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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.Phaser; |
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import java.util.concurrent.ExecutorService; |
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import java.util.concurrent.Executors; |
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import java.util.concurrent.atomic.AtomicLong; |
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import jsr166e.LongAdder; |
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|
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public class LongAdderDemo { |
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static final int INCS_PER_THREAD = 10000000; |
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static final int NCPU = Runtime.getRuntime().availableProcessors(); |
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static final ExecutorService pool = Executors.newCachedThreadPool(); |
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|
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public static void main(String[] args) { |
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System.out.println("Warmup..."); |
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int half = NCPU > 1 ? NCPU / 2 : 1; |
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casTest(half, 1000); |
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adderTest(half, 1000); |
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|
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for (int reps = 0; reps < 2; ++reps) { |
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System.out.println("Running..."); |
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for (int i = 1; i <= NCPU * 2; i <<= 1) { |
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casTest(i, INCS_PER_THREAD); |
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adderTest(i, INCS_PER_THREAD); |
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} |
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} |
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pool.shutdown(); |
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} |
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|
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static void casTest(int nthreads, int incs) { |
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System.out.print("AtomicLong "); |
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Phaser phaser = new Phaser(nthreads + 1); |
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AtomicLong a = new AtomicLong(); |
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for (int i = 0; i < nthreads; ++i) |
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pool.execute(new CasTask(a, phaser, incs)); |
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report(nthreads, incs, timeTasks(phaser), a.get()); |
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} |
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|
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static void adderTest(int nthreads, int incs) { |
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System.out.print("LongAdder "); |
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Phaser phaser = new Phaser(nthreads + 1); |
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LongAdder a = new LongAdder(); |
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for (int i = 0; i < nthreads; ++i) |
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pool.execute(new AdderTask(a, phaser, incs)); |
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report(nthreads, incs, timeTasks(phaser), a.sum()); |
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} |
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|
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static void report(int nthreads, int incs, long time, long sum) { |
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long total = (long)nthreads * incs; |
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if (sum != total) |
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throw new Error(sum + " != " + total); |
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double secs = (double)time / (1000L * 1000 * 1000); |
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long rate = total * (1000L) / time; |
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System.out.printf("threads:%3d Time: %7.3fsec Incs per microsec: %4d\n", |
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nthreads, secs, rate); |
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} |
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|
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static long timeTasks(Phaser phaser) { |
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phaser.arriveAndAwaitAdvance(); |
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long start = System.nanoTime(); |
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phaser.arriveAndAwaitAdvance(); |
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phaser.arriveAndAwaitAdvance(); |
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return System.nanoTime() - start; |
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} |
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|
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static final class AdderTask implements Runnable { |
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final LongAdder adder; |
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final Phaser phaser; |
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final int incs; |
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volatile long result; |
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AdderTask(LongAdder adder, Phaser phaser, int incs) { |
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this.adder = adder; |
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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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phaser.arriveAndAwaitAdvance(); |
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LongAdder a = adder; |
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for (int i = 0; i < incs; ++i) |
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a.increment(); |
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result = a.sum(); |
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phaser.arrive(); |
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} |
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} |
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|
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static final class CasTask implements Runnable { |
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final AtomicLong adder; |
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final Phaser phaser; |
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final int incs; |
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volatile long result; |
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CasTask(AtomicLong adder, Phaser phaser, int incs) { |
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this.adder = adder; |
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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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phaser.arriveAndAwaitAdvance(); |
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AtomicLong a = adder; |
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for (int i = 0; i < incs; ++i) |
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a.getAndIncrement(); |
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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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} |
