/*
* DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
*
* This code is free software; you can redistribute it and/or modify it
* under the terms of the GNU General Public License version 2 only, as
* published by the Free Software Foundation.
*
* This code is distributed in the hope that it will be useful, but WITHOUT
* ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
* FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License
* version 2 for more details (a copy is included in the LICENSE file that
* accompanied this code).
*
* You should have received a copy of the GNU General Public License version
* 2 along with this work; if not, write to the Free Software Foundation,
* Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
*
* Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
* or visit www.oracle.com if you need additional information or have any
* questions.
*/
/*
* This file is available under and governed by the GNU General Public
* License version 2 only, as published by the Free Software Foundation.
* However, the following notice accompanied the original version of this
* file:
*
* Written by Doug Lea with assistance from members of JCP JSR-166
* Expert Group and released to the public domain, as explained at
* http://creativecommons.org/publicdomain/zero/1.0/
*/
/*
* @test
* @bug 4486658
* @compile -source 1.5 SimpleReentrantLockLoops.java
* @run main/timeout=4500 SimpleReentrantLockLoops
* @summary multiple threads using a single lock
*/
import java.util.concurrent.*;
import java.util.concurrent.locks.*;
import java.util.*;
public final class SimpleReentrantLockLoops {
static final ExecutorService pool = Executors.newCachedThreadPool();
static final LoopHelpers.SimpleRandom rng = new LoopHelpers.SimpleRandom();
static boolean print = false;
static int iters = 1000000;
public static void main(String[] args) throws Exception {
int maxThreads = 5;
if (args.length > 0)
maxThreads = Integer.parseInt(args[0]);
print = true;
int reps = 2;
for (int i = 1; i <= maxThreads; i += (i+1) >>> 1) {
int n = reps;
if (reps > 1) --reps;
while (n-- > 0) {
System.out.print("Threads: " + i);
new ReentrantLockLoop(i).test();
Thread.sleep(100);
}
}
pool.shutdown();
if (! pool.awaitTermination(Long.MAX_VALUE, TimeUnit.NANOSECONDS))
throw new Error();
}
static final class ReentrantLockLoop implements Runnable {
private int v = rng.next();
private volatile int result = 17;
private final ReentrantLock lock = new ReentrantLock();
private final LoopHelpers.BarrierTimer timer = new LoopHelpers.BarrierTimer();
private final CyclicBarrier barrier;
private final int nthreads;
ReentrantLockLoop(int nthreads) {
this.nthreads = nthreads;
barrier = new CyclicBarrier(nthreads+1, timer);
}
final void test() throws Exception {
for (int i = 0; i < nthreads; ++i)
pool.execute(this);
barrier.await();
barrier.await();
if (print) {
long time = timer.getTime();
long tpi = time / ((long)iters * nthreads);
System.out.print("\t" + LoopHelpers.rightJustify(tpi) + " ns per lock");
double secs = (double)(time) / 1000000000.0;
System.out.println("\t " + secs + "s run time");
}
int r = result;
if (r == 0) // avoid overoptimization
System.out.println("useless result: " + r);
}
public final void run() {
try {
barrier.await();
int sum = v;
int x = 0;
int n = iters;
do {
lock.lock();
try {
if ((n & 255) == 0)
v = x = LoopHelpers.compute2(LoopHelpers.compute1(v));
else
v = x += ~(v - n);
}
finally {
lock.unlock();
}
// Once in a while, do something more expensive
if ((~n & 255) == 0) {
sum += LoopHelpers.compute1(LoopHelpers.compute2(x));
}
else
sum += sum ^ x;
} while (n-- > 0);
barrier.await();
result += sum;
}
catch (Exception ie) {
return;
}
}
}
}