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package com.mbien.opencl.util;
import com.mbien.opencl.CLCommandQueue;
import com.mbien.opencl.CLEventList;
import java.util.Collections;
import java.util.HashSet;
import java.util.Set;
import java.util.concurrent.CountDownLatch;
import java.util.concurrent.TimeUnit;
/**
* An utility for synchronizing multiple concurrent {@link CLCommandQueue}s.
* This Barrier can be reused after it has been broken.
* @author Michael Bien
*/
public class MultiQueueBarrier {
private CountDownLatch latch;
private final Set<CLCommandQueue> queues;
private final int count;
/**
* Creates a new MultiQueueBarrier with the given queueCount.
* It is recommented to use {@link #MultiQueueBarrier(CLCommandQueue... allowedQueues)} if possible
* which restricts the set of allowed queues for the barrier.
*/
public MultiQueueBarrier(int queueCount) {
if(queueCount == 0) {
throw new IllegalArgumentException("queueCount was 0");
}
this.latch = new CountDownLatch(queueCount);
this.queues = null;
this.count = queueCount;
}
/**
* Creates a new MultiQueueBarrier for the given queues.
*/
public MultiQueueBarrier(CLCommandQueue... allowedQueues) {
if(allowedQueues.length == 0) {
throw new IllegalArgumentException("allowedQueues was empty");
}
this.latch = new CountDownLatch(allowedQueues.length);
this.count = allowedQueues.length;
HashSet<CLCommandQueue> set = new HashSet<CLCommandQueue>(allowedQueues.length);
for (CLCommandQueue queue : allowedQueues) {
set.add(queue);
}
this.queues = Collections.unmodifiableSet(set);
}
/**
* Blocks the current Thread until all commands on the {@link CLCommandQueue} finished excecution.
* This method may be invoked concurrently without synchronization on the MultiQueueBarrier object
* as long each Thread passes a distinct CLCommandQueue as parameter to this method.
*/
public MultiQueueBarrier waitFor(CLCommandQueue queue) {
checkQueue(queue);
queue.putBarrier();
synchronized(this) {
latch.countDown();
}
return this;
}
/**
* Blocks the current Thread until the given events on the {@link CLCommandQueue} occurred.
* This method may be invoked concurrently without synchronization on the MultiQueueBarrier object
* as long each Thread passes a distinct CLCommandQueue as parameter to this method.
*/
public MultiQueueBarrier waitFor(CLCommandQueue queue, CLEventList events) {
checkQueue(queue);
queue.putWaitForEvents(events, true);
synchronized(this) {
latch.countDown();
}
return this;
}
/**
* Blocks until all Threads which called {@link #waitFor}
* continue execution.
* This method blocks only once, all subsequent calls are ignored.
*/
public MultiQueueBarrier await() throws InterruptedException {
latch.await();
rebuildBarrierIfBroken();
return this;
}
/**
* @see #await()
* @param timeout the maximum time to wait
* @param unit the time unit of the {@code timeout} argument
*/
public MultiQueueBarrier await(long timeout, TimeUnit unit) throws InterruptedException {
latch.await(timeout, unit);
rebuildBarrierIfBroken();
return this;
}
/**
* Resets this barrier and unblocks all waiting threads.
*/
public void resetBarrier() {
synchronized(this) {
while(latch.getCount() > 0) {
latch.countDown();
}
// thats OK. Another Thread can not rebuild the barrier since we have the lock.
// we have to rebuid it here in case there was no thread waiting.
latch = new CountDownLatch(count);
}
}
private void rebuildBarrierIfBroken() {
synchronized (this) {
if (latch.getCount() == 0) {
latch = new CountDownLatch(count);
}
}
}
/**
* Returns the current number of events which must occure before this barrier unblocks the waiting threads.
* This method is typically used for debugging and testing purposes.
*/
public long getCount() {
return latch.getCount();
}
private void checkQueue(CLCommandQueue queue) throws IllegalArgumentException {
if (queues != null && !queues.contains(queue)) {
throw new IllegalArgumentException(queue + " is not in the allowedQueues Set: " + queues);
}
}
}
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