CST is a programming language based on Smalltalk-80 that supports concurrency using locks, asynchronous messages, and distributed objects. Distributed objects have their state distributed across many nodes of a machin...
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CST is a programming language based on Smalltalk-80 that supports concurrency using locks, asynchronous messages, and distributed objects. Distributed objects have their state distributed across many nodes of a machine, but are referred to by a single name. Distributed objects are capable of processing many messages simultaneously and can be used to efficiently connect together large collections of objects. They can be used to construct a number of useful abstractions for concurrency. We describe the CST language and give examples of its use.
A description is given of DAPHNE, a system of tools and run-time support routines that allow programs to be broken into parts for distributed execution on different nodes of a heterogeneous computer network. This appr...
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(纸本)081860865X
A description is given of DAPHNE, a system of tools and run-time support routines that allow programs to be broken into parts for distributed execution on different nodes of a heterogeneous computer network. This approach serves as a natural basis for classical network services such as remote file access or remote login while at the same time allowing arbitrary distributed applications to be written in a standard programming language. The pivot of DAPHNE is a remote procedure call mechanism that is specifically adapted to a heterogeneous environment, notably heterogeneous systems software. The current language context of DAPHNE is Modula-2. Prototype software exists for a local area network including Unix and MS-DOS systems.
Partially interpreted program schemas are suggested as a tool for formally specifying and defining the range of applicability of patterns of communication. The body of a schema syntactically resembles a program, but c...
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Partially interpreted program schemas are suggested as a tool for formally specifying and defining the range of applicability of patterns of communication. The body of a schema syntactically resembles a program, but contains free variables which represent uninterpreted program sections, domains, functions, or other aspects of the program. The specification of the schema includes both applicability requirements and result assertions, as well as specifications for the free variables. A schema may be instantiated to obtain a correct program for a problem statement by matching a problem's assumptions and requirements to a schema specification, and appropriately substituting entities from the problem statement for the free variables in both the specification and the body of the schema. Examples are given of the types of schemas and specifications needed for distributed computing, and of the potential variety of instantiations.
Evaluating the performance of local area networks is a major concern of the research community and organizations that install this type of network. In data processing applications, sorting is one of the most important...
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Evaluating the performance of local area networks is a major concern of the research community and organizations that install this type of network. In data processing applications, sorting is one of the most important and frequently performed operations, because database operations can be performed efficiently on sorted files. The efficiency of sorting algorithms in local networks, therefore, plays a significant role in determining overall network performance. This paper evaluates four alternate methods of performing external sort in common-bus local networks. Each method has five steps: interrupt and synchronization, network data transfer by packets, local sorting, global sorting, and output. The execution time for each method is calculated for four cases using different overlaps among the time components. Each method is evaluated by observing its behavior at different network speeds, file sizes, network sizes, page sizes, I/O times, and interrupt and synchronization times. This paper shows how changing the value of these variables affects the performance of the sorting algorithms. These observations are useful in designing sorting algorithms and other general, parallel algorithms for common-bus local networks.
In this paper we investigate the possibilities to involve the object-oriented approach in the field of real-time processing and particularly for technical process control applications. We first discuss the relevant as...
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In this paper we investigate the possibilities to involve the object-oriented approach in the field of real-time processing and particularly for technical process control applications. We first discuss the relevant aspects for such an application and then show the particular problems associated with an object-oriented program design for real-time systems with the traditional object model. In order to be able to cope with these problems we have to take into account the peculiarities of the real-time system and review the traditional object concepts with these aspects in mind. In this sense we are developing a new concurrent object-oriented model which is based on an innovative view of objects, and a set of concurrent primitives. In the second part of the contribution we present the most important aspects of this model in relation to concurrency and to real-time processing, and we discuss the various design decisions underlying our approach.
We examine the functional capabilities of a symbolic execution subsystem for programs written in MIXAL assembly language and consider the procedure for selection of test data from the results of symbolic execution. Sy...
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We examine the functional capabilities of a symbolic execution subsystem for programs written in MIXAL assembly language and consider the procedure for selection of test data from the results of symbolic execution. Symbolic execution of a program involves its interpretation of symbolic input data. This symbolic execution subsystem is a component of a mutlipurpose integrated program development system in a assembly-type language implemented on ES computers.
In this paper a version of unstable merging of two neighbouring segments in an one-dimensional array is presented. The algorithm runs in O(1) space and in linear time. It is based on stable merging,1but its working ar...
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In this paper a version of unstable merging of two neighbouring segments in an one-dimensional array is presented. The algorithm runs in O(1) space and in linear time. It is based on stable merging,1but its working area is not chosen outside merged segments; instead it occupies the end of one of them. Despite the fact that there are no restrictions on segment sizes, the algorithm is the fastest in its class of those published so far.
This paper presents some modifications of stable merging by decomposition (referred to as DM here). The changes made reduce the time requirements considerably. Furthermore, a O(1)-space version of merging is described...
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This paper presents some modifications of stable merging by decomposition (referred to as DM here). The changes made reduce the time requirements considerably. Furthermore, a O(1)-space version of merging is described. The modifications of DM resemble improvements to the original Quicksort method for sorting, since both the algorithms are of the same generic scheme.
The method of sorting by address calculation is seldom discussed in the literature although it has been around for nearly three decades. This paper presents and discusses a sorting algorithm which is similar to the ad...
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The method of sorting by address calculation is seldom discussed in the literature although it has been around for nearly three decades. This paper presents and discusses a sorting algorithm which is similar to the address calculation sort method of Isaac and Singleton. Our algorithm is based on finding the smallest and the largest keys and makes use of assign and test-zero type operations. The complexity of the algorithm depends on a certain parameter. Under certain conditions, it is shown that the behaviour of the algorithm is linear. For another range of values of the parameter the algorithm is comparable to other good sorting algorithms. The algorithm is compared with the recursive Quicksort algorithm and comparative timings are given to illustrate its efficiency.
Several menu configurations were designed to provide an independent assessment of the influence of breadth, depth and number of responses on computer menu search performance. The menu hierarchy consisted of a binary t...
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Several menu configurations were designed to provide an independent assessment of the influence of breadth, depth and number of responses on computer menu search performance. The menu hierarchy consisted of a binary tree of category descriptor terms with 64 terminal options. Standard menus tested were 2 options on each of 6 sequential frames (2 6 ) and 4 options on 3 frames (4 3 ). Another menu (Upcoming Selections) was developed with 6 frames in which the binary choice on each frame was shown in the presence of options at the next menu level. Menus developed for separating the effects of number of frames and responses were configured with two menu levels per frame and responses were required to either one or both levels. Number of responses was the most important factor affecting execution time. The highest accuracy was found with the Upcoming Selections menu but that menu also resulted in the slowest execution time. A modified Upcoming Selections menu was developed which allowed participants to respond to each level or to bypass the higher level on each frame. Considering both speed and accuracy, that configuration yielded the best performance of all menus tested.
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