ppxscal/embedding_network huggingface dataset:
User-level distributed file systems projects
Authors: Chris McDonald
Venue: ACM SIGCSE Bulletin (1996)

One of the greatest benefits provided by computer networks, in particular local area networks, is the ability to access files served by other computers in a network. Whereas file system concepts are first introduced in Operating Systems units, many file system concepts need to be readdressed and generalized in later Computer Networks units. Moreover, as students become increasingly familiar with internetworking and programs such as ftp, many of the strong links between the Operating Systems and Computer Networks units may be reinforced. This paper discusses the successes experienced with two strongly related projects offered in our third year Computer Networks unit. Each project requires students to support a minimal distributed file system by implementing user-level libraries which redefine a handful of operating system system calls supporting remote file access.
Predicting string search speed
Authors: Arthur Gittleman
Venue: Journal of Experimental Algorithmics (JEA) (1996)

String search is fundamental in many text processing applications. Sunday recently gave several algorithms to find the first occurrence of a pattern string as a substring of a text, providing experimental data from searches in a text of about 200K characters to support his claim that his algorithms are faster than the standard Boyer-Moore algorithm. We present a methodology for the average-case analysis of the performance of string search algorithms---for such algorithms, a worst-case analysis does not yield much useful information, since the performance of the algorithm is directly affected by such characteristics as the size of the character set, the character frequencies, and the structure of the text. Knuth described a finite automaton which can be used to save information about character comparisons. Baeza-Yates, Gonnet, and Regnier gave a probabilistic analysis of the worst- and average-case behavior of a string search algorithm based upon such an automaton. We construct Knuth automata to model Sunday's algorithms and use the methods of Baeza-Yates et al. to obtain an average-case analysis which confirms Sunday's experimental data.
Tighter Lower Bounds on the Exact Complexity of String Matching
Authors: Richard Cole, Ramesh Hariharan, Mike Paterson, Uri Zwick
Venue: SIAM Journal on Computing (1995)

This paper considers the exact number of character comparisons needed to find all occurrences of a pattern of length $m$ in a text of length $n$ using on-line and general algorithms. For on-line algorithms, a lower bound of about $(1+\frac{9}{4(m+1)})\cdot n$ character comparisons is obtained. For general algorithms, a lower bound of about $(1+\frac{2}{m+3})\cdot n$ character comparisons is obtained. These lower bounds complement an on-line upper bound of about $(1+\frac{8}{3(m+1)})\cdot n$ comparisons obtained recently by Cole and Hariharan. The lower bounds are obtained by finding patterns with interesting combinatorial properties. It is also shown that for some patterns off-line algorithms can be more efficient than on-line algorithms.
The LRPD test: speculative run-time parallelization of loops with privatization and reduction parallelization
Authors: Lawrence Rauchwerger, David Padua
Venue: ACM SIGPLAN Notices (1995)

Current parallelizing compilers cannot identify a significant fraction of parallelizable loops because they have complex or statically insufficiently defined access patterns. As parallelizable loops arise frequently in practice, we advocate a novel framework for their identification: speculatively execute the loop as a doall, and apply a fully parallel data dependence test to determine if it had any cross-iteration dependences; if the test fails, then the loop is re-executed serially. Since, from our experience, a significant amount of the available parallelism in Fortran programs can be exploited by loops transformed through privatization and reduction parallelization, our methods can speculatively apply these transformations and then check their validity at run-time. Another important contribution of this paper is a novel method for reduction recognition which goes beyond syntactic pattern matching; it detects at run-time if the values stored in an array participate in a reduction operation, even if they are transferred through private variables and/or are affected by statically unpredictable control flow. We present experimental results on loops from the PERFECT Benchmarks which substantiate our claim that these techniques can yield significant speedups which are often superior to those obtainable by inspector/executor methods.
CLANGER: an interpreted systems programming language
Authors: Timothy Roscoe
Venue: ACM SIGOPS Operating Systems Review (1995)

Clanger is a powerful, yet simple, command language for the Nemesis operating system. It uses runtime type information to interface directly with operating system components. Clanger is a combination of command-line interpreter, scripting language, debugger and prototyping tool. This paper describes why such a language is possible, how it is being implemented, and outlines the language as it currently stands.
Offices are open systems
Authors: Carl Hewitt
Venue: ACM Transactions on Information Systems (TOIS) (1986)

This paper is intended as a contribution to analysis of the implications of viewing offices as open systems. It takes a prescriptive stance on how to establish the information-processing foundations for taking action and making decisions in office work from an open systems perspective. We propose due process as a central activity in organizational information processing. Computer systems are beginning to play important roles in mediating the ongoing activities of organizations. We expect that these roles will gradually increase in importance as computer systems take on more of the authority and responsibility for ongoing activities. At the same time we expect computer systems to acquire more of the characteristics and structure of human organizations.
Accountability in Electronic Commerce Protocols
Authors: Rajashekar Kailar
Venue: IEEE Transactions on Software Engineering (1996)

In most commercial and legal transactions, the ability to hold individuals or organizations accountable for transactions is important. Hence, electronic protocols that implement commercial transactions must be designed to provide adequate accountability assurances for transacting parties. Without such assurances, electronic transactions can be susceptible to disputes. Currently, protocol design for electronic commerce is done in an ad-hoc manner, a technique which has been shown to be error-prone by past experience with key distribution protocols [4]. Despite the importance of accountability in electronic commerce, and the subtlety of designing error-free protocols, currently, there are no analysis methods to examine whether a protocol design conforms to the accountability goals of the transaction that it implements. Since most current protocol analysis methods have been developed to analyze key management protocols, they focus on properties such as message replay detection, and key origin authentication (e.g., [20], [4], [11], [14], [18]).In this paper, a new framework is proposed for the analysis of communication protocols that require accountability, such as those for electronic commerce. This framework can be used to analyze protocol designs to detect accountability (or lack thereof). Arguments are presented to show that a heretofore unexplored property "provability" is pertinent to examining the potential use of communication protocols in the context of litigation, and in the context of audit. A set of postulates which are applicable to the analysis of proofs in general and the proofs of accountability in particular, are proposed. The proposed approach is more natural for the analysis of accountability than the existing belief logics (e.g., [4]) that have been used in the past for the analysis of key distribution protocols. Some recently proposed protocols for electronic commerce and public-key delegation are analyzed to illustrate the use of the new analysis framework in detecting (and suggesting remedies for eliminating) their lack of accountability, and in detecting and eliminating redundancies.
Handprinted Character Recognition Based on Spatial Topology Distance Measurement
Authors: Cheng-Yuan Liou, Hsin-Chang Yang
Venue: IEEE Transactions on Pattern Analysis and Machine Intelligence (1996)

In this work we present a self-organization matching approach to accomplish the recognition of handprinted characters drawn with thick strokes. This approach is used to flex the unknown handprinted character toward matching its object characters gradually. The extracted character features used in the self-organization matching are center loci, orientation, and major axes of ellipses which fit the inked area of the patterns. Simulations provide encouraging results using the proposed method.
HGA: a hardware-based genetic algorithm
Authors: Stephen D. Scott, Ashok Samal, Shared Seth
Venue: Proceedings of the 1995 ACM third international symposium on Field-programmable gate arrays (1995)

A genetic algorithm (GA) is a robust problem-solving method based on natural selection. Hardware's speed advantage and its ability to parallelize offer great rewards to genetic algorithms. Speedups of 1-3 orders of magnitude have been observed when frequently used software routines were implemented in hardware by way of reprogrammable field-programmable gate arrays (FPGAs). Reprogrammability is essential in a general-purpose GA engine because certain GA modules require changeability (e.g. the function to be optimized by the GA). Thus a hardware-based GA is both feasible and desirable. A fully functional hardware-based genetic algorithm (the HGA) is presented here as a proof-of-concept system. It was designed using VHDL to allow for easy scalability. It is designed to act as a coprocessor with the CPU of a PC. The user programs the FPGAs which implement the function to be optimized. Other GA parameters may also be specified by the user. Simulation results and performance analyses of the HGA are presented. A prototype HGA is described and compared to a similar GA implemented in software. In the simple tests, the prototype took about 6% as many clock cycles to run as the software-based GA. Further suggested improvements could realistically make the HGA 2&ndash;3 orders of magnitude faster than the software-based GA.
Design and evaluation of algorithms for image retrieval by spatial similarity
Authors: Venkat N. Gudivada, Vijay V. Raghavan
Venue: ACM Transactions on Information Systems (TOIS) (1995)

Similarity-based retrieval of images is an important task in many image database applications. A major class of users' requests requires retrieving those images in the database that are spatially similar to the query image. We propose an algorithm for computing the spatial similarity between two symbolic images. A symbolic image is a logical representation of the original image where the image objects are uniquely labeled with symbolic names. Spatial relationships in a symbolic image are represented as edges in a weighted graph referred to as spatial-orientation graph. Spatial similarity is then quantified in terms of the number of, as well as the extent to which, the edges of the spatial-orientation graph of the database image conform to the corresponding edges of the spatial-orientation graph of the query image.The proposed algorithm is robust in the sense that it can deal with translation, scale, and rotational variances in images. The algorithm has quadratic time complexity in terms of the total number of objects in both the database and query images. We also introduce the idea of quantifying a system's retrieval quality by having an expert specify the expected rank ordering with respect to each query for a set of test queries. This enables us to assess the quality of algorithms comprehensively for retrieval in image databases. The characteristics of the proposed algorithm are compared with those of the previously available algorithms using a testbed of images. The comparison demonstrated that our algorithm is not only more efficient but also provides a rank ordering of images that consistently matches with the expert's expected rank ordering.
Succeedings of the 8th international workshop on software specification and design
Authors: Jeff Kramer, Alexander L. Wolf
Venue: ACM SIGSOFT Software Engineering Notes (1996)

The 8th International Workshop on Software Specification and Design (IWSSD-8) was held at Schloss Velen, Germany, in March 1996. In order to foster informed and fruitful discussions, the workshop was an invitation-only event of limited size. Based on formal submissions, approximately 60 people were selected and invited. Like its predecessors, IWSSD-8 maintained the principle that the accepted papers should serve as background material for the workshop. Therefore, the workshop did not include formal paper presentations, but rather provided an opportunity to engage in real work, with intensive discussions focussed around major themes. Each theme was discussed in a separate working group directed by a Working Group Chair who organized their group members so as to discuss the research issues of that particular theme. This year the themes selected were Requirements Engineering, Design Engineering, Software Architecture, and Concurrency/Distribution.IWSSD has established a tradition of using "case studies" as a focus for individual working groups. These case studies, supplied in advance to participants, have proved to be a fruitful way of working. Evidence of this can be seen most clearly in the "succeedings" or workshop reports which have followed previous workshops. It was decided that for IWSSD-8, in order to provide common ground between the themes, a single common case study should be used. The "Report on the Inquiry into the London Ambulance Service" was selected, with each theme drawing on it in a manner appropriate to their own interests and concerns.The London Ambulance Service (LAS) is briefly summarized below and discussed in the first paper appearing in the proceedings. The case study was presented in a plenary session at the beginning of the workshop and the findings of the different working groups presented and discussed at the end of the workshop, again in a plenary session. In order to make best use of the time available, working group members were asked to prepare for the workshop by familiarizing themselves with the case study and the major issues in their area relevant to that case study. We believe that this format made it both attractive and rewarding for people to attend, and was a major reason for the success of this workshop.
Learning Bayesian Networks: The Combination of Knowledge and Statistical Data
Authors: David Heckerman, Dan Geiger, David M. Chickering
Venue: Machine Learning (1995)

We describe a Bayesian approach for learning Bayesian networks from a combination of prior knowledge and statistical data. First and foremost, we develop a methodology for assessing informative priors needed for learning. Our approach is derived from a set of assumptions made previously as well as the assumption of likelihood equivalence, which says that data should not help to discriminate network structures that represent the same assertions of conditional independence. We show that likelihood equivalence when combined with previously made assumptions implies that the user's priors for network parameters can be encoded in a single Bayesian network for the next case to be seen&mdash;a prior network&mdash;and a single measure of confidence for that network. Second, using these priors, we show how to compute the relative posterior probabilities of network structures given data. Third, we describe search methods for identifying network structures with high posterior probabilities. We describe polynomial algorithms for finding the highest-scoring network structures in the special case where every node has at most k &equals; 1 parent. For the general case (k > 1), which is NP-hard, we review heuristic search algorithms including local search, iterative local search, and simulated annealing. Finally, we describe a methodology for evaluating Bayesian-network learning algorithms, and apply this approach to a comparison of various approaches.
A Multiway Merge Sorting Network
Authors: De-Lei Lee, Kenneth E. Batcher
Venue: IEEE Transactions on Parallel and Distributed Systems (1995)

A multiway merge sorting network is presented, which generalizes the technique used in the odd-even merge sorting network. The merging network described here is composed of $m\ k$-way mergers and a combining network. It arranges $k$ ordered lists of length $n$ each into one ordered lists in $T(k) + \lceil \log_m n\rceil \lceil \log_2 k\rceil \lceil \log_2 m\rceil$ steps, where $T(k)$ is the number of steps needed to sort $k$ keys in order; and $k$ and $m$ are any integers no longer restricted to 2.Index Terms¿Sorting networks, odd-even merge, multiway merge, parallel processing.
The Demeter method: an efficient way to build adaptive software
Authors: Yang Liu, Salil Pradhan
Venue: ACM SIGICE Bulletin (1996)

Many object-oriented software developers often face the optimal class structure problem when a large, complex project starts. They have to find a class structure and improve it iteratively during the development process. Changes to the class structure cause substantial effort to maintain behaviors built upon the original class structure[5]. And a general application, like a project defect management system, is usually developed based on a class structure extracted from a specific problem domain, for example, software system defect tracking and repairing. Next time when similar requirements (i.e. a semiconductor system defect tracking and repairing) come in, the existing application is found hard to adapt to the new context for the reason that too many details of user-related class structure are included and encoded into the application implementation. Most developers would rather adopt the build-from-scratch techniques than reuse the current system, though they have very similar requirements.
Industrial experience using rule-driven retargetable code generation for multimedia applications
Authors: Clifford Liem, Pierre Paulin, Marco Cornero, Ahmed Jerraya
Venue: Proceedings of the 8th international symposium on System synthesis (1995)

Abstract: The increasing usage of application-specific instruction set processors (ASIPs) in audio and video telecommunications has made strong demands on the rapid availability of dedicated compilers. A rule-driven approach to code generation may have benefits over model-based approaches as the user is not confined to the capabilities supported by the model. However, the sole use of transformation rules may or may not be sufficient in optimization abilities depending on the target architecture. This paper outlines experiences with a rule-driven code generation approach for two applications in audio and video processing. The first is a controller for the VideoPhone codec at SGS-Thomson Microelectronics. The second is a VLIW (very large instruction word) processor for high-fidelity and MPEG audio at Thomson Consumer Electronic Components. The experience has shown that a rule-driven approach to compilation is applicable to both the controller and VLIW architectures; however, is limited in optimization abilities for the latter.
Reassessing the crypto debate
Authors: Peter G. Neumann
Venue: Communications of the ACM (1995)

This month we summarize the main issues relating to the increasing use of cryptography in the world&mdash;for example, in enhancing confidentiality, integrity, and authenticity in computers and communications. Earlier columns have considered some related topics [1].
High Accuracy Optical Character Recognition Using Neural Networks with Centroid Dithering
Authors: Hadar I. Avi-Itzhak, Thanh A. Diep, Harry Garland
Venue: IEEE Transactions on Pattern Analysis and Machine Intelligence (1995)

Optical character recognition (OCR) refers to a process whereby printed documents are transformed into ASCII files for the purpose of compact storage, editing, fast retrieval, and other file manipulations through the use of a computer. The recognition stage of an OCR process is made difficult by added noise, image distortion, and the various character typefaces, sizes, and fonts that a document may have. In this study a neural network approach is introduced to perform high accuracy recognition on multi-size and multi-font characters; a novel centroid-dithering training process with a low noise-sensitivity normalization procedure is used to achieve high accuracy results. The study consists of two parts. The first part focuses on single size and single font characters, and a two-layered neural network is trained to recognize the full set of 94 ASCII character images in 12-pt Courier font. The second part trades accuracy for additional font and size capability, and a larger two-layered neural network is trained to recognize the full set of 94 ASCII character images for all point sizes from 8 to 32 and for 12 commonly used fonts. The performance of these two networks is evaluated based on a database of more than one million character images from the testing data set.
Optimal Relaxed Controls for Infinite-Dimensional Stochastic Systems of Zakai Type
Authors: N. U. Ahmed
Venue: SIAM Journal on Control and Optimization (1996)

In this paper, we present some new results on partially observed control problems for infinite-dimensional stochastic systems in Hilbert space using a fundamental result of Da Prato and Zabczyk on an infinite-dimensional Kolmogorov operator. We prove the existence of optimal relaxed controls for an infinite-dimensional Zakai equation following a semigroup approach and the theory of measurable selections. This result is also extended to differential inclusion. We also present some necessary conditions of optimality.
A methodology for high-level software specification construction
Authors: Ying Jing, He Zhijun, Wu Zhaohui
Venue: ACM SIGSOFT Software Engineering Notes (1995)

This paper puts forward a kind of novel methodology for software system development, from the point of view of the problem existed in software development -- the gap between the requirement specification level and the program implementation level. We attempt to begin from the specification level of software development to touch the process of high-level specification construction profoundly. We propose a specification language to support multiple semantic dimensions and based on which build a unified functional model of software system in a specific domain. On the bases of these, we apply transformation and refinement methods to the model and transit it from the specification level to the implementation level. We expect such a process can change the current software producing procedure in nature. We also put this methodology into the application of the software development in real-time serving domain we focus on, which turns out to be encouraging.
Algorithm 745: computation of the complete and incomplete Fermi-Dirac integral
Authors: Michele Goano
Venue: ACM Transactions on Mathematical Software (TOMS) (1995)

Portable Fortran subroutines computing the Fermi-Dirac integral Fjx and the incomplete Fermi-Dirac integral Fjx,b are presented. For the first time a set of series expansions is implemented allowing these special functions to be evaluated efficiently within a prescribed accuracy for real jand x.
A randomized linear-time algorithm to find minimum spanning trees
Authors: David R. Karger, Philip N. Klein, Robert E. Tarjan
Venue: Journal of the ACM (JACM) (1995)

We present a randomized linear-time algorithm to find a minimum spanning tree in a connected graph with edge weights. The algorithm uses random sampling in combination with a recently discovered linear-time algorithm for verifying a minimum spanning tree. Our computational model is a unit-cost random-access machine with the restriction that the only operations allowed on edge weights are binary comparisons.