ppxscal/embedding_network huggingface dataset:
Randomised Techniques in Combinatorial Algorithmics
Authors: Michele Zito
Venue:  (1999)

Probabilistic techniques are becoming more and more important in Computer Science. Some of them are useful for the analysis of algorithms. The aim of this thesis is to describe and develop applications of these techniques. We first look at the problem of generating a graph uniformly at random from the set of all unlabelled graphs with n vertices, by means of efficient parallel algorithms. Our model of parallel computation is the well-known parallel random access machine (PRAM). The algorithms presented here are among the first parallel algorithms for random generation of combinatorial structures. We present two different parallel algorithms for the uniform generation of unlabelled graphs. The algorithms run in O(log^2 n) time with high probability on an EREW PRAM using O(n^2) processors. Combinatorial and algorithmic notions of approximation are another important thread in this thesis. We look at possible ways of approximating the parameters that describe the phase transitional behaviour (similar in some sense to the transition in Physics between solid and liquid state) of two important computational problems: that of deciding whether a graph is colourable using only three colours so that no two adjacent vertices receive the same colour, and that of deciding whether a propositional boolean formula in conjunctive normal form with clauses containing at most three literals is satisfiable. A specific notion of maximal solution and, for the second problem, the use of a probabilistic model called the (young) coupon collector allows us to improve the best known results for these problems. Finally we look at two graph theoretic matching problems. We first study the computational complexity of these problems and the algorithmic approximability of the optimal solutions, in particular classes of graphs. We also derive an algorithm that solves one of them optimally in linear time when the input graph is a tree as well as a number of non-approximability results. Then we make some assumptions about the input distribution, we study the expected structure of these matchings and we derive improved approximation results on several models of random graphs.
Cyclic Allocation of Two-Dimensional Data
Authors: Sunil Prabhakar, Khaled Abdel-Ghaffar, Divyakant Agrawal, Amr El Abbadi
Venue:  (1997)

Various proposals have been made for declustering two-dimensionally tiled data on multiple I/O devices. Recently, it was shown that strictly optimal solutions only exist under very restrictive conditions on the tiling of the two-dimensional space or for very few I/O devices. In this paper we explore allocation methods where no strictly optimal solution exists. We propose a general class of allocation methods, referred to as cyclic declustering methods, and show that many existing methods are instances of this class. As a result, various seemingly ad hoc and unrelated methods are presented in a single framework. Furthermore, the framework is used to develop new allocation methods that give better performance than any previous method and that approach the best feasible performance.
SIMULATING A DYNAMIC RAM IN COSMOS
Authors: Don Speck
Venue:  (1991)

This report describes the tricks involved in simulating a chip containing a 1-transistor style dynamic RAM using the COSMOS switch-level simulator. The reader is assumed to be familiar with this style of dynamic RAM. The specifics are drawn from a variant of the Caltech Mosaic RAM as modified at UCSC, but most of the tricks generalize to other CMOS dRAMs. The appendix gives a minimal list of attribute labels for the Mosaic RAM.
Minimizing Randomness in Minimum Spanning Tree, Parallel Connectivity, andSet Maxima Algorithms
Authors: Seth Pettie, Vijaya Ramachandran
Venue:  (2001)

There are several fundamental problems whose deterministic complexity remains unresolved, but for which there exist randomized algorithms whose complexity is equal to known lower bounds. Among such problems are the minimum spanning tree problem, the set maxima problem, the problem of computing connected components and (minimum) spanning trees in parallel, and the problem of performing sensitivity analysis on shortest path trees and minimum spanning trees. However, while each of these problems has a randomized algorithm whose performance meets a known lower bound, all of these randomized algorithms use a number of random bits which is linear in the number of operations they perform. We address the issue of reduucing the number of random bits used in these randomized algorithms. For each of the problems listed above, we present randomized algorithms that have optimal performance but use only a polylogarithmic number of random bits; for some of the problems our optimal algorithms use only log* n random bits. Our results represent an exponential savings in the amount of randomness used to achieve the same optimal performance as in the earlier algorithms. Our techniques are general and could likely be applied to other problems.
On the Use of Interactive Proofs for Formal Program Verification
Authors: U. Feige, K. Nissim
Venue:  (1997)

Automatic program verification is a computationally intense task. When a verifier declares a program correct, there still remains the question of whether the verifier itself made no errors in the verification procedure. Theoretically, such doubts can be relieved by an interactive protocol between the verifier and the program designer, using the recently developed theory of interactive proof systems. However, it is not clear whether this idea has any value in practice, due to the seemingly large overhead involved. In this work we experiment with the methodology suggested above. That is, we study the feasibility of using interactive proofs in formal program verification, and propose approaches to minimize the overhead involved. We demonstrate our ideas on two finite state mutual exclusion protocols.
Surface Reconstruction by Coupled Dept/Slope Model with Natural Boundary
Authors: Ying Li
Venue:  (1991)

This report reports on an IRIS project of reconstructing surface height from gradient. The coupled depth/slope model developed by J.G. Harris has been used and augmented with natural boundary conditions. Experiments have been conducted with emphasis on how to deal with uncertainties about boundary values. Experiments have shown that the reconstructed surfaces are confined to the original shapes if accurate boundary values are given. The algorithm fails to produce correct shapes when inaccurate boundary values are used. Natural boundary conditions are necessary conditions for the problem of variational calculus to be solved. Experiments have shown that natural boundary conditions can be relied upon when no estimations of boundary values can be made, except on occluding boundaries. When relative boundary values of occluding boundaries can be assumed, good reconstruction results can be obtained. The ACM Portal is published by the Association for Computing Machinery. Copyright © 2010 ACM, Inc. Terms of Usage Privacy Policy Code of Ethics Contact Us Useful downloads: Adobe Acrobat QuickTime Windows Media Player Real Player
Formal Verification: An Evaluation
Authors: Matthew Gibble, John C. Knight, Luis G. Nakano, Colleen DeJong
Venue:  (1997)

Despite extensive development over many years and significant demonstrated benefits, formal methods remain poorly accepted by industrial practitioners. Many reasons have been suggested for this situation such as a claim that they extend the development cycle, that they require difficult mathematics, that inadequate tools exist, and that they are incompatible with other software packages. There is little empirical evidence that any of these reasons is valid. The research presented here addresses the question of why formal methods are not used more widely. The approach used was to develop a formal specification for a safety-critical application using PVS and assess the results in a comprehensive evaluation framework. The results of the experiment suggests that there remain many impediments to the routine use of formal methods.
Information Retrieval from Annotated Texts with Applications to Hypertexts
Authors: A. S. Fraenkel, S. T. Klein
Venue:  (1995)

Methods for the correct and efficient handling of annotations in a full-text retrieval system are investigated, with applications to a Hypertext environment in which even the hyperlinks are considered as searchable annotations. The problem with annotations is that they cannot be treated as regular text, since this would disrupt proximity searches, but on the other hand, they cannot be ignored, as they may carry important information. Moreover, in some cases, a user may wish to restrict a search to prespecified subsets of annotations. We suggest a new way of indexing the terms of the database to overcome the above dilemma.
A Principle-Based System for Natural Language Analysis and Translation
Authors: Matthew W Crocker
Venue:  (1988)

Traditional views of grammatical theory hold that languages are characterized by sets of constructions. This approach entails the enumeration of all possible constructions for each language being described. Current theories of transformational generative grammar have established an alternative position. Specifically, Chomsky''s Government-Binding theory proposes a system of principles which are common to human language. Such a theory is referred to as a ``Universal Grammar'''' (UG). Associated with the principles of grammar are parameters of variation which account for the diversity of human languages. The grammar for a particular language is known as a ``Core Grammar'''', and is characterized by an appropriately parametrized instance of UG. Despite these advances in linguistic theory, construction-based approaches have remained the status quo within the field of natural language processing. This thesis investigates the possibility of developing a principle-based system which reflects the modular nature of the linguistic theory. That is, rather than stipulating the possible constructions of a language, a system is developed which uses the principles of grammar and language specific parameters to parse language. Specifically, a system is presented which performs syntactic analysis and translation for a subset of English and German. The cross-linguistic nature of the theory is reflected by the system which can be considered a procedural model of UG.
Patchable Instruction ROM Architecture
Authors: Timothy Sherwood, Brad Calder
Venue:  (2001)

Increased systems level integration has meant the movement of many traditionally off chip components onto a single chip including a processor, instruction storage, data path, and local memory. The design of these systems are driven by two conflicting goals, the need for reduced area and the need for rapid development times. The two current design options for instruction storage, ROM and Flash, are each highly optimized to one of these two goals but provide little compromise between them. ROM is used for highly area optimized instruction memory to minimize area per instruction, although this comes at a price of lengthy integration time because of it''s need to be correct before the chip is sent for fabrication. Flash is an alternative instruction memory that can significantly reduce the time to market by allowing embedded software to be upgraded after fabrication, which means that software test and fabrication can be overlapped. Unfortunately Flash takes over a factor of 2 times the area of the equivalent ROM based storage. In this paper we present the Patchable Instruction ROM as an architecture for instruction storage that can provide the best of both worlds -- reduced area and faster time to market. With area efficiency similar to a standard ROM and support for limited post fabrication software patching, Patchable Instruction ROM provides a new set of design points to consider when building embedded systems. For the programs we examine, we show that our hardware/software technique can achieve an area only 10% larger than ROM with only an 11% inflation in design time over a Flash based approach.
Effect of Touch Screen Target Location on User Accuracy
Authors: Michael Leahy, Deborah Hix
Venue:  (1990)

Users can be frustrated by touch screen applications that inaccurately record their touches. Enlarging touch sensitive regions can improve touch accuracy, but few specific quantitative guidelines are available. This paper reports on a controlled experiment that investigated the effect of target location and horizontal viewing location on user accuracy. Measurements showed that persons tended to touch below the target, with touch distance increasing as the target location moved down the screen. In addition, they tended to touch toward the sides of the screen. Using collected data for each of nine screen sectors, graphs were prepared that show the relationship between touch target size and expected accuracy. For example, a 36 mm-squared target in the top left sector would be expected to record accurately 99% of its touches. The empirically-derived, quantitative guidelines will help designers create screens that decrease user errors and frustrations.
Optimising Overlaped and Non-Overlapped Parallel Algorithms Using Bottleneck Analysis: A Case Study
Authors: M. J. Zemerly, J. Papay, G. R. Nudd
Venue:  (1995)

In this paper a methodology for parallel algorithm selection and optimisation based on performance prediction and bottleneck analysis is presented. The performance prediction method used here is based on an instruction set characterisation technique which assumes the availability of the sequential code and the compiler for the target machine. A "Processor Activity Graph" (PAG) which provides a graphical representation of the parallel system runtime behaviour is used to extend the applicability of the characterisation technique to overlapping parallel algorithms. The bottleneck analysis assumes that a bottleneck is caused by the slowest component of a computing system. These components are: memory, processor, communication and I/O. Three dimensionless ratios are used to identify and quantify bottlenecks, these are: the B-ratio, the communication-computation ratio and the memory-processing ratio. The optimisation methodology is illustrated and validated using a communication intensive linear solver algorithm (Givens rotations) which was implemented on a mesh connected distributed memory parallel computer (128 T800 Parsytec SuperCluster) using non-overlapping and overlapping parallelisation techniques.
Supporting Learners in a Remote Computer-Supported Collaborative Learning Environment: The Importance of Task and Communication
Authors: David Graves
Venue:  (1998)

This paper describes novel research in the area of remote Computer-Supported Collaborative Learning. A multimedia activity (Builder) was designed to allow a pair of players to build a house together, each working from his or her own computer. Features of the activity include: interactive graphical interface, two- and three-dimensional views, sound feedback, and real-time written and spoken communication. Mathematical concepts, including area, perimeter, volume, and tiling of surfaces, are embedded in the task. A field study with 134 elementary school children was undertaken to assess the learning and collaborative potential of the activity. Specifically, the study addressed how different modes of communication and different task directives affected learning, interpersonal attitudes, and the perceived value and enjoyment of the task. It was found that playing led to academic gains in the target math areas, and that the nature of how the task was specified had a significant impact on the size of the gains. The mode of communication was found to affect attitudes toward the game and toward the player''s partner. Gender differences were found in attitude toward the game, perceived collaboration and attitude toward partner. Note: There is an important attachment to this technical report which includes screenshots and tests used for learner evalution. This must be downloaded separately via FTP to ftp.cs.ubc.ca -- you should log in as anonymous, and then download the file: /pub/local/techreports/1997/TR-97-19a.ps.gz (note that the screenshots are in colour).
Parallel implementation of the Kohonen algorithm on Transputer
Authors: Roberto Togneri, Yianni Attikiouzel
Venue:  (1991)

In this paper a parallel implementation of the Kohonen algorithm is proposed using partitioning of the network. This allows an exact implementation of the Kohonen algorithm as opposed to partitioning the data. By using a simple routing strategy the parallel Kohonen algorithm was tested on a PC based transputer network without the need for any special distributed operating system. The execution time was measured for different sized networks and number of transputers. The execution time decreased as the number of transputers increased. However, for comparatively small sized neural networks the communication overhead caused the execution time to increase when more transputers were used. Thus, the proposed parallel implementation of the Kohonen algorithm is not suitable for massively parallel architectures.
Cracking analysis of reinforced concrete tension members using polynomial strain distribution function
Authors: H. G. Kwak, J. Y. Song
Venue: Proceedings of the eighth international conference on The application of artificial intelligence to civil and structural engineering computing (2001)

In this paper, an analytical model which can simulate the post-cracking behaviour and tension stiffening effect in a reinforced concrete (RC) tension member is proposed. Unlike the classical approaches using the bond stress-slip relationship or the assumed bond stress distribution, the tension stiffening effect at post-cracking stage is quantified on the basis of polynomial strain distribution functions of steel and concrete, and its contribution is implemented into the reinforcing steel. The loads carried by concrete and by reinforcing steel along the member axis can be directly evaluated on the basis of the introduced model. The prediction of cracking loads and elongations of reinforced steel using the introduced model shows good agreements with results from previous analytical studies and experimental data.
Stabilization of DAEs and invariant manifolds
Authors: Uri M. Ascher, Hongsheng Qin, Sebastian Reich
Venue:  (1992)

Many methods have been proposed for the stabilization of higher index differential-algebraic equations (DAEs). Such methods often involve constraint differentiation and problem stabilization, thus obtaining a stabilized index reduction. A popular method is Baumgarte stabilization, but the choice of parameters to make it robust is unclear in practice. Here we explain why the Baumgarte method may run into trouble. We then show how to improve it. We further develop a unifying theory for stabilization methods which includes many of the various techniques proposed in the literature. Our approach is to (i) consider stabilization of ODEs with invariants, (ii) discretize the stabilizing term in a simple way, generally different from the ODE discretization, and (iii) use orthogonal projections whenever possible. We discuss the best methods thus obtained and make concrete algorithmic suggestions.
Internet Based Real-Time Multiuser Simulation: Ppong!
Authors: Begole James "Bo", Shaffer Clifford
Venue:  (1997)

There is a growing demand for real-time collaborative applications through the World Wide Web. New techniques are required for real-time applications to perform well in the face of changing network conditions that often include long delays. We present some of the key issues for implementors of real-time web-based applications, including choices on centralized versus distributed control, two versus multiuser considerations, synchronous versus asynchronous message protocols, and simulation divergence. We present an implementation for a web-based version of the classic Pong game, called Ppong!. Ppong! was selected for implementation since it strips to its essentials many components of real-time collaborative simulation. A key feature of Ppong! is implementation of a heuristic for "retarding" a user''s view of the simulation to accommodate network delays.
A Taxonomy for the Evaluation of Computer Documentation
Authors: K. T Stevens, James D. Arthur, Richard E. Nance
Venue:  (1988)

The evaluation of software documentation is a key issue in the more general framework of evaluating products of a software development process. The research described in this report focuses on (1) a general taxonomy of document characteristics that support an assessment of documentation adequacy, and (2) the refining of the general evaluation taxonomy to a specific application, namely, the Automated Design Description System (ADDS).
Hardware Optimizations Enabled by a Decoupled Fetch Architecture
Authors: Glenn Reinman
Venue:  (2001)

In the pursuit of instruction-level parallelism, significant demands are placed on a processor''s instruction delivery mechanism. In order to provide the performance necessary to meet future processor execution targets, the instruction delivery mechanism must scale with the execution core. Attaining these targets is a challenging task due to I-cache misses, branch mispredictions, and taken branches in the instruction stream. Moreover, there are a number of hardware scaling issues such as wire latency, clock scaling, and energy dissipation that can impact processor design. To address these issues, this thesis presents a fetch architecture that decouples the branch predictor from the instruction fetch unit. A Fetch Target Queue (FTQ) is inserted between the branch predictor and instruction cache. This allows the branch predictor to run far in advance of the address currently being fetched by the instruction cache. The decoupling enables a number of architectural optimizations including multi-level branch predictor design and fetch directed instruction prefetching. A multi-level branch predictor design consists of a small first level predictor that can scale well to future technology sizes and larger higher level predictors that can provide capacity for accurate branch prediction. Fetch directed instruction cache prefetching uses the stream of fetch addresses contained in the FTQ to guide instruction cache prefetching. By following the predicted fetch path, this technique provides more accurate prefetching than simply following a sequential fetch path. Fetch directed prefetching using a contemporary set-associative instruction cache has some complexity and energy dissipation concerns. Set-associative caches provide a great deal of performance benefit, but dissipate a large amount of energy by blindly driving a number of associative ways. By decoupling the tag and data components of the instruction cache, a complexity effective and energy efficient scheme for fetch directed instruction cache prefetching can be enabled. This thesis explores the decoupled front-end design and these related optimizations, and suggests future research directions.
PROTEIN MODELING USING HIDDEN MARKOV MODELS: ANALYSIS OF GLOBINS
Authors: David Haussler, Anders Krogh, Saira Mian, Kimmen Sjolander
Venue:  (1992)

We apply Hidden Markov Models (HMMs) to the problem of statistical modeling and multiple sequence alignment of protein families. A variant of the Expectation Maximization (EM) algorithm known as the Viterbi algorithm is used to obtain the statistical model from the unaligned sequences. In a detailed series of experiments, we have taken 400 unaligned globin sequences, and produced a statistical model entirely automatically from the primary (unaligned) sequences. We use no prior knowledge of globin structure. Using this model, we obtained a multiple alignment of the 400 sequences and 225 other globin sequences that agrees almost perfectly with a structural alignment by Bashford et al. This model can also discriminate all these 625 globins from nonglobin protein sequences with greater than 99% accuracy, and can thus be used for database searches.