ppxscal/embedding_network huggingface dataset:
Modeling and simulation of heterogeneous real-time systems based on a deterministic discrete event model
Authors: J. Teich, L. Thiele, E. A. Lee
Venue: Proceedings of the 8th international symposium on System synthesis (1995)

Abstract: An approach to system-level modeling and simulation of a class of heterogeneous real-time systems the timing behaviour of which can be modeled by deterministic discrete event systems is described. Examples of systems we consider are self-timed systems, synchronously clocked systems, and mixed asynchronous/synchronous systems. Our model is based on several extensions to the model of timed marked graphs. Basically, we augment this model by adding new schedule constraints such that we can express simultaneity, synchronicity, finite buffering as well as arbitrary combinations of min- and max-constraints. We prove that these extensions allow efficient timing analysis and we show how to simulate realistic systems using the Ptolemy design system.
Turmoil at NASA, and numerous funding announcements
Authors: Xiaolei Qian
Venue: ACM SIGMOD Record (1995)

Since the last issue of this column six months ago, there have been many interesting program announcements, some of which have already passed deadline. We'll go over these announcements anyway, with the hope that they can get the readers better prepared for future funding opportunities. But first, we'll talk about the continuing budget battle at Congress, and the recent turmoil at NASA.
Disjoint Task Allocation Algorithms for MIN Machines with Minimal Conflicts
Authors: Chansu Yu, Chita R. Das
Venue: IEEE Transactions on Parallel and Distributed Systems (1995)

This paper addresses task allocation schemes for MIN-based multiprocessors. Two types of allocation policies, cubic and noncubic, are discussed here. Conflicts through the network and inability to partition the system effectively are the main bottlenecks in a MIN-based system. To solve both the problems, a renaming scheme for input and output ports of a MIN is proposed. We use the baseline MIN as an example in this work and call the renaming scheme as bit reversal (BR) matchingpattern. Allocation with the new matching pattern minimizes conflicts and partitions the system completely into independent subsystems. The novelty of this matching pattern is that we can use any dynamic cubic allocation and/or scheduling scheme developed for the hypercubes also for the MIN machines. The BR matching pattern can be used with any kind of MIN. An allocation policy for noncubic tasks is also presented with this matching pattern. Various performance measures with different allocation algorithms are compared via simulation. The advantages of the algorithms with the proposed matching pattern are shown in terms of system efficiency, delay and task miss ratio.
SMART requirements
Authors: Mike Mannion, Barry Keepence
Venue: ACM SIGSOFT Software Engineering Notes (1995)

Systems Analysis, or as it is increasingly known as today, Requirements Engineering, is a time consuming, expensive but critical phase in software (and system) development. The "perfect" Requirements Specification should exhibit a number of qualities including correctness, completeness and consistency. Within a Requirements Specification individual requirements at the microscopic level should be justified, clear, unambiguous and verifiable. However, in many cases Systems Analysts or Requirements Engineers describe requirements which fall short of these demands. In addition, outside reviewers faced with presenting an independent qualitative assessment of a Requirements Specification have few guidelines to assist them. In this paper we present a simple technique, borrowed from objective setting in Management Psychology, to assist the construction and evaluation of individual requirements.
Topology and geometry of single hidden layer network, least squares weight solutions
Authors: Frans M. Coetzee, Virginia L. Stonick
Venue: Neural Computation (1995)

In this paper the topological and geometric properties of the weight solutions for multilayer perceptron (MLP) networks under the MSE error criterion are characterized. The characterization is obtained by analyzing a homotopy from linear to nonlinear networks in which the hidden node function is slowly transformed from a linear to the final sigmoidal nonlinearity. Two different geometric perspectives for this optimization process are developed. The generic topology of the nonlinear MLP weight solutions is described and related to the geometric interpretations, error surfaces, and homotopy paths, both analytically and using carefully constructed examples. These results illustrate that although the natural homotopy provides a practically valuable heuristic for training, it suffers from a number of theoretical and practical difficulties. The linear system is a bifurcation point of the homotopy equations, and solution paths are therefore generically discontinuous. Bifurcations and infinite solutions further occur for data sets that are not of measure zero. These results weaken the guarantees on global convergence and exhaustive behavior normally associated with homotopy methods. However, the analyses presented provide a clear understanding of the relationship between linear and nonlinear perceptron networks, and thus a firm foundation for development of more powerful training methods. The geometric perspectives and generic topological results describing the nature of the solutions are further generally applicable to network analysis and algorithm evaluation.
The Zebra striped network file system
Authors: John H. Hartman, John K. Ousterhout
Venue: ACM Transactions on Computer Systems (TOCS) (1995)

Zebra is a network file system that increases throughput by striping the file data across multiple servers. Rather than striping each file separately, Zebra forms all the new data from each client into a single stream, which it then stripes using an approach similar to a log-structured file system. This provides high performance for writes of small files as well as for reads and writes of large files. Zebra also writes parity information in each stripe in the style of RAID disk arrays; this increases storage costs slightly, but allows the system to continue operation while a single storage server is unavailable. A prototype implementation of Zebra, built in the Sprite operating system, provides 4&ndash;5 times the throughput of the standard Sprite file system or NFS for large files and a 15&ndash;300% improvement for writing small files.
Optimality and inefficiency: what isn't a cost model of the lambda calculus?
Authors: Julia L. Lawall, Harry G. Mairson
Venue: ACM SIGPLAN Notices (1996)

We investigate the computational efficiency of the sharing graphs of Lamping [Lam90], Gonthier, Abadi, and L eacute;vy [GAL92], and Asperti [Asp94], designed to effect so-called optimal evaluation, with the goal of reconciling optimality, efficiency, and the clarification of reasonable cost models for the lambda;-calculus. Do these graphs suggest reasonable cost models for the lambda;-calculus? If they are optimal, are they efficient?We present a brief survey of these optimal evaluators, identifying their common characteristics, as well as their shared failures. We give a lower bound on the efficiency of sharing graphs by identifying a class of lambda;-terms that are normalizable in Theta;(n) time, and require Theta;(n) "fan interactions," but require Omega;(2n) bookkeeping steps. For [GAL92], we analyze this anomaly in terms of the dynamic maintenance of deBruijn indices for intermediate terms. We give another lower bound showing that sharing graphs can do Omega;(2n) work (via fan interactions) on graphs that have no beta;-redexes. Finally, we criticize a proposed cost model for lambda;-calculus given by Frandsen and Sturtivant [FS91], showing by example that the model does not take account of the size of intermediate forms. Our example is a term requiring Theta;(2n) steps while having proposed cost Theta;(n). We propose some cost models that both reflect this parameter, and simultaneously reconcile key concepts from optimal reduction.
Synapse models for neural networks: from ion channel kinetics to multiplicative coefficient wij
Authors: François Chapeau-Blondeau, Nicolas Chambet
Venue: Neural Computation (1995)

This paper relates different levels at which the modeling of synaptic transmission can be grounded in neural networks: the level of ion channel kinetics, the level of synaptic conductance dynamics, and the level of a scalar synaptic coefficient. The important assumptions to reduce a synapse model from one level to the next are explicitly exhibited. This coherent progression provides control on what is discarded and what is retained in the modeling process, and is useful to appreciate the significance and limitations of the resulting neural networks. This methodic simplification terminates with a scalar synaptic efficacy as it is very often used in neural networks, but here its conditions of validity are explicitly displayed. This scalar synapse also comes with an expression that directly relates it to basic quantities of synaptic functioning, and it can be endowed with meaningful physical units and realistic numerical values. In addition, it is shown that the scalar synapse does not receive the same expression in neural networks operating with spikes or with firing rates. These coherent modeling elements can help to improve, adjust, and refine the investigation of neural systems and their remarkable collective properties for information processing.
A Parallelism Analyzer for Conservative Parallel Simulation
Authors: Yung-Chang Wong, Shu-Yuen Hwang, Jason Yi-Bing Lin
Venue: IEEE Transactions on Parallel and Distributed Systems (1995)

Most small-scale simulation applications are implemented by sequential simulation techniques. As the problem size increases, however, sequential techniques may be unable to manage the time complexity of the simulation applications adequately. It is natural to consider re-implementing the corresponding large-scale simulations using parallel techniques, which have been reported to be successful in reducing the time complexity for several examples. However, parallel simulation may not be effective for every application. Since the implementation of parallel simulation for an application is usually very expensive, it is required to investigate the performance of parallel simulation for a particular application before re-implementing the simulation. The Chandy-Misra parallel, discrete-event simulation paradigm has been utilized in many large-scale simulation experiments, and several significant extensions have been based on it. Hence the Chandy-Misra protocol is adopted here as a basic model of parallel simulation to which our performance prediction techniques are applied. For an existing sequential simulation program based on the process interaction model, this paper proposes a technique for evaluating Chandy-Misra parallel simulation without actually implementing the parallel program. The idea is to insert parallelism analysis code into the sequential simulation program. When the modified sequential program is executed, the time complexity of the parallel simulation based on the Chandy-Misra protocol is computed. Our technique has been used to determine whether a giant Signaling System 7 simulation (sequential implementation) should be re-implemented using the parallel simulation approach.Index Terms¿Chandy-Misra protocol, critical path analysis, Discrete event simulation, parallelism, parallel simulation
Functionality and usability
Authors: Nancy C. Goodwin
Venue: Communications of the ACM (1987)

Instead of limiting functionality, usability complements functionality. It affects how and with what effectiveness a system is used, and even whether or not it is used at all.
A situated evaluation of the Object Management Group's (OMG) Object Management Architecture (OMA)
Authors: Evan Wallace, Kurt C. Wallnau
Venue: ACM SIGPLAN Notices (1996)

It has been difficult to objectively assess the real value or maturity of the Object Management Group's Object Management Architecture (OMA). While experience reports have appeared in the literature, these have focused more on the functionality of the end-system than on systematically exploring the strengths and weaknesses of the OMA, and providing practical guidelines on the effective use of the OMA for specific software-engineering problems. In this paper we describe a case study in the use of the OMA to integrate legacy software components into a distributed object system. We assess the OMA in this problem context, and indicate strengths and weaknesses of the specification and current implementations. We extrapolate our experience to a broader class of component-based software systems, and recommend an architectural strategy for the effective use of the OMA to this class of systems.
Simulation of flexible control strategies
Authors: Glen D. Smith, D. J. Medeiros
Venue: Proceedings of the 27th conference on Winter simulation (1995)

Flexibility in developing and testing operating policies for manufacturing systems requires the ability to quickly and easily change a simulation model to incorporate the new policy. To achieve this goal, the model of the system control strategy should be separated from the model of the physical system. Using a flexible manufacturing cell as an example, we first show how this separation can be accomplished, and then discuss desirable features in a language that would simplify the approach.
Iterative aggregation/disaggregation techniques for nearly uncoupled markov chains
Authors: Wei-Lu Cao, William J. Stewart
Venue: Journal of the ACM (JACM) (1985)

Iterative aggregation/disaggregation methods provide an efficient approach for computing the stationary probability vector of nearly uncoupled (also known as nearly completely decomposable) Markov chains. Three such methods that have appeared in the literature recently are considered and their similarities and differences are outlined. Specifically, it is shown that the method of Takahashi corresponds to a modified block Gauss-Seidel step and aggregation, whereas that of Vantilborgh corresponds to a modified block Jacobi step and aggregation. The third method, that of Koury et al., is equivalent to a standard block Gauss-Seidel step and iteration. For each of these methods, a lemma is established, which shows that the unique fixed point of the iterative scheme is the left eigenvector corresponding to the dominant unit eigenvalue of the stochastic transition probability matrix. In addition, conditions are established for the convergence of the first two of these methods; convergence conditions for the third having already been established by Stewart et al. All three methods are shown to have the same asymptotic rate of convergence.
Towards Automatic Multigrid Algorithms for SPD, Nonsymmetric and Indefinite Problems
Authors: Yair Shapira, Moshe Israeli, Avram Sidi
Venue: SIAM Journal on Scientific Computing (1996)

A new multigrid algorithm is constructed for the solution of linear systems of equations which arise from the discretization of elliptic PDEs. It is defined in terms of the difference scheme on the fine grid only, and no rediscretization of the PDE is required. Numerical experiments show that this algorithm gives high convergence rates for several classes of problems: symmetric, nonsymmetric and problems with discontinuous coefficients, nonuniform grids, and nonrectangular domains. When supplemented with an acceleration method, good convergence is achieved also for pure convection problems and indefinite Helmholtz equations.
Accurate Recovery of Three-Dimensional Shape from Image Focus
Authors: Murali Subbarao, Tae Choi
Venue: IEEE Transactions on Pattern Analysis and Machine Intelligence (1995)

A new shape-from-focus method is described which is based on a new concept named Focused Image Surface (FIS). FIS of an object is defined as the surface formed by the set of points at which the object points are focused by a camera lens. According to paraxial-geometric optics, there is a one-to-one correspondence between the shape of an object and the shape of its FIS. Therefore, the problem of shape recovery can be posed as the problem of determining the shape of the FIS. From the shape of FIS the shape of the object is easily obtained. In this paper the shape of the FIS is determined by searching for a shape which maximizes a focus measure. In contrast to previous literature where the focus measure is computed over the planar image detector of the camera, here the focus measure is computed over the FIS. This results in more accurate shape recovery than the traditional methods. Also, using FIS, a more accurate focused image can be reconstructed from a sequence of images than is possible with traditional methods. The new method has been implemented on an actual camera system, and the results of shape recovery and focused image reconstruction are presented.
The first programming paradigm and language dilemma
Authors: Susan S. Brilliant, Timothy R. Wiseman
Venue: ACM SIGCSE Bulletin (1996)

In recent years there has been increasing controversy surrounding the choice of a language for introducing programming to computer science majors. The issue has been complicated by the increasing acceptance of the importance of non-procedural paradigms. This paper compares the available vehicles for teaching programming to beginners. These comparisons are based on the results of a survey conducted by the authors in early 1995 and on the published reports and opinions of other workers in this area.
A train operations simulation for Miami's SR 836 corridor
Authors: Onala M. Atala, John S. Carson
Venue: Proceedings of the 27th conference on Winter simulation (1995)

Presents a general model of a rapid transit system with automatic train control and automatic train protection (ATC/ATP). It has been used to study potential transit technologies, track layouts and block designs for ATC/ATP for the Miami State Road 836 East-West Multimodal Corridor Study Alternatives Analysis (AA). Results of the study have been used in a Draft Environmental Impact Statement (AA/DEIS) and a preliminary engineering report. The purpose of the "screening level" analysis presented in this paper is to propose a few technologically sound, cost-effective public transit technologies that can be carried forward into the conceptual design process, allowing further analysis of technology and alignment options as additional information is generated.
Explaining inheritance: a code reusability perspective
Authors: Robert Biddle, Ewan Tempero
Venue: ACM SIGCSE Bulletin (1996)

Programmers new to the object-oriented paradigm often have difficulty learning how to use inheritance properly. In this paper we introduce an approach to explaining inheritance that is based on understanding the nature of reusability. We show how the important aspect of inheritance is interface conformance, and explain the role this plays in supporting reusability. We then outline a method for determining when and how to use both single inheritance and multiple inheritance, and discuss the implications of our approach.
Identifying the Minimal Transversals of a Hypergraph and Related Problems
Authors: Thomas Eiter, Georg Gottlob
Venue: SIAM Journal on Computing (1995)

The paper considers two decision problems on hypergraphs, hypergraph saturation and recognition of the transversal hypergraph, and discusses their significance for several search problems in applied computer science. Hypergraph saturation (i.e., given a hypergraph $\cal H$, decide if every subset of vertices is contained in or contains some edge of $\cal H$) is shown to be co-NP-complete. A certain subproblem of hypergraph saturation, the saturation of simple hypergraphs (i.e., Sperner families), is shown to be under polynomial transformation equivalent to transversal hypergraph recognition; i.e., given two hypergraphs ${\cal H}_{1}, {\cal H}_{2}$, decide if the sets in ${\cal H}_{2}$ are all the minimal transversals of ${\cal H}_{1}$. The complexity of the search problem related to the recognition of the transversal hypergraph, the computation of the transversal hypergraph, is an open problem. This task needs time exponential in the input size; it is unknown whether an output-polynomial algorithm exists. For several important subcases, for instance if an upper or lower bound is imposed on the edge size or for acyclic hypergraphs, output-polynomial algorithms are presented. Computing or recognizing the minimal transversals of a hypergraph is a frequent problem in practice, which is pointed out by identifying important applications in database theory, Boolean switching theory, logic, and artificial intelligence (AI), particularly in model-based diagnosis.
A set of extensions to the SIMAN/ARENA simulation environment
Authors: Marcelo J. Torres, Peter W. Glynn
Venue: Proceedings of the 27th conference on Winter simulation (1995)

In this paper, we introduce a set of SIMAN/ARENA language constructs. These constructs are intended to add correlated variate generation and importance sampling capabilities to the SIMAN/ARENA simulation environment. It is our purpose to demonstrate that such enhancements are feasible in virtually all simulation languages. These extensions are useful in the analysis of rare events and/or in systems driven by processes exhibiting some degree of correlation. Models arising in communications, manufacturing, physics, and biology may require this type of simulation capability. We describe how the constructs function, including activation, parameter specification, and behavior. In the case of the correlated variate construct, we describe the Markov modulation used to generate our correlations. For the importance sampling construct, we discuss the class of "exponentially twisted" changes-of-measure implemented within our construct, and provide some explanatory theoretical background.
Remark on &ldquo;Fast floating-point processing in Common Lisp&rdquo;
Authors: J. K. Reid
Venue: ACM Transactions on Mathematical Software (TOMS) (1996)

We explain why we feel that the comparison betwen Common Lisp and Fortran in a recent article by Fateman et al. in this journal is not entirely fair.
A multiple cause mixture model for unsupervised learning
Authors: Eric Saund
Venue: Neural Computation (1995)

This paper presents a formulation for unsupervised learning of clusters reflecting multiple causal structure in binary data. Unlike the "hard" k-means clustering algorithm and the "soft" mixture model, each of which assumes that a single hidden event generates each data point, a multiple cause model accounts for observed data by combining assertions from many hidden causes, each of which can pertain to varying degree to any subset of the observable dimensions. We employ an objective function and iterative gradient descent learning algorithm resembling the conventional mixture model. A crucial issue is the mixing function for combining beliefs from different cluster centers in order to generate data predictions whose errors are minimized both during recognition and learning. The mixing function constitutes a prior assumption about underlying structural regularities of the data domain; we demonstrate a weakness inherent to the popular weighted sum followed by sigmoid squashing, and offer alternative forms of the nonlinearity for two types of data domain. Results are presented demonstrating the algorithm's ability successfully to discover coherent multiple causal representations in several experimental data sets.