/* Director for Kahn-MacQueen process network semantics.
Copyright (c) 1998-2009 The Regents of the University of California.
All rights reserved.
Permission is hereby granted, without written agreement and without
license or royalty fees, to use, copy, modify, and distribute this
software and its documentation for any purpose, provided that the above
copyright notice and the following two paragraphs appear in all copies
of this software.
IN NO EVENT SHALL THE UNIVERSITY OF CALIFORNIA BE LIABLE TO ANY PARTY
FOR DIRECT, INDIRECT, SPECIAL, INCIDENTAL, OR CONSEQUENTIAL DAMAGES
ARISING OUT OF THE USE OF THIS SOFTWARE AND ITS DOCUMENTATION, EVEN IF
THE UNIVERSITY OF CALIFORNIA HAS BEEN ADVISED OF THE POSSIBILITY OF
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INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES OF
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PT_COPYRIGHT_VERSION_2
COPYRIGHTENDKEY
*/
package ptolemy.domains.pn.kernel;
import java.lang.ref.WeakReference;
import java.util.HashMap;
import java.util.Iterator;
import java.util.LinkedList;
import java.util.ListIterator;
import ptolemy.actor.CompositeActor;
import ptolemy.actor.IORelation;
import ptolemy.actor.Receiver;
import ptolemy.actor.process.CompositeProcessDirector;
import ptolemy.actor.process.ProcessReceiver;
import ptolemy.data.IntToken;
import ptolemy.data.expr.Parameter;
import ptolemy.data.type.BaseType;
import ptolemy.domains.pn.kernel.event.PNProcessListener;
import ptolemy.kernel.CompositeEntity;
import ptolemy.kernel.util.IllegalActionException;
import ptolemy.kernel.util.InternalErrorException;
import ptolemy.kernel.util.NameDuplicationException;
import ptolemy.kernel.util.Workspace;
//////////////////////////////////////////////////////////////////////////
//// PNDirector
/**
<p>A PNDirector governs the execution of a CompositeActor with extended
Kahn-MacQueen process networks (PN) semantics. This model of computation has
been extended to support mutations of graphs in a non-deterministic way.
</p><p>
The thread that calls the various execution methods (initialize, prefire, fire
and postfire) on the director is referred to as the <i>directing thread</i>.
This directing thread might be the main thread responsible for the execution
of the entire simulation or might be the thread created by the executive
director of the containing composite actor.
</p><p>
In the PN domain, the director creates a thread (an instance of
ProcessThread), representing a Kahn process, for each actor in the model.
The threads are created in initialize() and started in the prefire() method
of the ProcessDirector. A process is considered <i>active</i> from its
creation until its termination. An active process can block when trying to
read from a channel (read-blocked), when trying to write to a channel
(write-blocked) or when waiting for a queued topology change request to be
processed (mutation-blocked).
</p><p>
A <i>deadlock</i> is when all the active processes are blocked.
The director is responsible for handling deadlocks during execution.
This director handles two different sorts of deadlocks, <i>real deadlock</i>
and <i>artificial deadlock</i>.
</p><p>
A real deadlock is when all the processes are blocked on a read meaning that
no process can proceed until it receives new data. The execution can be
terminated, if desired, in such a situation. If the container of this director
does not have any input ports (as is in the case of a top-level composite
actor), then the executive director or manager terminates the execution.
If the container has input ports, then it is up to the
executive director of the container to decide on the termination of the
execution. To terminate the execution after detection of a real deadlock, the
manager or the executive director calls wrapup() on the director.
</p><p>
An artificial deadlock is when all processes are blocked and at least one
process is blocked on a write. In this case the director increases the
capacity of the receiver with the smallest capacity amongst all the
receivers on which a process is blocked on a write.
This breaks the deadlock and the execution can resume.
If the increase results in a capacity that exceeds the value of
<i>maximumQueueCapacity</i>, then instead of breaking the deadlock,
an exception is thrown. This can be used to detect erroneous models
that require unbounded queues.</p>
<p>There are at least three ways for a PN model to terminate itself:
<ol>
<li>Have the model starve itself. Typically, a boolean switch is used.
See the PN OrderedMerge demo at
<a href="ptolemy/domains/pn/demo/OrderedMerge/OrderedMerge.xml"><code>ptolemy/domains/pn/demo/OrderedMerge/OrderedMerge.xml</code></a>
<li>Have the model call the Stop actor. See the PN RemoveNilTokens demo at
<a href="ptolemy/domains/pn/demo/RemoveNilTokens/RemoveNilTokens.xml"><code>ptolemy/domains/pn/demo/RemoveNilTokens/RemoveNilTokens.xmll</code></a>
<li>Set the <i>firingCountLimit</i>
({@link ptolemy.actor.lib.LimitedFiringSource#_firingCountLimit}) actor
parameter to the number of iterations desired. Actors such as Ramp
extend LimitedFiringSource and have the <i>firingCountLimit</i> parameter.
</ol>
@author Mudit Goel, Edward A. Lee, Xiaowen Xin
@version $Id$
@since Ptolemy II 0.2
@Pt.ProposedRating Green (mudit)
@Pt.AcceptedRating Green (davisj)
*/
public class PNDirector extends CompositeProcessDirector {
/** Construct a director in the default workspace with an empty string
* as its name. The director is added to the list of objects in
* the workspace. Increment the version number of the workspace.
* Create a director parameter "initialQueueCapacity" with the default
* value 1. This sets the initial capacities of the queues in all
* the receivers created in the PN domain.
* @exception IllegalActionException If the name has a period in it, or
* the director is not compatible with the specified container.
* @exception NameDuplicationException If the container already contains
* an entity with the specified name.
*/
public PNDirector() throws IllegalActionException, NameDuplicationException {
super();
_init();
}
/** Construct a director in the workspace with an empty name.
* The director is added to the list of objects in the workspace.
* Increment the version number of the workspace.
* Create a director parameter "initialQueueCapacity" with the default
* value 1. This sets the initial capacities of the queues in all
* the receivers created in the PN domain.
* @param workspace The workspace of this object.
* @exception IllegalActionException If the name has a period in it, or
* the director is not compatible with the specified container.
* @exception NameDuplicationException If the container already contains
* an entity with the specified name.
*/
public PNDirector(Workspace workspace) throws IllegalActionException,
NameDuplicationException {
super(workspace);
_init();
}
/** Construct a director in the given container with the given name.
* If the container argument must not be null, or a
* NullPointerException will be thrown.
* If the name argument is null, then the name is set to the
* empty string. Increment the version number of the workspace.
*
* Create a director parameter "initialQueueCapacity" with the default
* value 1. This sets the initial capacities of the queues in all
* the receivers created in the PN domain.
* @param container Container of the director.
* @param name Name of this director.
* @exception IllegalActionException If the director is not compatible
* with the specified container. Thrown in derived classes.
* @exception NameDuplicationException If the container not a
* CompositeActor and the name collides with an entity in the container.
*/
public PNDirector(CompositeEntity container, String name)
throws IllegalActionException, NameDuplicationException {
super(container, name);
_init();
}
///////////////////////////////////////////////////////////////////
//// parameters ////
/** The initial size of the queues for each communication channel.
* This is an integer that defaults to 1.
*/
public Parameter initialQueueCapacity;
/** The maximum size of the queues for each communication channel.
* This is an integer that defaults to 65536. To specify unbounded
* queues, set this to 0.
*/
public Parameter maximumQueueCapacity;
///////////////////////////////////////////////////////////////////
//// public methods ////
/** Add a process state change listener to this director. The listener
* will be notified of each change to the state of a process.
* @param listener The PNProcessListener to add.
* @see #removeProcessListener(PNProcessListener)
*/
public void addProcessListener(PNProcessListener listener) {
_processListeners.add(listener);
}
/** Clone the director into the specified workspace. The new object is
* <i>not</i> added to the directory of that workspace (It must be added
* by the user if he wants it to be there).
* The result is a new director with no container, no pending mutations,
* and no topology listeners. The count of active processes is zero.
*
* @param workspace The workspace for the cloned object.
* @exception CloneNotSupportedException If one of the attributes
* cannot be cloned.
* @return The new PNDirector.
*/
public Object clone(Workspace workspace) throws CloneNotSupportedException {
PNDirector newObject = (PNDirector) super.clone(workspace);
newObject._readBlockedQueues = new HashMap();
newObject._writeBlockedQueues = new HashMap();
return newObject;
}
/** Invoke the initialize() method of ProcessDirector. Also set all the
* state variables to the their initial values. The list of process
* listeners is not reset as the developer might want to reuse the
* list of listeners.
* @exception IllegalActionException If the initialize() method of one
* of the deeply contained actors throws it.
*/
public void initialize() throws IllegalActionException {
// Initialize these counts BEFORE creating threads.
_readBlockedQueues.clear();
_writeBlockedQueues.clear();
super.initialize();
}
/** Return a new receiver compatible with this director. The receiver
* is an instance of PNQueueReceiver. Set the initial capacity
* of the FIFO queue in the receiver to the value specified by the
* director parameter "initialQueueCapacity". The default value
* of the parameter is 1.
* @return A new PNQueueReceiver.
*/
public Receiver newReceiver() {
PNQueueReceiver receiver = new PNQueueReceiver();
_receivers.add(new WeakReference(receiver));
// Set the capacity to the default. Note that it will also
// be set in preinitialize().
try {
int capacity = ((IntToken) initialQueueCapacity.getToken())
.intValue();
receiver.setCapacity(capacity);
} catch (IllegalActionException e) {
throw new InternalErrorException(e);
}
return receiver;
}
/** Return true if the containing composite actor contains active
* processes and the composite actor has input ports and if stop()
* has not been called. Return false otherwise. This method is
* normally called only after detecting a real deadlock, or if
* stopFire() is called. True is returned to indicate that the
* composite actor can start its execution again if it
* receives data on any of its input ports.
* @return true to indicate that the composite actor can continue
* executing on receiving additional input on its input ports.
* @exception IllegalActionException Not thrown in this base class. May be
* thrown by derived classes.
*/
public boolean postfire() throws IllegalActionException {
_notDone = super.postfire();
// If the container has input ports and there are active processes
// in the container, then the execution might restart on receiving
// additional data.
if (!((((CompositeActor) getContainer()).inputPortList()).isEmpty())
&& (_getActiveThreadsCount() != 0)) {
// Avoid returning false on detected deadlock.
return !_stopRequested;
} else {
return _notDone;
}
}
/** Override the base class to reset the capacities of all the receivers.
* @exception IllegalActionException If the superclass throws it.
*/
public void preinitialize() throws IllegalActionException {
super.preinitialize();
// Check that no relation has multiple sources of data connected to it.
// FIXME: This only detects the error at this level of the hierarchy.
// Probably need to recursively descend into composite actors.
CompositeEntity container = (CompositeEntity) getContainer();
Iterator relations = container.relationList().iterator();
while (relations.hasNext()) {
IORelation relation = (IORelation) relations.next();
if (relation.linkedSourcePortList().size() > 1) {
throw new IllegalActionException(relation,
"Relation has multiple sources of data,"
+ " which is not allowed in PN."
+ " If you want nondeterministic merge,"
+ " use the NondeterministicMerge actor.");
}
}
// Reset the capacities of all the receivers.
Parameter parameter = (Parameter) getAttribute("initialQueueCapacity");
int capacity = ((IntToken) parameter.getToken()).intValue();
ListIterator receivers = _receivers.listIterator();
while (receivers.hasNext()) {
WeakReference reference = (WeakReference) receivers.next();
if (reference.get() == null) {
// Reference has been garbage collected.
receivers.remove();
} else {
PNQueueReceiver receiver = (PNQueueReceiver) reference.get();
if (receiver.getDirector() == this) {
receiver.clear();
receiver.setCapacity(capacity);
} else {
// If the director is not this, then
// the receiver is no longer in use and
// can be removed.
receivers.remove();
}
}
}
}
/** Remove a process listener from this director.
* If the listener is not attached to this director, do nothing.
*
* @param listener The PNProcessListener to be removed.
* @see #addProcessListener(PNProcessListener)
*/
public void removeProcessListener(PNProcessListener listener) {
_processListeners.remove(listener);
}
/** Return an array of suggested ModalModel directors to use with
* PNDirector. The default director is MultirateFSMDirector, the
* alternative director is FSMDirector.
* @return An array of suggested directors to be used with ModalModel.
* @see ptolemy.actor.Director#suggestedModalModelDirectors()
*/
public String[] suggestedModalModelDirectors() {
return new String[] {
"ptolemy.domains.fsm.kernel.MultirateFSMDirector",
"ptolemy.domains.fsm.kernel.FSMDirector" };
}
/** Return true to indicate that a ModalModel under control
* of this director supports multirate firing.
* @return True indicating a ModalModel under control of this director
* supports multirate firing.
*/
public boolean supportMultirateFiring() {
return true;
}
/** Notify the director that the specified thread is blocked
* on an I/O operation.
* @param thread The thread.
* @param receiver The receiver handling the I/O operation,
* or null if it is not a specific receiver.
* @param readOrWrite Either READ_BLOCKED or WRITE_BLOCKED
* to indicate whether the thread is blocked on read or write.
* @see CompositeProcessDirector#threadBlocked(Thread, ProcessReceiver)
*/
public synchronized void threadBlocked(Thread thread,
ProcessReceiver receiver, boolean readOrWrite) {
if (readOrWrite == READ_BLOCKED) {
_readBlockedQueues.put(receiver, thread);
} else {
_writeBlockedQueues.put(receiver, thread);
}
super.threadBlocked(thread, receiver);
}
/** Notify the director that the specified thread is unblocked
* on an I/O operation. If the thread has
* not been registered with threadBlocked(), then this call is
* ignored.
* @param thread The thread.
* @param receiver The receiver handling the I/O operation,
* or null if it is not a specific receiver.
* @param readOrWrite Either READ_BLOCKED or WRITE_BLOCKED
* to indicate whether the thread is blocked on read or write.
* @see CompositeProcessDirector#threadUnblocked(Thread, ProcessReceiver)
*/
public synchronized void threadUnblocked(Thread thread,
ProcessReceiver receiver, boolean readOrWrite) {
if (readOrWrite == READ_BLOCKED) {
_readBlockedQueues.remove(receiver);
} else {
_writeBlockedQueues.remove(receiver);
}
super.threadUnblocked(thread, receiver);
}
///////////////////////////////////////////////////////////////////
//// public variables ////
/** Indicator that a thread is read blocked. */
public static final boolean READ_BLOCKED = true;
/** Indicator that a thread is write blocked. */
public static final boolean WRITE_BLOCKED = false;
///////////////////////////////////////////////////////////////////
//// protected methods ////
/** Double the capacity of one of the queues with the smallest
* capacity belonging to a receiver on which a process is blocked
* while attempting to write. <p>Traverse through the list of receivers
* on which a process is blocked on a write and choose the one containing
* the queue with the smallest capacity. Double the capacity
* if the capacity is non-negative. In case the capacity is
* negative, set the capacity to 1.
* Unblock the process blocked on a write to the receiver containing this
* queue.
* Notify the thread corresponding to the blocked process to resume
* its execution and return.</p>
* @exception IllegalActionException If the resulting capacity would
* exceed the value of <i>maximumQueueCapacity</i>.
*/
protected synchronized void _incrementLowestWriteCapacityPort()
throws IllegalActionException {
// NOTE: This is synchronized as a precaution, although in theory
// it gets called only within a synchronized block of the fire()
// method of the parent ProcessDirector. It must be synchronized
// because of the notifyAll() call at the end.
PNQueueReceiver smallestCapacityQueue = null;
int smallestCapacity = -1;
Iterator receivers = _writeBlockedQueues.keySet().iterator();
if (!receivers.hasNext()) {
return;
}
while (receivers.hasNext()) {
PNQueueReceiver queue = (PNQueueReceiver) receivers.next();
if (smallestCapacity == -1) {
smallestCapacityQueue = queue;
smallestCapacity = queue.getCapacity();
} else if (smallestCapacity > queue.getCapacity()) {
smallestCapacityQueue = queue;
smallestCapacity = queue.getCapacity();
}
}
int capacity = smallestCapacityQueue.getCapacity();
if (capacity <= 0) {
smallestCapacityQueue.setCapacity(1);
capacity = 1;
} else {
int maximumCapacity = ((IntToken) maximumQueueCapacity.getToken())
.intValue();
if ((maximumCapacity > 0) && ((capacity * 2) > maximumCapacity)) {
String msg = "Queue size " + (capacity * 2)
+ " exceeds the maximum capacity in port "
+ smallestCapacityQueue.getContainer().getFullName()
+ ". Perhaps you have an unbounded queue?";
if (_debugging) {
_debug(msg);
}
throw new IllegalActionException(this, msg);
}
smallestCapacityQueue.setCapacity(capacity * 2);
}
if (_debugging) {
_debug("increasing the capacity of receiver "
+ smallestCapacityQueue.getContainer() + " to "
+ smallestCapacityQueue.getCapacity());
}
// Need to mark any thread that is blocked on
// this receiver unblocked now, before the notification,
// or we will detect deadlock all over again and
// again increase the buffer sizes.
threadUnblocked(
(Thread) _writeBlockedQueues.get(smallestCapacityQueue),
smallestCapacityQueue, WRITE_BLOCKED);
return;
}
/** Resolve an artificial deadlock and return true. If the
* deadlock is not an artificial deadlock (it is a real deadlock),
* then return false.
* If it is an artificial deadlock, select the
* receiver with the smallest queue capacity on which any process is
* blocked on a write and increment the capacity of the contained queue.
* If the capacity is non-negative, then increment the capacity by 1.
* Otherwise set the capacity to 1. Unblock the process blocked on
* this receiver. Notify the thread corresponding to the blocked
* process and return true.
* <p>
* If derived classes introduce new forms of deadlocks, they should
* override this method to introduce mechanisms of handling those
* deadlocks. This method is called from the fire() method of the director
* alone.</p>
* @return True after handling an artificial deadlock. Otherwise return
* false.
* @exception IllegalActionException If the maximum queue capacity
* is exceeded.
* This might be thrown by derived classes.
*/
protected boolean _resolveInternalDeadlock() throws IllegalActionException {
if ((_writeBlockedQueues.isEmpty()) && (!_readBlockedQueues.isEmpty())) {
// There is a real deadlock.
if (_debugging) {
_debug("Deadlock detected: no processes blocked on write, but some are blocked on read.");
}
return false;
} else if (_getActiveThreadsCount() == 0) {
// There is a real deadlock as no processes are active.
if (_debugging) {
_debug("No more active processes.");
}
return false;
} else {
// This is an artificial deadlock. Hence find the input port with
// lowest capacity queue that is blocked on a write and increment
// its capacity;
if (_debugging) {
_debug("Artificial Deadlock - increasing queue capacity.");
}
_incrementLowestWriteCapacityPort();
return true;
}
}
///////////////////////////////////////////////////////////////////
//// protected variables ////
/** The set of processes blocked on a read from a receiver. */
protected HashMap _readBlockedQueues = new HashMap();
/** The set of receivers blocked on a write to a receiver. */
protected HashMap _writeBlockedQueues = new HashMap();
///////////////////////////////////////////////////////////////////
//// private methods ////
private void _init() throws IllegalActionException,
NameDuplicationException {
initialQueueCapacity = new Parameter(this, "initialQueueCapacity",
new IntToken(1));
initialQueueCapacity.setTypeEquals(BaseType.INT);
maximumQueueCapacity = new Parameter(this, "maximumQueueCapacity",
new IntToken(65536));
maximumQueueCapacity.setTypeEquals(BaseType.INT);
}
///////////////////////////////////////////////////////////////////
//// private variables ////
/** List of process listeners. */
private LinkedList _processListeners = new LinkedList();
/** The list of all receivers that this director has created. */
private LinkedList _receivers = new LinkedList();
}