at:tutorial:actors
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at:tutorial:actors [2007/06/19 16:12] – tvcutsem | at:tutorial:actors [2007/07/18 10:09] – elisag | ||
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====== Concurrent Programming with Actors ====== | ====== Concurrent Programming with Actors ====== | ||
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Generally speaking, an active object is an object that encapsulates its own thread of control. An active object also has a message queue or mailbox from which it processes incoming messages. Each message is processed sequentially. An active object responds to an incoming message by invoking the method corresponding to the message. The method is executed by the active object' | Generally speaking, an active object is an object that encapsulates its own thread of control. An active object also has a message queue or mailbox from which it processes incoming messages. Each message is processed sequentially. An active object responds to an incoming message by invoking the method corresponding to the message. The method is executed by the active object' | ||
- | ===== Actors and Far References ===== | + | ===== AmbientTalk |
In AmbientTalk, | In AmbientTalk, | ||
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As you can see, actors are created similar to objects. The '' | As you can see, actors are created similar to objects. The '' | ||
- | So what exactly is a far reference to an object? The terminology stems from the E language: it is an object reference that refers to an object hosted by another actor. The main difference between regular object references and far references is that regular references allow direct, synchronous access to an object, while far references | + | So what exactly is a far reference to an object? The terminology stems from the E language: it is an object reference that refers to an object hosted by another actor. The main difference between regular object references and far references is that regular references allow direct, synchronous access to an object, while far references |
- | Note that, if the object referred to by a far reference is tagged with one or more type tags, the far reference itself is tagged with the same type tags. Hence, an object located on a remote actor can be tested for its types // | + | < |
+ | If the object referred to by a far reference is tagged with one or more type tags, the far reference itself is tagged with the same type tags. Hence, an object located on a remote actor can be tested for its types // | ||
+ | </ | ||
+ | |||
+ | The figure below summarizes AmbientTalk' | ||
+ | |||
+ | {{ : | ||
===== Asynchronous Message Sending ===== | ===== Asynchronous Message Sending ===== | ||
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The parameter passing semantics defined above rule out any possibility for an object to be passed by copy. The reason for this semantics is that objects encapsulate a lexical scope, and parameter passing an object by copy would require the entire lexical scope to be parameter-passed as well. | The parameter passing semantics defined above rule out any possibility for an object to be passed by copy. The reason for this semantics is that objects encapsulate a lexical scope, and parameter passing an object by copy would require the entire lexical scope to be parameter-passed as well. | ||
- | To enable objects to be passed by copy between actors, a special type of objects is introduced. These objects are called **isolates** because they are // | + | To enable objects to be passed by copy between actors, a special type of objects is introduced. These objects are called **isolates** because they are // |
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</ | </ | ||
- | < | + | < |
- | A word of warning: isolates are objects that are copied freely between actors. As a result, they should be objects whose actual object identity is of little importance. Usually, the identity of by-copy objects is determined by the value of some of the object' | + | A word of warning: isolates are objects that are (deep) |
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def ==(other) { | def ==(other) { | ||
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</ | </ | ||
- | It is important to note that an isolate has no access whatsoever to its encompassing scope. | + | As already explained, |
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</ | </ | ||
- | Sometimes | + | However, sometimes |
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</ | </ | ||
- | Or, you can specify a stripe | + | Or, you can specify a type tag to only catch specific exceptions: |
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When the future for ''< | When the future for ''< | ||
- | ==== Futures and Striped | + | ==== Futures and Annotated |
- | As previously explained, there are two modes for enabling futures in AmbientTalk. Invoking '' | + | As previously explained, there are two modes for enabling futures in AmbientTalk. Invoking '' |
- | When a message send is striped | + | When a message send is annotated |
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</ | </ | ||
- | When a message send is striped | + | When a message send is annotated |
< | < |
at/tutorial/actors.txt · Last modified: 2020/02/05 21:26 by elisag