			"ns");
37	dl	1.1	}
38
39			static final class MyThread extends Thread {
40			volatile Thread other;
41			volatile int nparks;
42
43			public void run() {
44	dl	1.3	final AtomicReference t = turn;
45			final Thread other = this.other;
46			if (turn == null \|\| other == null)
47			throw new NullPointerException();
48	dl	1.1	int p = 0;
49			for (int i = 0; i < iters; ++i) {
50	dl	1.3	while (!t.compareAndSet(other, this)) {
51	dl	1.1	LockSupport.park();
52			++p;
53			}
54			LockSupport.unpark(other);
55			}
56			LockSupport.unpark(other);
57			nparks = p;
58			System.out.println("parks: " + p);
59
60			}
61			}
62			}
63
64