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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.CyclicBarrier; |
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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.locks.ReentrantLock; |
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|
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public final class LockOncePerThreadLoops { |
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static final ExecutorService pool = Executors.newCachedThreadPool(); |
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static final LoopHelpers.SimpleRandom rng = new LoopHelpers.SimpleRandom(); |
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static boolean print = false; |
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static int nlocks = 500000; |
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static int nthreads = 100; |
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static int replications = 20; |
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|
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public static void main(String[] args) throws Exception { |
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if (args.length > 0) |
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replications = Integer.parseInt(args[0]); |
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|
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if (args.length > 1) |
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nlocks = Integer.parseInt(args[1]); |
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|
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print = true; |
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|
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for (int i = 0; i < replications; ++i) { |
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System.out.print("Iteration: " + i); |
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new ReentrantLockLoop().test(); |
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Thread.sleep(100); |
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} |
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pool.shutdown(); |
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} |
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|
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static final class ReentrantLockLoop implements Runnable { |
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private int v = rng.next(); |
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private volatile int result = 17; |
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final ReentrantLock[]locks = new ReentrantLock[nlocks]; |
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|
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private final ReentrantLock lock = new ReentrantLock(); |
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private final LoopHelpers.BarrierTimer timer = new LoopHelpers.BarrierTimer(); |
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private final CyclicBarrier barrier; |
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ReentrantLockLoop() { |
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barrier = new CyclicBarrier(nthreads+1, timer); |
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for (int i = 0; i < nlocks; ++i) |
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locks[i] = new ReentrantLock(); |
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} |
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|
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final void test() throws Exception { |
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for (int i = 0; i < nthreads; ++i) |
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pool.execute(this); |
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barrier.await(); |
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barrier.await(); |
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if (print) { |
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long time = timer.getTime(); |
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double secs = (double) time / 1000000000.0; |
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System.out.println("\t " + secs + "s run time"); |
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} |
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|
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int r = result; |
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if (r == 0) // avoid overoptimization |
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System.out.println("useless result: " + r); |
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} |
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|
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public final void run() { |
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try { |
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barrier.await(); |
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int sum = v; |
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int x = 0; |
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for (int i = 0; i < locks.length; ++i) { |
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locks[i].lock(); |
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try { |
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v = x += ~(v - i); |
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} |
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finally { |
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locks[i].unlock(); |
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} |
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// Once in a while, do something more expensive |
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if ((~i & 255) == 0) { |
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sum += LoopHelpers.compute1(LoopHelpers.compute2(x)); |
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} |
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else |
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sum += sum ^ x; |
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} |
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barrier.await(); |
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result += sum; |
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} |
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catch (Exception ie) { |
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return; |
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} |
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} |
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} |
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|
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} |
