ppxscal/embedding_network huggingface dataset:
Relaxed heaps: an alternative to Fibonacci heaps with applications to parallel computation
Authors: James R. Driscoll, Harold N. Gabow, Ruth Shrairman, Robert E. Tarjan
Venue: Communications of the ACM (1988)

The relaxed heap is a priority queue data structure that achieves the same amortized time bounds as the Fibonacci heap&mdash;a sequence of m decrease_key and n delete_min operations takes time O(m + n log n). A variant of relaxed heaps achieves similar bounds in the worst case&mdash;O(1) time for decrease_key and O(log n) for delete_min. Relaxed heaps give a processor-efficient parallel implementation of Dijkstra's shortest path algorithm, and hence other algorithms in network optimization. A relaxed heap is a type of binomial queue that allows heap order to be violated.
Negotiating IS: Observations on changes in structure from a negotiated order perspective
Authors: D. C. Gash
Venue: Proceedings of the ACM SIGCPR conference on Management of information systems personnel (1988)

A variety of current forces have created pressures for the restructuring of organizational units responsible for supporting information services. Changes in the internal structure of information systems units, however, are not always made through formal, rational, and organizationally-planned procedures, but often emerge as a result of ongoing negotiations between members of IS departments. Members of various specialty groups, such as data processing, office automation, and information center staffs, may in fact engage in substantial political maneuvering and jockeying for position as subunit roles become redefined and resources are reallocated. This paper proposes that it may be fruitful to study the process through which internal structures of information systems or services units are modified from perspectives of organizational negotiation, encompassing notions of political strategies and alliances, segmentation and intersection of subunits, and the creation of negotiable issues. The negotiated order perspective, borrowed from sociology, provides useful ontological and methodological frameworks for this endeavor. Data from larger case analyses are presented to illustrate instances of renegotiation of role relationships among specialist groups, who attempt to create distinctive competencies to ensure their survival and guard their domains.
Maintaining availability in partitioned replicated databases
Authors: A. El Abbadi, S. Toueg
Venue: ACM Transactions on Database Systems (TODS) (1989)

In a replicated database, a data item may have copies residing on several sites. A replica control protocol is necessary to ensure that data items with several copies behave as if they consist of a single copy, as far as users can tell. We describe a new replica control protocol that allows the accessing of data in spite of site failures and network partitioning. This protocol provides the database designer with a large degree of flexibility in deciding the degree of data availability, as well as the cost of accessing data.
Using simulation to explore potential improvements in an existing automated assembly system
Authors: C. J. Erickson
Venue: Proceedings of the 21st conference on Winter simulation (1989)

A newly-installed, nonsynchronous, palletized assembly system was analyzed extensively, using simulation and automatically-collected machine fault data, to examine the viability of proposed improvements and to identify additional areas of opportunity for improvement.The completely serial line, with very limited buffering, performed at a fraction of its specified throughput when first installed. Simulation, using the SIMAN simulation language (Systems Modeling Corp., Sewickley, Pennsylvania), was first employed to determine the effects of certain proposed changes. Thorough model validation and accurate analysis were facilitated through the use of computer-collected machine fault data. By fitting probability distributions to the data, the data could be easily manipulated for experimentation.When the simulation showed that the proposed changes would fail to produce the required output, the simulation study continued, with the objectives of isolating the areas of greatest opportunity and steering redesign efforts in the direction of greatest return.And finally during the course of the study, the simulation model came to be relied on as an operational tool, used to understand the implications of, and requirements for, short-term changes in operating patterns and production requirements.This paper will explore the methodology employed, including data preparation, and the conclusions reached.
On the Complexity of Single Fault Set Diagnosability and Diagnosis Problems
Authors: A. K. Somani, V. K. Agarwal, D. Avis
Venue: IEEE Transactions on Computers (1989)

The complexity of the single-fault (SF) set diagnosability and SF-diagnosis problems under the symmetric invalidation models is discussed. It is shown that the SF-diagnosis problem under both these models is co-NP-complete and the SF-diagnosability problem is also co-NP-complete under the asymmetric invalidation model. The SF-diagnosability problem is also studied under the symmetric-invalidation model and a polynomial time-complexity algorithm is presented. These results are in contrast with the corresponding t-diagnosability and t-diagnosis problems, which are known to have polynomial time-complexity algorithms.
Contextualism as a world view for the reformation of meetings
Authors: John Whiteside, Dennis Wixon
Venue: Proceedings of the 1988 ACM conference on Computer-supported cooperative work (1988)

The foundations for research and action in the area of group work are examined. Four alternative &ldquo;world views&rdquo; are presented. One of these, contextualism, is discussed in depth. Its methodological consequences for research and implications for reform of group meetings are explored.
Multiprocessor Smalltalk: a case study of a multiprocessor-based programming environment
Authors: J. Pallas, D. Ungar
Venue: Proceedings of the ACM SIGPLAN 1988 conference on Programming Language design and Implementation (1988)

We have adapted an interactive programming system (Smalltalk) to a multiprocessor (the Firefly). The task was not as difficult as might be expected, thanks to the application of three basic strategies: serialization, replication, and reorganization. Serialization of access to resources disallows concurrent access. Replication provides multiple instances of resources when they cannot or should not be serialized. Reorganization allows us to restructure part of the system when the other two strategies cannot be applied. We serialized I/O, memory allocation, garbage collection, and scheduling, we replicated the interpreter process, software caches, and a free-list, and we reorganized portions of the scheduling system to deal with some deep-seated assumptions. Our changes yielded a fairly low static overhead. We attribute our success to the choice of a small, flexible operating system, a set of constraints which simplified the problem, and the versality of the three strategies for dealing with concurrency. The current system has a moderate amount of overhead when parallelism is being used&mdash;25% to 65%. It is acceptable, but we believe it can be improved.
The Optimal Control of Heterogeneous Queueing Systems: A Paradigm for Load-Sharing and Routing
Authors: S. Shenker, A. Weinrib
Venue: IEEE Transactions on Computers (1989)

The essence of the basic control decisions implicit in load-sharing and routing algorithms is captured in a simple model of heterogeneous queue control. The authors solve for the optimal control policy and investigate the performance of previously proposed policies in a tractable limit of this model. Using their understanding of this solvable limit, the authors propose heuristic policies for the general model. Simulation data for these policies suggest that they perform well over a wide range of system parameters.
The importance of direct dependences for automatic parallelization
Authors: T. Brandes
Venue: Proceedings of the 2nd international conference on Supercomputing (1988)

For the automatic vectorization and concurrentization of Fortran- or Pascal-like programs the dependencies have to be determined and to be observed with every transformation. The full dependence relation is a transitive relation. Direct dependencies are defined as such dependencies that cannot be represented transitively by other dependencies. It will be shown that information about the direct dependencies is useful for renaming and expansion of structured variables. Indeed, many other transformations that are applied for automatic parallelization and program restructuring can be extended in this way. Though some extensions have already been made by other authors, with the concept of direct dependencies a uniform theoretical background for all these transformations is given. As most known dependence tests do not give information about direct dependencies, it is also explained how to determine direct dependencies.
Distributed form management
Authors: Heikki Hämmäinen, Eero Eloranta, Jari Alasuvanto
Venue: ACM Transactions on Information Systems (TOIS) (1990)

An open architecture for distributed form management is described. The model employs object-orientation in describing organizational units as well as individual users as entities with uniform external interfaces. Each entity is represented by an autonomous user agent which operates on local and migrating forms. The form concept encapsulates data, layout, and rules into a unified object which is the basic unit of presentation, processing, storage, and communication. All functionality of the system appears in rules of form classes and all data in instances of these form classes. This approach applies the techniques of computer supported cooperative work to provide a flexible mechanism for interpersonal, intraoffice, and interoffice procedures. The main challenge is to organize the collaboration without affecting the autonomy of individual user agents. In this respect, the contribution of the model is the mechanism for form migration. The dynamic integration of forms into different agents is solved with the coordinated interchange of form classes. A specific inheritance scheme provides the desired flexibility by separating the interrelated private and public form operations within each agent. The paper first describes the architecture by starting from a single agent and moving progressively towards a set of cooperating agents. Then an agent implementation called PAGES is described, experiences reported, and the open issues discussed. A typical distributed ordering procedure is used as an example throughout the text.
An adaptive mesh-moving and local refinement method for time-dependent partial differential equations
Authors: David C. Arney, Joseph E. Flaherty
Venue: ACM Transactions on Mathematical Software (TOMS) (1990)

We discuss mesh-moving, static mesh-regeneration, and local mesh-refinement algorithms that can be used with a finite difference or finite element scheme to solve initial-boundary value problems for vector systems of time-dependent partial differential equations in two space dimensions and time. A coarse base mesh of quadrilateral cells is moved by an algebraic mesh-movement function so as to follow and isolate spatially distinct phenomena. The local mesh-refinement method recursively divides the time step and spatial cells of the moving base mesh in regions where error indicators are high until a prescribed tolerance is satisfied. The static mesh-regeneration procedure is used to create a new base mesh when the existing one becomes too distorted. The adaptive methods have been combined with a MacCormack finite difference scheme for hyperbolic systems and an error indicator based upon estimates of the local discretization error obtained by Richardson extrapolation. Results are presented for several computational examples.
Exception Handling in Robotics
Authors: I. J. Cox, N. H. Gehani
Venue: Computer (1989)

The construction of robust and reliable robot systems able to handle errors arising from abnormal operating conditions is addressed. It is assumed that the robot program is logically correct but fails due to hardware or external state errors. The error-handling technique called exception handling is treated. The type of errors that can occur in a robot system and their error-handling requirements are described, and approaches to error handling and recovery are reviewed. Exception-handling facilities in Ada and AML/X are mentioned, and Exceptional C, the language chosen for exposition, is described. The use of exception-handling facilities is illustrated with two examples.
A deterministic approach to adjacency testing for delay faults
Authors: C. T. Glover, M. R. Mercer
Venue: Proceedings of the 26th ACM/IEEE Design Automation Conference (1989)

Adjacency testing for delay faults is examined in both theory and implementation. We shall show that the necessary and sufficient conditions for adjacency testability yield an efficient method of robust delay test generation. Empirical results (including several different cost measurements) are presented which demonstrate that our technique: (1) achieves high fault coverages under both the robust and nonrobust delay fault models and (2) is cost effective.
Triangulating a non-convex polytype
Authors: B. Chazelle, L. Palios
Venue: Proceedings of the fifth annual symposium on Computational geometry (1989)

This paper is concerned with the problem of partitioning a three-dimensional polytope into a small number of elementary convex parts. The need for such decompositions arises in tool design, computer-aided manufacturing, finite-element methods, and robotics. Our main result is an algorithm for decomposing a polytope with n vertices and r reflex edges into &Ogr;(n+r2) tetrahedra. This bound is asymptotically tight in the worst case. The algorithm is simple and practical. Its running time is &Ogr;(nr + r2 log r).
From network to artwork
Authors: L. Stok, G. P. Koster
Venue: Proceedings of the 26th ACM/IEEE Design Automation Conference (1989)

In this paper a computer program for the construction of a schematic diagram (the artwork) from a net list (the network) is presented. The network-to-artwork generator is composed of a separate placement (Pablo) and a routing part (Eureka). For both parts algorithms, following guidelines traditionally used in manual drawing of schematic diagrams, are used. Several examples are shown and some data on the speed of the algorithms are listed.
Accurate Low-Cost Methods for Performance Evaluation of Cache Memory Systems
Authors: S. Laha, J. H. Patel, R. K. Iyer
Venue: IEEE Transactions on Computers (1988)

Trace-driven simulation is a simple way of evaluating cache memory systems with varying hardware parameters. But to evaluate realistic workloads, simulating even a few million addresses is not adequate and such large scale simulation is impractical from the consideration of space and time requirements. New methods of simulation based on statistical techniques are proposed for decreasing the need for large trace measurements and for predicting true program behavior. In the method, sampling techniques are applied while collecting the address trace from a workload. This drastically reduces the space and time needed to collect the trace. New simulation techniques are developed to use the sample data not only to predict the mean miss rate of the cache, but also to provide an empirical estimate of its actual distribution. Finally, a new concept of primed cache is introduced to simulate large caches by the sampling-based method.
Quadtree Traversal Algorithms for Pointer-Based and Depth-First Representations
Authors: D. R. Fuhrmann
Venue: IEEE Transactions on Pattern Analysis and Machine Intelligence (1988)

Simple top-down pointer-based quadtree traversal algorithms for four-neighbor traversal, eight-neighbor traversal, and connected-component labeling are proposed. It is shown that for this class of algorithms there exist efficient pointer-based representations that can require as little as 2N bytes, where N is total number of nodes in the tree. The algorithms can also be implemented using a depth-first quadtree representation, at the cost of additional nonrecursive walks over the data structure to locate the arbitrary sons of interior nodes.
Modeling Defect Spatial Distribution
Authors: F. J. Meyer, D. K. Pradhan
Venue: IEEE Transactions on Computers (1989)

The center-satellite model for describing the distribution of defects on wafers is discussed. This model assigns each defect to a cluster. The distribution of cluster centers on a wafer is one basic component of the model. The other basic component is the distribution of defects (satellites) about the cluster centers. Physical justification for the model is provided. Current yield models are quite accurate for VLSI designs without redundancy. A more flexible model is needed to evaluate the redundancy techniques that will be an integral part of WSI. An example is provided to demonstrate the type of analysis necessary to analyze fault-tolerant designs using the model. Empirical research needed to obtain parameters for the model is commented on, as is the need to reevaluate prior empirical research in which assumptions were made that are relaxed by the center-satellite model.
On Designing and Reconfiguring k-Fault-Tolerant Tree Architectures
Authors: Shantanu Dutt, J. P. Hayes
Venue: IEEE Transactions on Computers (1990)

A general approach to designing tree structured multiprocessors with optimal or near-optimal fault tolerance properties is developed. A multiprocessor architecture with a static interconnection network is represented by a graph whose nodes are processors and whose edges are interprocessor communication links. The design of k-fault-tolerant (FT) trees for arbitrary k is considered, with the primary goal of minimizing the number of spare nodes and edges. Also presented are strategies for reconfiguring a k-FT supergraph of a tree T around faults to obtain a fault-free tree isomorphic to T. A systematic methodology is presented for designing k-FT nonhomogeneous symmetry d-ary trees based on a concept termed node covering. The designs are shown to be optimal when k>d and near-optimal otherwise. It is also shown that these k-FT designs can be implemented efficiently using switches to share redundant links.
Modeling the semantics of smalltalk-80 with Petri nets
Authors: D. N. Christodoulakis
Venue: Proceedings of the 1988 ACM SIGPLAN workshop on Object-based concurrent programming (1988)

Over the last ten years, as the use of concurrent programming languages increased with a corresponding increase in the effort spent for building parallel machines, the importance of Petri nets grow. During this period Petri nets have been widely used for the specification, design and verification of nonsequential systems, and lots of effort has been spent for the development of software tools supporting Petri nets. Examples include the GRASPIN software engineering environment which supports Petri nets for graphical representation and formal specification of nonsequential systems [5], different net editors, etc.Since about one year we have started to use Petri nets in order to describe the semantics of object oriented languages (O-O for short), and in particular as a semantic model of the most representative O-O language, namely Smalltalk-80 [1]. Recent attempts towards possible extensions of Smalltalk-80 with concurrency have shown that semantic models of Smalltalk-80 like the above presented here, are not only useful for compiler writers, but their aid also towards identification and control of concurrency in the existing Smalltalk-80 systems; to specify possible computational models for a "concurrent" Smalltalk-80; and to indicate a possible semantic model for O-O distributed databases. Finally, since Petri nets provide the necessary theory for verification purposes, such a semantic model can be utilised for the verification of Smalltalk-80 programs as well.Main objective of this paper is to give an outline of the semantic function, described in next section. Subsequentialy, we discuss very short how the semantic function can be used for concurrency identiffication and control, and program verification.For the ongoing discussion we suppose that the reader is familiar with basic notions from Petri net theory [2, 3, 4].
Legally speaking: should program algorithms be patented
Authors: Pamela Samuelson
Venue: Communications of the ACM (1990)

In the Legally Speaking column last May [6], we reported on a survey conducted at last year's ACM-sponsored Conference on Computer-Human Interaction in Austin, Tex. Among the issues about which the survey inquired was whether the respondents thought patent protection should be available for various aspects of computer programs. The 667 respondents overwhelmingly supported copyright protection for source and object code although they strongly opposed copyright or patent protection for &ldquo;look and feel&rdquo; and most other aspects of programs. Algorithms were the only aspect of programs for which there was more than a small minority of support for patent protection. Nevertheless, more than half of the respondents I opposed either copyright or patent protection for algorithms. However, nearly 40 percent of the respondents regarded algorithms as appropriately protected by patents. (Another eight percent would have copyright law protect them.)We should not be surprised that these survey findings reflect division within the technical community about patents as a form of protection for this important kind of computer program innovation. A number of prominent computer professionals who have written or spoken about patent protection for algorithms or other innovative aspects of programs have either opposed or expressed reservations about this form of protection for software [2, 4, 5].This division of opinion, of course, has not stopped many firms and some individuals from seeking patent protection for algorithms or other software innovations [8]. Although the Refac Technology patent infringement lawsuit against Lotus and other spreadsheet producers may be in some jeopardy, it and other software patent lawsuits have increased awareness of the new availability of software patents. This situation, in turn, has generated some heated discussion over whether this form of legal protection will be in the industry's (and society's) long-term best interests.The aim of this column is to acquaint readers with the legal debate on patent protection for algorithms and other computer program innovations, an issue which seems to be as divisive among lawyers as those in the computer field. [3, 9].
AUTO STAR&mdash;a software development system
Authors: M. Y. Zhu
Venue: ACM SIGPLAN Notices (1989)

This report summarizes the AUTO STAR project. AUTO STAR is a software development system which accepts the algebraic specification of a given software system and produces an Ada implementation of that system."In many applications, algorithms play almost no role, and certainly present almost no problem. The real problem is the mass of detailed requirements; and the only solution is the discovery or invention of general rules and abstractions which cover the many thousands of cases with as few exceptions as possible. This is what makes a program short, simple, and reliable, as compared with one which attempts to treat every case as a special case. But the discovery of such general rules and classifications demands at least the same inventive genius as that of a classificatory biologist, or the grammarian of a natural language, or even a theoretical physicist".