ppxscal/embedding_network huggingface dataset:
Fault-tolerant architectures for continuous media servers
Authors: Banu Özden, Rajeev Rastogi, Prashant Shenoy, Avi Silberschatz
Venue: ACM SIGMOD Record (1996)

Continuous media servers that provide support for the storage and retrieval of continuous media data (e.g., video, audio) at guaranteed rates are becoming increasingly important. Such servers, typically, rely on several disks to service a large number of clients, and are thus highly susceptible to disk failures. We have developed two fault-tolerant approaches that rely on admission control in order to meet rate guarantees for continuous media requests. The schemes enable data to be retrieved from disks at the required rate even if a certain disk were to fail. For both approaches, we present data placement strategies and admission control algorithms. We also present design techniques for maximizing the number of clients that can be supported by a continuous media server. Finally, through extensive simulations, we demonstrate the effectiveness of our schemes.
A time-sensitive object model for real-time systems
Authors: H. Rebecca Callison
Venue: ACM Transactions on Software Engineering and Methodology (TOSEM) (1995)

Process-oriented models for real-time systems focus on the timing constraints of processes, a focus that can adversely affect resulting designs. Data dependencies between processes create scheduling interactions that limit the times at which processes may execute. Processes are then designed to fit available windows in the overall system schedule. &ldquo;Fitting in&rdquo; frequently involves fragmenting processes to fit scheduling windows and/or designing program and data structures for speed rather than for program comprehension. The result is often a system with very sensitive timing that is hard to understand and maintain. As an alternative to process-oriented design, we present time-sensitive objects: a data-oriented model for real-time systems. The time-sensitive object (TSO) model structures systems as time-constrained data, rather than time constrained processing. Object values are extended to object histories in which a sequence of time constrained values describe the evolution of the object over time. Systems comprise a set of objects and their dependencies. The TSO model describes the effects of object operations and the propagation of change among related objects. Periodic objects, a class of objects within the TSO model, are described in detail in this article and compared with traditional periodic processes. Advantages of time-sensitive objects are identified, including greater scheduling independence when processes have data dependencies, more opportunity for concurrency, and greater inherent capability for detection of and tolerance to timing errors.
Hierarchical triangulation for multiresolution surface description
Authors: Leila De Floriani, Enrico Puppo
Venue: ACM Transactions on Graphics (TOG) (1995)

A new hierarchical triangle-based model for representing surfaces over sampled data is proposed, which is based on the subdivision of the surface domain into nested triangulations, called a hierarchical triangulation (HT). The model allows compression of spatial data and representation of a surface at successively finer degrees of resolution. An HT is a collection of triangulations organized in a tree, where each node, except for the root, is a triangulation refining a face belonging to its parent in the hierarchy. We present a topological model for representing an HT, and algorithms for its construction and for the extraction of a triangulation at a given degree of resolution. The surface model, called a hierarchical triangulated surface (HTS) is obtained by associating data values with the vertices of triangles, and by defining suitable functions that describe the surface over each triangular patch. We consider an application of a piecewise-linear version of the HTS to interpolate topographical data, and we describe a specialized version of the construction algorithm that builds an HTS for a terrain starting from a high-resolution rectangular grid of sampled data. Finally, we present an algorithm for extracting representations of terrain at variable resolution over the domain.
An Optimal Execution Time Estimate of Static versus Dynamic Allocation in Multiprocessor Systems
Authors: Hakan Lennerstad, Lars Lundberg
Venue: SIAM Journal on Computing (1995)

Consider a multiprocessor with $k$ identical processors, executing parallel programs consisting of $n$ processes. Let $T_s(P)$ and $T_d(P)$ denote the execution times for the program $P$ with optimal static and dynamic allocations respectively, i. e. allocations giving minimal execution time. We derive a general and explicit formula for the maximal execution time ratio $g(n,k)=\max T_s(P)/T_d(P)$, where the maximum is taken over all programs $P$ consisting of $n$ processes. Any interprocess dependency structure for the programs $P$ is allowed, only avoiding deadlock. Overhead for synchronization and reallocation is neglected. Basic properties of the function $g(n,k)$ are established, from which we obtain a global description of the function. Plots of $g(n,k)$ are included. The results are obtained by investigating a mathematical formulation. The mathematical tools involved are essentially tools of elementary combinatorics. The formula is a combinatorial function applied on certain extremal matrices corresponding to extremal programs. It is mathematically complicated but rapidly computed for reasonable $n$ and $k$, in contrast to the np-completeness of the problems of finding optimal allocations.
Self-similarity through high-variability: statistical analysis of ethernet LAN traffic at the source level
Authors: Walter Willinger, Murad S. Taqqu, Robert Sherman, Daniel V. Wilson
Venue: ACM SIGCOMM Computer Communication Review (1995)

A number of recent empirical studies of traffic measurements from a variety of working packet networks have convincingly demonstrated that actual network traffic is self-similar or long-range dependent in nature (i.e., bursty over a wide range of time scales) - in sharp contrast to commonly made traffic modeling assumptions. In this paper, we provide a plausible physical explanation for the occurrence of self-similarity in high-speed network traffic. Our explanation is based on convergence results for processes that exhibit high variability (i.e., infinite variance) and is supported by detailed statistical analyses of real-time traffic measurements from Ethernet LAN's at the level of individual sources.Our key mathematical result states that the superposition of many ON/OFF sources (also known as packet trains) whose ON-periods and OFF-periods exhibit the Noah Effect (i.e., have high variability or infinite variance) produces aggregate network traffic that features the Joseph Effect (i.e., is self-similar or long-range dependent). There is, moreover, a simple relation between the parameters describing the intensities of the Noah Effect (high variability) and the Joseph Effect (self-similarity). An extensive statistical analysis of two sets of high time-resolution traffic measurements from two Ethernet LAN's (involving a few hundred active source-destination pairs) confirms that the data at the level of individual sources or source-destination pairs are consistent with the Noah Effect. We also discuss implications of this simple physical explanation for the presence of self-similar traffic patterns in modern high-speed network traffic for (i) parsimonious traffic modeling (ii) efficient synthetic generation of realistic traffic patterns, and (iii) relevant network performance and protocol analysis.
The Performance of Camera Translation Direction Estimators From Optical Flow: Analysis, Comparison, and Theoretical Limits
Authors: A. Mark Earnshaw, Steven D. Blostein
Venue: IEEE Transactions on Pattern Analysis and Machine Intelligence (1996)

A noniterative method using optical flow to recover the translation direction of a moving camera has been previously proposed in [4]. We present a detailed explanation of the bias in this algorithm and compare methods for eliminating this bias, as well as presenting a comprehensive error analysis. This analysis includes a necessary modification to the Cramér-Rao lower bound (CRLB). We propose a simple iterative modification to the algorithm which produces unbiased translation direction estimates that approach the CRLB. Numerical results are used to compare the various techniques on synthetic and real image sequences.
Beyond formal processes: augmenting workflow with group interaction techniques
Authors: Pedro Antunes, Nuno Guimarăes, Javier Segovia, Jesús Cardeñosa
Venue: Proceedings of conference on Organizational computing systems (1995)

The main scope of workflow systems has been the automation of formal procedures in the workplace. On the other hand, Communication and Group Support systems have addressed the informal aspects of organizational interactions. We argue that the formal versus informal separation is artificial and a cause of systems ineffectiveness. This paper proposes an approach to increase mutual awareness when integrating support for workflow systems and group interaction techniques.
A systems analysis and model of real-time skin cancer treatment
Authors: J. Harold Pardue, Thomas D. Clark,  Jr., Armand B. Cognetta,  Jr.
Venue: Proceedings of the 27th conference on Winter simulation (1995)

Savings in health care costs, system efficiency, and improved patient satisfaction accruing from a real-time (simultaneous) approach to treatment of skin cancer is examined. The hypothesized benefits of a real-time system design are estimated using a SLAM based simulation model of a typical dermatology clinic specializing in the treatment of basal cell and squamous cell carcinomas.
Evaluation of design alternatives for a multiprocessor microprocessor
Authors: Basem A. Nayfeh, Lance Hammond, Kunle Olukotun
Venue: Proceedings of the 23rd annual international symposium on Computer architecture (1996)

In the future, advanced integrated circuit processing and packaging technology will allow for several design options for multiprocessor microprocessors. In this paper we consider three architectures: shared-primary cache, shared-secondary cache, and shared-memory. We evaluate these three architectures using a complete system simulation environment which models the CPU, memory hierarchy and I/O devices in sufficient detail to boot and run a commercial operating system. Within our simulation environment, we measure performance using representative hand and compiler generated parallel applications, and a multiprogramming workload. Our results show that when applications exhibit fine-grained sharing, both shared-primary and shared-secondary architectures perform similarly when the full costs of sharing the primary cache are included.
Destage algorithms for disk arrays with non-volatile caches
Authors: Anujan Varma, Quinn Jacobson
Venue: ACM SIGARCH Computer Architecture News (1995)

In a disk array with a nonvolatile write cache, destages from the cache to the disk are performed in the background asynchronously while read requests from the host system are serviced in the foreground. In this paper, we study a number of algorithms for scheduling destages in a RAID-5 system. We introduce a new scheduling algorithm, called linear threshold scheduling, that adaptively varies the rate of destages to disks based on the instantaneous occupancy of the write cache. The performance of the algorithm is compared with that of a number of alternative scheduling approaches such as least-cost scheduling and high/low mark. The algorithms are evaluated in terms of their effectiveness in making destages transparent to the servicing of read requests from the host, disk utilization, and their ability to tolerate bursts in the workload without causing an overflow of the write cache. Our results show that linear threshold scheduling provides the best read performance of all the algorithms compared, while still maintaining a high degree of burst tolerance. An approximate implementation of the linear-threshold scheduling algorithm is also described. The approximate algorithm can be implemented with much lower overhead, yet its performance is virtually identical to that of the ideal algorithm.
Sign Pattern Analysis of Control Coefficients of Metabolic Pathways
Authors: Thomas Lundy, Asok K. Sen
Venue: SIAM Journal on Matrix Analysis and Applications (1995)

Using directed graphs we analyze the sign pattern of the control coefficients of the enzymes in linear metabolic pathways. The following pathways axe examined: linear pathways with (a) neither feedback nor feedforward regulation and (b) possible feedback and/or feedforward loops. We establish the different pathway topologies that lead to a sign-nonsingular elasticity matrix. For a given topology with a sign-nonsingular elasticity matrix, we determine the control coefficients that have their signs unambiguously determined and the control coefficients that are sign-indeterminate. The enzymes and metabolites whose control coefficients are sign-indeterminate can be identified directly from the topology of the feedback and feedforward loops in the metabolic pathway.
The case for persistent-connection HTTP
Authors: Jeffrey C. Mogul
Venue: Proceedings of the conference on Applications, technologies, architectures, and protocols for computer communication (1995)

The success of the World-Wide Web is largely due to the simplicity, hence ease of implementation, of the Hypertext Transfer Protocol (HTTP). HTTP, however, makes inefficient use of network and server resources, and adds unnecessary latencies, by creating a new TCP connection for each request. Modifications to HTTP have been proposed that would transport multiple requests over each TCP connection. These modifications have led to debate over their actual impact on users, on servers, and on the network. This paper reports the results of log-driven simulations of several variants of the proposed modifications, which demonstrate the value of persistent connections.
Distributed information management in the National HPCC Software Exchange
Authors: Shirley Browne, Jack Dongarra, Geoffrey C. Fox, Ken Hawick, Ken Kennedy, Rick Stevens, Robert Olson, Tom Rowan
Venue: Proceedings of the 1995 ACM/IEEE conference on Supercomputing (CDROM) (1995)

Currently, most approaches to retrieving textual materials from scientific databases depend on a lexical match between words in usersý requests and those in or assigned to documents in a database. Because of the tremendous diversity in the words people use to describe the same document, lexical methods are necessarily incomplete and imprecise. Using the singular value decomposition (SVD), one can take advantage of the implicit higher-order structure in the association of terms with documents by determining the SVD of large sparse term by document matrices. Terms and documents represented by 200-300 of the largest singular vectors are then matched against user queries. We call this retrieval method Latent Semantic Indexing (LSI) because the subspace represents important associative relationships between terms and documents that are not evident in individual documents. LSI is a completely automatic yet intelligent indexing method, widely applicable, and a promising way to improve usersý access to many kinds of textual materials, or to documents and services for which textual descriptions are available. A survey of the computational requirements for managing LSI-encoded databases as well as current and future applications of LSI is presented.
MDL-Based Segmentation and Motion Modeling in a Long Image Sequence of Scene with Multiple Independently Moving Objects
Authors: Haisong Gu, Yoshiaki Shirai, Minoru Asada
Venue: IEEE Transactions on Pattern Analysis and Machine Intelligence (1996)

This paper presents a method for spatiotemporal segmentation of long image sequences of scenes which include multiple independently moving objects, based on the minimum description length (MDL) principle. First, a family of motion models is constructed, each of which corresponds to a physically meaningful motion such as translation with constant velocity or a combination of translation and rotation. Then, the motion description length is formulated. When an object changes the type of the motion or a new part of an object appears, the corresponding temporal or spatial segmentation is carried out. Ambiguous segmentation of two consecutive images can be resolved by minimizing the motion description length in a long sequence of images. Experiments on several real image sequences show the validity of our method.
EVENODD: An Efficient Scheme for Tolerating Double Disk Failures in RAID Architectures
Authors: Mario Blaum, Jim Brady, Jehoshua Bruck, Jai Menon
Venue: IEEE Transactions on Computers (1995)

We present a novel method, that we call EVENODD, for tolerating up to two disk failures in RAID architectures. EVENODD employs the addition of only two redundant disks and consists of simple exclusive-OR computations. This redundant storage is optimal, in the sense that two failed disks cannot be retrieved with less than two redundant disks. A major advantage of EVENODD is that it only requires parity hardware, which is typically present in standard RAID-5 controllers. Hence, EVENODD can be implemented on standard RAID-5 controllers without any hardware changes. The most commonly used scheme that employes optimal redundant storage (i.e., two extra disks) is based on Reed¿Solomon (RS) error-correcting codes. This scheme requires computation over finite fields and results in a more complex implementation. For example, we show that the complexity of implementing EVENODD in a disk array with 15 disks is about 50% of the one required when using the RS scheme. The new scheme is not limited to RAID architectures: it can be used in any system requiring large symbols and relatively short codes, for instance, in multitrack magnetic recording. To this end, we also present a decoding algorithm for one column (track) in error.Index Terms¿RAID architectures, erasure-correcting codes, Reed¿Solomon codes, disk arrays.
A simple and efficient bus management scheme that supports continuous streams
Authors: Saied Hosseini-Khayat, Andreas D. Bovopoulos
Venue: ACM Transactions on Computer Systems (TOCS) (1995)

An efficient bandwidth management and access arbitration scheme for an I/O bus in a multimedia workstation is presented. It assumes that a multimedia workstation consists of a number of processing modules which are interconnected by a packet bus. The scheme is efficient in the sense that it allows the bus to support both continuous media transfers and regular random transactions in such a way that continuous streams can meet their real-time constraints independently of random traffic, and random traffic is not delayed significantly by continuous traffic except when traffic load is very high. Implementation guidelines are provided to show that the scheme is practical. Finally, the performance of this scheme is compared with alternative solutions through simulation.
The correctly analyzed system which behaves incorrectly
Authors: Ivan Ryant
Venue: ACM SIGSOFT Software Engineering Notes (1995)

Many systems analysts believe that strictly following a methodology prevents them from producing incorrect system specification. In fact, banking systems, telephone exchanges and other information and control systems may fail in any moment because of hidden errors. This article explains that the most widespread methodologies nowadays aid rising of dangerous synchronization errors in the specification. What's the matter? The methodologies isolate interacting concurrent processes one from other. In order to analyze concurrent behavior, we need to consider interactions as a whole. We must not split interactions into separate processes.Systems analysis aims to specify information systems. There are several approaches to the systems analysis. The two main streams today are structured and object oriented analysis. Unfortunately, both of them hide the danger of incorrect synchronization without giving the analyst any chance to control it. Perhaps, the most delusive case of incorrect synchronization are time - dependent errors. Concurrent system is the system of concurrent (sequential) processes that may interact (communicate or synchronize each other).
Predicting the future: resource requirements and predictive optimism
Authors: Bradley L. Noble, Roger D. Chamberlain
Venue: ACM SIGSIM Simulation Digest (1995)

The partitioning of systems for parallel simulation is a complex task, requiring consideration of both computational load requirements and communications activity. Typically, this information is not accurately known prior to execution. This paper investigates the use of historical information for the prediction of future requirements, both for computation and communications. In addition, for optimistic simulation algorithms, we present a novel technique (which we call predictive optimism) whereby binary prediction schemes can be used to increase the accuracy of optimistic assumptions, thereby decreasing rollbacks and potentially improving overall simulator performance.
Who are the variables in your neighborhood
Authors: Shipra Panda, Fabio Somenzi
Venue: Proceedings of the 1995 IEEE/ACM international conference on Computer-aided design (1995)

Dynamic reordering techniques have had considerable success in reducing the impact of the initial variable order on the size of decision diagrams. Sifting, in particular, has emerged as a very good compromise between low CPU time requirements and high quality of results. Sifting, however, has the absolute position of a variable as the primary objective, and only considers the relative positions of groups of variables indirectly. In this paper we propose an extension to sifting that may move groups of variables simultaneously to produce better results. Variables are aggregated by checking whether they have a strong affinity to their neighbors. (Hence the title.) Our experiments show an average improvement in size of 11%. This improvement, coupled with the greater robustness of the algorithm, more than offsets the modest increase in CPU time that is sometimes incurred.
Enumeration of Concrete Regular Covering Projections
Authors: M. Hofmeister
Venue: SIAM Journal on Discrete Mathematics (1995)

Counting covering spaces of graphs is one of the rapidly progressing aspects within the enumerative branch of topological graph theory. A covering projection is said to be concrete if it is accompanied by an explicit partition of the vertex set of the covering graph into "sheets" such that each sheet meets each vertex fiber exactly once. The natural projection (subscript erasure) of the voltage graph construction is the prototype of a concrete projection. An isomorphism of concrete covering projections maps sheets to sheets. Polya and DeBruijn enumerative methods and Moebius inversion are used to derive a formula to count the isomorphism classes of regular covering projections of a graph.
A comparison of the model-based algebraic styles of specification as a basis for test specification
Authors: Richard Denney
Venue: ACM SIGSOFT Software Engineering Notes (1996)

The use of formal specifications as a basis for specifying functional tests has been discussed by a numbers of researchers with most work focusing on one style of specification or another separately. But is any single style an adequate basis for writing functional tests? The strengths, weaknesses and complementary nature of two popular styles of software specification, model-based and algebraic, are examined as a basis for functional test specification.