inmos ltd. occam 2 Reference Manual. Series in Computer Science, Prentice Hall International, 1988. 19  Home/Search   Document Not in Database   Summary   Related Articles   Check

....[ABC 88] analyses a program to determine its data and control dependencies this information is then used to construct a 14 parallel program satisfying these dependencies. Most recent work into parallel imperative languages centres around languages with explicit parallel constructs, like occam [INM84] or extensions to existing languages such as the MPI library [Mes93] for C. In functional languages introducing parallelism is slightly easier because they do not allow side e ects. Purely implicit approaches typically use evaluation transformation to determine what parts may be done in ....

INMOS, Ltd. The occam programming manual. Prentice-Hall International, Englewood Clis, 1984.

....to ordering of m by P . So a message gets ordered by all processors within 3d time of it being formed and sent, if all processors are non faulty. q 5. Implementation and Performance Measurements We have implemented three different versions of a TMR node on a network of T800 Inmos transputers [INMOS88], each of them incorporating a distinct order protocol for the ordering of input messages. Sets of experiments have been carried out on the various node versions implemented, and the performance in each case has been measured. In this section we describe the node versions implemented and ....

INMOS Limited, Transputer Instruction Set, Prentice Hall International (UK) Ltd, 1988, ISBN 013 -929100-8.

....of syntactic transformations. For example, the processes ABFTX, ABFRC introduced in Section 3.3.2 could be implemented in OCCAM in a rather straightforward way. Such techniques have been investigated in the ProCoS project [10] with the objective to generate OCCAM code for the Inmos Transputer [46]. In the UniForM project [88] a similar approach will be undertaken to generate PLC code from normalised CSP process representations. If the sequential CSP process P still represents rather an abstract view on the system, possibly not yet showing all the relevant implementation details, further ....

Inmos Ltd., Occam 2 Reference Manual. Prentice-Hall International, Englewood Cliffs N J, (1988).

....programs. The internal program behavior is non deterministic, unlike the applications one wants to treat. Task handling incurs run time overhead. Execution times are hard to control. There are almost no generic simulation and debugging tools. Oocurretprogrammig laguages such as ADA [1] or OCCAM [31] are more elaborate. They naturally permit hierarchical and modular program development. Their tasking mechanism and communication primitives are defined at the language level and are portable. They often provide their user with interface and data manipulation facilities, allowing him to program ....

INMOS LTD., Tte Occam Programmig Maual, Prentice-Hall International (954).

....the same node as the file server, the filer has to see if the results have to be sent back to the same node, or to another node. 19 4 Conclusions Clearly ALPS supports topology independence. Conventional methods, such as restructuring compilers [7] concurrent programming languages (like Occam [6] and Ada [8] and operating system interfaces (like Mach [1] and V kernel [3] may be used for topology independent pro gramming. However, these systems either require the programmer to specify the mapping of processes on to the processors, or mapping is done by a compiler. ALPS does not require ....

Inmos. OCCAM Programming Manual. Prentice Hall International, 1984.

....illustrated as arrows in figure 3 is implemented by passing tokens from thread to thread via objects of a channel class CHAN which implements a directed point to point connection between exactly two threads. This is similar to the way communication takes place in the programming language OCCAM [2]. The class CHAN provides one method for sending and another for receiving data over the channel in order to hide the explicit synchronization constructs available in JAVA. The implementation of the CHAN class is similar to that used in JavaPP 3 which provides a lot more OCCAM and CSP mechanisms ....

INMOS Limited. Occam 2 Reference Manual. Prentice Hall International, Englewood Cliffs, 1988.

....(although direct evidence for this belief is still lacking) Java comes with builtin multithreading. Independent threads may be scheduled on di erent processors by a suitable runtime. In any case multithreading can be very convenient in explicit message passing styles of parallel programming [24]. We will return to the question of whether parallel computing may have implications for the development of Java in section 5. The acronym HPJava was coined in a draft white paper produced by members of the PCRC consortium in the rst half of 1996 [10] At NPAC we have been experimenting with ....

....we could run a preprocessor over Java, but this is not a natural procedure in existing Java environments 5 Scienti c programmers have expected to program inter process communication at a higher level, if at all. More successful schemes include Message passing through language level support [24, 15] or higher level library interfaces [14] Data parallelism. We restrict the de nition of data parallelism to cover algorithms that achieve parallelism through operations on distributed arrays. Synchronization is usually limited to bulk synchronization occuring naturally through collective ....

Inmos Ltd. occam 2 Reference Manual. Prentice-Hall International, 1988. ISBN: 0-13-629312-3.

....for this belief is still lacking) Java comes with builtin multithreading. On a shared memory platform independent threads may be scheduled on different processors by a suitable runtime. In any case multithreading can be very convenient in explicit messagepassing styles of parallel programming [21]. We will return to the question of whether parallel computing may have implications for the development of Java in section 5. Section 2 of this article outlines various options for parallel programming in Java possible ways to express parallelism, and ways to handle inter process ....

....in scheduling communications that is missing from raw C. We will give an example of socket programming in section 3. 1, but traditionally this has not been a popular paradigm in the parallel processing world, where more succesful schemes include Message passing through language level support [21, 13] or higher level library interfaces [12] Data parallelism, which we take to mean the style of programming in which parallelism is achieved through operations on distributed arrays, with synchronization typically limited to bulk synchronization occuring naturally through collective array ....

Inmos Ltd. occam 2 Reference Manual. Prentice-Hall International, 1988. ISBN: 0-13-629312-3.

....while the Actor model uses asynchronous messages. 3 The same abstraction is used in the CSP model [Hoa85] It is worth to see the evolution of the communication scheme at the CSP model: The first CSP [Hoa78] used direct naming in the communication. A language realization of CSP called OCCAM [Inm88a] replaces direct naming to channels. The full CSP [Hoa85] however, uses neither naming of the communication partner nor channels but environmental abstraction. Nevertheless, communication remained synchronous in CSP since synchronization of distributed processes is based on the synchronous ....

....[Fer94a, Fer94b] CCRs used in the Monads DP model can be nested into each other (see [Fer94b] for further discussion) 2.1. 7 Process Creation: PAR In a Monads DP program the number of execution threads are created explicitly by structured parallel commands like the PAR construction of OCCAM [Inm88a] see Sect. 2.2.2) By default, each instance of an abstract data type, i.e. an object has got a single execution thread started at object creation time. This feature is inherited from DP. If the initial thread terminates after initializing the internal variables of the object, the object ....

Inmos. OCCAM2 Reference Manual. Series in Computer Science. Prentice-Hall International, 1988.

....communication. Secondly, many specification and description languages rely on synchronous communication primitives, for example the process algebra based specification 6 P. B. Ladkin and S. Leue languages CSP [Hoa85] CCS [Mil89] and LOTOS [ISO88] the CSP implementation language OCCAM [Inm84] and the family of so called synchronous languages such as ESTEREL [BG88] BG92] SIGNAL [BLJ91, BL90] and LUSTRE [BB91] For such formal methods to avail themselves of MFG analysis techniques, it is necessary that synchronous primitives be handled in MFGs. Thirdly, within the context of ....

Inmos Ltd. The Occam Programming Manual. Prentice-Hall International, 1984.

....nature of system calls led to programs that were difficult to maintain. Programming language researchers have over the past decade begun to investigate the design of programming constructs based on models of concurrency described above as a means of remedying this problem. Examples include occam [Inm88] which arose out of the work done on CSP [Hoa85] synchronous programming languages such as ESTEREL [BG92] and LUSTRE [Hal93] which evolved from dataflow models [Kah74, KM77] and PICT [PT95a, PT95b] CML [Rep92] and Facile [TLK96] which are functional concurrent programming languages based ....

Inmos International. occam-2 Reference Manual, Prentice-Hall International, Englewood Cliffs, NJ, 1988.

....transition are modified for synchrony. But why include synchrony Firstly, some arguments [27] 42] suggest that effective formal methods are easier to devise for synchronous primitives. Secondly, many relevant languages rely on synchronous primitives, e.g. CSP [27] CCS [42] LOTOS [33] OCCAM [30], ESTEREL [9] 10] SIGNAL [8, 7] and LUSTRE [6] Thirdly, in some languages synchrony and asynchrony co exist, e.g. the dialect ESTELLE [22, 23] of ESTELLE [32] and a suggested extension of SDL [28] For such languages to avail themselves of MSCs, synchronous primitives must be handled. ....

Inmos Ltd. The Occam Programming Manual. Prentice-Hall International, 1984.

....is a transputer array with a software communications harness. In the first place, we consider only programs which have a static structure, with all processes defined at compile time, and with no variables shared between top level concurrent processes. This is necessarily the structure of ooccam [7] programs, but there are many other programs written in essentially the same way as a concurrent set of communicating sequential processes (the CSP model [8] We have made these restrictions so as to cut down the problem to a manageable size, not because we think that other types of program are ....

Inmos Ltd, Occam 2 Reference Manual, Prentice Hall International 1988.

....if the originator is not faulty. The implemented design allows detection of one Byzantine or deterministic fault in a four lane system and recognition of a deterministic fault in a three lane system. 2. 2 Goals of Communication Behavior Analysis Both FML and AVI software are implemented in occam [7], consisting of systems of processes running concurrently and communicating via internal channels and partly using shared memory to exchange data without the additional communication overhead. The software is structured hierarchically: larger processes, each consisting of several subprocesses, ....

inmos ltd. occam 2 Reference Manual. Series in Computer Science. Prentice Hall International, 1988.

....fi od; which is incorrect (consider the refusals) It is ruled out by the hypothesis in law 9, since I contains #out #in ) out = 2 ref : Therefore we adopt the latter approach and use assignment to refine (11) quoting law 11 (11) v st : st hx i: 5. 7 Deterministic Choice From occam (see [17]) we take the following concepts (though the programming syntax in which we express them comes from CSP) A guarded process is a sequential composition of a communication action (an input or output) and a process. A deterministic choice (or external choice, or alternation) comprises a collection ....

INMOS Limited. OCCAM Programming Manual. Prentice Hall International, 1984.

....algorithms, 2. timing operators for decoration of sequential algorithms, assigning execution times to their logical behaviour, and 3. parallel composition of timed sequential algorithms, introducing concurrency for the sake of both expressivity and efficiency. TimedPL is closely related to occam [inm88a], albeit dropping some features from occam for scientific treatability, but seriously adding to its expressivity in ProCoS s central field of research, namely real time software development. Like in occam, a program is a set of sequential processes executing in parallel and communicating with each ....

INMOS ltd. occam 2 Reference Manual. Prentice Hall International, 1988.

....programming languages, to the behaviour of highly parallel arrangements of gates and flip flops that constitute digital hardware implementations. We suggest that there is such a descriptive framework in the language and algebra of CSP [1] and its embodiment as the occam programming language [2]. We believe that a program can have the necessary expressive power to enable it to serve as an executable specification of a system, whether it be entirely in hardware, entirely in software, or in a combination of the two. Moreover, we believe that programs are the only reasonable basis for a ....

Inmos, The occam2 Programming Manual, Prentice-Hall International, 1988.

....we show that di#erent ways of partitioning an action system into parallel components corresponds to di#erent kinds of communication mechanisms. We exemplify three such mechanisms: shared variable communication, shared action communication (of which CSP Occam communication is a special case [16, 17]) and remote procedure calls (of which, e.g. Ada rendez vous is a special case [22] A fourth communication mechanism is provided by persistent variables in sequential composition of action systems. We end this treatment with a short discussion on how to extend an existing modular programming ....

INMOS Ltd. occam Programming Manual. Prentice--Hall International, 1984.

....implementation is adequate for the correctness of a program which uses it. Concepts An alternation is a process which is simultaneously prepared to communicate with a number of other processes, and which selects exactly one of those that are prepared to communicate with it. In the occam languages[1, 2], the simplest form of alternation consists of a number of branches each beginning with an input process. The alternation executes exactly one of these inputs and the process which follows it, making its selection from amongst those inputs using channels on which another process is already ....

inmos Limited, occam 2 Reference Manual, Prentice-Hall International, 1988.

....implementation is adequate for the correctness of a program which uses it. Concepts An alternation is a process which is simultaneously prepared to communicate with a number of other processes, and which selects exactly one of those that are prepared to communicate with it. In the occam languages[1, 2], the simplest form of alternation consists of a number of branches each beginning with an input process. The alternation executes exactly one of these inputs and the process which follows it, making its selection from amongst those inputs using channels on which another process is already ....

inmos Limited, occam Programming Manual, Prentice-Hall International, 1984.

....systems with procedures can be treated within the refinement calculus. As a case study we have chosen to stepwise derive a sender receiver system among a set of processes. This will be treated in section 6. We also describe how procedures can be understood as CSP occam communication statements [13, 14]. We end in section 7 with some concluding remarks. 2 Action systems An action system (with procedures) is a statement of the form A = j[ var x 1 ; x h : x 1 0; x h 0; proc p 1 = P 1 ; p n = P n ; do A 1 [ Am od ]j: z ; v The identifiers x 1 ; ....

INMOS Ltd. occam Programming Manual. Prentice--Hall International, 1984.

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inmos ltd. occam 2 Reference Manual. Series in Computer Science, Prentice Hall International, 1988. 19

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Inmos Ltd. OccamProgramming Manual. Prentice Hall International, London, 1984. 98

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INMOS Ltd. OCCAM Programming Manual. Prentice-Hall International, 1984.

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Inmos Ltd., Occam 2 Reference Manual. Prentice-Hall International, Englewood Cliffs NJ, (1988).

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