ppxscal/embedding_network huggingface dataset:
APLELEGANCE&mdash;the art of staying within one's depth
Authors: Norman Thomson
Venue: ACM SIGAPL APL Quote Quad (1990)

A barrier to the successful use of APL2 is the need to control the changes of depth which arise from using the operator each with functions such as enclose and disclose. The &ldquo;spilt pepper&rdquo; effect following a deluge of &ldquo;each&rdquo;'s can be just as damaging as the chains of left-brackets, and of quotes with their accompanying @@@@'s which are the sign of an ISO APL programmer losing his or her mental grip. The temptations of a fast interactive system as a substitute for thought are considerable, and should be resisted. To this end there are places in which informal perceptions of how APL2 functions and operators work can be more valuable than the formal descriptions given in the manuals, and this paper focuses on some points where such pedagogical issues arise. It consists of 4 sections, each with rules or precepts for the disciplined and controlled use of nestedness.
A high-speed hardware unit for a subset of logic resolution
Authors: D. Wong
Venue: Proceedings of the 21st annual workshop on Microprogramming and microarchitecture (1988)

High-speed engines for logic programming have been the target of much recent research. Here, we present a high-level hardware design and its custom data formats for directly performing a subset of logic resolution. This design uses parallelism in unifying arguments and substituting variable bindings which is distinct from the widely discussed OR and AND parallelism.
An algebra for structured office documents
Authors: Ralf Hartmut Güting, Roberto Zicari, David M. Choy
Venue: ACM Transactions on Information Systems (TOIS) (1989)

We describe a data model for structured office information objects, which we generically call &ldquo;documents,&rdquo; and a practically useful algebraic language for the retrieval and manipulation of such objects. Documents are viewed as hierarchical structures; their layout (presentation) aspect is to be treated separately. The syntax and semantics of the language are defined precisely in terms of the formal model, an extended relational algebra. The proposed approach has several new features, some of which are particularly useful for the management of office information. The data model is based on nested sequences of tuples rather than nested relations. Therefore, sorting and sequence operations and the explicit handling of duplicates can be described by the model. Furthermore, this is the first model based on a many-sorted instead of a one-sorted algebra, which means that atomic data values as well as nested structures are objects of the algebra. As a consequence, arithmetic operations, aggregate functions, and so forth can be treated inside the model and need not be introduced as query language extensions to the model. Many-sorted algebra also allows arbitrary algebra expressions (with Boolean result) to be admitted as selection or join conditions and the results of arbitrary expressions to be embedded into tuples. In contrast to other formal models, this algebra can be used directly as a rich query language for office documents with precisely defined semantics.
Choosing between methods: analysing the user's decision space in terms of schemas and linear models
Authors: R. M. Young, A. MacLean
Venue: Proceedings of the SIGCHI conference on Human factors in computing systems (1988)

We offer an account of how users choose between alternative methods which take different times to accomplish the same task. Users offered a choice between two methods do not necessarily pick the faster. We argue that users reduce the complexity of the decision space by applying a 'simple compensation schema' acquired from everyday experience. Linear models of performance time enable us to predict how users will view the situation in terms of this schema, and how accurate assessment of the optimal choices within the schema-based assimilations can result in an apparent bias in favour of one method.
Structured expert system design
Authors: D. Smellie, F. Evans
Venue: ACM SIGAPL APL Quote Quad (1990)

An ordered approach to expert system design is offered by a shell in which modularization of all data and inferential structures is a feature. The system is completely menu driven, and all APL code is transparent. The user can move easily between design mode and run mode at any time, without any loss of current data. Complex systems can be systematically developed from constituent subsystems. Uncertainty is accommodated by the use of fuzzy logic. All aspects of the expert system are editable at all times.
An adaptive dependency source model for data compression
Authors: David M. Abrahamson
Venue: Communications of the ACM (1989)

By dynamically recoding data on the basis of current intercharacter probabilities, the entropy of encoded messages can be significantly reduced.
Pitfalls in the design of distributed routing algorithms
Authors: R. Perlman, G. Varghese
Venue: Symposium proceedings on Communications architectures and protocols (1988)

The bridge algorithm adopted by the IEEE 802.1 committee for interconnecting 802 LANs requires the topology of the Extended LAN to be a Spanning Tree. A distributed algorithm to compute a spanning tree dynamically has already been published [1], and adopted by the IEEE 802.1 committee [2]. In this paper, however, we describe an alternative distributed algorithm to compute a spanning tree. This algorithm, variants of which have been implemented, initially appears simpler than the IEEE 802.1 algorithm; we show, however, that it has subtle failure modes that makes it unattractive in practice. We also show that some failure modes of the Spanning Tree Algorithm introduced in this paper are characteristic of a broader class of distributed graph algorithms. Such algorithms potentially examine all possible path combinations between a source and destination in a graph. Thus, they suffer from exponential message overhead in topologies that have an exponential number of paths between source and destination. Attempts to fix this problem lead to extra complexity (in terms of CPU, bandwidth, memory) when compared to other algorithms. We briefly describe a second example belonging to this class, and propose that designers avoid such algorithms if restricting the topology or scale of the network is unacceptable.
An open enviornment for building parallel programming systems
Authors: Brian N. Bershad, Edward D. Lazowska, Henry M. Levy, David B. Wagner
Venue: Proceedings of the ACM/SIGPLAN conference on Parallel programming: experience with applications, languages and systems (1988)

PRESTO is a set of tools for building parallel programming systems on shared-memory multiprocessors. PRESTO's goal is to provide a framework within which one can easily build efficient support for any of a wide variety of &ldquo;models&rdquo; of parallel programming. PRESTO is designed for easy modification and extension, not only at the level of the primitives and structures made available for the application programmer's use, but also at the level of the run-time kernel that supports parallel applications. PRESTO is implemented in the object-oriented language C++ on a Sequent Balance 21000 and has been used in a number of applications that are described in this paper.
A logic of authentication
Authors: Michael Burrows, Martin Abadi, Roger Needham
Venue: ACM Transactions on Computer Systems (TOCS) (1990)

Authentication protocols are the basis of security in many distributed systems, and it is therefore essential to ensure that these protocols function correctly. Unfortunately, their design has been extremely error prone. Most of the protocols found in the literature contain redundancies or security flaws. A simple logic has allowed us to describe the beliefs of trustworthy parties involved in authentication protocols and the evolution of these beliefs as a consequence of communication. We have been able to explain a variety of authentication protocols formally, to discover subtleties and errors in them, and to suggest improvements. In this paper we present the logic and then give the results of our analysis of four published protocols, chosen either because of their practical importance or because they serve to illustrate our method.
FIDE: a REDUCE package for automation of FInite difference method for solving pDE
Authors: R. Liska, L. Drsda
Venue: Proceedings of the international symposium on Symbolic and algebraic computation (1990)

The article deals with automation of the process of numerical solving of partial differential equations systems (PDES) by means of computer algebra. For solving PDES the finite difference method is applied. The computer algebra system REDUCE and the numerical programming language FORTRAN are used in the methodology presented, its main aim being to speed up the process of preparing numerical programs for solving PDES. Quite often, especially for complicated systems, this process is a tedious and time consuming task. In the process several stages can be found in which computer algebra can be used for performing routine analytical calculations, namely: transformation of differential equations into different coordinate systems, discretization of differential equations, analysis of difference schemes, and generation of numerical programs. The FIDE package consists of the following modules that have been built, tested, and documented: EXPRESS for transforming PDES into any orthogonal coordinate system. IIMET for discretization of PDES by integro-interpolation method. APPROX for determining the order of approximation of difference schemes. CHARPOL for calculating the amplification matrix and characteristic polynomial of difference schemes, which are needed in the Fourier stability analysis. HURWP for locating polynomial roots necessary in verifying the von Neumann stability condition. LINBAND for generating the block of FORTRAN code, which solves a system of linear algebraic equations with band matrix appearing frequently in difference schemes. The FIDE package is applied to two physical problems. The first one is the nonlinear Schr&ouml;dinger equation, which describes several physical phenomena, e.g. the Langmuir waves in plasma. The second one is the Fokker-Planck equation in diffusive approximation, which is used to describe the kinetics of electrons in plasma, including interactions of electrons with a laser beam through inverse bremsstrahlung. The numerical programs have been tested and compared with similar calculations published so far.
Using Dynamic Programming for Solving Variational Problems in Vision
Authors: A. A. Amini, T. E. Weymouth, R. C. Jain
Venue: IEEE Transactions on Pattern Analysis and Machine Intelligence (1990)

Early image understanding seeks to derive analytic representations from image intensities. The authors present steps towards this goal by considering the inference of surfaces from three-dimensional images. Only smooth surfaces are considered and the focus is on the coupled problems of inferring the trace points (the points through which the surface passes) and estimating the associated differential structure given by the principal curvature and direction fields over the estimated smooth surfaces. Computation of these fields is based on determining an atlas of local charts or parameterizations at estimated surface points. Algorithm robustness and the stability of results are essential for analyzing real images; to this end, the authors present a functional minimization algorithm utilizing overlapping local charts to refine surface points and curvature estimates, and develop an implementation as an iterative constraint satisfaction procedure based on local surface smoothness properties. Examples of the recovery of local structure are presented for synthetic images degraded by noise and for clinical magnetic resonance images.
A cache coherence approach for large multiprocessor systems
Authors: J. K. Archibald
Venue: Proceedings of the 2nd international conference on Supercomputing (1988)

This paper explores the architecture of high-performance large scale multiprocessors using private caches for each processor. The caches reduce the average memory access time, but they also result in the well known cache coherence problem. Multiple copies of each memory location are allowed to exist but they must be kept consistent with each other. In this paper, we present a solution to the cache coherence problem specifically for shared bus multiprocessors that adapts dynamically to the reference pattern. Simulation results are presented that demonstrate the high level of performance relative to other protocols particularly during intervals with high levels of sharing. The paper then presents a coherence solution for large multiprocessor systems organized around a hierarchy of buses. One of the first solutions of this kind, the hierarchical protocol is an extension of the adaptive shared bus approach described in this paper.
Higher order attribute grammars
Authors: H. H. Vogt, S. D. Swierstra, M. F. Kuiper
Venue: Proceedings of the ACM SIGPLAN 1989 Conference on Programming language design and implementation (1989)

A new kind of attribute grammars, called higher order attribute grammars, is defined. In higher order attribute grammars the structure tree can be expanded as a result of attribute computation. A structure tree may be stored in an attribute. The term higher order is used because of the analogy with higher order functions, where a function can be the result or parameter of another function. A relatively simple method, using OAGs, is described to derive an evaluation order on the defining attribute occurrences which comprises all possible direct and indirect attribute dependencies. As in OAGs, visit-sequences are computed from which an efficient algorithm for attribute evaluation can be derived.
A view matcher for learning Smalltalk
Authors: John M. Carroll, Janice A. Singer, Rachel K. E. Bellamy, Sherman R. Alpert
Venue: Proceedings of the SIGCHI conference on Human factors in computing systems: Empowering people (1990)

The View Matcher is a structured browser for Smalltalk/V. It presents a set of integrated and dynamic views of a running application, intended to coordinate and rationalize a programmer's early understanding of Smalltalk and its environment. We describe the system through two user scenarios involving exploration of the model-view-controller paradigm.
Approximate Analysis of Single and Multiple Ring Networks
Authors: Laxmi N. Bhuyan, Dipak Ghosal, Qing Yang
Venue: IEEE Transactions on Computers (1989)

Asynchronous packet-switched interconnection networks with decentralized control are very appropriate for multiprocessing and data-flow architectures. The authors present performance models of single- and multiple-ring networks based on token-ring, slotted-ring, and register-insertion-ring protocols. The multiple ring networks have the advantage of being reliable, expandable, and cost effective. An approximate and uniform analysis, based on the gate M/G/1 queuing model, has been developed to evaluate the performance of both existing single-ring networks and the proposed multiple-ring networks. Approximations are good for low and medium load. The analyses are based on symmetric ring structure with nonexhaustive service policy and infinite queue length at each station. They essentially involve modeling of queues with single- and multiple-walking servers. The results obtained from the analytical models are compared to those obtained from simulation.
Establishing Ada repositories for reuse
Authors: B. Kitaoka
Venue: Proceedings of the conference on Tri-Ada '89: Ada technology in context: application, development, and deployment (1989)

Ideally, a software reuse repository is a robust, dynamic interchange among software designers. This constantly growing and improving resource assists with&mdash;and influences&mdash;the creation of quality, cost-efficient software systems. Setting this process in motion and sustaining its momentum calls for many of the approaches used in system design and development. Its stable yet flexible structure anticipates the technical requirements of present and future users. But the successful repository reflects a broader perspective, a long-term commitment, and attention to a number of other technical and nontechnical issues. It must maintain components beyond the development cycle of supported projects. It must have a capability for continuity. And most important, it must be a value-added, self-sustaining resource. SAIC's experience with three significant Ada reuse repositories has given us insights into a number of relevant issues and challenges, and has shown us the intricate relationships that link the technical, economic, human and other contributing factors affecting repository development and operation. These three repositories&mdash;STARS, AFLC and SAIC Corporate&mdash;support software reuse and a number of additional specialized requirements. The Software Technology for Adaptable, Reliable Systems (STARS) repository serves as a testbed for repository and reuse technology. Additional requirements include a means for sharing program-related information such as meeting minutes, presentations, Contract Data Requirements Lists (CDRL) items and peer reviews. The Air Force Logistics Command (AFLC) Ada Software Repository has been established to provide a means of sharing domain-specific information among software development and maintenance personnel at the air logistics commands. With the wide variety of domain-specific software developed at SAIC, the company has decided to institute a reuse program to enhance the quality of this domain software and to encourage cross-domain reuse. Common objectives for these projects include long-term continuity and self-sustaining capabilities. Our experience to date has shown that these objectives impact four principal areas of the repository system: content acquisition/update technical information services operational support facilities
Performance of Fault-Tolerant Diagnostics in the Hypercube Systems
Authors: A. Ghafoor, P. Solé
Venue: IEEE Transactions on Computers (1989)

The concept of fault-tolerant self-diagnostics is introduced for distributed systems, and it is shown that there exists a performance tradeoff between the complexity of a self-diagnostic algorithm and the level of fault tolerance inherited by the algorithm. Hypercube systems are selected, and it is shown that designing an optimal algorithm for such systems has an equivalent coding theory formulation which belongs to the case of NP-hard problems. An efficient diagnostic scheme is proposed for these systems, and the performance tradeoff of the proposed algorithm, which is based on a combinatorial structure called the Hadamard matrix, is studied. The tradeoff between the fault tolerance and traffic complexity of the proposed diagnostic algorithm for hypercubes of small size is evaluated. An interesting compromise is exhibited for the hypercube with an arbitrary size.
Automatic binding time analysis for a typed &lgr;-calculus
Authors: F. Nielson
Venue: Proceedings of the 15th ACM SIGPLAN-SIGACT symposium on Principles of programming languages (1988)

For a typed &lgr;-calculus we develop an algorithm that, given some partial information about what must happen at run-time, will work out what actually can be computed at compile-time and what must be deferred to run-time.
Comparative Analysis of Different Implementations of Multiple-Input Signature Analyzers
Authors: P. C. Maxwell
Venue: IEEE Transactions on Computers (1988)

Signature analysis is an accepted method of obtaining data compression for built-in testing applications. The author deals with a unified approach to the analysis of multiple-input signature analyzers by considering them as finite state switching circuits. This approach is used to investigate and compare different implementations, and it is shown that there is a large range of alternatives to achieve a given characteristic polynomial. Particular emphasis is placed on the two most common implementations. It is shown that both perform polynomial division, with each input of one circuit being equivalent to a combination of inputs of the other. The approach also gives a method of expressing aliasing patterns for both implementations, which leads to a study of the differences with regard to certain error detection capabilities.
On global wire ordering for macro-cell routing
Authors: P. Groenveld
Venue: Proceedings of the 26th ACM/IEEE Design Automation Conference (1989)

In an automatic routing system for macro-cell layout the wiring area is decomposed into a number of smaller regions. These regions are routed separately by a detailed router such as a channel router or a switch-box router. The position of the pins at the junction between two adjacent regions is usually determined by the detailed router. The locality of this 'bottom-up' ordering disregards the global topologies of the nets which usually span several routing regions. This may result in twisted wires, unnecessary vias and waste of area. An algorithm to prevent twisted wires during detailed routing is presented. A consistent order is determined for the junction pins which ensures that no unnecessary wire twisting is introduced. If wires have to cross their intersection will preferably be placed in such a position that the chip area is least affected.
Augmenting linear control variates using transformations
Authors: J. J. Swain
Venue: Proceedings of the 21st conference on Winter simulation (1989)

Linear control variates provide a convenient means for variance reduction in a wide variety of simulation and Monte Carlo sampling problems. The effectiveness of control variates can often be improved using appropriate transformations which increase the correlation between the primary variate and the transformed control variate. Possible transformations include polynomials, the Box-Cox family of power transformations, and the inverse-normal probability transformation. Here we consider generalized transformations using cubic splines which provide a virtually unrestricted source of transformations. To illustrate the transformation methodology, a nonlinear regression problem is used. In the illustration, the transformed control is compared to the control when estimating the mean of the sampling distribution of the estimated parameters.
An efficient output-sensitive hidden surface removal algorithm and its parallelization
Authors: J. H. Reif, S. Sen
Venue: Proceedings of the fourth annual symposium on Computational geometry (1988)

In this paper we present an algorithm for hidden surface removal for a class of polyhedral surfaces which have a property that they can be ordered relatively quickly like the terrain maps. A distinguishing feature of this algorithm is that its running time is sensitive to the actual size of the visible image rather than the total number of intersections in the image plane which can be much larger than the visible image. The time complexity of this algorithm is &Ogr;((k +n)lognloglogn) where n and k are respectively the input and the output sizes. Thus, in a significant number of situations this will be faster than the worst case optimal algorithms which have running time &OHgr;(n2) irrespective of the output size (where as the output size k is &Ogr;(n2) only in the worst case). We also present a parallel algorithm based on a similar approach which runs in time &Ogr;(log4(n+k)) using &Ogr;((n + k)/log(n+k)) processors in a CREW PRAM model. All our bounds are obtained using ammortized analysis.
Design of Fiducials for Accurate Registration Using Machine Vision
Authors: C. B. Bose, I. Amir
Venue: IEEE Transactions on Pattern Analysis and Machine Intelligence (1990)

The effect of the shape and size of a standard feature (fiducial) on the positional accuracy of the centroid in machine-vision applications is studied. It is shown that a circular fiducial provides superior subpixel registration accuracy among the fiducial shapes typically used today.