D. Caromel. Concurrency: an Object Oriented Approach. In J. Bezivin, B. Meyer, and J.-M. Nerson, editors, Technology of Object-Oriented Languages and Systems (TOOLS'90), pages 183-197. Angkor, June 1990.  Home/Search   Document Not in Database   Summary   Related Articles   Check

....described in [Agh87, Lie87, Yon87b] every object is an active object. Having a process (or thread) per object is simply not practical on existing hardware or software systems since a program may construct millions of objects. Instead most active object systems take a hybrid approach (for example [Act92, Ame87a, Car90a, Ish87, Jal93, Kar92, Lh92, Mey96, Nie92, Yok87]) where each active object encapsulates a high level activity or service, and contains within it non active objects that are communicated with via normal synchronous invocation, using the thread of control of the host 15 active object. An application usually contains much fewer activities, that ....

....hardly a satisfactory situation for a concurrent system. To correct this, most active object systems employ asynchronous invocations where the caller does not wait for a reply from the callee. To deal with the results that are expected from invocations, systems use mechanisms described by Caromel [Car90a] as wait by necessity the caller proceeds until it needs the result of the invocation. This can be achieved implicitly, as is done in SCOOP [Mey96] and Eiffel [Car90a] or explicitly using the notion of a proxy [Lh92] or future object [Lie87] In some systems, notably Hybrid [Nie92] and ....

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Caromel D., "Concurrency: An Object-Oriented Approach", Proceedings of the second conference on Technology of Object-Oriented Languages and Systems (TOOLS USA), pp183-197, 1990

....described in [Agh87, Lie87, Yon87b] every object is an active object. Having a process (or thread) per object is simply not practical on existing hardware or software systems since a program may construct millions of objects. Instead most active object systems take a hybrid approach (for example [Act92, Ame87a, Car90a, Ish87, Jal93, Kar92, Lh92, Mey96, Nie92, Yok87]) where each active object encapsulates a high level activity or service, and contains within it non active objects that are communicated with via normal synchronous invocation, using the thread of control of the host 15 active object. An application usually contains much fewer activities, that ....

....hardly a satisfactory situation for a concurrent system. To correct this, most active object systems employ asynchronous invocations where the caller does not wait for a reply from the callee. To deal with the results that are expected from invocations, systems use mechanisms described by Caromel [Car90a] as wait by necessity the caller proceeds until it needs the result of the invocation. This can be achieved implicitly, as is done in SCOOP [Mey96] and Eiffel [Car90a] or explicitly using the notion of a proxy [Lh92] or future object [Lie87] In some systems, notably Hybrid [Nie92] and ....

[Article contains additional citation context not shown here]

Caromel D., "Concurrency: An Object-Oriented Approach", Proceedings of the second conference on Technology of Object-Oriented Languages and Systems (TOOLS USA), pp183-197, 1990

....object around the object which is to be the actor. A message targeted to the enclosed object is sent to the semaphore. The semaphore is acquired and the message is relegated to the enclosed object. This prevents multiple threads from accessing the enclosed object. 28 Eiffel Eiffel [55, 54, 56, 57, 58] extends the Eiffel language and supports both passive and active objects (actors) A call to a passive object is synchronous, just like any procedure call. A call to an active object (process object) is an asynchronous message send and relies on the destination process to explicitly receive the ....

Denis Caromel. Concurrency: An Object-Oriented Approach. In Proceedings of TOOLS 1990, pages 183--198, June 1990.

....adopted in object oriented languages such as, for example, Smalltalk[GR83] Trellis Owl[MK87] and Emerald[BHJL86] The process synchronization constructs are semaphores in Smalltalk, lock blocks in Trellis Owl and monitors in Emerald. 46 cf. e.g. Act [KL89] and a concurrent version of Eiffel[Car90] 17 A first simple approach is to allow only one active thread of execution for mutable objects (i.e. objects which can have their internal variables changed) and an unlimited number of active threads for immutable objects. Examples of languages that use this approach are ABCL 1[YBS86] and ....

....51 cf. e.g. the answer statement in POOL2[Ame89, Section 3. 2] 52 This is adopted in many object oriented languages, such as for example actor languages[Hew77, Agh86, Lie87] ABCL 1[YBS86] ConcurrentSmalltalk[YT86] and suggested adaptations of Eiffel to cover concurrent programming[Mey90, Car90, Mey93] 53 This has been adopted in languages such as for example ConcurrentSmalltalk[YT86] Act [KL89] and ofi[Jon93b] 54 Like, for example, with the answer statement in POOL2[Ame89] 18 2. Use activation conditions . These may be predicates associated with methods 55 that may depend ....

Denis Caromel. Concurrency: An Object-Oriented Approach. In Proceedings of TOOLS90, pages 183--197, 1990.

....without their own thread of control, but whose methods are executed in threads of control that originate from other objects. Concurrent object oriented languages exist which support purely active models [Agh87, Lie87] purely passive [Baq95, Gos96, McH94, Mit95, Str91] or a hybrid combination [Act92, Ame87, Car90a, Jal93, Kar92, Loh92, Mey96, Nie92, Yok87]. 2 The pure active models were based on the notion of ACTORS [Agh86] but having a process (or thread) per object is simply not a practical on existing hardware systems, thus the OOCP systems tended to move towards hybrid approaches where passive objects are contained within active ones. On the ....

....from interfering requires synchronisation, either of the senders or of the receiver. In object oriented systems we can view synchronisation of concurrent objects as the control of message acceptance: what messages will be accepted, when and from whom. In active object languages, such Eiffel [Car90a], CSS [Jal93] and Hybrid [Nie92] to name a few, each active object contains one or more threads of control responsible for receiving and processing messages. In these systems synchronisation involves examining the next message and determining if the object is prepared to accept and process that ....

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Caromel D., "Concurrency: An Object-Oriented Approach", Proceedings of TOOLS-2, pp183-197, 25 1990

....be accessed simultaneously by several processes. This model can support concurrency within an object. In other systems, objects are deemed to be active: they have a thread of control which receives requests and schedules them for service. Some active object models (e.g. Hybrid [18] and Caromel [9]) have just a single thread within an object which both schedules and services requests. This object model does not support concurrency within objects, though usually some form of inter object concurrency is supported. Other active object models do support internal concurrency. For example, an ....

....and schedules requests; and when a request may start execution, another thread is created to service it [17] Most mechanisms have inherent limitations which makes then suitable for only one object model, and less suitable, or even totally unsuitable, for others. For example, Caromel s mechanism [9] provides good support for scheduling requests; however it provides no facilities to manage internal concurrency, thus limiting its usability to singlethreaded, active objects. Conversely, the main strength of synchronisation counters [11, 12] is in managing internal concurrency rather than ....

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Denis Caromel. Concurrency: An Object-Oriented Approach. In Jean B'ezivin, Bertrand Meyer, and Jean-Marc Nerson, editors, TOOLS 2 (Technology of ObjectOriented Languages and Systems), pages 183--197. Angkor, 1990.

.... from parent to child class) or column 4 (synchronisation constraints are never re implemented on top of an existing synchronised class; rather they are (re)applied to the unsynchronised equivalent) Eiffel k Inheritance of operations and inheritance of synchronisation constraints in Eiffel k [2] are independent of each other. In other words, a change in synchronisation constraints does not necessitate a rewrite of the operations, and visa versa. Unfortunately, the monolithic approach of specifying all synchronisation constraints in a single routine, Live, means that there is no ....

Denis Caromel. Concurrency: An Object-Oriented Approach. In Jean B'ezivin, Bertrand Meyer, and Jean-Marc Nerson, editors, TOOLS 2, pages 183--197. Angkor, 1990.

....mechanisms may provide this ability: ffl One way is for the synchronisation mechanism to provide a statement whose purpose is to initiate execution of the invocation. Examples include the spawn and exec statements in Mediators [GC86, pg. 470] and the serve operations in Eiffelk [Car90a, pg. 185] ffl A variation of this occurs in synchronisation mechanisms that employ locking type primitives. In such mechanisms, releasing a lock causes an invocation waiting on that lock to continue execution. Examples include condition variables in Monitors [Hoa74] and delay queues in Hybrid ....

.... C( f : g synchronisation int clk; int arr time local to A, B, C; start(Foo) clk : 0; arrival(A, B, C) this inv.arr time : clk ; g Figure 8: Implementing the relative arrival time of invocations Several synchronisation mechanisms (e.g. Scheduling Predicates, Eiffelk [Car90a] and CEiffel [Loh91] provide programmers with access to the relative arrival time of invocations. The above example illustrates that, as for synchronisation counters, this functionality is simply a form of syntactic sugar for synchronisation variables. As with synchronisation counters, Esp ....

[Article contains additional citation context not shown here]

Denis Caromel. Concurrency: An Object-Oriented Approach. In Jean B'ezivin, Bertrand Meyer, and Jean-Marc Nerson, editors, TOOLS 2 (Technology of Object-Oriented Languages and Systems), pages 183--197. Angkor, 1990.

....mechanisms provide this ability: ffl One way is for the synchronisation mechanism to provide a statement whose purpose is to initiate execution of the invocation. Examples include the spawn and exec statements in Mediators [GC86, pg. 470] and the serve operations in Eiffelk [Car90a, pg. 185] ffl A variation of this occurs in synchronisation mechanisms that employ locking type primitives. In such mechanisms, releasing a lock causes an invocation waiting on that lock to continue execution. Examples include condition variables in Monitors [Hoa74] and delay queues in Hybrid ....

....: f : g synchronisation int clk; int arr time local to A, B, C; start(Foo) clk : 0; arrival(A, B, C) this inv.arr time : clk ; g Figure 4. 3: Implementing the relative arrival time of invocations Several synchronisation mechanisms (e.g. Scheduling Predicates, Eiffelk [Car90a] and CEiffel [Loh91] provide programmers with access to the relative arrival time of invocations. The above example illustrates that, as for synchronisation counters, this functionality is simply a form of syntactic sugar for synchronisation variables. As with synchronisation counters, Esp ....

Denis Caromel. Concurrency: An Object-Oriented Approach. In Jean B'ezivin, Bertrand Meyer, and Jean-Marc Nerson, editors, TOOLS 2 (Technology of Object-Oriented Languages and Systems), pages 183--197. Angkor, 1990.

....them. The hold construct discussed on page 21 was their suggestion. Iamalso grateful to UTS for the opportunity to work on the topic of objectoriented concurrency during my stay there from August to October,1992. The design of the lazy wait facility was influenced by the work of Denis Caromel [6]. Important insights were gained at various 54 SYSTEMATIC CONCURRENT OBJECT ORIENTED PROGRAMMING 7 stages of this work from discussions with Richard Bielak, John Bruno, Carlo Ghezzi, Peter L hr,Dino Mandrioli, Jean Marc Nerson, Robert Switzer and Kim Wald n. ....

Denis Caromel, "Concurrency: An Object-Oriented Approach.", in TOOLS 9 (Proceedings of TOOLS EUROPE 1990), ed. Jean Bézivin et al., pp. 183-197, SOL/Angkor, Paris, 1990.

No context found.

D. Caromel. Concurrency: an Object Oriented Approach. In J. Bezivin, B. Meyer, and J.-M. Nerson, editors, Technology of Object-Oriented Languages and Systems (TOOLS'90), pages 183-197. Angkor, June 1990.

No context found.

D. Caromel. Concurrency: An object-oriented approach. In Technology of Object-Oriented Languages and Systems (TOOLS'90), pages 183--197, June 1990.

....has given more importance to data than to function or control. Symmetrically, it is not the control that plays the central role here, but the data. This inversion leads to reusability and flexibility in concurrent systems. At this point the model description is complete, for more detail see [3, 5, 7]. Let us try to summarize the concepts we introduced: 6 process type module Class concept encompasses Module, Type, and Process concepts. A process is an object, an abstract data type implementation, with a thread of control. inter process communication feature call Process entry ....

Caromel, D. "Concurrency: an Object-Oriented Approach", TOOLS'90, Paris, June 1990.

....need this precision we will see later that, in fact, we don t want it. However, this kind of fine control becomes really important when programming realtime applications. The decision about which request to serve might completely change the global system behavior; an example may be found in [Car90a] The second advantage of an explicit control is: 2. the expression of personal actions. The main activity of an active object consists of serving the requests it receives however, it is not the only one. In many cases, there are some operations, independent of any requests that need to be ....

D. Caromel. Concurrency: An objectoriented approach. In TOOLS'90, June 1990.

....to the object b (in routine f for example) will now use the code of B2. This class being a process, the routine and function calls will be asynchronous, leading to concurrency. This situation is very general and occurs either in sequential to parallel reuse or in parallel to parallel ones in [5] we use this scheme as a basis to define a method for building concurrent systems. However, this mechanism alone is insufficient : we need to add synchronization for the function calls (in 3 this example, the call to func1 within the routine f) otherwise the result (here v) might be used when it ....

D. Caromel. Concurrency : an object-oriented approach. In TOOLS'90, June 1990. Also Internal Report 90-R-214, Centre de Recherche en Informatique de Nancy.

....ref Obj#4 z = 3; v2 = 9; neighbor = ref Obj#5 v3 = 9: Obj#4 : Obj#5 : point2d; point2d; x = 1; x = 0; y = 0; y = 1; neighbor = ref nil z = 1; neighbor = ref nil Figure 5: Resulting object list. Future work will start from the current semantic definition to specify the semantics of Eiffel [2, 3], a parallel extension of Eiffel. Our ultimate goal is to achieve formal transformations and verification of parallel programs. ....

Caromel, D. "Concurrency: an Object-Oriented Approach", TOOLS'90, Paris, 1990.

No context found.

D. Caromel. Concurrency: an Object Oriented Approach. In J. Bezivin, B. Meyer, and J.-M. Nerson, editors, Technology of Object-Oriented Languages and Systems (TOOLS'90), pages 183 197. Angkor, June 1990.

....of generic parameters and renaming. This last feature should not modify the overall structure of the semantics since all the modifications should take place within the inheritance module. Future work will start from the current semantic definition to specify the semantics of Eiffel [2, 3], a parallel extension of Eiffel. Our ultimate goal is to achieve formal transformations and verification of parallel programs. ....

Caromel, D. "Concurrency: an Object-Oriented Approach", TOOLS'90, Paris, 1990.

No context found.

D. Caromel. Concurrency: An object-oriented approach. In Technology of Object-Oriented Languages and Systems (TOOLS'90), pages 183--197, June 1990.

No context found.

D. Caromel. #Concurrency: An object-oriented approach," TOOLS-2 Conference Proceedings, #eds. J. Bexivin, B. Meyer and J. M. Nerson#, pp. 183#197, 1990.

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