1 files changed, 109 insertions, 0 deletions
diff --git a/src/com/mbien/opencl/MultiQueueBarrier.java b/src/com/mbien/opencl/MultiQueueBarrier.java
new file mode 100644
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+++ b/src/com/mbien/opencl/MultiQueueBarrier.java
@@ -0,0 +1,109 @@
+package com.mbien.opencl;
+
+import java.util.Collections;
+import java.util.HashSet;
+import java.util.Set;
+import java.util.concurrent.CountDownLatch;
+import java.util.concurrent.TimeUnit;
+
+/**
+ * A high-level utility to synchronize multiple {@link CLCommandQueue}s.
+ * @author Michael Bien
+ */
+public class MultiQueueBarrier {
+
+    private CountDownLatch latch;
+    private final Set<CLCommandQueue> queues;
+
+    /**
+     * 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) {
+        this.latch = new CountDownLatch(queueCount);
+        this.queues = null;
+    }
+
+    /**
+     * Creates a new MultiQueueBarrier for the given queues.
+     */
+    public MultiQueueBarrier(CLCommandQueue... allowedQueues) {
+        this.latch = new CountDownLatch(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();
+        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);
+        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();
+        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);
+        return this;
+    }
+    
+    /**
+     * Cancels this barrier and unblocks all waiting threads.
+     */
+    public void cancelBarrier() {
+        while(latch.getCount() > 0)
+            latch.countDown();
+    }
+
+    /**
+     * 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);
+        }
+    }
+
+}