Package ptolemy.actor.lib.hoc

Class IterateOverArray

  • All Implemented Interfaces:
    java.lang.Cloneable, Actor, Executable, FiringsRecordable, Initializable, TypedActor, Changeable, Debuggable, DebugListener, Derivable, Instantiable, ModelErrorHandler, MoMLExportable, Moveable, Nameable, HandlesInternalLinks
    public class IterateOverArray
extends MirrorComposite
    This actor iterates the contained actor or model over input arrays. To use it, either drop an actor on it and provide arrays to the inputs, or use a default configuration where the actor is effectively a composite actor. In the latter case, you can simply look inside and populate that actor with a submodel that will be applied to the array elements. The submodel is required to have a director. An SDF director will often be sufficient for operations taken on array elements, but other directors can be used as well. Note that this inside director should not impose a limit on the number of iterations of the inside model. If it does, then that limit will be respected, which may result in a failure to iterate over all the input data.

    Each input port expects an array. When this actor fires, an array is read on each input port that has one, and its contents are provided sequentially to the contained actor or model. This actor then iterates the contained actor or model until either there are no more input data for the actor or the prefire() method of the actor or model returns false. If postfire() of the actor returns false, then postfire() of this actor will return false, requesting a halt to execution of the model. The outputs from the contained actor are collected into arrays that are produced on the outputs of this actor.

    A special variable named "iterationCount" can be used in any expression setting the value of a parameter of this actor or its contents. This variable has an integer value that starts at 1 during the first iteration of the contained actor(s) and is incremented by 1 on each firing. If the inside actors consume one token on each firing, then its final value will be the size of the input array(s).

    This actor is properly viewed as a "higher-order component" in that its contained actor is a parameter that specifies how to operate on input arrays. It is inspired by the higher-order functions of functional languages, but unlike those, the contained actor need not be functional. That is, it can have state.

    Note that you cannot place class definitions inside this actor. There should be no need to because class instances inside it can be instances of classes defined outside of it.

    This actor (and many of the other higher-order components) has its intellectual roots in the higher-order functions of functional languages, which have been in use since the 1970s. Similar actors were implemented in Ptolemy Classic, and are described in Lee & Parks, "Dataflow Process Networks," Proceedings of the IEEE, 1995. Those were inspired by [2]. Alternative approaches are found dataflow visual programming since the beginning (Sutherland in the 1960s, Prograph and Labview in the 1980s), and in time-based visual languages (Simulink in the 1990s).

    There are a number of known bugs or limitations in this implementation:

    • FIXME: When you drop in an actor, and then another actor, and then select "undo," the second actor is deleted without the first one being re-created. Thus, undo is only a partial undo. The fix to this is extremely complicated. Probably the only viable mechanism is to use UndoStackAttribute.getUndoInfo() to get the undo stack and then to manipulate the contents of that stack directly.
    • FIXME: There should be an option to reset between firings of the inside actor.
    • FIXME: If you drop a new actor onto an IterateOverArray in a subclass, it will replace the version inherited from the prototype. This is not right, since it violates the derivation invariant. Any attempt to modify the contained object in the prototype will trigger an exception. There are two possible fixes. One is to relax the derivation invariant and allow derived objects to not perfectly mirror the hierarchy of the prototype. Another is for this class to somehow refuse to accept the new object in a subclass. But it is not obvious how to do this.
    • FIXME: If an instance of IterateOverArray in a derived class has overridden values of parameters, those are lost if contained entity of the instance in the base class is replaced and then an undo is requested.
    References
    1. E. A. Lee and T. M. Parks, "Dataflow Process Networks," Proceedings of the IEEE, 83(5): 773-801, May, 1995.
    2. H. J. Reekie, Realtime Signal Processing: Dataflow, Visual, and Functional Programming," Ph.D. Thesis, University of Technology, Sydney, Sydney, Australia, 1995.
    Since:
    Ptolemy II 4.1
    Version:
    $Id$
    Author:
    Edward A. Lee, Steve Neuendorffer
    Pt.AcceptedRating:
    Red (neuendor)
    Pt.ProposedRating:
    Yellow (eal)

    • Constructor Detail

      • IterateOverArray

        public IterateOverArray​(CompositeEntity container,
                        java.lang.String name)
                 throws IllegalActionException,
                        NameDuplicationException
        Create an actor with a name and a container. The container argument must not be null, or a NullPointerException will be thrown. This actor will use the workspace of the container for synchronization and version counts. If the name argument is null, then the name is set to the empty string. Increment the version of the workspace. This actor will have no local director initially, and its executive director will be simply the director of the container. You should set a director before attempting to execute it.
        Parameters:
        container - The container actor.
        name - The name of this actor.
        Throws:
        IllegalActionException - If the container is incompatible with this actor.
        NameDuplicationException - If the name coincides with an actor already in the container.

      • IterateOverArray

        public IterateOverArray​(Workspace workspace)
                 throws IllegalActionException,
                        NameDuplicationException
        Construct an IterateOverArray in the specified workspace with no container and an empty string as a name. You can then change the name with setName(). If the workspace argument is null, then use the default workspace. You should set the local director or executive director before attempting to send data to the actor or to execute it. Add the actor to the workspace directory. Increment the version number of the workspace.
        Parameters:
        workspace - The workspace that will list the actor.
        Throws:
        IllegalActionException - If the container is incompatible with this actor.
        NameDuplicationException - If the name coincides with an actor already in the container.

    • Method Detail

      • clone

        public java.lang.Object clone​(Workspace workspace)
                       throws java.lang.CloneNotSupportedException
        Clone the object into the specified workspace. This overrides the base class to instantiate a new IterateDirector and to set the association with iterationCount.
        Overrides:
        clone in class ReflectComposite
        Parameters:
        workspace - The workspace for the new object.
        Returns:
        A new NamedObj.
        Throws:
        java.lang.CloneNotSupportedException - If any of the attributes cannot be cloned.
        See Also:
        CompositeEntity.exportMoML(Writer, int, String)

      • newPort

        public Port newPort​(java.lang.String name)
             throws NameDuplicationException
        Override the base class to return a specialized port.
        Overrides:
        newPort in class ReflectComposite
        Parameters:
        name - The name of the port to create.
        Returns:
        A new instance of IteratePort, an inner class.
        Throws:
        NameDuplicationException - If the container already has a port with this name.

      • _checkTypesFromTo

        protected java.util.List _checkTypesFromTo​(TypedIOPort sourcePort,
                                           java.util.List destinationPortList)
        Check types from a source port to a group of destination ports, assuming the source port is connected to all the ports in the group of destination ports. Return a list of instances of Inequality that have type conflicts. This overrides the base class so that if one of the ports belongs to this IterateOverArray actor, then its element type is compared against the inside port.
        Overrides:
        _checkTypesFromTo in class TypedCompositeActor
        Parameters:
        sourcePort - The source port.
        destinationPortList - A list of destination ports.
        Returns:
        A list of instances of Inequality indicating the type constraints that are not satisfied.

      • _destinationTypeConstraints

        protected java.util.List _destinationTypeConstraints​(TypedIOPort sourcePort)
        Return the type constraints on all connections starting from the specified source port to all the ports in a group of destination ports. This overrides the base class to ensure that if the source port or the destination port is a port of this composite, then the port is forced to be an array type and the proper constraint on the element type of the array is made. If the source port has no possible sources of data, then no type constraints are added for it.
        Overrides:
        _destinationTypeConstraints in class TypedCompositeActor
        Parameters:
        sourcePort - The source port.
        Returns:
        A list of instances of Inequality.