// from gee.cs.oswego.edu/home/jsr166/jsr166
package jsr166tests.loops;
/*
* 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/licenses/publicdomain
*/
import java.util.concurrent.*;
import java.util.concurrent.locks.*;
import java.util.*;
public final class NoopLockLoops {
static final ExecutorService pool = Executors.newCachedThreadPool();
static final LoopHelpers.SimpleRandom rng = new LoopHelpers.SimpleRandom();
static boolean print = false;
static int iters = 20000000;
public static void main(String[] args) throws Exception {
int maxThreads = 100;
if (args.length > 0)
maxThreads = Integer.parseInt(args[0]);
new ReentrantLockLoop(1).test();
new ReentrantLockLoop(1).test();
print = true;
int k = 1;
for (int i = 1; i <= maxThreads;) {
System.out.print("Threads: " + i);
new ReentrantLockLoop(i).test();
Thread.sleep(100);
if (i == k) {
k = i << 1;
i = i + (i >>> 1);
}
else
i = k;
}
pool.shutdown();
}
static final class ReentrantLockLoop implements Runnable {
private int v = rng.next();
private volatile int result = 17;
private final LoopHelpers.BarrierTimer timer = new LoopHelpers.BarrierTimer();
private final CyclicBarrier barrier;
private final int nthreads;
private volatile int readBarrier;
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 + 1;
int x = sum + 1;
int n = iters;
while (n-- > 0) {
synchronized(this) {
x = LoopHelpers.compute4(x);
}
sum += x;
if ((x += readBarrier) == 0)
++readBarrier;
}
barrier.await();
result += sum;
}
catch (Exception ie) {
return;
}
}
}
}