Przemyslaw Szczepaniak | b8b7511 | 2016-03-11 15:59:10 +0000 | [diff] [blame] | 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 | * http://creativecommons.org/publicdomain/zero/1.0/ |
| 5 | */ |
| 6 | |
| 7 | package jsr166; |
| 8 | |
| 9 | import java.util.concurrent.Executors; |
| 10 | import java.util.concurrent.ExecutorService; |
| 11 | import java.util.concurrent.Phaser; |
| 12 | import java.util.concurrent.atomic.LongAccumulator; |
| 13 | |
| 14 | import junit.framework.Test; |
| 15 | import junit.framework.TestSuite; |
| 16 | |
| 17 | public class LongAccumulatorTest extends JSR166TestCase { |
| 18 | // android-note: Removed because the CTS runner does a bad job of |
| 19 | // retrying tests that have suite() declarations. |
| 20 | // |
| 21 | // public static void main(String[] args) { |
| 22 | // main(suite(), args); |
| 23 | // } |
| 24 | // public static Test suite() { |
| 25 | // return new TestSuite(LongAccumulatorTest.class); |
| 26 | // } |
| 27 | |
| 28 | /** |
| 29 | * default constructed initializes to zero |
| 30 | */ |
| 31 | public void testConstructor() { |
| 32 | LongAccumulator ai = new LongAccumulator(Long::max, 0L); |
| 33 | assertEquals(0, ai.get()); |
| 34 | } |
| 35 | |
| 36 | /** |
| 37 | * accumulate accumulates given value to current, and get returns current value |
| 38 | */ |
| 39 | public void testAccumulateAndGet() { |
| 40 | LongAccumulator ai = new LongAccumulator(Long::max, 0L); |
| 41 | ai.accumulate(2); |
| 42 | assertEquals(2, ai.get()); |
| 43 | ai.accumulate(-4); |
| 44 | assertEquals(2, ai.get()); |
| 45 | ai.accumulate(4); |
| 46 | assertEquals(4, ai.get()); |
| 47 | } |
| 48 | |
| 49 | /** |
| 50 | * reset() causes subsequent get() to return zero |
| 51 | */ |
| 52 | public void testReset() { |
| 53 | LongAccumulator ai = new LongAccumulator(Long::max, 0L); |
| 54 | ai.accumulate(2); |
| 55 | assertEquals(2, ai.get()); |
| 56 | ai.reset(); |
| 57 | assertEquals(0, ai.get()); |
| 58 | } |
| 59 | |
| 60 | /** |
| 61 | * getThenReset() returns current value; subsequent get() returns zero |
| 62 | */ |
| 63 | public void testGetThenReset() { |
| 64 | LongAccumulator ai = new LongAccumulator(Long::max, 0L); |
| 65 | ai.accumulate(2); |
| 66 | assertEquals(2, ai.get()); |
| 67 | assertEquals(2, ai.getThenReset()); |
| 68 | assertEquals(0, ai.get()); |
| 69 | } |
| 70 | |
| 71 | /** |
| 72 | * toString returns current value. |
| 73 | */ |
| 74 | public void testToString() { |
| 75 | LongAccumulator ai = new LongAccumulator(Long::max, 0L); |
| 76 | assertEquals("0", ai.toString()); |
| 77 | ai.accumulate(1); |
| 78 | assertEquals(Long.toString(1), ai.toString()); |
| 79 | } |
| 80 | |
| 81 | /** |
| 82 | * intValue returns current value. |
| 83 | */ |
| 84 | public void testIntValue() { |
| 85 | LongAccumulator ai = new LongAccumulator(Long::max, 0L); |
| 86 | assertEquals(0, ai.intValue()); |
| 87 | ai.accumulate(1); |
| 88 | assertEquals(1, ai.intValue()); |
| 89 | } |
| 90 | |
| 91 | /** |
| 92 | * longValue returns current value. |
| 93 | */ |
| 94 | public void testLongValue() { |
| 95 | LongAccumulator ai = new LongAccumulator(Long::max, 0L); |
| 96 | assertEquals(0, ai.longValue()); |
| 97 | ai.accumulate(1); |
| 98 | assertEquals(1, ai.longValue()); |
| 99 | } |
| 100 | |
| 101 | /** |
| 102 | * floatValue returns current value. |
| 103 | */ |
| 104 | public void testFloatValue() { |
| 105 | LongAccumulator ai = new LongAccumulator(Long::max, 0L); |
| 106 | assertEquals(0.0f, ai.floatValue()); |
| 107 | ai.accumulate(1); |
| 108 | assertEquals(1.0f, ai.floatValue()); |
| 109 | } |
| 110 | |
| 111 | /** |
| 112 | * doubleValue returns current value. |
| 113 | */ |
| 114 | public void testDoubleValue() { |
| 115 | LongAccumulator ai = new LongAccumulator(Long::max, 0L); |
| 116 | assertEquals(0.0, ai.doubleValue()); |
| 117 | ai.accumulate(1); |
| 118 | assertEquals(1.0, ai.doubleValue()); |
| 119 | } |
| 120 | |
| 121 | /** |
| 122 | * accumulates by multiple threads produce correct result |
| 123 | */ |
| 124 | public void testAccumulateAndGetMT() { |
| 125 | final int incs = 1000000; |
| 126 | final int nthreads = 4; |
| 127 | final ExecutorService pool = Executors.newCachedThreadPool(); |
| 128 | LongAccumulator a = new LongAccumulator(Long::max, 0L); |
| 129 | Phaser phaser = new Phaser(nthreads + 1); |
| 130 | for (int i = 0; i < nthreads; ++i) |
| 131 | pool.execute(new AccTask(a, phaser, incs)); |
| 132 | phaser.arriveAndAwaitAdvance(); |
| 133 | phaser.arriveAndAwaitAdvance(); |
| 134 | long expected = incs - 1; |
| 135 | long result = a.get(); |
| 136 | assertEquals(expected, result); |
| 137 | pool.shutdown(); |
| 138 | } |
| 139 | |
| 140 | static final class AccTask implements Runnable { |
| 141 | final LongAccumulator acc; |
| 142 | final Phaser phaser; |
| 143 | final int incs; |
| 144 | volatile long result; |
| 145 | AccTask(LongAccumulator acc, Phaser phaser, int incs) { |
| 146 | this.acc = acc; |
| 147 | this.phaser = phaser; |
| 148 | this.incs = incs; |
| 149 | } |
| 150 | |
| 151 | public void run() { |
| 152 | phaser.arriveAndAwaitAdvance(); |
| 153 | LongAccumulator a = acc; |
| 154 | for (int i = 0; i < incs; ++i) |
| 155 | a.accumulate(i); |
| 156 | result = a.get(); |
| 157 | phaser.arrive(); |
| 158 | } |
| 159 | } |
| 160 | |
| 161 | } |