A semantic measure of the execution time in linear logic

We give a semantic account of the execution time (i.e. the number of cut elimination steps leading to the normal form) of an untyped MELL net. We first prove that: (1) a net is head-normalizable (i.e. normalizable at depth 0) if and only if its interpretation in the multiset based relational semantics is not empty and (2) a net is normalizable if and only if its exhaustive interpretation (a suitable restriction of its interpretation) is not empty. We then give a semantic measure of execution time: we prove that we can compute the number of cut elimination steps leading to a cut free normal form of the net obtained by connecting two cut free nets by means of a cut-link, from the interpretations of the two cut free nets. These results are inspired by similar ones obtained by the first author for the untyped lambda-calculus.     

Software concurrency in real time control systems: A software nucleus

This paper gives the rationale for the design of a nucleus to support real time control applications. In particular, mechanisms for communication between concurrent tasks are reviewed and analysed in the context of this application area. Finally, although no implementation is discussed in detail, techniques which have proved useful in implementing this nucleus on three different machines are described.     

用MATLAB求取线性系统的时域性能指标

采用MATLAB编程求取线性系统的时域性能指标,用户只需从键盘上输入线性系统的传递函数的分子,分母多项式系数,就可以获得该系统的时域性能指标和阶跃响应图,使得时域性能指标的求取变得简单、容易、准确、应用实例验证了所设计的程序的有效性,该程序可用于线性系统的分析和设计。     

On the stabilization of linear discrete time systems subject to input saturation

In this paper, an exponentially unstable linear discrete time system subject to input saturation is shown to be exponentially stabilizable on any compact subset of the constrained asymptotically stabilizable set by a linear periodic variable structure controller. We also point out that any marginally stable system² subject to input saturation can be globally asymptotically stabilized via linear feedback.     

A time domain approach to robust fault detection of linear time-varying systems

This paper gives the optimal solutions to several robust fault detection problems such as ?₋/?_∞, ?₂/?_∞ and ?_∞/?_∞ problems for linear time-varying systems in a time domain, which extends the previous results on linear time-invariant systems in a frequency domain. It is shown that all three problems have the same optimal detection filter and the filter is a simple observer obtained by solving a standard differential Riccati equation. Finally, an example is given to illustrate our results.     

A novel algorithm for performance prediction of web-based software systems

Performance metrics can be predicted with appropriate performance models and evaluation algorithms. The goal of our work is to adapt the Mean-Value Analysis evaluation algorithm to model the behavior of the thread pool. The computation time and the computational complexity of the proposed algorithm have been provided. The limit of the response time and the throughput sequences computed by the novel algorithm has been determined. It has been shown that the proposed algorithm can be applied to performance prediction of web-based software systems in ASP.NET environment. The proposed algorithm has been validated and the correctness of performance prediction with the novel algorithm has been verified with performance measurements. Error analysis has been performed to verify the correctness of performance prediction.     

A unified approach to modelling the performance of concurrent systems

Quantitative design is crucial to ICT and it is therefore important to integrate performance modelling techniques into support environments that facilitate the correct construction of computer systems. We consider Performance Modelling Interchange Formats (PMIFs), which allow models to be specified in a uniform way and ported to a number of tools that solve them. We focus on extending the class of models describable in a PMIF that can be solved analytically – specifically, yielding a product-form solution for their equilibrium state probabilities. We use an extension of an established theorem, called the ‘reversed compound agent theorem’ (RCAT) as the basis of the analytical modelling tool into which the extended PMIF feeds models. We describe the RCAT methodology in practical terms, how it is integrated into an extended PMIF, and illustrate our methodology with three examples.     

Using Scrum to guide the execution of software process improvement in small organizations

For software process improvement - SPI - there are few small organizations using models that guide the management and deployment of their improvement initiatives. This is largely because a lot of these models do not consider the special characteristics of small businesses, nor the appropriate strategies for deploying an SPI initiative in this type of organization. It should also be noted that the models which direct improvement implementation for small settings do not present an explicit process with which to organize and guide the internal work of the employees involved in the implementation of the improvement opportunities. In this paper we propose a lightweight process, which takes into account appropriate strategies for this type of organization. Our proposal, known as a “Lightweight process to incorporate improvements”, uses the philosophy of the Scrum agile method, aiming to give detailed guidelines for supporting the management and performance of the incorporation of improvement opportunities within processes and their putting into practice in small companies. We have applied the proposed process in two small companies by means of the case study research method, and from the initial results, we have observed that it is indeed suitable for small businesses.     

A unique methodology for the stability robustness of multiple time delay systems

The stability robustness is considered for linear time invariant (LTI) systems with rationally independent multiple time delays against delay uncertainties. The problem is known to be notoriously complex, primarily because the systems are infinite dimensional due to delays. Multiplicity of the delays in this study complicates the analysis even further. And “rationally independent” feature of the delays makes the problem prohibitively challenging as opposed to the TDS with commensurate time delays (where time delays are rationally related). A unique framework is described for this broadly studied problem and the enabling propositions are proven. We show that this procedure analytically reveals all possible stability regions exclusively in the space of the delays. As an added strength, it does not require the delay-free system under consideration to be stable. Our methodology offers a resolution to this question, which has been studied from variety of directions in the past four decades. None of these respectable investigations can, however, deliver an exact and exhaustive robustness declaration. From this stand point the new method has a unique contribution.     

A formal approach to reactive systems software: A telecommunications application in Esterel

Esterel is a formally-defined language designed for programming reactive systems; namely, those that maintain a permanent interaction with their environment. The AT&T 5ESS^® telephone switching system is an example of a reactive system. We describe an implementation in Esterel of one feature of a 5ESS switch; this implementation has been tested in the 5ESS switch simulator. Furthermore, it has been formally verified that this implementation satisfies some safety properties stated by 5ESS software development. Our experience indicates that Esterel is suitable for programming industrial-strength reactive systems, and affords significant advantages in software development over more traditional programming languages used in industrial settings.An earlier version of this paper appeared in the Proceedings of the Workshop on Industrial-Strength Formal Specification Techniques, Boca Raton, Florida, 1995.The author is currently supported by a Fulbright fellowship from Spain's Ministry of Science and Education. The work described here was performed while the author was visiting AT&T Bell Laboratories.     

A tool to aid in the installation of complex software systems

This paper describes a programming language, SIDL, in which various aspects of software installation can be modeled. SIDL supports hierarchical file systems, computers, and processes for executing programs to produce new programs and data. An example, illustrating the installation of Ratfor, and experience with the use of SIDL for describing the installation of a large software system are included.     

EClass: An execution classification approach to improving the energy-efficiency of software via machine learning

Energy efficiency at the software level has gained much attention in the past decade. This paper presents a performance-aware frequency assignment algorithm for reducing processor energy consumption using Dynamic Voltage and Frequency Scaling (DVFS). Existing energy-saving techniques often rely on simplified predictions or domain knowledge to extract energy savings for specialized software (such as multimedia or mobile applications) or hardware (such as NPU or sensor nodes). We present an innovative framework, known as EClass, for general-purpose DVFS processors by recognizing short and repetitive utilization patterns efficiently using machine learning. Our algorithm is lightweight and can save up to 52.9% of the energy consumption compared with the classical PAST algorithm. It achieves an average savings of 9.1% when compared with an existing online learning algorithm that also utilizes the statistics from the current execution only. We have simulated the algorithms on a cycle-accurate power simulator. Experimental results show that EClass can effectively save energy for real life applications that exhibit mixed CPU utilization patterns during executions. Our research challenges an assumption among previous work in the research community that a simple and efficient heuristic should be used to adjust the processor frequency online. Our empirical result shows that the use of an advanced algorithm such as machine learning can not only compensate for the energy needed to run such an algorithm, but also outperforms prior techniques based on the above assumption.     

A contribution to the evaluation of the reliability of iterative‐execution software †

This paper deals with the reliability of software executed iteratively, as for example in process control applications. The probability of mission survival is evaluated taking account of two characteristics of iterative software: (a) system failure, defined in terms of the behaviour of the software over successive iterations, because the controlled system can usually tolerate short bursts of errors; (b) the probabilistic correlation between successive executions of the software, which is to be expected for various reasons. The paper presents models accounting for these characteristics and evaluates their effects. The interesting case of fault‐tolerant software is considered as well. Using the example of a ‘pair‐and‐spare’ type fault‐tolerant scheme, the relationships between different aspects of failure behaviour that are covered by the models developed here, and those used elsewhere for fault‐tolerant software, are shown. Copyright © 1999 John Wiley & Sons, Ltd.     

On stability of linear neutral systems with mixed time delays: A discretized Lyapunov functional approach

This paper focuses on the stability problem for a class of linear neutral systems with mixed neutral and discrete delays. A discretized Lyapunov functional approach is developed for such kinds of systems. The resulting stability criteria are formulated in the form of a linear matrix inequality (LMI). These criteria are applicable to linear neutral systems with both small and non-small discrete delays. For nominal systems, the analytical results can be approached with fine discretization. For uncertain systems, the new approach is much less conservative. Numerical examples show significant improvement over approaches in the literature.     

Self-organizing multi-modeling: A different way to design intelligent predictors

Identification of nonlinear systems is an important task for a large number of areas dealing with real-world applications and requirements. Recently, multiple works proposed “multi-model” based approaches to model nonlinear systems. Contrary to the conventional point of view, we propose to deem the multi-modeling as building a modular architecture, inspired from Artificial Neural Networks operation mode, where each neuron (module), represented by one of the local models, realizes some higher level transfer function. This article, deals with generalization of this new multi-modeling concept in the frame of nonlinear system's behavior identification and prediction context. Several multi-model construction strategies and identifiers issued architectures are presented and discussed. Experimental results validating presented multi-model based identifiers have been reported and discussed.     

A performance model for analysis of heterogeneous multi-cluster systems

This paper addresses the problem of performance modeling for large-scale heterogeneous distributed systems with emphases on multi-cluster computing systems. Since the overall performance of distributed systems is often depends on the effectiveness of its communication network, the study of the interconnection networks for these systems is very important. Performance modeling is required to avoid poorly chosen components and architectures as well as discovering a serious shortfall during system testing just prior to deployment time. However, the multiplicity of components and associated complexity make performance analysis of distributed computing systems a challenging task. To this end, we present an analytical performance model for the interconnection networks of heterogeneous multi-cluster systems. The analysis is based on a parametric family of fat-trees, the m-port n-tree, and a deterministic routing algorithm, which is proposed in this paper. The model is validated through comprehensive simulation, which demonstrated that the proposed model exhibits a good degree of accuracy for various system organizations and under different working conditions.     

A practical implementation of stochastic programming: an application to the evaluation of option contracts in supply chains

Stochastic programming is a powerful analytical method in order to solve sequential decision-making problems under uncertainty. We describe an approach to build such stochastic linear programming models. We show that algebraic modeling languages make it possible for non-specialist users to formulate complex problems and have solved them by powerful commercial solvers. We illustrate our point in the case of option contracts in supply chain management and propose a numerical analysis of performance. We propose easy-to-implement discretization procedures of the stochastic process in order to limit the size of the event tree in a multi-period environment.     

Map focus: A way to reconcile reactivity and deliberation in multirobot systems

Cooperative multirobot systems require both real-time responsiveness and some form of coordination to get the desired overall behavior. This can be obtained with a combined use of reactive and deliberative subsystems. In this paper, we illustrate an effective technique for putting together these two components. The method is based on the idea that every robot maintains a local map and then dynamically focuses its attention on the part which is relevant in the current context. The framework, which is fully distributed and scalable, is enriched with cooperative behaviors, i.e. behaviors pursued by more than one robot. We provide the details of how the proposed idea has been studied in a simulated cooperative foraging task and proved to be effective.     

On the choice of dither in extremum seeking systems: A case study

We discuss how the choice of dither (excitation signal) affects the performance of extremum seeking using a benchmark situation: a static scalar map; and a simple scalar extremum seeking scheme. Our comparisons are based on the performance of the system with different dithers in terms of three performance indicators: the speed of convergence, domain of attraction and accuracy (i.e. the ultimate bound on trajectories). Our analysis explicitly shows how the dither shape affects each of these performance indicators. Our study suggests that the practitioners using extremum seeking control should consider the dither shape as an important design parameter. Computer simulations support our theoretical findings.