ppxscal/embedding_network huggingface dataset:
On-line Steiner trees in the Euclidean plane
Authors: Noga Alon, Yossi Azar
Venue: Proceedings of the eighth annual symposium on Computational geometry (1992)

Suppose we are given a sequence of n points v1,&hellip;,vn in the Euclidean plane, and our objective is to construct, on-line, a connected graph that connects all of them, trying to minimize the total sum of lengths of its edges. We assume that the points appear one at a time, vi arriving at step i. At the end of step i, the on-line algorithm must construct a connected graph Ti-1. This can be done by joining vi (not necessarily by a straight line) to any point of Ti-1, which need not necessarily be one of the previously given points vj. The performance of our algorithm is measured by its competitive ratio: the supremum, over all sequences v1,&hellip;,vn as above, of the ratio between the total length of the graph constructed by our algorithm and the total length of the best Steiner tree that connects all the points v1,&hellip;, vn. There are known on-line algorithms whose competitive ratio is O(log n), but there is no known nontrivial lower bound for the best possible competitive ratio. Here we prove that the upper bound is almost tight by establishing an &OHgr;(log n/log log n) lower bound for the competitive ratio of any on-line algorithm. The lower bound holds for deterministic algorithms as well as for randomized ones, and obviously holds in any Euclidean space of dimension greater than 2 as well.
Routing for generalized chordal rings
Authors: Bruce W. Arden, Kit-Ming W. Tang
Venue: Proceedings of the 1990 ACM annual conference on Cooperation (1990)

A recursive routing algorithm is presented for generalized chordal ring (GCR) graphs. This algorithm consists of two parts. The first part deals with an one-time establishment of a database, and the second part determines a path of length less than or equal to 2l where l is the smallest integer that such a path exists. Note that l &le; d where d satisfies 2d-1 < diameter &le; 2d. The inherent symmetry and the modular arithmetic connectivity of the GCR are exploited to achieve a parallel time complexity of O(log2 diameter) and a serial time complexity of O(diameter).
An object-oriented data model for partition processing in distributed databases
Authors: Rizwan Mithani
Venue: ACM SIGSMALL/PC Notes (1991)

Data replication in a distributed database system can lead to inconsistencies when communication breaks down due to partition failures. Correctness can be ensured if the data model used for representing and manipulating data properly captures real-world semantics.An object-oriented data model which attempts to bridge the gap between real-world semantics and its representation is proposed. Essentially, data is stored in an attributed graph with the nodes representing real-world objects and the arcs representing the relationships between them. A superimposed rule system is employed in the model to enforce consistency and semantic constraints.The model easily incorporates partition processing strategies like Data-patching, Quorum Consensus and Failure mode integrity constraints.
An implementation of ID3 that creates executable rules (abstract)
Authors: Tai-Sheng Zhang, William W. McMillan
Venue: Proceedings of the 1990 ACM annual conference on Cooperation (1990)

Quinlan's ID3 procedure creates a classification tree from a series of examples. Each example is a description of an object, in the form of a set of attribute-value pairs, and the name of the class to which the object belongs. (Attributes might be features such as color, shape, etc.) At each node of the classification tree, ID3 picks an attribute to use at that point in the classification tree. The attribute whose use results in the greatest change in information at that point is selected. At the root all attributes can be used. After examples have been split according to the best attribute, ID3 is applied recursively to the subsets. The process stops when a subset of examples contains members of only one class. The tree can then be used to classify new objects. On different paths to classifications, attributes may be used in different orders. A drawback to many implementations of ID3 is that the resulting decision tree is not in a readily usable form, say for an expert system. We have written Prolog routines that implement ID3 and that write executable Prolog rules. The attribute-value descriptions of examples are stored as standard Prolog predicates. This system allows the direct use of one of the most robust machine learning techniques in a programming environment that is widely used for artificial intelligence applications.
A stepwise refinement heuristic for protocol construction
Authors: A. Udaya Shankar, Simon S. Lam
Venue: ACM Transactions on Programming Languages and Systems (TOPLAS) (1992)

A stepwise refinement heuristic to construct distributed systems is presented. The heuristic is based on a conditional refinement relation between system specifications, and a &ldquo;Marking&rdquo;. It is applied to construct four sliding window protocols that provide reliable data transfer over unreliable communication channels. The protocols use modulo-N sequence numbers. The first protocol is for channels that can only lose messages in transit. By refining this protocol, we obtain three protocols for channels that can lose, reorder, and duplicate messages in transit. The protocols herein are less restrictive and easier to implement than sliding window protocols previously studied in the protocol verification literature.
An Optimistic Locking Technique for Concurrency Control in Distributed Databases
Authors: Ugur Halici, Asuman Dogac
Venue: IEEE Transactions on Software Engineering (1991)

A method called optimistic method with dummy locks (ODL) is suggested for concurrency control in distributed databases. It is shown that by using long-term dummy locks, the need for the information about the write sets of validated transactions is eliminated and, during the validation test, only the related sites are checked. The transactions to be aborted are immediately recognized before the validation test, reducing the costs of restarts. Usual read and write locks are used as short-term locks during the validation test. The use of short-term locks in the optimistic approach eliminates the need for the system-wide critical section and results in a distributed and parallel validation test. The performance of ODL is compared with strict two-phase locking (2PL) through simulation, and it is found out that for the low conflict cases they perform almost the same, but for the high conflicting cases, ODL performs better than strict 2PL.
Comparing structurally different views of a VLSI design
Authors: Mike Spreitzer
Venue: Proceedings of the 27th ACM/IEEE Design Automation Conference (1991)

In large design projects, it is desirable to compare alternate views that use different hierarchies. However, existing techniques either require essentially identical hierarchies (which is sometimes an unacceptable restriction) or must flatten to remove the differences (which may be very costly). A new technique, Informed Comparison, has neither shortcoming. First, hierarchy transformations are applied to reconcile the structures of the views; then a hierarchical base comparison finishes the task. The reconciliation is guided by a small amount of additional design information: the intended relationship between the hierarchies of the views. Some qualities of Informed Comparison depend on the reconciliation repertoire and the base comparison. Two examples are studied.
Studying the performance properties of concurrent programs by simulation experiments on synthetic programs
Authors: Rosemary Candlin, Peter Fisk, Joe Phillips, Neil Skilling
Venue: ACM SIGMETRICS Performance Evaluation Review (1992)

We have developed a methodology for constructing performance models of different types of concurrent programs, and hence obtaining estimates of execution times on different multiprocessor machines. A given class of program is characterized in terms of a small set of parameters which summarise the behaviour of the program over time. Synthetic programs with selected sets of parameters can then be generated and their execution simulated on a model of some given parallel machine. By varying the parameters systematically, we can discover which factors most affect performance. Our approach has been to conduct factorial experiments from which we can obtain quantitative predictions of performance for arbitrary concurrent programs whose parameter values lie within the extreme factor levels, and whose synchronization behaviour conforms to one of a number of common patterns.
On the two-dimensional davenport-schinzel problem
Authors: Jacob T. Schwartz, Micha Sharir
Venue: Journal of Symbolic Computation (1990)

We analyse the combinatorial complexity @k(F) of the minimum M(x,y) of a collection F of n continuous bivariate functions f"1(x,y), ... , f"n(x,y), such that each triple of function graphs intersect in at most s points, and each pair of functions intersect in a curve having at most t singular points. The following is proved. (1) If the intersection curve of each pair of functions intersects each plane x = const in exactly one point and s = 1 (but not if s = 2) then @k(F) is at most O(n), and can be calculated in time 0(n log n) by a method extending Shamos' algorithm for the calculation of planar Voronoi diagrams, (2) If s = 2 and the intersection of each pair of functions is connected then @k(F)= 0(n^2). (3) If the intersection curve of each pair of functions intersects every plane x = const in at most two points, then @k(F) is at most O(n@l"s"+"2(n)), where the constant of proportionality depends on s and t, and where @l,(q) is the (almost linear) maximum length of a (q,r) Davenport-Schinzel sequence. We also present an algorithm for calculating M in this case, running in time O(n@l"s"+"2(n) log n). (4) Finally, we present some geometric applications of these results.
Towards a theory of nearly constant time parallel algorithms
Authors: Joseph Gil, Yossi Matias, Uzi Vishkin
Venue: Proceedings of the 32nd annual symposium on Foundations of computer science (1991)

It is demonstrated that randomization is an extremely powerful tool for designing very fast and efficient parallel algorithms. Specifically, a running time of O(lg* n) (nearly-constant), with high probability, is achieved using n/lg* n (optimal speedup) processors for a wide range of fundamental problems. Also given is a constant time algorithm which, using n processors, approximates the sum of n positive numbers to within an error which is smaller than the sum by an order of magnitude. A variety of known and new techniques are used. New techniques, which are of independent interest, include estimation of the size of a set in constant time for several settings, and ways for deriving superfast optimal algorithms from superfast nonoptimal ones.
Simulating the Grassfire Transform Using an Active Contour Model
Authors: Frédéric Leymarie, Martin D. Levine
Venue: IEEE Transactions on Pattern Analysis and Machine Intelligence (1992)

A method for shape description of planar objects that integrates both region and boundary features is presented. The method is an implementation of a 2D dynamic grassfire that relies on a distance surface on which elastic contours minimize an energy function. The method is based on an active contour model. Numerous implementation aspects of the shape description method were optimized. A Euclidean metric was used for optimal accuracy, and the active contour model permits bypassing some of the discretization limitations inherent in using a digital grid. Noise filtering was performed on the basis of both contour feature measures and region measures, that is, curvature extremum significance and ridge support, respectively, to obtain robust shape descriptors. Other improvements and variations of the algorithmic implementation are proposed.
Future general purpose supercomputer architectures
Authors: J. E. Smith, W.-C. Hsu, C. Hsiung
Venue: Proceedings of the 1990 ACM/IEEE conference on Supercomputing (1990)

This paper discusses the challenges facing designers of future general purpose supercomputers, and describes architectural features and characteristics that may be used to meet these challenges. The scope of the discussion ranges from individual processor architecture to large-scale multiprocessor systems. Performance trends and projections for general purpose supercomputer systems are given as part of the discussion.
Predicting intonational boundaries automatically from text: the ATIS domain
Authors: Michelle Q. Wang, Julia Hirschberg
Venue: Proceedings of the workshop on Speech and Natural Language (1991)

Relating the intonational characteristics of an utterance to other features inferable from its text is important both for speech recognition and for speech synthesis. This work investigates techniques for predicting the location of intonational phrase boundaries in natural speech, through analyzing a utterances from the DARPA Air Travel Information Service database. For statistical modeling, we employ Classification and Regression Tree (CART) techniques. We achieve success rates of just over 90%.
Performance analysis of a broadcast communications protocol
Authors: P. M. Melliar-Smith, Louise E. Moser
Venue: ACM SIGMETRICS Performance Evaluation Review (1991)

The Trans protocol is a communications protocol that exploits the broadcast capability of local area networks. Classical Markov models and queueing theory are used to analyze the performance of components of this protocol, but cannot be applied directly to determine the performance of the protocol as a whole. Instead, Laplace transforms of the distributions for the components are first derived and then combined into a transform for the entire protocol. This transform is evaluated by contour integration to yield the latency for the protocol.
A Practical View of Software Measurement and Implementation Experiences Within Motorola
Authors: Michael K. Daskalantonakis
Venue: IEEE Transactions on Software Engineering (1992)

A practical view of software measurement that formed the basis for a companywide software metrics initiative within Motorola is described. A multidimensional view of measurement is provided by identifying different dimensions (e.g., metric usefulness/utility, metric types or categories, metric audiences, etc.) that were considered in this companywide metrics implementation process. The definitions of the common set of Motorola software metrics, as well as the charts used for presenting these metrics, are included. The metrics were derived using the goal/question metric approach to measurement. A distinction is made between the use of metrics for process improvement over time across projects and the use of metrics for in-process project control. Important experiences in implementing the software metrics initiative within Motorola are also included.
A software tool for modular database design
Authors: M. A. Casanova, A. L. Furtado, L. Tucherman
Venue: ACM Transactions on Database Systems (TODS) (1991)

A modularization discipline for database schemas is first described. The dicipline incorporates both a strategy for enforcing integrity constraints and a tactic for organizing large sets of database structures, integrity constraints, and operations. A software tool that helps the development and maintenance of database schemas modularized according to the discipline is then presented. It offers a user-friendly interface that guides the designer through the various stages of the creation of a new module or through the process of changing objects of existing modules. The tool incorporates, in a declarative style, a description of the design and redesign rules behind the modularization discipline, hence facilitating the incremental addition of new expertise about database design.
An Insider's Evaluation of PAISLey
Authors: Pamela Zave
Venue: IEEE Transactions on Software Engineering (1991)

An executable specification language called PAISLey is evaluated. The language is accompanied by specification methods, analysis techniques, and software tools. The actual results of the PAISLey project are summarized. Research methods, how the results were obtained, and how the project might have been improved are discussed.
Computing dendritic growth
Authors: P. Hamilton
Venue: ACM SIGBIO Newsletter (1992)

We have developed an interactive tool for the construction and simulation of nervecell-models. Based on a semi-CAD platform, the program is able to build single objects in a described way and in a later stage to put them together for observation of their interactions. The user is able to define strings in a graph-grammar fashion, which can be combined with other influencing parameters. This gives the opportunity to build up very natural dendritic trees. Our emphasis is that biological objects are put together as a set of well defined rules, which are overlaid by a distinct statistical variance.
Integration of knowledge and method in real-world discovery
Authors: Jan M. Żytkow
Venue: ACM SIGART Bulletin (1991)

An architecture which controls automated discovery of empirical knowledge must integrate a robotic component which interacts with the real world, knowledge network which accumulates knowledge, a discovery method, and the currently executed discovery tasks. We describe such an architecture implemented in the FAHRENHEIT system, concentrating on the integration and interaction between elements. The robotic component includes hardware connections to the external instruments and manipulators, operational procedures to control the hardware, and a process that controls outstanding requests for measurements and manipulations. Knowledge network describes the actual state of knowledge about the world, including all discoveries that have been made. The state of knowledge expands as the discovery process continues. Operational procedures are expanded and refined as a result of discoveries. Better procedures, in turn, allow FAHRENHEIT to collect better data and to improve its knowledge. The discovery method consists of a network of generic goals and plans for goal execution. Discovery goals require search, so most of the generic plans are solution schemes to search problems. All search problems are defined by the application of a uniform search template. Actual goals and plans executed at any given time form a recursive network of instances of generic goals and plans. The instances are selected based on the generic network of goals and plans, and the current state of knowledge. The selected plans are search instances. At any given time a number of search instances of various types may be in progress, each of them plan leading to new discoveries.
Similarity-based cognitive architecture
Authors: Kenneth D. Forbus, Dedre Gentner
Venue: ACM SIGART Bulletin (1991)

Similarity permeates human cognition. There is evidence that objects are categorized based partly on similarity to previous category members and that the likelihood of transfer is governed by the similarity between the original and current situations. New problems are often solved by analogy to prior problems. Similarity is responsible for many human errors, such as perceptual confusions and many recall intrusions; but at the same time, analogy and similarity are important in scientific discovery. Consequently, we are developing a cognitive architecture in which similarity computations play a central role. This is unlike most architectural approaches, which either do not treat analogy and similarity computations play a central role. This is unlike most architectural approaches, which either do not treat analogy and similarity at all, or relegate them to a subsidiary role, to be called in sporadically when other mechanisms are stuck. We are using Gentner's Structure-Mapping theory [12] as our framework for defining similarity computations.The rest of this note addresses the list of issues suggested by the symposium organizers.
The effects of virtually addressed caches on virtual memory design and performance
Authors: Jon Inouye, Ravindranath Konuru, Jonathan Walpole, Bart Sears
Venue: ACM SIGOPS Operating Systems Review (1992)

Recent times have witnessed rapid advances in microprocessor technology resulting in an order of magnitude performance improvement every few years. These developments in hardware have been paralleled by several prominent trends in operating system design, the most notable being a move towards message-passing micro-kernels. However, operating system performance has not kept pace with that of the underlying hardware. It has become apparent that design changes to enhance processor performance can have adverse effects on operating system performance. This problem arises when the architectural assumptions implicit in an operating system's design are inappropriate for the architectures on which it executes.This paper examines one specific area in which operating system design assumptions appear to be in conflict with trends in modern processor architecture. We focus on the performance effects of virtually addressed caches on two contemporary operating systems (Mach and Chorus). We present experimental results to illustrate the impact of virtually addressed caches on the performance of primitive virtual memory operations, and higher-level operations, such as inter-process communication, that utilize these primitive operations. The main goal of the paper is to encourage operating system designers to revisit some of the basic architectural assumptions implicit in modern operating system designs.
Coded time-symbolic simulation using shared binary decision diagram
Authors: Nagisa Ishiura, Yutaka Deguchi, Shuzo Yajima
Venue: Proceedings of the 27th ACM/IEEE Design Automation Conference (1991)

In this paper we propose a new timing verification technique named coded time-symbolic simulation, CTSS. We are concerned with simulation of logic circuits consisting of gates whose delay is specified only by its minimum and maximum values. We encode the cases of possible delay values of each gate by binary values and simulate all the possible combinations of the delay values by means of symbolic simulation. This simulation technique can deal with logic circuits containing feedback loops as well as combinational circuits. We implemented an efficient simulator by using a shared binary decision diagram (SBDD) as an internal representation of Boolean functions. We also propose novel techniques of analyzing the results of CTSS.
Finding composition factors of permutation groups of degree n≤106
Authors: William M. Kantor
Venue: Journal of Symbolic Computation (1991)

Given a subgroup G= of S"n specified in terms of a generating set @C, when n@?10^6 we present algorithms to test the simplicity of G, to find all of its composition factors, and to find a composition series. While there are already existing algorithms for these purposes (due to Luks or Neumann) valid for all n, the ones in the present note are designed to replace many group theoretic computations by arithmetic calculations using properties of n and |G|.
A training algorithm for optimal margin classifiers
Authors: Bernhard E. Boser, Isabelle M. Guyon, Vladimir N. Vapnik
Venue: Proceedings of the fifth annual workshop on Computational learning theory (1992)

A training algorithm that maximizes the margin between the training patterns and the decision boundary is presented. The technique is applicable to a wide variety of the classification functions, including Perceptrons, polynomials, and Radial Basis Functions. The effective number of parameters is adjusted automatically to match the complexity of the problem. The solution is expressed as a linear combination of supporting patterns. These are the subset of training patterns that are closest to the decision boundary. Bounds on the generalization performance based on the leave-one-out method and the VC-dimension are given. Experimental results on optical character recognition problems demonstrate the good generalization obtained when compared with other learning algorithms.