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/*
* 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/publicdomain/zero/1.0/
*/
package jsr166;
import java.util.concurrent.Executors;
import java.util.concurrent.ExecutorService;
import java.util.concurrent.Phaser;
import java.util.concurrent.atomic.DoubleAccumulator;
import junit.framework.Test;
import junit.framework.TestSuite;
public class DoubleAccumulatorTest extends JSR166TestCase {
// android-note: Removed because the CTS runner does a bad job of
// retrying tests that have suite() declarations.
//
// public static void main(String[] args) {
// main(suite(), args);
// }
// public static Test suite() {
// return new TestSuite(DoubleAccumulatorTest.class);
// }
/**
* default constructed initializes to zero
*/
public void testConstructor() {
DoubleAccumulator ai = new DoubleAccumulator(Double::max, 0.0);
assertEquals(0.0, ai.get());
}
/**
* accumulate accumulates given value to current, and get returns current value
*/
public void testAccumulateAndGet() {
DoubleAccumulator ai = new DoubleAccumulator(Double::max, 0.0);
ai.accumulate(2.0);
assertEquals(2.0, ai.get());
ai.accumulate(-4.0);
assertEquals(2.0, ai.get());
ai.accumulate(4.0);
assertEquals(4.0, ai.get());
}
/**
* reset() causes subsequent get() to return zero
*/
public void testReset() {
DoubleAccumulator ai = new DoubleAccumulator(Double::max, 0.0);
ai.accumulate(2.0);
assertEquals(2.0, ai.get());
ai.reset();
assertEquals(0.0, ai.get());
}
/**
* getThenReset() returns current value; subsequent get() returns zero
*/
public void testGetThenReset() {
DoubleAccumulator ai = new DoubleAccumulator(Double::max, 0.0);
ai.accumulate(2.0);
assertEquals(2.0, ai.get());
assertEquals(2.0, ai.getThenReset());
assertEquals(0.0, ai.get());
}
/**
* toString returns current value.
*/
public void testToString() {
DoubleAccumulator ai = new DoubleAccumulator(Double::max, 0.0);
assertEquals("0.0", ai.toString());
ai.accumulate(1.0);
assertEquals(Double.toString(1.0), ai.toString());
}
/**
* intValue returns current value.
*/
public void testIntValue() {
DoubleAccumulator ai = new DoubleAccumulator(Double::max, 0.0);
assertEquals(0, ai.intValue());
ai.accumulate(1.0);
assertEquals(1, ai.intValue());
}
/**
* longValue returns current value.
*/
public void testLongValue() {
DoubleAccumulator ai = new DoubleAccumulator(Double::max, 0.0);
assertEquals(0, ai.longValue());
ai.accumulate(1.0);
assertEquals(1, ai.longValue());
}
/**
* floatValue returns current value.
*/
public void testFloatValue() {
DoubleAccumulator ai = new DoubleAccumulator(Double::max, 0.0);
assertEquals(0.0f, ai.floatValue());
ai.accumulate(1.0);
assertEquals(1.0f, ai.floatValue());
}
/**
* doubleValue returns current value.
*/
public void testDoubleValue() {
DoubleAccumulator ai = new DoubleAccumulator(Double::max, 0.0);
assertEquals(0.0, ai.doubleValue());
ai.accumulate(1.0);
assertEquals(1.0, ai.doubleValue());
}
/**
* accumulates by multiple threads produce correct result
*/
public void testAccumulateAndGetMT() {
final int incs = 1000000;
final int nthreads = 4;
final ExecutorService pool = Executors.newCachedThreadPool();
DoubleAccumulator a = new DoubleAccumulator(Double::max, 0.0);
Phaser phaser = new Phaser(nthreads + 1);
for (int i = 0; i < nthreads; ++i)
pool.execute(new AccTask(a, phaser, incs));
phaser.arriveAndAwaitAdvance();
phaser.arriveAndAwaitAdvance();
double expected = incs - 1;
double result = a.get();
assertEquals(expected, result);
pool.shutdown();
}
static final class AccTask implements Runnable {
final DoubleAccumulator acc;
final Phaser phaser;
final int incs;
volatile double result;
AccTask(DoubleAccumulator acc, Phaser phaser, int incs) {
this.acc = acc;
this.phaser = phaser;
this.incs = incs;
}
public void run() {
phaser.arriveAndAwaitAdvance();
DoubleAccumulator a = acc;
for (int i = 0; i < incs; ++i)
a.accumulate(i);
result = a.get();
phaser.arrive();
}
}
}
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