Improved event queues, added test for large queues

Author: Admin

JSimpleSim/src/org/simplesim/core/scheduling/AbstractBucketQueue.java

@@ -36,7 +36,7 @@ abstract class AbstractBucketQueue<E, M extends Map<Time, List<E>>> implements E
 	private final M map;
 
 	/** number of total events, accessible for subclasses */
-	int size=0;
+	private int size=0;
 
 	@SuppressWarnings("serial")
 	static class UnexpectedEmptyBucketException extends RuntimeException {
@@ -61,12 +61,15 @@ M getMap() {
 	 */
 	@Override
 	public Time getTime(E event) {
-		for (final Time time : getMap().keySet()) {
-			final List<E> bucket=getMap().get(time);
-			if (bucket.contains(event)) return time;
+		for (Map.Entry<Time, List<E>> entry : getMap().entrySet()) {
+			if (entry.getValue().contains(event)) return entry.getKey();
 		}
 		return null;
 	}
+	
+	void removeEmptyBucket(Time time) {
+		getMap().remove(time);		
+	}
 
 	/*
 	 * (non-Javadoc)
@@ -75,16 +78,16 @@ public Time getTime(E event) {
 	 */
 	@Override
 	public Time dequeue(E event) {
-		for (final Time time : getMap().keySet()) {
-			final List<E> bucket=getMap().get(time);
-			if (bucket.contains(event)) {
-				bucket.remove(event);
-				if (bucket.isEmpty()) getMap().remove(time);
+		for (Map.Entry<Time, List<E>> entry : getMap().entrySet()) {
+			if (entry.getValue().contains(event)) {
+				entry.getValue().remove(event);
 				size--;
-				return time;
+				final Time result=entry.getKey();
+				if (entry.getValue().isEmpty()) removeEmptyBucket(result);
+				return result;
 			}
 		}
-		return null;
+		return null;	
 	}
 
 	/*
@@ -136,7 +139,7 @@ public E dequeue() {
 		final List<E> bucket=getMap().get(min);
 		if (bucket.isEmpty()) throw new UnexpectedEmptyBucketException();
 		final E result=bucket.remove(bucket.size()-1);
-		if (bucket.isEmpty()) getMap().remove(min);
+		if (bucket.isEmpty()) removeEmptyBucket(min);
 		size--;
 		return result;
 	}

JSimpleSim/src/org/simplesim/core/scheduling/HashedBucketQueue.java

@@ -4,35 +4,35 @@
  *
  * This software is published as open source and licensed under the terms of GNU
  * GPLv3.
- * 
+ *
  * Contributors:
  * 	- Rene Kuhlemann - development and initial implementation
- * 
+ *
  */
 package org.simplesim.core.scheduling;
 
 import java.util.HashMap;
-import java.util.Iterator;
 import java.util.List;
 
 /**
  * Event queue based on a simple time to bucket mapping, each bucket containing
- * events with equal time stamps.
+ * events with equal time stamps. The value of the most imminent time stamp is
+ * saved to accelerate {@code getMin()} and has to be kept in sync.
  * <p>
- * Elements of this queue type are unsorted, so {@code getMin()} always has a complexity of O(n).
- * <p>
- * Note: This queue is suitable for a global event queue, especially if there are a lot
- * of events with the same time stamp. This implementation has a smaller memory
- * footprint than the {@code SortedBucketQueue} and {@code HeapBucketQueue}, but all time-based look up
- * operations (including {@code getMin()}, {@code dequeue()} and
- * {@code dequeAll()}) are slower.
+ * Note: This queue is suitable for a global event queue, especially if there
+ * are a lot of events with the same time stamp. This implementation has a
+ * smaller memory footprint than the {@code SortedBucketQueue} and
+ * {@code HeapBucketQueue}, but on all dequeue operation, the new minimal time
+ * stamp has to be found with a complexity of O(n).
  *
  * @param <E> event type
- * 
+ *
  * @see SortedBucketQueue
  * @see HeapBucketQueue
  */
-public final class HashedBucketQueue<E> extends AbstractBucketQueue<E,HashMap<Time,List<E>>> {
+public final class HashedBucketQueue<E> extends AbstractBucketQueue<E, HashMap<Time, List<E>>> {
+
+	private Time minTime=Time.INFINITY;
 
 	public HashedBucketQueue() {
 		super(new HashMap<>());
@@ -41,17 +41,48 @@ public HashedBucketQueue() {
 	/*
 	 * (non-Javadoc)
 	 *
-	 * @see org.simplesim.core.scheduling.EventQueue#getMin()
+	 * @see org.simplesim.core.scheduling.EventQueue#enqueue(java.lang.Object,
+	 * org.simplesim.core.scheduling.Time)
 	 */
 	@Override
-	public Time getMin() {
-		final Iterator<Time> iterator=getMap().keySet().iterator();
-		Time min=iterator.next();
-		while (iterator.hasNext()) {
-			final Time time=iterator.next();
-			if (time.compareTo(min)<0) min=time;
+	public void enqueue(E event, Time time) {
+		if (time.getTicks()<minTime.getTicks()) minTime=time;
+		super.enqueue(event,time);
+	}
+
+	@Override
+	void removeEmptyBucket(Time time) {
+		super.removeEmptyBucket(time);
+		if (time.equals(minTime)) minTime=findNewMinTime();
+	}
+
+	/*
+	 * (non-Javadoc)
+	 *
+	 * @see org.simplesim.core.scheduling.EventQueue#dequeueAll(org.simplesim.core.
+	 * scheduling.Time)
+	 */
+	@Override
+	public List<E> dequeueAll(Time time) {
+		final List<E> result=super.dequeueAll(time);
+		if (time.equals(minTime)) minTime=findNewMinTime();
+		return result;
+	}
+
+	private Time findNewMinTime() {
+		Time result=Time.INFINITY;
+		if (!getMap().isEmpty()) for (Time time : getMap().keySet()) {
+			if (time.getTicks()<result.getTicks()) result=time;
 		}
-		return min;
+		return result;
 	}
 
+	/*
+	 * (non-Javadoc)
+	 *
+	 * @see org.simplesim.core.scheduling.EventQueue#getMin()
+	 */
+	@Override
+	public Time getMin() { return minTime; }
+
 }

JSimpleSim/src/org/simplesim/core/scheduling/HeapBucketQueue.java

@@ -10,9 +10,8 @@
  */
 package org.simplesim.core.scheduling;
 
-import java.util.ArrayList;
+import java.util.Collections;
 import java.util.HashMap;
-import java.util.Iterator;
 import java.util.List;
 import java.util.PriorityQueue;
 import java.util.Queue;
@@ -23,15 +22,12 @@
  * Just as the other bucket queues, this one is also based on a simple time to
  * bucket mapping, each bucket containing events with equal time stamps. In this
  * implementation, an additional {@code PriorityQueue} is used to accelerate
- * access to the minimal time stamp by {@code getMin()}. Within this queue, an
- * {@code EventQueueEntry} couples the time stamp with the bucket. Because of
- * the underlying heap structure, the look-up of the first element is faster
- * than in a {@code HashedBucketQueue}.
+ * lookup of the minimal time stamp by {@code getMin()}. Thus, the queue has to
+ * be maintained in parallel to the map and kept in sync.
  * <p>
- * Note: This queue type performs best for dequeuing <i>all</i> events
- * with minimal time stamp ({@link #dequeueAll()}). It is well suited for a
- * global event queue and has a performance similar to the
- * {@code SortedBucketQueue}.
+ * Note: This queue type performs best for dequeuing <i>all</i> events with
+ * minimal time stamp ({@link #dequeueAll()}). It is well suited for a global
+ * event queue and has a performance similar to the {@code SortedBucketQueue}.
  *
  * @param <E> event type
  *
@@ -41,70 +37,30 @@
 public final class HeapBucketQueue<E> extends AbstractBucketQueue<E, HashMap<Time, List<E>>> {
 
 	// additional heap structure to facilitate getMin()
-	private final Queue<EventQueueEntry<List<E>>> queue=new PriorityQueue<>();
+	private final Queue<Time> queue=new PriorityQueue<>();
 
 	public HeapBucketQueue() {
 		super(new HashMap<>());
 	}
 
-	private Queue<EventQueueEntry<List<E>>> getQueue() {
-		return queue;
-	}
+	private Queue<Time> getQueue() { return queue; }
 
-	/*
-	 * (non-Javadoc)
-	 *
-	 * @see org.simplesim.core.scheduling.EventQueue#dequeue(java.lang.Object)
-	 */
 	@Override
-	public Time dequeue(E event) {
-		final Iterator<EventQueueEntry<List<E>>> iterator=getQueue().iterator();
-		while (iterator.hasNext()) {
-			final EventQueueEntry<List<E>> entry=iterator.next();
-			final List<E> bucket=entry.getEvent();
-			if (bucket.contains(event)) {
-				bucket.remove(event);
-				if (bucket.isEmpty()) {
-					getMap().remove(entry.getTime());
-					getQueue().remove(entry);
-				}
-				size--;
-				return entry.getTime();
-			}
-		}
-		return null;
+	void removeEmptyBucket(Time time) {
+		super.removeEmptyBucket(time);
+		getQueue().remove(time);
 	}
 
 	/*
 	 * (non-Javadoc)
 	 *
-	 * @see org.simplesim.core.scheduling.EventQueue#dequeue()
+	 * @see org.simplesim.core.scheduling.EventQueue#enqueue(java.lang.Object,
+	 * org.simplesim.core.scheduling.Time)
 	 */
-	@Override
-	public E dequeue() {
-		if (isEmpty()) return null;
-		final Time min=getMin();
-		final List<E> bucket=getMap().get(min);
-		if (bucket.isEmpty()) throw new UnexpectedEmptyBucketException();
-		final E result=bucket.remove(bucket.size()-1);
-		if (bucket.isEmpty()) {
-			getMap().remove(min);
-			getQueue().poll();
-		}
-		size--;
-		return result;
-	}
-
 	@Override
 	public void enqueue(E event, Time time) {
-		List<E> bucket=getMap().get(time);
-		if (bucket==null) { // time stamp has not been added to queue, yet
-			bucket=new ArrayList<>();
-			getMap().put(time,bucket);
-			getQueue().add(new EventQueueEntry<>(time,bucket));
-		} // now we definitely have a valid entry queued in the heap
-		bucket.add(event); // add the event to the bucket
-		size++;
+		if (!getMap().containsKey(time)) getQueue().add(time);
+		super.enqueue(event,time);
 	}
 
 	/*
@@ -116,16 +72,7 @@ public void enqueue(E event, Time time) {
 	@Override
 	public List<E> dequeueAll(Time time) {
 		final List<E> bucket=super.dequeueAll(time);
-		if (!bucket.isEmpty()) { // remove bucket also from queue
-			final Iterator<EventQueueEntry<List<E>>> iterator=getQueue().iterator();
-			while (iterator.hasNext()) {
-				final EventQueueEntry<List<E>> entry=iterator.next();
-				if (time.equals(entry.getTime())) {
-					iterator.remove();
-					return bucket;
-				}
-			}
-		}
+		if (!bucket.isEmpty()) getQueue().remove(time);
 		return bucket;
 	}
 
@@ -136,11 +83,8 @@ public List<E> dequeueAll(Time time) {
 	 */
 	@Override
 	public List<E> dequeueAll() {
-		final List<E> bucket=getMap().remove(getMin());
-		if (bucket.isEmpty()) throw new UnexpectedEmptyBucketException();
-		getQueue().poll();
-		size-=bucket.size();
-		return bucket;
+		if (getQueue().isEmpty()) return Collections.emptyList();
+		return super.dequeueAll(getQueue().poll());
 	}
 
 	/*
@@ -149,8 +93,6 @@ public List<E> dequeueAll() {
 	 * @see org.simplesim.core.scheduling.EventQueue#getMin()
 	 */
 	@Override
-	public Time getMin() {
-		return getQueue().peek().getTime();
-	}
+	public Time getMin() { return getQueue().peek(); }
 
 }