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jsr166 |
1.1 |
/* |
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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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import java.util.concurrent.atomic.DoubleAccumulator; |
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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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public class DoubleAccumulatorLoops { |
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public static void main(String[] args) { |
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final int NCPU = Runtime.getRuntime().availableProcessors(); |
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int minThreads = 1; |
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int maxThreads = 2 * NCPU; |
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long iters = 300_000_000L; |
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nextArg: for (String arg : args) { |
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String[] fields = arg.split("="); |
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if (fields.length == 2) { |
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String prop = fields[0], val = fields[1]; |
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switch (prop) { |
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case "threads": |
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minThreads = maxThreads = Integer.valueOf(val); |
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continue nextArg; |
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case "minThreads": |
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minThreads = Integer.valueOf(val); |
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continue nextArg; |
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case "maxThreads": |
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maxThreads = Integer.valueOf(val); |
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continue nextArg; |
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case "iters": |
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iters = Long.valueOf(val); |
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continue nextArg; |
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} |
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} |
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throw new Error("Usage: DoubleAccumulatorLoops minThreads=n maxThreads=n threads=n iters=n"); |
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} |
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final ExecutorService pool = Executors.newCachedThreadPool(); |
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for (int i = minThreads; i <= maxThreads; i += (i+1) >>> 1) |
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accumulatorTest(pool, i, iters); |
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pool.shutdown(); |
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} |
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static void accumulatorTest(ExecutorService pool, int nthreads, long iters) { |
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System.out.print("DoubleAccumulator "); |
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Phaser phaser = new Phaser(nthreads + 1); |
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DoubleAccumulator a = new DoubleAccumulator(Double::max, Double.NEGATIVE_INFINITY); |
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for (int i = 0; i < nthreads; ++i) |
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pool.execute(new AccumulatorTask(a, phaser, iters)); |
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report(nthreads, iters, timeTasks(phaser), a.get()); |
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} |
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static void report(int nthreads, long iters, long time, double result) { |
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double secs = (double)time / (1000L * 1000 * 1000); |
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long rate = nthreads * iters * (1000L) / time; |
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System.out.printf("threads:%3d Time: %7.3fsec Iters per microsec: %4d\n", |
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nthreads, secs, rate); |
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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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static final class AccumulatorTask implements Runnable { |
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final DoubleAccumulator accumulator; |
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final Phaser phaser; |
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final long iters; |
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volatile double result; |
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AccumulatorTask(DoubleAccumulator accumulator, Phaser phaser, long iters) { |
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this.accumulator = accumulator; |
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this.phaser = phaser; |
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this.iters = iters; |
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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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DoubleAccumulator a = accumulator; |
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for (long i = 0; i < iters; ++i) |
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a.accumulate(2.0); |
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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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} |
