ppxscal/embedding_network huggingface dataset:
Slow shadowing and macrodiversity in the capture-division packet access (CDPA)
Authors: Flaminio Borgonovo, Michele Zorzi, Luigi Fratta
Venue: Wireless Networks (1997)

Recently, a new method for achieving spectrum reuse in cellular systems, called Capture-Division Packet Access (CDPA), has been introduced. The method uses a single frequency in all cells, and exploits packet switching and packet retransmission as a means to overcome destructive cochannel interference. As the CDPA key factor is packet retransmission, it is also very effective in fighting lognormal shadowing attenuation as long as this attenuation can be considered independent from slot to slot. In this paper we analyze CDPA in presence of &ldquo;slow shadowing&rdquo;, to account for situations in which obstacles obscure the receiver for several transmission periods. The results show a severe throughput impairment with respect to the &ldquo;fast shadowing&rdquo; model. A variation of CDPA, Macrodiversity CDPA, that uses three corner fed antennas and three packet receivers is analyzed. The numerical results show that M-CDPA is more efficient than CDPA and that it is only slightly affected by both fast and slow shadowing. To further investigate its robustness, a non-lognormal slow shadowing model, the hard shadowing model, is also analyzed.
A multidimensional study on the feasibility of parallel switch-level circuit simulation
Authors: Yu-an Chen, Vikas Jha, Rajive Bagrodia
Venue: ACM SIGSIM Simulation Digest (1997)

This paper presents the results of an experimental study to evaluate the effectiveness of multiple synchronization protocols and partitioning algorithms in reducing the execution time of switch-level models of VLSI circuits. Specific contributions of this paper include: (i) parallelizing an existing switch-level simulator such that the model can be executed using conservative and optimistic simulation protocols with minor changes, (ii) evaluating effectiveness of several partitioning algorithms for parallel simulation, and (iii) demonstrating speedups with both conservative and optimistic simulation protocols for seven circuits, ranging in size from 3K transistors to about 87K transistors.
Adding Support for Persistence to CLOS via Its Metaobject Protocol
Authors: Arthur H. Lee, Joseph L. Zachary
Venue: Lisp and Symbolic Computation (1997)

Language-level support for object persistence frees programmers from having to confront a broad class of database issues from within their applications. By virtue of its metaobject protocol, CLOS is a language whose semantics can be tailored by individual programmers. We used the metaobject protocol to extend CLOS with support for object persistence. Our goal was to obtain a version of CLOS with persistence to which we could easily port a commercial geometric CAD modeling system. We describe the design and implementation of our persistence extension and highlight the strengths and weaknesses exhibited by the CLOS metaobject protocol during our experiment. For many aspects of the implementation we found that the metaobject protocol was ideal. In other cases we had to choose among paying a large performance penalty, extending the protocol, and bypassing the protocol by modifying the language implementation directly.
Lines and Points in Three Views and the Trifocal Tensor
Authors: Richard I. Hartley
Venue: International Journal of Computer Vision (1997)

This paper discusses the basic role of the trifocal tensor in scene reconstruction from three views. This 3\times 3\times 3 tensor plays a role in the analysis of scenes from three views analogous to the role played by the fundamental matrix in the two-view case. In particular, the trifocal tensor may be computed by a linear algorithm from a set of 13 line correspondences in three views. It is further shown in this paper, that the trifocal tensor is essentially identical to a set of coefficients introduced by Shashua to effect point transfer in the three view case. This observation means that the 13-line algorithm may be extended to allow for the computation of the trifocal tensor given any mixture of sufficiently many line and point correspondences. From the trifocal tensor the camera matrices of the images may be computed, and the scene may be reconstructed. For unrelated uncalibrated cameras, this reconstruction will be unique up to projectivity. Thus, projective reconstruction of a set of lines and points may be carried out linearly from three views.
An Ordering on the Even Discrete Torus
Authors: Oliver Riordan
Venue: SIAM Journal on Discrete Mathematics (1998)

The even discrete torus Tn(k1,...,kn) is the graph on $(\Z/k_1\Z) \times \cdots \times (\Z/k_n\Z)$, where each ki is even and x = (x1,...,xn) is joined to y = (y1,...,yn) if for some i we have xi = yi pm 1 and xj = yj for all $j\ne i$. The main aim of this paper is to describe an ordering on the even discrete torus whose initial segments give a best possible isoperimetric inequality. This extends the partial solution of Bollobás and Leader [SIAM J. Discrete Math., 3 (1990), pp. 32--37] to a problem posed by Wang and Wang [SIAM J. Appl. Math., 33 (1977), pp. 55--59].
A formal basis for architectural connection
Authors: Robert Allen, David Garlan
Venue: ACM Transactions on Software Engineering and Methodology (TOSEM) (1997)

As software systems become more complex, the overall system structure&mdash;or software architecture&mdash;becomes a central design problem. An important step toward an engineering discipline of software is a formal basis for describing and analyzing these designs. In the article we present a formal approach to one aspect of architectural design: the interactions among components. The key idea is to define architectural connectors as explicit semantic entities. These are specified as a collection of protocols that characterize each of the participant roles in an interaction and how these roles interact. We illustrate how this scheme can be used to define a variety of common architectural connectors. We further provide a formal semantics and show how this leads to a system in which architectural compatibility can be checked in a way analogous to type-checking in programming languages.
A tailored design language: putting model based formal specification into practice
Authors: R. A. Lees
Venue: Proceedings of the conference on TRI-ADA '90 (1990)

This paper introduces a model based formal design language aimed at supporting the practical use of rigorous methods within an industrial framework. The language consists of a core that is tailored to suit particular implementation languages, enabling the syntax and semantics of design and implementation languages to be matched in the design language. Particular features of the design language are described, a version of the language tailored for Ada is outlined, and current work with the language is described.
New Geometric Methods for Computer Vision: An Application toStructure and Motion Estimation
Authors: J. Lasenby, W. J. Fitzgerald, A. N. Lasenby, C. J. L. Doran
Venue: International Journal of Computer Vision (1998)

We discuss a coordinate-free approach to the geometry of computer vision problems. The technique we use to analyse the three-dimensional transformations involved will be that of geometric algebra: a framework based on the algebras of Clifford and Grassmann. This is not a system designed specifically for the task in hand, but rather a framework for all mathematical physics. Central to the power of this approach is the way in which the formalism deals with rotations; for example, if we have two arbitrary sets of vectors, known to be related via a 3D rotation, the rotation is easily recoverable if the vectors are given. Extracting the rotation by conventional means is not as straightforward. The calculus associated with geometric algebra is particularly powerful, enabling one, in a very natural way, to take derivatives with respect to any multivector (general element of the algebra). What this means in practice is that we can minimize with respect to rotors representing rotations, vectors representing translations, or any other relevant geometric quantity. This has important implications for many of the least-squares problems in computer vision where one attempts to find optimal rotations, translations etc., given observed vector quantities. We will illustrate this by analysing the problem of estimating motion from a pair of images, looking particularly at the more difficult case in which we have available only 2D information and no information on range. While this problem has already been much discussed in the literature, we believe the present formulation to be the only one in which least-squares estimates of the motion and structure are derived simultaneously using analytic derivatives.
Loop optimization for horizontal microcoded machines
Authors: François Bodin, François Charot
Venue: ACM SIGARCH Computer Architecture News (1990)

Long Instruction Word (LIW) architectures exploit parallelism between various functional units. In order to produce efficient code for such an architecture, the microcode compiler will have to expose a relatively large degree of fine grain parallelism and it will have to take into account the fine level characteristics of the architecture. This paper aims at describing a microcode compiler developed at IRISA for such architectures. After a brief overview of the compilation process, we focus on loop scheduling techniques. The software pipelining algorithm is firstly described. Then a new unrolling-based optimization algorithm is introduced and compared to the classical software pipelining algorithm. This algorithm differs from the traditional loop unrolling algorithm because the unrolling of the loop is only used to find a cyclic scheduling of the loop, then this scheduling allows a software pipelining to be constructed.
Port calling: a transformation for reducing I/O during multi-package functional partitioning
Authors: Frank Vahid
Venue: Proceedings of the 10th international symposium on System synthesis (1997)

Partitioning a system among multiple input and output pin (I/O) limited packages is a widely researched and hard to solve problem. We previously described a new approach yielding large improvements, which partitioned functions rather than structure, and which used a single bus for all inter-package data transfer. In this paper, we describe an extension permitting arbitrary distribution of I/O among the packages, and highlight experiments demonstrating even further I/O reductions as well as surprisingly improved performance, with nearly no penalty.
Utilising the student model in distance learning
Authors: R. Alan Whitehurst, Christopher L. Powell, Jason S. Izatt
Venue: ACM SIGCSE Bulletin (1998)

A key to effective automated learning systems is the ability to dynamically adapt learning strategies to the needs of individual students. This presentation will describe the dynamic presentation facility of the DANDIE distance-based learning system that utilises a student model and intelligent system techniques to optimise presentation content and form to meet individual needs. Given a knowledge-base of course material, the system adapts the information through the selection of predefined learning strategies, dynamically constructs an interconnected set of presentation modules, and evaluates the effectiveness of the presentation strategy with respect to the individual student.
POSC&mdash;a partitioning and optimizing SISAL compiler
Authors: Vivek Sarkar, David Cann
Venue: Proceedings of the 4th international conference on Supercomputing (1990)

Single-assignment languages like SISAL offer parallelism at all levels&mdash;among arbitrary operations, conditionals, loop iterations, and function calls. All control and data dependencies are local, and can be easily determined from the program. Various studies of SISAL programs have shown that they contain massive amounts of potential parallelism. There are two major challenges in converting this potential parallelism into real speedup on multiprocessor systems. First, it is important to carefully select the useful parallelism in a SISAL program, so as to obtain good speedup by trading off parallelism with overhead. Second, it is important to do sequential optimizations, so that the sequential components (tasks) of the SISAL program have comparable execution times with sequential languages such as Fortran, Pascal and C. The POSC compiler system described in this paper addresses both issues by integrating previous work on efficient sequential implementation of SISAL programs with previous work on selecting the useful parallelism in a SISAL program. The combined approach is validated by real speedup measurements on a Sequent Balance multiprocessor.
An efficient multicast protocol using de Bruijn structure for mobile computing
Authors: David S. L. Wei, Kshirasagar Naik
Venue: ACM SIGCOMM Computer Communication Review (1997)

In this paper, we design a protocol to efficiently deliver multicast messages to mobile computers. The main concern in the design of such a protocol is to ensure that each message is delivered exactly once to each mobile host in a multicast group. However, the requirements of avoiding multiple delivery of a message, and of a host not missing a message are not easy to efficiently satisfy in a mobile environment. To satisfy these requirements, an earlier work had to actually broadcast a multicast message. The novelty of our approach is that we satisfy the multicast requirements without broadcasting a message, which is central to the efficiency of our protocol. We structure the mobile support stations (MSS) as a de Bruijn network, and define a multicast tree on the network. A multicast message is routed on a multicast tree on a de Bruijn network. Assuming that there are N MSS's in a network, a multicast group of mobile hosts belong to the cells of N MSS's, tau; is the maximum of the time to route a message between two adjacent MSS's, Lambda; is the sum of the mobility rates of all mobiles in a multicast group, lambda;max is the maximum among the mobility rates, and phi; is the cell cross-over time of a mobile, our protocol runs with a message complexity of O(min(N log N, N) + Lambda; log N) and a communication delay of O( tau; log N + lambda;max phi;). Thus, our protocol is very efficient when a message is multicast to a small number of mobile hosts. To show the practicability of structuring a set of MSS's as a de Bruijn network, we have demonstrated how a de Bruijn network can be emulated as a collection of virtual paths on an arbitrarily connected ATM network.
Interweaving Kohonen Maps of Different Dimensions to Handle MeasureZero Constraints on Topological Mappings
Authors: L. Manevitz
Venue: Neural Processing Letters (1997)

The usual &rsquo;Kohonen&lsquo; algorithm uses samples of points in a domain to develop a topological correspondence between a grid of &rsquo;neurons&lsquo; and a continuous domain. &rsquo;Topological&lsquo; means that near points are mapped to near points. However, for many applications there are additional constraints, which are given by sets of measure zero, which are not preserved by this method, because of insufficient sampling. In particular, boundary points do not typically map to boundary points because in general the likelihood of a sample point from a two-dimensional domain falling on the boundary is typically zero for continuous data, and extremely small for numerical data. A specific application, (assigning meshes for the finite element method), was recently solved by interweaving a two-dimensional Kohonen mapping on the entire grid with a one-dimensional Kohonen mapping on the boundary. While the precise method of interweaving was heuristic, the underlying rationale seems widely applicable. This general method is problem independent and suggests a direct generalization to higher dimensions as well.
A scheme for integrated controller-datapath fault testing
Authors: M. Nourani, J. Carletta, C. Papachristou
Venue: Proceedings of the 34th annual Design Automation Conference (1997)

In systems consisting of interacting datapaths and controllersand utilizing built-in self test (BIST), the datapaths andcontrollers are traditionally tested separately by isolatingeach component from the environment of the system duringtest.This work facilitates the testing of datapath-controllerpairs in an integrated fashion.The key to the approach isthe addition of logic to the system that interacts with theexisting controller to push the effects of controller faults intothe data flow, so that they can be observed at the datapathregisters rather than directly at the controller outputs.Theresult is to reduce the BIST overhead over what is neededif the datapath and controller are tested independently, andto allow a more complete test of the interface between datapathand controller.Fault coverage and overhead resultsare given for four example circuits.
Automated Modelling of Physiological Processes During PostharvestDistribution of Agricultural Products
Authors: M. Sloof
Venue: Artificial Intelligence Review (1998)

In this paper, we present an approach to automated modelling of physiological processes occurring during postharvest distribution of agricultural products. The approach involves reasoning about the reuse of both qualitative and mathematical models for physiological processes, and constructs quantitative simulation models for the postharvest behaviour of agricultural products. The qualitative models are used to bridge the gap between the modeller&lsquo;s knowledge about the physiological phenomenon and the mathematical models. The qualitative models are represented by knowledge graphs, that are conceptual graphs containing only causal relations, aggregation relations, and generalisation relations between domain quantities. The relationships between the mathematical models and the qualitative models are explicitly represented in application frames.The automated modelling task consists of two subtasks. In the first subtask, Qualitative Process Analysis, a process structure graph is constructed using the qualitative models as building blocks. The process structure graph is a qualitative description of the phenomenon under study, that contains the processes that are responsible for the behaviour of the phenomenon. The process structure graph serves as a focus for the second subtask, Simulation Model Construction. This subtask uses a library of mathematical models to compose a quantitative simulation model that corresponds to the process structure graph constructed in the first subtask. The approach is illustrated with the construction of a model for the occurrence of chilling injury in bell peppers.
UFO: a personal global file system based on user-level extensions to the operating system
Authors: Albert D. Alexandrov, Maximilian Ibel, Klaus E. Schauser, Chris J. Scheiman
Venue: ACM Transactions on Computer Systems (TOCS) (1998)

In this article we show how to extend a wide range of functionality of standard operation systems completely at the user level. Our approach works by intercepting selected system calls at the user level, using tracing facilities such as the /proc file system provided by many Unix operating systems. The behavior of some intercepted system calls is then modified to implement new functionality. This approach does not require any relinking or recompilation of existing applications. In fact, the extensions can even be dynamically &ldquo;installed&rdquo; into already running processes. The extensions work completely at the user level and install without system administrator assistance. Individual users can choose what extensions to run, in effect creating a personalized operating system view for themselves. We used this approach to implement a global file system, called Ufo, which allows users to treat remote files exactly as if they were local. Currently, Ufo supports file access through the FTP and HTTP protocols and allows new protocols to be plugged in. While several other projects have implemented global file system abstractions, they all require either changes to the operating system or modifications to standard libraries. The article gives a detailed performance analysis of our approach to extending the OS and establishes that Ufo introduces acceptable overhead for common applications even though intercepting individual system calls incurs a high cost.
The threshold of event simultaneity
Authors: Frederick Wieland
Venue: ACM SIGSIM Simulation Digest (1997)

We revisit the notion of event simultaneity in the context of parallel and distributed simulation. Although the simulation community has recognized this problem for years, it has focused mainly on the mechanics of breaking event-time ties and has neither measured its extent nor considered its implications. Exant simulators (both serial and parallel) prohibit simultaneity either by user-specified event priorities or by an arbitrary (but well-documented) tie-breaking mechanism. We show, theoretically and empirically, that these strategies may lead to an invalid simulation. In doing so, we introduce the threshold of event simultaneity and use it to understand the semantics of simultaneity.
On the Precision in Estimating the Location of Edges and Corners
Authors: Karl Rohr
Venue: Journal of Mathematical Imaging and Vision (1997)

Recently, in Rohr [13], we analyzed the systematic localization errors introduced by local operators for detecting grey-value corners. These errors are inherently due to the differential structure of the operators and, in general, are enlarged by discretization and noise effects. Here, we take the statistical point of view to analyze the localization errors caused by noisy data. We consider a continuous image model that represents the blur as well as noise introduced by an imaging system. In general, the systematic intensity variations are nonlinear functions of the location parameters. For this model we derive analytic results stating lower bounds for the location uncertainty of image features. The lower bounds are evaluated for explicit edge and corner models. We show that the precision of localization in general depends on the noise level, on the size of the observation window, on the width of the intensity transitions, as well as on other parameters describing the systematic intensity variations. We also point out that the uncertainty lower bounds in localizing these image features can in principle be attained by fitting parametric models directly to the image intensities. To give an impression of the achievable accuracy numerical examples are presented.
Routing algorithm for gate array macro cells
Authors: Atreyi Chakraverti, Moon Jung Chung
Venue: Proceedings of the 25th ACM/IEEE Design Automation Conference (1988)

We will present an efficient dynamic algorithm for routing pre-placed gate array macro-cells. A novel data-structure based on corner stitching is introduced to represent the routing environment in a general gate array, where an uniform grid cannot be superimposed on the basic-cells. The near-optimal routing is accomplished in iterations with an initial shortest-path routing followed by conflict resolution using a coloring procedure and net reordering.
Automatic inline allocation of objects
Authors: Julian Dolby
Venue: Proceedings of the ACM SIGPLAN 1997 conference on Programming language design and implementation (1997)

Object-oriented languages like Java and Smalltalk provide a uniform object model that simplifies programming by providing a consistent, abstract model of object behavior. But direct implementations introduce overhead, removal of which requires aggressive implementation techniques (e.g. type inference, function specialization); in this paper, we introduce object inlining, an optimization that automatically inline allocates objects within containers (as is done by hand in C++) within a uniform model. We present our technique, which includes novel program analyses that track how inlinable objects are used throughout the program. We evaluated object inlining on several object-oriented benchmarks. It produces performance up to three times as fast as a dynamic model without inlining and roughly equal to that of manually-inlined codes.