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jsr166 |
1.1 |
/* |
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* Written by Doug Lea and Martin Buchholz with assistance from |
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* members of JCP JSR-166 Expert Group and released to the public |
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* domain, as explained at |
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* http://creativecommons.org/publicdomain/zero/1.0/ |
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*/ |
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import static java.util.concurrent.TimeUnit.MILLISECONDS; |
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import static java.util.concurrent.TimeUnit.SECONDS; |
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import java.util.concurrent.CountedCompleter; |
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import java.util.concurrent.ThreadLocalRandom; |
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import java.util.concurrent.atomic.AtomicInteger; |
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import java.util.function.BiConsumer; |
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import java.util.function.Consumer; |
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import junit.framework.Test; |
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import junit.framework.TestSuite; |
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public class CountedCompleter8Test 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(CountedCompleter8Test.class); |
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} |
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/** CountedCompleter class javadoc code sample, version 1. */ |
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public static <E> void forEach1(E[] array, Consumer<E> action) { |
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class Task extends CountedCompleter<Void> { |
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final int lo, hi; |
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Task(Task parent, int lo, int hi) { |
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super(parent); this.lo = lo; this.hi = hi; |
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} |
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public void compute() { |
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if (hi - lo >= 2) { |
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int mid = (lo + hi) >>> 1; |
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// must set pending count before fork |
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setPendingCount(2); |
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new Task(this, mid, hi).fork(); // right child |
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new Task(this, lo, mid).fork(); // left child |
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} |
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else if (hi > lo) |
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action.accept(array[lo]); |
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tryComplete(); |
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} |
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} |
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new Task(null, 0, array.length).invoke(); |
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} |
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/** CountedCompleter class javadoc code sample, version 2. */ |
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public static <E> void forEach2(E[] array, Consumer<E> action) { |
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class Task extends CountedCompleter<Void> { |
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final int lo, hi; |
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Task(Task parent, int lo, int hi) { |
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super(parent); this.lo = lo; this.hi = hi; |
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} |
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public void compute() { |
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if (hi - lo >= 2) { |
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int mid = (lo + hi) >>> 1; |
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setPendingCount(1); // looks off by one, but correct! |
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new Task(this, mid, hi).fork(); // right child |
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new Task(this, lo, mid).compute(); // direct invoke |
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} else { |
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if (hi > lo) |
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action.accept(array[lo]); |
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tryComplete(); |
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} |
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} |
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} |
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new Task(null, 0, array.length).invoke(); |
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} |
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/** CountedCompleter class javadoc code sample, version 3. */ |
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public static <E> void forEach3(E[] array, Consumer<E> action) { |
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class Task extends CountedCompleter<Void> { |
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final int lo, hi; |
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Task(Task parent, int lo, int hi) { |
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super(parent); this.lo = lo; this.hi = hi; |
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} |
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public void compute() { |
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int n = hi - lo; |
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for (; n >= 2; n /= 2) { |
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addToPendingCount(1); |
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new Task(this, lo + n/2, lo + n).fork(); |
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} |
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if (n > 0) |
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action.accept(array[lo]); |
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propagateCompletion(); |
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} |
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} |
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new Task(null, 0, array.length).invoke(); |
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} |
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/** CountedCompleter class javadoc code sample, version 4. */ |
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public static <E> void forEach4(E[] array, Consumer<E> action) { |
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class Task extends CountedCompleter<Void> { |
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final int lo, hi; |
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Task(Task parent, int lo, int hi) { |
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super(parent, 31 - Integer.numberOfLeadingZeros(hi - lo)); |
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this.lo = lo; this.hi = hi; |
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} |
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public void compute() { |
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for (int n = hi - lo; n >= 2; n /= 2) |
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new Task(this, lo + n/2, lo + n).fork(); |
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action.accept(array[lo]); |
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propagateCompletion(); |
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} |
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} |
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if (array.length > 0) |
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new Task(null, 0, array.length).invoke(); |
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} |
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void testRecursiveDecomposition( |
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BiConsumer<Integer[], Consumer<Integer>> action) { |
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int n = ThreadLocalRandom.current().nextInt(8); |
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Integer[] a = new Integer[n]; |
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for (int i = 0; i < n; i++) a[i] = i + 1; |
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AtomicInteger ai = new AtomicInteger(0); |
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action.accept(a, (x) -> ai.addAndGet(x)); |
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assertEquals(n * (n + 1) / 2, ai.get()); |
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} |
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/** |
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* Variants of divide-by-two recursive decomposition into leaf tasks, |
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* as described in the CountedCompleter class javadoc code samples |
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*/ |
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public void testRecursiveDecomposition() { |
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testRecursiveDecomposition(CountedCompleter8Test::forEach1); |
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testRecursiveDecomposition(CountedCompleter8Test::forEach2); |
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testRecursiveDecomposition(CountedCompleter8Test::forEach3); |
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testRecursiveDecomposition(CountedCompleter8Test::forEach4); |
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} |
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} |
