ppxscal/embedding_network huggingface dataset:
Improving the Variable Ordering of OBDDs Is NP-Complete
Authors: Beate Bollig, Ingo Wegener
Venue: IEEE Transactions on Computers (1996)

Ordered binary decision diagrams are a useful representation of Boolean functions, if a good variable ordering is known. Variable orderings are computed by heuristic algorithms and then improved with local search and simulated annealing algorithms. This approach is based on the conjecture that the following problem is NP-complete. Given an OBDD G representing f and a size bound s, does there exist an OBDD G* (respecting an arbitrary variable ordering) representing f with at most s nodes? This conjecture is proved.
Making a digital library: the chemistry online retrieval experiment
Authors: Richard Entlich, Lorrin Garson, Michael Lesk, Lorraine Normore, Stuart Weibel
Venue: Communications of the ACM (1995)

The CORE project is an electronic library of primary journal articles in chemistry, containing about five years of twenty primary journals published by the American Chemical Society (about 425,000 pages). Unlike many digital library projects, CORE includes both a scanned image and a marked-up ASCII version (represented in Standard Generalized Markup Language, or SGML) for each page of the publisher's database. Each page was scanned and segmented, with graphical units isolated and linked to figure references in the articles. The original machine-readable typography was converted to SGML format and the results were used to build databases with indexes for full-text Boolean searching; a single search engine served data for each of three X-Window interfaces.
United Kingdom: support group provides national focus for computer graphics education
Authors: K. W. Brodlie, A. M. Mumford
Venue: ACM SIGGRAPH Computer Graphics (1996)

This article gives a flavor of graphics education in the United Kingdom. We begin with a short section on the educational system within which graphics is taught at universities and then look at national support for graphics educators through the Advisory Group for Computer Graphics. We finish with a description of a typical graphics offering at a U.K. university.
Synchronous Kahn networks
Authors: Paul Caspi, Marc Pouzet
Venue: Proceedings of the first ACM SIGPLAN international conference on Functional programming (1996)

Synchronous data-flow is a programming paradigm which has been successfully applied in reactive systems. In this context, it can be characterized as some class of static bounded memory data-flow networks. In particular, these networks are not recursively defined, and obey some kind of "synchronous" constraints (clock calculus). Based on Kahn's relationship between data-flow and stream functions, the synchronous constraints can be related to Wadler's listlessness, and can be seen as sufficient conditions ensuring listless evaluation. As a by-product, those networks enjoy efficient compiling techniques. In this paper, we show that it is possible to extend the class of static synchronous data-flow to higher order and dynamical networks, thus giving sense to a larger class of synchronous data-flow networks.This is done by extending both the synchronous operational semantics, the clock calculus and the compiling technique of static data-flow networks, to these more general networks.
Synthesis of system-level communication by an allocation-based approach
Authors: Jean-Marc Daveau, Tarek Ben Ismail, Ahmed Amine Jerraya
Venue: Proceedings of the 8th international symposium on System synthesis (1995)

Abstract: Communication synthesis aims to transform a system with processes that communicate via high level primitives through channels into interconnected processes that communicate via signals and share communication control. We present a new algorithm that performs binding/allocation of communication units. This algorithm makes use of a cost function to evaluate different allocation alternatives. The proposed communication synthesis approach deals with both protocol selection and interface synthesis and is based on binding/allocation of communication units. We illustrate through an example the usefulness of the algorithm for allocating automatically different protocols within the same system.
Rendezvous Search on the Line With Distinguishable Players
Authors: Steve Alpern, Shmuel Gal
Venue: SIAM Journal on Control and Optimization (1995)

Two players are placed on the real line at a distance $d$ with a distribution $F$ known to both. Neither knows the direction of the other, nor do they have a common notion of a positive direction on the line. We seek the least expected rendezvous time $R=R\left(F\right)$ in which they can meet, given maximum speeds of one. We consider the cases where $F$ is a bounded, point, discrete, or finite mean distribution. We obtain upper bounds or exact values for $R$ and in one case an optimality condition for search strategies. A connection with Beck's linear search problem is established.
An interview with the 1986 A. M. Turing Award recipients&mdash;John E. Hopcroft and Robert E. Tarjan
Authors: Karen A. Frenkel
Venue: Communications of the ACM (1987)

In the following interview, which took place at the 1986 Fall Joint Computer Conference in Dallas, Texas, John Hopcroft and Robert Tarjan discuss their collaboration and its influence on their separate research today. They also comment on supercomputing and parallelism, particularly with regard to statements by FJCC Keynote speakers Kenneth Wilson, Nobel laureate and director of Cornell University's Supercomputer Center, and C. Gordon Bell, chief architect on the team that designed DEC's VAX and now with the National Science Foundation. Finally the Turing Award winners air their views on the direction of computer science as a whole and on funding and the Strategic Defense Initiative.
A distributed routing algorithm for mobile wireless networks
Authors: M. Scott Corson, Anthony Ephremides
Venue: Wireless Networks (1995)

We present a loop-free, distributed routing protocol for mobile packet radio networks. The protocol is intended for use in networks where the rate of topological change is not so fast as to make &ldquo;flooding&rdquo; the only possible routing method, but not so slow as to make one of the existing protocols for a nearly-static topology applicable. The routing algorithm adapts asynchronously in a distributed fashion to arbitrary changes in topology in the absence of global topological knowledge. The protocol's uniqueness stems from its ability to maintain source-initiated, loop-free multipath routing only to desired destinations with minimal overhead in a randomly varying topology. The protocol's performance, measured in terms of end-to-end packet delay and throughput, is compared with that of pure flooding and an alternative algorithm which is well-suited to the high-rate topological change environment envisioned here. For each protocol, emphasis is placed on examining how these performance measures vary as a function of the rate of topological changes, network topology, and message traffic level. The results indicate the new protocol generally outperforms the alternative protocol at all rates of change for heavy traffic conditions, whereas the opposite is true for light traffic. Both protocols significantly outperform flooding for all rates of change except at ultra-high rates where all algorithms collapse. The network topology, whether dense or sparsely connected, is not seen to be a major factor in the relative performance of the algorithms.
Declarative updates of relational databases
Authors: Weidong Chen
Venue: ACM Transactions on Database Systems (TODS) (1995)

This article presents a declarative language, called update calculus, of relational database updates. A formula in update calculus involves conditions for the current database, as well as assertions about a new database. Logical connectives and quantifiers become constructors of complex updates, offering flexible specifications of database transformations. Update calculus can express all nondeterministic database transformations that are polynomial time.For set-at-a-time evaluation of updates, we present a corresponding update algebra. Existing techniques of query processing can be incorporated into update evaluation. We show that updates in update calculus can be translated into expressions in update algebra and vice versa.
The CHI '95 doctoral consortium
Authors: Catherine Marshall
Venue: ACM SIGCHI Bulletin (1995)

For the past 10 years, SIGCHI has sponsored a Doctoral Consortium which is held at the annual CHI conference. Traditionally, the Doctoral Consortium has been a closed event in which an invited group of doctoral candidates present their research-in-progress to each other and to a faculty committee. In addition to the presentations, there are typically group exercises and discussion sessions which are designed to allow the Doctoral Consortium participants to get to know one another better, to think about their research in the larger context of the CHI field, and to become more fully integrated citizens of the CHI community. Participants in the Doctoral Consortium also are encouraged to participate in the CHI conference poster event.The CHI '95 Doctoral Consortium, held May 7-8 in Denver, Colorado, followed the traditional format described above. However, in keeping with the approach of continuous innovation and iterative design which is ingrained in the CHI conference planning process, the students and faculty who participated in this year's event also thought about ways to improve upon that format. The main opportunity we see for the future is to create more of a link between the Doctoral Consortium and the main conference. The sections below will report on both the key events of this year's Doctoral Consortium and on the ideas we have for the future.
A Numerical Method for the Incompressible Navier--Stokes Equations Based on an Approximate Projection
Authors: Ann S. Almgren, John B. Bell, William G. Szymczak
Venue: SIAM Journal on Scientific Computing (1996)

In this method we present a fractional step discretization of the time-dependent incompressible Navier--Stokes equations. The method is based on a projection formulation in which we first solve diffusion--convection equations to predict intermediate velocities, which are then projected onto the space of divergence-free vector fields. Our treatment of the diffusion--convection step uses a specialized second-order upwind method for differencing the nonlinear convective terms that provides a robust treatment of these terms at a high Reynolds number. In contrast to conventional projection-type discretizations that impose a discrete form of the divergence-free constraint, we only approximately impose the constraint; i.e., the velocity field we compute is not exactly divergence-free. The approximate projection is computed using a conventional discretization of the Laplacian and the resulting linear system is solved using conventional multigrid methods. Numerical examples are presented to validate the second-order convergence of the method for Euler, finite Reynolds number, and Stokes flow. A second example illustrating the behavior of the algorithm on an unstable shear layer is also presented.
A comprehensive estimation technique for high-level synthesis
Authors: Seong Y. Ohm, Fadi J. Kurdahi, Nikil Dutt, Min Xu
Venue: Proceedings of the 8th international symposium on System synthesis (1995)

Abstract: We present an integrated approach aimed at predicting layout area needed to implement a behavioral description for a given performance goal. Our approach is novel because: (1) it accounts for all types of RT level components (FUs, buses, registers), (2) it is highly flexible, allowing the designer to tradeoff one type of resource with another and considers dependencies between these different types, (3) it is vertically integrated to include provably accurate physical level estimators, and hence provides realistic accounting of layout effects, and (4) it uses a timing model with finer granularity, accounting for various delays in RTL datapaths. We demonstrate our technique on a variety of HLS benchmarks and show that efficient and effective design space exploration can be accomplished using this technique.
An algorithm for pronominal anaphora resolution
Authors: Shalom Lappin, Herbert J. Leass
Venue: Computational Linguistics (1994)

This paper presents an algorithm for identifying the noun phrase antecedents of third person pronouns and lexical anaphors (reflexives and reciprocals). The algorithm applies to the syntactic representations generated by McCord's Slot Grammar parser and relies on salience measures derived from syntactic structure and a simple dynamic model of attentional state. Like the parser, the algorithm is implemented in Prolog. The authors have tested it extensively on computer manual texts and conducted a blind test on manual text containing 360 pronoun occurrences. The algorithm successfully identifies the antecedent of the pronoun for 86% of these pronoun occurrences. The relative contributions of the algorithm's components to its overall success rate in this blind test are examined. Experiments were conducted with an enhancement of the algorithm that contributes statistically modelled information concerning semantic and real-world relations to the algorithm's decision procedure. Interestingly, this enhancement only marginally improves the algorithm's performance (by 2%). The algorithm is compared with other approaches to anaphora resolution that have been proposed in the literature. In particular, the search procedure of Hobbs' algorithm was implemented in the Slot Grammar framework and applied to the sentences in teh blind test set. The authors' algorithm achieves a higher rate of success (4%) than Hobbs' algorithm. The relation of the algorithm to the centering approach is discussed, as well as to models of anaphora resolution that invoke a variety of informational factors in ranking antecedent candidates.
A Remark on Minc's Maximal Eigenvector Bound for Positive Matrices
Authors: Geoff A. Latham
Venue: SIAM Journal on Matrix Analysis and Applications (1995)

A maximal eigenvector bound resembling that of Minc [ SIAM J. Math. Anal., 7 (1970), pp.~424--427] is derived for structured nonnegative matrices which, when applied to certain positive matrices, improves on the estimate derived from Minc's bound.
The Totem single-ring ordering and membership protocol
Authors: Y. Amir, L. E. Moser, P. M. Melliar-Smith, D. A. Agarwal, P. Ciarfella
Venue: ACM Transactions on Computer Systems (TOCS) (1995)

Fault-tolerant distributed systems are becoming more important, but in existing systems, maintaining the consistency of replicated data is quite expensive. The Totem single-ring protocol supports consistent concurrent operations by placing a total order on broadcast messages. This total order is derived from the sequence number in a token that circulates around a logical ring imposed on a set of processors in a broadcast domain. The protocol handles reconfiguration of the system when processors fail and restart or when the network partitions and remerges. Extended virtual synchrony ensures that processors deliver messages and configuration changes to the application in a consistent, systemwide total order. An effective flow control mechanism enables the Totem single-ring protocol to achieve message-ordering rates significantly higher than the best prior total-ordering protocols.
A Branch and Bound Incremental Conceptual Clusterer
Authors: Arthur J. Nevins
Venue: Machine Learning (1995)

A computer program is described that is capable of learning multiple concepts and their structural descriptions from observations of examples. It decomposes this conceptual clustering problem into two modules. The first module is concerned with forming a generalization from a pair of examples by extracting their common structure and calculating an information measure for each structural description. The second module, which is the subject of this paper, incrementally incorporates these generalizations into a hierarchy of concepts. This second module operates without reference to any underlying representation language and utilizes only the information measure provided by the first module, while employing a branch and bound procedure to search the hierarchy for concepts from which to form new clusters. This ability to search the hierarchy is used as the basis of a hill climbing strategy which has as its goal the avoidance of local peaks so as to reduce the sensitivity of the program to the order in which the observations are encountered.
k-Arcs, Hyperovals, Partial Flocks and Flocks
Authors: J. A. Thas
Venue: Designs, Codes and Cryptography (1996)

Some recent results on k-arcs and hyperovals of PG(2,q), on partial flocks and flocks of quadratic cones of PG(3,q), and on line spreads in PG(3,q) are surveyed. Also, there is an appendix on how to use Veronese varieties as tools in proving theorems.
Normalization in OODB design
Authors: Byung S. Lee
Venue: ACM SIGMOD Record (1995)

When we design an object-oriented database schema, we need to normalize object classes as we do for relations when designing a relational database schema. However, the normalization process for an object class cannot be the same as that of a relation, because of the distinct characteristics of an object-oriented data model such as complex attributes, collection data types, and the usage of object identifiers in place of relational key attributes. We need only one kind of dependency proposed here -- the object functional dependency -- which specifies the dependency of object attributes with respect to the object identifier. We also propose the object normal form of an object class, for which all determinants of object functional dependencies are object identifiers. There is no risk of update anomalies as long as all object classes are in the object normal form.
On Bufferless Routing of Variable Length Messages in Leveled Networks
Authors: Sandeep N. Bhatt, Gianfranco Bilardi, Geppino Pucci, Abhiram Ranade, Arnold L. Rosenberg, Eric J. Schwabe
Venue: IEEE Transactions on Computers (1996)

We study the most general communication paradigm on a multiprocessor, wherein each processor has a distinct message (of possibly distinct lengths) for each other processor. We study this paradigm, which we call chatting, on multiprocessors that do not allow messages once dispatched ever to be delayed on their routes. By insisting on oblivious routes for messages, we convert the communication problem to a pure scheduling problem. We introduce the notion of a virtual chatting schedule, and we show how efficient chatting schedules can often be produced from efficient virtual chatting schedules. We present a number of strategies for producing efficient virtual chatting schedules on a variety of network topologies.
Reducing I/O demand in video-on-demand storage servers
Authors: Leana Golubchik, John C. S. Lui, Richard Muntz
Venue: Proceedings of the 1995 ACM SIGMETRICS joint international conference on Measurement and modeling of computer systems (1995)

Recent technological advances have made multimedia on-demand services, such as home entertainment and home-shopping, important to the consumer market. One of the most challenging aspects of this type of service is providing access either instantaneously or within a small and reasonable latency upon request. In this paper, we discuss a novel approach, termed adaptive piggybacking, which can be used to provide on-demand or nearly-on-demand service and at the same time reduce the I/O demand on the multimedia storage server.
Influence of cross-interferences on blocked loops: a case study with matrix-vector multiply
Authors: Christine Fricker, Olivier Temam, William Jalby
Venue: ACM Transactions on Programming Languages and Systems (TOPLAS) (1995)

State-of-the art data locality optimizing algorithms are targeted for local memories rather than for cache memories. Recent work on cache interferences seems to indicate that these phenomena can severely affect blocked algorithms cache performance. Because of cache conflicts, it is not possible to know the precise gain brought by blocking. It is even difficult to determine for which problem sizes blocking is useful. Computing the actual optimal block size is difficult because cache conflicts are highly irregular. In this article, we illustrate the issue of precisely evaluating cross-interferences in blocked loops with blocked matrix-vector multiply. Most significant interference phenomena are captured because unusual parameters such as array base addresses are being considered. The techniques used allow us to compute the precise improvement due to blocking and the threshold value of problem parameters for which the blocked loop should be preferred. It is also possible to derive an expression of the optimal block size as a function of problem parameters. Finally, it is shown that a precise rather than an approximate evaluation of cache conflicts is sometimes necessary to obtain near-optimal performance.
Defining reference models and software architectural styles for cooperative systems
Authors: Gregory D. Abowd
Venue: ACM SIGOIS Bulletin (1995)

The emergence of software architecture as a field of study is a relatively recent phenomenon[2]. As a discipline, its goals are to better understand the high-level organization of software in terms of computational elements and the interactions between them. This proposal to attend a workshop on software architectures for cooperative systems comes from a researcher in software architecture who is only remotely aware of the specific issues in the design of cooperative systems. In this proposal I will explain what contribution can be made from someone outside of CSCW. I also expect that the critical examination of a complex domain such as cooperative systems will greatly inform my own understanding of software architecture.Within any software domain, such as CSCW, it is important to make explicit the high level design invariants of the software architecture. Such reflection leads to the definition of models or reference architectures intended to positively influence the future development of similar systems. As explained above, this process of defining a reference architecture requires expertise in the general area of software architecture as well as domain expertise. One need not look far outside the scope of CSCW to find an example of a reference architecture with profound influence on design. From the mid 1980's, many user interface management systems have based their highest level abstractions on the Seeheim model [4], with the separation implied by the API, dialogue controller and presentation. One can ask to what extent the authors of the Seeheim model anticipated the influence of their work and gave due consideration to all of the problems involved in UI design.My own interest in software architecture falls into two categories -- semi-formal, structured evaluation of architectural artifacts for non-functional qualities and formal definition of architectural patterns or styles. I will briefly decribe each.
Precise Documentation of Well-Structured Programs
Authors: David Lorge Parnas, Jan Madey, Michal Iglewski
Venue: IEEE Transactions on Software Engineering (1994)

Describes a new form of program documentation that is precise, systematic and readable. This documentation comprises a set of displays supplemented by a lexicon and an index. Each display presents a program fragment in such a way that its correctness can be examined without looking at any other display. Each display has three parts: (1) the specification of the program presented in the display, (2) the program itself, and (3) the specifications of programs invoked by this program. The displays are intended to be used by software engineers as a reference document during inspection and maintenance. This paper also introduces a specification technique that is a refinement of H.D. Mills's (1975) functional approach to program documentation and verification; programs are specified and described in tabular form.