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  • 1
    Electronic Resource
    Electronic Resource
    Springer
    Real-time systems 1 (1989), S. 7-25 
    ISSN: 1573-1383
    Source: Springer Online Journal Archives 1860-2000
    Topics: Computer Science
    Notes: Abstract Periodic processes are major parts of many real-time embedded computer applications. The programming language Ada permits programming simple periodic processes, but it has some serious limitations; producing Ada programs with real-time performance comparable to those produced to date using traditional cyclic executives requires resorting to techniques that are specific to one machine or compiler. We present and evaluate the cyclic executive model for controlling periodic processes. The features and limitations of Ada for programming cyclic executive software are discussed and demonstrated, and some practical techniques for circumventing Ada limitations are described.
    Type of Medium: Electronic Resource
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  • 2
    ISSN: 1573-1383
    Keywords: Concurrency control ; database ; scheduler ; performance evaluation
    Source: Springer Online Journal Archives 1860-2000
    Topics: Computer Science
    Notes: Abstract Thecautious scheduler, recently proposed for the concurrency control of database systems, never resorts to abortions or rollbacks for the purpose of concurrency control. The comprehensive performance evaluation study among different cautious schedulers and conventional non-cautious schedulers, however, has not yet been attempted. In this paper, we consider five scheduling algorithms and investigate their performance by means of simulation studies. Two of these algorithms are non-cautious; that is, thetwo-phase locking algorithm (2PL) (the most popular transaction scheduling algorithm in practical systems) and theconflict serializable algorithm (CSR) (a typical scheduling algorithm among those not using a locking mechanism; also calledD-serializable algorithm, conflict preserving serializable algorithm, orWW-serializable algorithm). The others are cautious scheduling algorithms modified from the above2PL andCSR; that is,cautious two-phase locking algorithm (C2PL), exclusive preclaimed two-phase locking algorithm (EP2PL), andcautious conflict serializable algoritm (CCSR). The results demonstrate the superiority of the cautious conflict serializable algorithm over the conventional two-phase locking algorithm, especially in the on-line system environment.
    Type of Medium: Electronic Resource
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  • 3
    ISSN: 1573-1383
    Source: Springer Online Journal Archives 1860-2000
    Topics: Computer Science
    Notes: Abstract In many real-time applications, the set of tasks in the system, as well as the characteristics of the tasks, change during system execution. Specifically, the system moves from one mode of execution to another as its mission progresses. A mode change is characterized by the deletion of some tasks, addition of new tasks, or changes in the parameters of certain tasks, for example, increasing the sampling rate to obtain a more accurate result. This paper discusses how mode changes can be accommodated within a given framework of priority driven real-time scheduling.
    Type of Medium: Electronic Resource
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  • 4
    Electronic Resource
    Electronic Resource
    Springer
    Real-time systems 1 (1990), S. 297-297 
    ISSN: 1573-1383
    Source: Springer Online Journal Archives 1860-2000
    Topics: Computer Science
    Type of Medium: Electronic Resource
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  • 5
    ISSN: 1573-1383
    Source: Springer Online Journal Archives 1860-2000
    Topics: Computer Science
    Notes: Abstract This paper presents an application of structural modeling and automated reasoning as a software development environment for real-time systems. This application satisfies two major requirements for such an environment: (1) to synthesize an absolutely correct program and, (2) to increase software productivity. The real-time systems, which consist of concurrent programs, are described by a Prolog based concurrent object-oriented language, called MENDEL/87. As a typical concurrent program consists of two parts: functional and synchronization parts; the functional part in the reusable component to be registered in a library will be generated by a structural modeling through the use of structuring functions with respect to data flows. The synchronization part will be synthesized from temporal logic specifications by the use of an automated reasoning mechanism. This paper also describes the MENDELS ZONE implemented on a Prolog machine, which is the working base for the presented application method.
    Type of Medium: Electronic Resource
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  • 6
    Electronic Resource
    Electronic Resource
    Springer
    Real-time systems 1 (1990), S. 333-350 
    ISSN: 1573-1383
    Source: Springer Online Journal Archives 1860-2000
    Topics: Computer Science
    Notes: Abstract This paper presents an extended architecture and a scheduling algorithm for a dataflow computer aimed at real-time processing. From the real-time processing point of view, current dataflow computers have several problems which stem from their hardware mechanisms for scheduling instructions based on data synchronization. This mechanism extracts as many eligible instructions as possible for execution of a program, then executes them in parallel. Hence, the computation in a dataflow computer is generally difficult to interrupt and schedule using software. To realize a controllable dataflow computation, two basic mechanisms are introduced for serializing concurrent processes and interrupting the execution of a process. A parallel and distributed algorithm for the scheduler is presented, with these two mechanisms, which controls and decides state transitions and execution order of the processes based on priority and execution depth, while still maintaining the number of the running state processes at a preferred value. To gear the scheduler algorithm to meet one of the requirements for real-time processing, such as time-constrained computing, a data-parallel algorithm for selection of the user-process with the current highest priority in O (x log x n) time is proposed, where n is the number of priority levels.
    Type of Medium: Electronic Resource
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  • 7
    Electronic Resource
    Electronic Resource
    Springer
    Real-time systems 1 (1990), S. 351-363 
    ISSN: 1573-1383
    Source: Springer Online Journal Archives 1860-2000
    Topics: Computer Science
    Notes: Abstract In real-time systems, the scheduling plays an important role to carry out all tasks within predefined time frames. The scheduling problem, however, is known to be intractable, that is, NP-hard or NP-complete for most cases (Garey and Johnson 1979). In this paper, one of the neural computation techniques is introduced to solve it within a limited time under the hard real-time environment, instead of improving algorithms on conventional computers. Although the neural computation can be realized on a multiprocessor, a special hardware using neural networks is designed to obtain the schedule results without overhead.
    Type of Medium: Electronic Resource
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  • 8
    ISSN: 1573-1383
    Source: Springer Online Journal Archives 1860-2000
    Topics: Computer Science
    Notes: Abstract In this paper, we investigate the problem of scheduling soft aperiodic requests in systems where periodic tasks are scheduled on a fixed-priority, preemptive basis. First, we show that given any queueing discipline for the aperiodic requests, no scheduling algorithm can minimize the response time of every aperiodic request and guarantee that the deadlines of the periodic tasks are met when the periodic tasks are scheduled on a fixed-priority, preemptive basis. We then develop two algorithms: Algorithm $$\mathcal{L}$$ is locally optimal in that it minimizes the response time of the aperiodic request at the head of the aperiodic service queue. Algorithm $$\mathcal{G}$$ is globally optimal in that it completes the current backlog of work in the aperiodic service queue as early as possible.
    Type of Medium: Electronic Resource
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  • 9
    Electronic Resource
    Electronic Resource
    Springer
    Real-time systems 10 (1996), S. 179-210 
    ISSN: 1573-1383
    Source: Springer Online Journal Archives 1860-2000
    Topics: Computer Science
    Notes: Abstract In this paper we present five new on-line algorithms for servicing soft aperiodic requests in realtime systems, where a set of hard periodic tasks is scheduled using the Earliest Deadline First (EDF) algorithm. All the proposed solutions can achieve full processor utilization and enhance aperiodic responsiveness, still guaranteeing the execution of the periodic tasks. Operation of the algorithms, performance, schedulability analysis, and implementation complexity are discussed and compared with classical alternative solutions, such as background and polling service. Extensive simulations show that algorithms with contained run-time overhead present nearly optimal responsiveness. A valuable contribution of this work is to provide the real-time system designer with a wide range of practical solutions which allow to balance efficiency against implementation complexity.
    Type of Medium: Electronic Resource
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  • 10
    ISSN: 1573-1383
    Keywords: Temporal Behaviour Specification ; Reactive Systems ; Rigorous Proof ; Automated Proof ; Safety Properties ; Utility Properties ; Timed Statecharts ; Real Time Logic ; Proofpower HOL
    Source: Springer Online Journal Archives 1860-2000
    Topics: Computer Science
    Notes: Abstract In this paper we present an approach to the specification and verification of reactive systems. The approach uses Timed Statecharts and Real Time Logic for the specification of temporal behaviour, and theorem proving techniques for the verification of safety and utility properties. Formal verification is achieved through the automation of semi-formal (rigorous) proofs using a theorem prover (Proofpower HOL). To illustrate the approach, we use the Railroad Crossing Problem, which has been proposed, along with a set of criteria for assessment, as a benchmark for the comparison of real-time formalisms. We conclude with our assessment of the approach against the proposed criteria.
    Type of Medium: Electronic Resource
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