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/* |
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* Written by Doug Lea with assistance from members of JCP JSR-166 |
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* Expert Group and released to the public domain, as explained at |
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* http://creativecommons.org/publicdomain/zero/1.0/ |
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*/ |
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|
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import java.util.concurrent.Executors; |
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import java.util.concurrent.ExecutorService; |
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import java.util.concurrent.Phaser; |
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import java.util.concurrent.ThreadLocalRandom; |
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import java.util.concurrent.atomic.LongAccumulator; |
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|
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import junit.framework.Test; |
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import junit.framework.TestSuite; |
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|
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public class LongAccumulatorTest extends JSR166TestCase { |
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public static void main(String[] args) { |
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main(suite(), args); |
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} |
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public static Test suite() { |
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return new TestSuite(LongAccumulatorTest.class); |
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} |
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|
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/** |
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* new instance initialized to supplied identity |
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*/ |
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public void testConstructor() { |
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for (long identity : new long[] { Long.MIN_VALUE, 0, Long.MAX_VALUE }) |
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assertEquals(identity, |
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new LongAccumulator(Long::max, identity).get()); |
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} |
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|
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/** |
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* accumulate accumulates given value to current, and get returns current value |
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*/ |
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public void testAccumulateAndGet() { |
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LongAccumulator acc = new LongAccumulator(Long::max, 0L); |
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acc.accumulate(2); |
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assertEquals(2, acc.get()); |
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acc.accumulate(-4); |
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assertEquals(2, acc.get()); |
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acc.accumulate(4); |
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assertEquals(4, acc.get()); |
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} |
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|
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/** |
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* reset() causes subsequent get() to return zero |
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*/ |
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public void testReset() { |
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LongAccumulator acc = new LongAccumulator(Long::max, 0L); |
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acc.accumulate(2); |
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assertEquals(2, acc.get()); |
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acc.reset(); |
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assertEquals(0, acc.get()); |
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} |
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|
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/** |
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* getThenReset() returns current value; subsequent get() returns zero |
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*/ |
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public void testGetThenReset() { |
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LongAccumulator acc = new LongAccumulator(Long::max, 0L); |
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acc.accumulate(2); |
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assertEquals(2, acc.get()); |
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assertEquals(2, acc.getThenReset()); |
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assertEquals(0, acc.get()); |
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} |
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|
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/** |
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* toString returns current value. |
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*/ |
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public void testToString() { |
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LongAccumulator acc = new LongAccumulator(Long::max, 0L); |
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assertEquals("0", acc.toString()); |
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acc.accumulate(1); |
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assertEquals(Long.toString(1), acc.toString()); |
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} |
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|
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/** |
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* intValue returns current value. |
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*/ |
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public void testIntValue() { |
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LongAccumulator acc = new LongAccumulator(Long::max, 0L); |
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assertEquals(0, acc.intValue()); |
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acc.accumulate(1); |
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assertEquals(1, acc.intValue()); |
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} |
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|
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/** |
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* longValue returns current value. |
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*/ |
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public void testLongValue() { |
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LongAccumulator acc = new LongAccumulator(Long::max, 0L); |
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assertEquals(0, acc.longValue()); |
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acc.accumulate(1); |
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assertEquals(1, acc.longValue()); |
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} |
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|
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/** |
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* floatValue returns current value. |
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*/ |
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public void testFloatValue() { |
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LongAccumulator acc = new LongAccumulator(Long::max, 0L); |
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assertEquals(0.0f, acc.floatValue()); |
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acc.accumulate(1); |
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assertEquals(1.0f, acc.floatValue()); |
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} |
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|
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/** |
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* doubleValue returns current value. |
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*/ |
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public void testDoubleValue() { |
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LongAccumulator acc = new LongAccumulator(Long::max, 0L); |
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assertEquals(0.0, acc.doubleValue()); |
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acc.accumulate(1); |
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assertEquals(1.0, acc.doubleValue()); |
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} |
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|
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/** |
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* accumulates by multiple threads produce correct result |
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*/ |
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public void testAccumulateAndGetMT() { |
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final LongAccumulator acc |
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= new LongAccumulator((x, y) -> x + y, 0L); |
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final int nThreads = ThreadLocalRandom.current().nextInt(1, 5); |
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final Phaser phaser = new Phaser(nThreads + 1); |
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final int incs = expensiveTests ? 1_000_000 : 100_000; |
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final long total = nThreads * incs/2L * (incs - 1); // Gauss |
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final Runnable task = () -> { |
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phaser.arriveAndAwaitAdvance(); |
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for (int i = 0; i < incs; i++) { |
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acc.accumulate((long) i); |
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assertTrue(acc.get() <= total); |
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} |
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phaser.arrive(); |
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}; |
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final ExecutorService p = Executors.newCachedThreadPool(); |
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try (PoolCleaner cleaner = cleaner(p)) { |
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for (int i = nThreads; i-->0; ) |
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p.execute(task); |
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phaser.arriveAndAwaitAdvance(); |
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phaser.arriveAndAwaitAdvance(); |
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assertEquals(total, acc.get()); |
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} |
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} |
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|
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} |
