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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.atomic.DoubleAccumulator; |
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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 DoubleAccumulatorTest 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(DoubleAccumulatorTest.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 (double identity : new double[] { |
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Double.NEGATIVE_INFINITY, |
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Double.POSITIVE_INFINITY, |
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Double.MIN_VALUE, |
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Double.MAX_VALUE, |
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0.0, |
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}) |
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assertEquals(identity, |
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new DoubleAccumulator(Double::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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DoubleAccumulator acc = new DoubleAccumulator(Double::max, 0.0); |
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acc.accumulate(2.0); |
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assertEquals(2.0, acc.get()); |
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acc.accumulate(-4.0); |
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assertEquals(2.0, acc.get()); |
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acc.accumulate(4.0); |
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assertEquals(4.0, 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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DoubleAccumulator acc = new DoubleAccumulator(Double::max, 0.0); |
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acc.accumulate(2.0); |
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assertEquals(2.0, acc.get()); |
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acc.reset(); |
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assertEquals(0.0, 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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DoubleAccumulator acc = new DoubleAccumulator(Double::max, 0.0); |
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acc.accumulate(2.0); |
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assertEquals(2.0, acc.get()); |
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assertEquals(2.0, acc.getThenReset()); |
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assertEquals(0.0, 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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DoubleAccumulator acc = new DoubleAccumulator(Double::max, 0.0); |
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assertEquals("0.0", acc.toString()); |
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acc.accumulate(1.0); |
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assertEquals(Double.toString(1.0), 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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DoubleAccumulator acc = new DoubleAccumulator(Double::max, 0.0); |
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assertEquals(0, acc.intValue()); |
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acc.accumulate(1.0); |
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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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DoubleAccumulator acc = new DoubleAccumulator(Double::max, 0.0); |
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assertEquals(0, acc.longValue()); |
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acc.accumulate(1.0); |
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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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DoubleAccumulator acc = new DoubleAccumulator(Double::max, 0.0); |
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assertEquals(0.0f, acc.floatValue()); |
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acc.accumulate(1.0); |
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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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DoubleAccumulator acc = new DoubleAccumulator(Double::max, 0.0); |
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assertEquals(0.0, acc.doubleValue()); |
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acc.accumulate(1.0); |
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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 int incs = 1000000; |
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final int nthreads = 4; |
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final ExecutorService pool = Executors.newCachedThreadPool(); |
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DoubleAccumulator a = new DoubleAccumulator(Double::max, 0.0); |
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Phaser phaser = new Phaser(nthreads + 1); |
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for (int i = 0; i < nthreads; ++i) |
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pool.execute(new AccTask(a, phaser, incs)); |
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phaser.arriveAndAwaitAdvance(); |
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phaser.arriveAndAwaitAdvance(); |
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double expected = incs - 1; |
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double result = a.get(); |
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assertEquals(expected, result); |
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pool.shutdown(); |
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} |
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|
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static final class AccTask implements Runnable { |
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final DoubleAccumulator acc; |
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final Phaser phaser; |
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final int incs; |
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volatile double result; |
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AccTask(DoubleAccumulator acc, Phaser phaser, int incs) { |
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this.acc = acc; |
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this.phaser = phaser; |
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this.incs = incs; |
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} |
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|
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public void run() { |
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phaser.arriveAndAwaitAdvance(); |
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DoubleAccumulator a = acc; |
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for (int i = 0; i < incs; ++i) |
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a.accumulate(i); |
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result = a.get(); |
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phaser.arrive(); |
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} |
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} |
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|
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} |
