Package ptolemy.actor.sched

Class Schedule

java.lang.Object

ptolemy.actor.sched.ScheduleElement

ptolemy.actor.sched.Schedule

Direct Known Subclasses:

SequenceSchedule

public class Schedule
extends ScheduleElement

This class represents a static schedule of actor executions. An instance of this class is returned by the scheduler of a model to represent order of actor firings in the model. A schedule consists of a list of schedule elements and the number of times the schedule should repeat (called the iteration count).

Each element of the schedule is represented by an instance of the ScheduleElement class. Each element may correspond to a number of firings of a single actor (represented by the Firing class) or an entire sub-schedule (represented by a hierarchically contained instance of this class). This nesting allows this concise representation of looped schedules. The nesting can be arbitrarily deep, but must be a tree where the leaf nodes represent actor firings. It is up to the scheduler to enforce this requirement.

The add() and remove() methods are used to add or remove schedule elements. Only elements of type ScheduleElement (Schedule or Firing) may be added to the schedule list. Otherwise an exception will occur.

The iteration count is set by the setIterationCount() method. If this method is not invoked, a default value of one will be used.

As an example, suppose that we have an SDF graph containing actors A, B, C, and D, with the firing order ABCBCBCDD.

This firing order can be represented by a simple looped schedule. The code to create this schedule appears below.

 Schedule S = new Schedule();
 Firing S1 = new Firing();
 Schedule S2 = new Schedule();
 Firing S3 = new Firing();
 S.add(S1);
 S.add(S2);
 S.add(S3);
 S1.setActor(A);
 S2.setIterationCount(3);
 Firing S2_1 = new Firing();
 Firing S2_2 = new Firing();
 S2_1.setActor(B);
 S2_2.setActor(C);
 S2.add(S2_1);
 S2.add(S2_2);
 S3.setIterationCount(2);
 S3.setActor(D);
 

Note that this implementation is not synchronized. It is therefore not safe for a thread to make modifications to the schedule structure while multiple threads are concurrently accessing the schedule.

References

S. S. Bhattacharyya, P K. Murthy, and E. A. Lee, Software Syntheses from Dataflow Graphs, Kluwer Academic Publishers, 1996.

Since:

Ptolemy II 1.0

Version:

$Id$

Author:

Brian K. Vogel, Steve Neuendorffer

See Also:

Firing, ScheduleElement

Pt.AcceptedRating:

Yellow (chf)

Pt.ProposedRating:

Green (vogel)

Field Summary

Fields

Modifier and Type	Field	Description
protected java.util.List<ScheduleElement>	_schedule	The list of schedule elements contained by this schedule.

Fields inherited from class ptolemy.actor.sched.ScheduleElement

_parent

Constructor Summary

Constructors

Constructor	Description
Schedule()	Construct a schedule with iteration count of one and an empty schedule list.

Method Summary

Modifier and Type	Method	Description
java.util.Iterator	actorIterator()	Return the actor sequence in the schedule.
void	add(int index, ScheduleElement element)	Insert the specified schedule element at the specified position in the schedule list.
void	add(ScheduleElement element)	Append the specified schedule element to the end of the schedule list.
java.util.Iterator	firingIterator()	Return the actor invocation sequence of this schedule in the form of a sequence of firings.
ScheduleElement	get(int index)	Return the element at the specified position in the list.
java.util.Iterator	iterator()	Return an iterator over the schedule elements of this schedule.
ScheduleElement	remove(int index)	Remove the schedule element at the specified position in the schedule list.
int	size()	Return the number of elements in this list.
java.lang.String	toString()	Output a string representation of this Schedule.

Methods inherited from class ptolemy.actor.sched.ScheduleElement

_getVersion, _incrementVersion, getIterationCount, setIterationCount, setParent

Methods inherited from class java.lang.Object

clone, equals, finalize, getClass, hashCode, notify, notifyAll, wait, wait, wait

Field Detail

_schedule

protected java.util.List<ScheduleElement> _schedule

The list of schedule elements contained by this schedule.

Constructor Detail

Schedule

public Schedule()

Construct a schedule with iteration count of one and an empty schedule list. This constructor should be used when creating a root schedule. The constructor that takes a parameter should be used when creating a subschedule.

Method Detail

actorIterator

public java.util.Iterator actorIterator()

Return the actor sequence in the schedule. A runtime exception is thrown if the underlying schedule structure is modified while the iterator is active.

Implementation note: This method is optimized to be memory efficient. It walks the schedule tree structure as the iterator methods are invoked.

Specified by:

actorIterator in class ScheduleElement

Returns:

An iterator over instances of Firing.

Throws:

java.util.ConcurrentModificationException - If the underlying schedule structure is modified while the iterator is active.

InternalErrorException - If the schedule contains any leaf nodes that are not an instance of Firing.

add

public void add(ScheduleElement element)

Append the specified schedule element to the end of the schedule list. This element must be an instance of ScheduleElement.

Parameters:

element - The schedule element to add.

add

public void add(int index,
                ScheduleElement element)

Insert the specified schedule element at the specified position in the schedule list. This element must be an instance of ScheduleElement. An exception is thrown if the index is out of range.

Parameters:

index - The index at which the specified element is to be inserted.

element - The schedule element to add.

Throws:

java.lang.IndexOutOfBoundsException - If the specified index is out of range (index < 0 || index > size()).

firingIterator

public java.util.Iterator firingIterator()

Return the actor invocation sequence of this schedule in the form of a sequence of firings. All of the lowest-level nodes of the schedule should be an instance of Firing. Otherwise an exception will occur at some point in the iteration.

A runtime exception is thrown if the underlying schedule structure is modified while the iterator is active.

Implementation note: This method is optimized to be memory efficient. It walks the schedule tree structure as the iterator methods are invoked.

Specified by:

firingIterator in class ScheduleElement

Returns:

An iterator over a sequence of firings.

Throws:

java.util.ConcurrentModificationException - If the underlying schedule structure is modified while the iterator is active.

get

public ScheduleElement get(int index)

Return the element at the specified position in the list.

Parameters:

index - The index of the element to return.

Returns:

The element at the specified position in the list.

iterator

public java.util.Iterator iterator()

Return an iterator over the schedule elements of this schedule. The ordering of elements in the iterator sequence is the order of the schedule list. The elements of the iterator sequence are instances of Firing or Schedule.

A runtime exception is thrown if the underlying schedule structure is modified while the iterator is active.

Returns:

An iterator over the schedule elements of this schedule.

Throws:

java.util.ConcurrentModificationException - If the underlying schedule structure is modified while the iterator is active.

remove

public ScheduleElement remove(int index)

Remove the schedule element at the specified position in the schedule list.

Parameters:

index - The index of the schedule element to be removed.

Returns:

The schedule element that was removed.

size

public int size()

Return the number of elements in this list.

Returns:

The number of elements in this list.

toString

public java.lang.String toString()

Output a string representation of this Schedule.

Overrides:

toString in class java.lang.Object