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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.*; |
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import java.util.concurrent.atomic.*; |
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|
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/** |
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* A simple test for evaluating different implementations of |
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* CopyOnWriteArrayList.addIfAbsent. |
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*/ |
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public class COWALAddIfAbsentLoops { |
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|
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static final int SIZE = 35000; |
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|
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/** |
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* Set to 1 for 0% cache hit ratio (every addIfAbsent a cache miss). |
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* Set to 2 for 50% cache hit ratio. |
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*/ |
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static final int CACHE_HIT_FACTOR = 1; |
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|
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public static void main(String[] args) throws Exception { |
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for (int reps = 0; reps < 4; ++reps) { |
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for (int i = 1; i <= 4; ++i) |
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test(i); |
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} |
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} |
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|
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static final AtomicInteger result = new AtomicInteger(); |
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|
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public static void test(int n) throws Exception { |
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result.set(0); |
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Thread[] ts = new Thread[CACHE_HIT_FACTOR*n]; |
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Phaser started = new Phaser(ts.length + 1); |
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CopyOnWriteArrayList<Integer> list = new CopyOnWriteArrayList<Integer>(); |
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for (int i = 0; i < ts.length; ++i) |
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(ts[i] = new Thread(new Task(i%n, n, list, started))).start(); |
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long p = started.arriveAndAwaitAdvance(); |
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long st = System.nanoTime(); |
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for (Thread thread : ts) |
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thread.join(); |
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double secs = ((double)System.nanoTime() - st) / (1000L * 1000 * 1000); |
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System.out.println("Threads: " + n + " Time: " + secs); |
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if (result.get() != SIZE) |
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throw new Error(); |
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} |
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|
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static final class Task implements Runnable { |
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final int id, stride; |
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final CopyOnWriteArrayList<Integer> list; |
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final Phaser started; |
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Task(int id, int stride, |
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CopyOnWriteArrayList<Integer> list, Phaser started) { |
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this.id = id; |
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this.stride = stride; |
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this.list = list; |
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this.started = started; |
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} |
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public void run() { |
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final CopyOnWriteArrayList<Integer> list = this.list; |
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int origin = id, inc = stride, adds = 0; |
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started.arriveAndAwaitAdvance(); |
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for (int i = origin; i < SIZE; i += inc) { |
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if (list.addIfAbsent(i)) |
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++adds; |
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} |
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result.getAndAdd(adds); |
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} |
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} |
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} |
