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
177
178
179
180
181
182
183

/*
 * Copyright (c) 2011.  Peter Lawrey
 *
 * "THE BEER-WARE LICENSE" (Revision 128)
 * As long as you retain this notice you can do whatever you want with this stuff.
 * If we meet some day, and you think this stuff is worth it, you can buy me a beer in return
 * There is no warranty.
 */

package com.google.code.java.core.threads;

import org.junit.Test;

import java.util.Map;
import java.util.TreeMap;
import java.util.concurrent.ExecutorService;
import java.util.concurrent.Executors;
import java.util.concurrent.TimeUnit;
import java.util.concurrent.atomic.AtomicInteger;
import java.util.concurrent.locks.Lock;
import java.util.concurrent.locks.ReentrantLock;

public class SynchronizedVsLockTest {
  static final Object mutex1 = new Object();
  static final Object mutex2 = new Object();
  static final Lock lock1 = new ReentrantLock();
  static final Lock lock2 = new ReentrantLock();
  static int counter1 = 0;
  static int counter2 = 0;
  static final AtomicInteger counter3 = new AtomicInteger();
  static final AtomicInteger counter4 = new AtomicInteger();
  public static final int LOOPS = 50 * 1000 * 1000;
  static final Map<Integer, double[]> results = new TreeMap<Integer, double[]>();

  @Test
  public void testSvL() throws InterruptedException {
    testSvL1();
    testSvL2();

    for (Map.Entry<Integer, double[]> entry : results.entrySet()) {
      System.out.print("<tr><td align=\"right\">");
      System.out.print(entry.getKey());
      for (double v : entry.getValue()) {
        System.out.print("</td><td>");
        System.out.printf("%.3f", v);
      }
      System.out.println("</td></tr>");
    }
  }

  static void testSvL1() throws InterruptedException {
    for (final int t : new int[]{1, 2, 4, 8, 16, 32, 64}) {
      doTest(t, 0, new Runnable() {
        @Override
        public void run() {
          for (int i = 0; i < LOOPS / t; i++) {
            synchronized (mutex1) {
              counter1++;
            }
          }
        }

        @Override
        public String toString() {
          return "1x synchronized {}";
        }
      });
      doTest(t, 1, new Runnable() {
        @Override
        public void run() {
          for (int i = 0; i < LOOPS / t; i++) {
            lock1.lock();
            try {
              counter1++;
            } finally {
              lock1.unlock();
            }
          }
        }

        @Override
        public String toString() {
          return "1x Lock.lock()/unlock()";
        }
      });
      doTest(t, 2, new Runnable() {
        @Override
        public void run() {
          for (int i = 0; i < LOOPS / t; i++) {
            counter3.getAndIncrement();
          }
        }

        @Override
        public String toString() {
          return "1x AtomicInteger";
        }
      });
    }
  }

  static void testSvL2() throws InterruptedException {
    for (final int t : new int[]{1, 2, 4, 8, 16, 32, 64}) {
      doTest(t, 3, new Runnable() {
        @Override
        public void run() {
          for (int i = 0; i < LOOPS / t; i++) {
            synchronized (mutex1) {
              counter1++;
            }
            synchronized (mutex2) {
              counter2++;
            }
          }
        }

        @Override
        public String toString() {
          return "2x synchronized {}";
        }
      });
      doTest(t, 4, new Runnable() {
        @Override
        public void run() {
          for (int i = 0; i < LOOPS / t; i++) {
            lock1.lock();
            try {
              counter1++;
            } finally {
              lock1.unlock();
            }
            lock2.lock();
            try {
              counter2++;
            } finally {
              lock2.unlock();
            }
          }
        }

        @Override
        public String toString() {
          return "2x Lock.lock()/unlock()";
        }
      });
      doTest(t, 5, new Runnable() {
        @Override
        public void run() {
          for (int i = 0; i < LOOPS / t; i++) {
            counter3.getAndIncrement();
            counter4.getAndIncrement();
          }
        }

        @Override
        public String toString() {
          return "2x AtomicInteger";
        }
      });
    }
  }

  private static void doTest(int threads, int testNum, Runnable runnable) throws InterruptedException {
    ExecutorService es = Executors.newFixedThreadPool(threads);
    long start = System.nanoTime();
    try {
      for (int i = 0; i < threads; i++)
        es.execute(runnable.getClass().getDeclaredConstructor(int.class).newInstance(threads));

    } catch (Exception e) {
      throw new AssertionError(e);
    } finally {
      es.shutdown();
    }
    es.awaitTermination(1, TimeUnit.MINUTES);
    long time = (System.nanoTime() - start) / 1000000;
    System.out.printf("%s with %d threads took %.3f seconds%n", runnable.toString(), threads, time / 1e3);
    double[] times = results.get(threads);
    if (times == null)
      results.put(threads, times = new double[6]);
    times[testNum] = time / 1e3;
  }
}