--- jsr166/src/test/tck/DoubleAccumulatorTest.java	2014/12/31 19:05:42	1.3
+++ jsr166/src/test/tck/DoubleAccumulatorTest.java	2019/09/09 01:05:22	1.9
@@ -7,6 +7,7 @@
 import java.util.concurrent.Executors;
 import java.util.concurrent.ExecutorService;
 import java.util.concurrent.Phaser;
+import java.util.concurrent.ThreadLocalRandom;
 import java.util.concurrent.atomic.DoubleAccumulator;
 
 import junit.framework.Test;
@@ -14,142 +15,137 @@ import junit.framework.TestSuite;
 
 public class DoubleAccumulatorTest extends JSR166TestCase {
     public static void main(String[] args) {
-        junit.textui.TestRunner.run(suite());
+        main(suite(), args);
     }
     public static Test suite() {
         return new TestSuite(DoubleAccumulatorTest.class);
     }
 
     /**
-     * default constructed initializes to zero
+     * new instance initialized to supplied identity
      */
     public void testConstructor() {
-        DoubleAccumulator ai = new DoubleAccumulator(Double::max, 0.0);
-        assertEquals(0.0, ai.get());
+        for (double identity : new double[] {
+                 Double.NEGATIVE_INFINITY,
+                 Double.POSITIVE_INFINITY,
+                 Double.MIN_VALUE,
+                 Double.MAX_VALUE,
+                 0.0,
+             })
+            assertEquals(identity,
+                         new DoubleAccumulator(Double::max, identity).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());
+        DoubleAccumulator acc = new DoubleAccumulator(Double::max, 0.0);
+        acc.accumulate(2.0);
+        assertEquals(2.0, acc.get());
+        acc.accumulate(-4.0);
+        assertEquals(2.0, acc.get());
+        acc.accumulate(4.0);
+        assertEquals(4.0, acc.get());
     }
 
     /**
-     * reset zeroes 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());
+        DoubleAccumulator acc = new DoubleAccumulator(Double::max, 0.0);
+        acc.accumulate(2.0);
+        assertEquals(2.0, acc.get());
+        acc.reset();
+        assertEquals(0.0, acc.get());
     }
 
     /**
-     * getThenReset returns get then zeros
+     * 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());
+        DoubleAccumulator acc = new DoubleAccumulator(Double::max, 0.0);
+        acc.accumulate(2.0);
+        assertEquals(2.0, acc.get());
+        assertEquals(2.0, acc.getThenReset());
+        assertEquals(0.0, acc.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());
+        DoubleAccumulator acc = new DoubleAccumulator(Double::max, 0.0);
+        assertEquals("0.0", acc.toString());
+        acc.accumulate(1.0);
+        assertEquals(Double.toString(1.0), acc.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());
+        DoubleAccumulator acc = new DoubleAccumulator(Double::max, 0.0);
+        assertEquals(0, acc.intValue());
+        acc.accumulate(1.0);
+        assertEquals(1, acc.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());
+        DoubleAccumulator acc = new DoubleAccumulator(Double::max, 0.0);
+        assertEquals(0, acc.longValue());
+        acc.accumulate(1.0);
+        assertEquals(1, acc.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());
+        DoubleAccumulator acc = new DoubleAccumulator(Double::max, 0.0);
+        assertEquals(0.0f, acc.floatValue());
+        acc.accumulate(1.0);
+        assertEquals(1.0f, acc.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());
+        DoubleAccumulator acc = new DoubleAccumulator(Double::max, 0.0);
+        assertEquals(0.0, acc.doubleValue());
+        acc.accumulate(1.0);
+        assertEquals(1.0, acc.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() {
+        final DoubleAccumulator acc
+            = new DoubleAccumulator((x, y) -> x + y, 0.0);
+        final int nThreads = ThreadLocalRandom.current().nextInt(1, 5);
+        final Phaser phaser = new Phaser(nThreads + 1);
+        final int incs = expensiveTests ? 1_000_000 : 100_000;
+        final double total = nThreads * incs/2.0 * (incs - 1); // Gauss
+        final Runnable task = () -> {
             phaser.arriveAndAwaitAdvance();
-            DoubleAccumulator a = acc;
-            for (int i = 0; i < incs; ++i)
-                a.accumulate(i);
-            result = a.get();
+            for (int i = 0; i < incs; i++) {
+                acc.accumulate((double) i);
+                assertTrue(acc.get() <= total);
+            }
             phaser.arrive();
+        };
+        final ExecutorService p = Executors.newCachedThreadPool();
+        try (PoolCleaner cleaner = cleaner(p)) {
+            for (int i = nThreads; i-->0; )
+                p.execute(task);
+            phaser.arriveAndAwaitAdvance();
+            phaser.arriveAndAwaitAdvance();
+            assertEquals(total, acc.get());
         }
     }