E - public class SpscAtomicArrayQueue<E> extends AbstractQueue<E>
This implementation is a mashup of the Fast Flow
algorithm with an optimization of the offer method taken from the BQueue algorithm (a variation on Fast
Flow), and adjusted to comply with Queue.offer semantics with regards to capacity.
For convenience the relevant papers are available in the resources folder:
2010 - Pisa - SPSC Queues on Shared Cache Multi-Core Systems.pdf
2012 - Junchang- BQueue- Efficient and Practical Queuing.pdf
This implementation is wait free.
MessagePassingQueue.Consumer<T>, MessagePassingQueue.ExitCondition, MessagePassingQueue.Supplier<T>, MessagePassingQueue.WaitStrategy| Modifier and Type | Field and Description |
|---|---|
protected AtomicReferenceArray<E> |
buffer |
protected long |
consumerIndex |
protected int |
lookAheadStep |
protected int |
mask |
static int |
MAX_LOOK_AHEAD_STEP |
protected long |
producerIndex |
protected long |
producerLimit |
UNBOUNDED_CAPACITY| Constructor and Description |
|---|
SpscAtomicArrayQueue(int capacity) |
| Modifier and Type | Method and Description |
|---|---|
protected int |
calcElementOffset(long index) |
protected int |
calcElementOffset(long index,
int mask) |
int |
capacity() |
void |
clear()
Removes all items from the queue.
|
long |
currentConsumerIndex()
This method has no concurrent visibility semantics.
|
long |
currentProducerIndex()
This method has no concurrent visibility semantics.
|
int |
drain(MessagePassingQueue.Consumer<E> c)
Remove all available item from the queue and hand to consume.
|
int |
drain(MessagePassingQueue.Consumer<E> c,
int limit)
Remove up to limit elements from the queue and hand to consume.
|
void |
drain(MessagePassingQueue.Consumer<E> c,
MessagePassingQueue.WaitStrategy w,
MessagePassingQueue.ExitCondition exit)
Remove elements from the queue and hand to consume forever.
|
int |
fill(MessagePassingQueue.Supplier<E> s)
Stuff the queue with elements from the supplier.
|
int |
fill(MessagePassingQueue.Supplier<E> s,
int limit)
Stuff the queue with up to limit elements from the supplier.
|
void |
fill(MessagePassingQueue.Supplier<E> s,
MessagePassingQueue.WaitStrategy w,
MessagePassingQueue.ExitCondition e)
Stuff the queue with elements from the supplier forever.
|
boolean |
isEmpty()
This method's accuracy is subject to concurrent modifications happening as the observation is carried
out.
|
Iterator<E> |
iterator() |
static <E> E |
lpElement(AtomicReferenceArray<E> buffer,
int offset) |
protected E |
lpElement(int offset) |
long |
lvConsumerIndex() |
static <E> E |
lvElement(AtomicReferenceArray<E> buffer,
int offset) |
protected E |
lvElement(int offset) |
long |
lvProducerIndex() |
boolean |
offer(E e)
Called from a producer thread subject to the restrictions appropriate to the implementation and
according to the
Queue.offer(Object) interface. |
E |
peek()
Called from the consumer thread subject to the restrictions appropriate to the implementation and
according to the
Queue.peek() interface. |
E |
poll()
Called from the consumer thread subject to the restrictions appropriate to the implementation and
according to the
Queue.poll() interface. |
boolean |
relaxedOffer(E message)
Called from a producer thread subject to the restrictions appropriate to the implementation.
|
E |
relaxedPeek()
Called from the consumer thread subject to the restrictions appropriate to the implementation.
|
E |
relaxedPoll()
Called from the consumer thread subject to the restrictions appropriate to the implementation.
|
int |
size()
This method's accuracy is subject to concurrent modifications happening as the size is estimated and as
such is a best effort rather than absolute value.
|
protected void |
soConsumerIndex(long newValue) |
static <E> void |
soElement(AtomicReferenceArray<E> buffer,
int offset,
E value) |
protected void |
soElement(int offset,
E value) |
protected void |
soProducerIndex(long newValue) |
static <E> void |
spElement(AtomicReferenceArray<E> buffer,
int offset,
E value) |
protected void |
spElement(int offset,
E value) |
static <E> void |
svElement(AtomicReferenceArray<E> buffer,
int offset,
E value) |
String |
toString() |
add, addAll, element, removecontains, containsAll, remove, removeAll, retainAll, toArray, toArrayclone, equals, finalize, getClass, hashCode, notify, notifyAll, wait, wait, waitcontains, containsAll, equals, hashCode, parallelStream, remove, removeAll, removeIf, retainAll, spliterator, stream, toArray, toArrayprotected volatile long consumerIndex
protected volatile long producerIndex
protected long producerLimit
public static final int MAX_LOOK_AHEAD_STEP
protected final int lookAheadStep
protected final AtomicReferenceArray<E> buffer
protected final int mask
public boolean offer(E e)
Queue.offer(Object) interface.
This implementation is correct for single producer thread use only.
e - not null, will throw NPE if it ispublic E poll()
Queue.poll() interface.
This implementation is correct for single consumer thread use only.
public E peek()
Queue.peek() interface.
This implementation is correct for single consumer thread use only.
public boolean relaxedOffer(E message)
MessagePassingQueueQueue.offer(Object) this method may return false without the queue being full.message - not null, will throw NPE if it ispublic E relaxedPoll()
MessagePassingQueueQueue.poll() this method may return null without the queue being empty.public E relaxedPeek()
MessagePassingQueueQueue.peek() this method may return null without the queue being empty.public int drain(MessagePassingQueue.Consumer<E> c)
MessagePassingQueue
M m;
while((m = relaxedPoll()) != null){
c.accept(m);
}
public int fill(MessagePassingQueue.Supplier<E> s)
MessagePassingQueue
while(relaxedOffer(s.get());
public int drain(MessagePassingQueue.Consumer<E> c, int limit)
MessagePassingQueue
M m;
int i = 0;
for(;i < limit && (m = relaxedPoll()) != null; i++){
c.accept(m);
}
return i;
There's no strong commitment to the queue being empty at the end of a drain. Called from a consumer thread subject to the restrictions appropriate to the implementation.
public int fill(MessagePassingQueue.Supplier<E> s, int limit)
MessagePassingQueue
for(int i=0; i < limit && relaxedOffer(s.get()); i++);
There's no strong commitment to the queue being full at the end of a fill. Called from a producer thread subject to the restrictions appropriate to the implementation.
public void drain(MessagePassingQueue.Consumer<E> c, MessagePassingQueue.WaitStrategy w, MessagePassingQueue.ExitCondition exit)
MessagePassingQueue
int idleCounter = 0;
while (exit.keepRunning()) {
E e = relaxedPoll();
if(e==null){
idleCounter = wait.idle(idleCounter);
continue;
}
idleCounter = 0;
c.accept(e);
}
Called from a consumer thread subject to the restrictions appropriate to the implementation.
public void fill(MessagePassingQueue.Supplier<E> s, MessagePassingQueue.WaitStrategy w, MessagePassingQueue.ExitCondition e)
MessagePassingQueue
int idleCounter = 0;
while (exit.keepRunning()) {
E e = s.get();
while (!relaxedOffer(e)) {
idleCounter = wait.idle(idleCounter);
continue;
}
idleCounter = 0;
}
Called from a producer thread subject to the restrictions appropriate to the implementation.
public final long lvConsumerIndex()
protected final void soConsumerIndex(long newValue)
public final long lvProducerIndex()
protected final void soProducerIndex(long newValue)
public Iterator<E> iterator()
iterator in interface Iterable<E>iterator in interface Collection<E>iterator in class AbstractCollection<E>public String toString()
toString in class AbstractCollection<E>public void clear()
MessagePassingQueueCollection.clear() interface.clear in interface Collection<E>clear in interface MessagePassingQueue<E>clear in class AbstractQueue<E>protected final int calcElementOffset(long index,
int mask)
protected final int calcElementOffset(long index)
public static <E> E lvElement(AtomicReferenceArray<E> buffer, int offset)
public static <E> E lpElement(AtomicReferenceArray<E> buffer, int offset)
protected final E lpElement(int offset)
public static <E> void spElement(AtomicReferenceArray<E> buffer, int offset, E value)
protected final void spElement(int offset,
E value)
public static <E> void soElement(AtomicReferenceArray<E> buffer, int offset, E value)
protected final void soElement(int offset,
E value)
public static <E> void svElement(AtomicReferenceArray<E> buffer, int offset, E value)
protected final E lvElement(int offset)
public final int capacity()
capacity in interface MessagePassingQueue<E>MessagePassingQueue.UNBOUNDED_CAPACITY if not boundedpublic final int size()
size in interface Collection<E>size in interface MessagePassingQueue<E>size in class AbstractCollection<E>Integer.MAX_VALUE but less or equals to
capacity (if bounded).public final boolean isEmpty()
MessagePassingQueueisEmpty in interface Collection<E>isEmpty in interface MessagePassingQueue<E>isEmpty in class AbstractCollection<E>public final long currentProducerIndex()
QueueProgressIndicatorscurrentProducerIndex in interface QueueProgressIndicatorspublic final long currentConsumerIndex()
QueueProgressIndicatorscurrentConsumerIndex in interface QueueProgressIndicatorsCopyright © 2013–2018. All rights reserved.