ppxscal/embedding_network huggingface dataset:
EVIDENCE FOR A SATISFIABILITY THRESHOLD FOR RANDOM 3CNF FORMULAS
Authors: Tracy Larrabee, Yumi Tsuji
Venue:  (1992)

This paper presents empirical evidence of a satisfiability threshold in random 3CNF formulas. The paper also expands on and supports the conjecture of Mitchell, Selman, and Levesque that *hard* randomly generated CNF formulas will be hard for any reasonable satisfiability algorithm. We report statistics for a much larger set of variables than have been previously reported; in particular, we show that for each clause to variable ratio less than 4.2, the percentage of satisfiable formulas increases, and for each clause to variable ratio greater than 4.2, the percentage of satisfiable formulas decreases as a function of number of variables. We found that several algorithms behaved qualitatively in the same fashion. We report on the relative performance of each algorithm.
On the Importance of Tuning in Incremental View Maintenance: An Experience Case Study
Authors: K. O''Gorman, D. Agrawal, A. E Abbadi
Venue:  (2000)

We originally set out to explore the performance of a particular algorithm for incremental maintenance of a materialized view in a data warehouse. We chose to use a substantial database schema and population, derived from the TPC-D family of benchmarks, with a population size of around one gigabyte. In the process, we discovered that at this size, unexpected issues with the query and update processing had to be understood and dealt with before the results would be meaningful. We discover that incremental maintenance is feasible over a wide range of update sizes (granularities), and that in all cases a cursor-based version of the algorithm performs the best. This is a report of both the results of the original inquiry and of some of the events encountered.
Multiresolution Image Analysis Based on Local Symmetries
Authors: A. P. King, R. G. Wilson
Venue:  (1993)

This report describes two seemingly distinct areas of work. First, there is the derivation of a new multiresolution image restoration algorithm, and secondly there is the development of a new approach to feature extraction. A review of these two areas is presented, the new algorithms outlined, and some results presented. The unifying principle behind this work is the idea of image symmetries. The background of this concept is reviewed, and its applicability to the current work explained. Finally, some speculations and expectations concerning the future direction of this research is included.
Longest Common Subsequences
Authors: M. S. Paterson, Vlado Dancik
Venue:  (1994)

The length of a longest common subsequence (LLCS) of two or more strings is a useful measure of their similarity. The LLCS of a pair of strings is related to the `edit distance'', or number of mutations/errors/editing steps required in passing from one string to the other. In this talk, we explore some of the combinatorial properties of the sub- and super-sequence relations, survey various algorithms for computing the LLCS, and introduce some results on the expected LLCS for pairs of random strings.
Will networks on chip close the productivity gap?
Authors: Axel Jantsch, Hannu Tenhunen
Venue: Networks on chip (2003)

We introduce two properties of the design process called the arbitrary composability and the linear effort properties. We argue that a design paradigm, which has these two properties is scalable and has the potential to keep up with the pace of technology advances. Then we discuss some of the trends that will enforce significant changes on current design methodologies and techniques. Finally, we argue that the emerging Network-on-Chip (NoC) paradigm promises to address these trends and challenges and has all prerequisites to provide the arbitrary composability and the linear effort properties. Consequently we conclude that NoC is a likely basis for future System-on-Chip platforms and methodologies.
Distributed Transaction Processing on an Ordering Network
Authors: Craig Williams, Paul F. Reynolds
Venue:  (2001)

The increasing demand for high throughputs in transaction processing systems leads to high degrees of transaction concurrency and hence high data contention. The conventional dynamic two-phase locking (2PL) concurrency control (CC) technique causes system thrashing at high data contention levels, restricting transaction throughput. Optimistic concurrency control (OCC) is an alternative strategy, but OCC techniques suffer from wasted resources caused by repeated transaction restarts. We propose a new technique, ORDER, that enlists the aid of the interconnection network in a distributed database system in order to coordinate transactions. The network in an ORDER system provides total ordering of messages at a low cost, enabling efficient CC. We compare the performance of dynamic 2PL and ORDER, using both an analytical model and a simulation. Unlike previously-proposed models for 2PL, our analytical model predicts performance accurately even under high data contention. We study the effects of various parameters on performance, and demonstrate that ORDER outperforms dynamic 2PL for a wide range of workloads.
Deterministic Polylog Approximation for Minimum Communication Spanning Trees
Authors: D. Peleg, E. Reshef
Venue:  (1998)

This paper considers the problem of selecting a minimum communication spanning tree (MCT) for a given weighted network, namely, a tree that minimizes the total cost of transmitting a given set of communication requirements between n sites over the tree edges [Hu74]. A slightly stronger formulation of the problem [AKPW95] is based on the concept of a minimum average stretch spanning tree (MAST) for weighted connected multigraphs. In particular, a r-solution for the MAST problem (namely, an algorithm for constructing a spanning tree with average stretch rho) in the special case of complete weighted graphs implies an approximation algorithm for the MCT problem with approximation ratio rho. It is conjectured in [AKPW95] that for any given weighted multigraph there exists a spanning tree with average stretch O(logn) (which is the best possible, in view of the Omega(logn) lower bound given therein). However, the (deterministic) construction presented (which is the best construction to date) yields only a bound of O(exp(O(logn))) on the average stretch. For the restricted case of complete weighted graphs, there is a better, albeit randomized, construction yielding average stretch O(log2 n) [Bartal96]. This implies a randomized approximation algorithm for MCT with the same ratio. This paper narrows the gap between the deterministic and randomized solutions for the complete case (and hence for the MCT problem), by presenting a deterministic algorithm that for every weighted complete multigraph constructs a spanning tree whose average stretch is bounded by O(log3 n). This yields a deterministic polynomial-time approximation algorithm for MCT with ratio O(log3 n). In addition, our solution approach confirms the conjecture of [AKPW95] in the special case of d-dimensional Euclidean complete multigraphs for fixed d, where our construction yields spanning trees with O(logn) average stretch.
Parallel Recognition of Complement Reducible Graphs and Cotree Construction
Authors: David G. Kirkpatrick, Teresa M Przytycka
Venue:  (1988)

A simple parallel algorithm is presented for constructing parse tree representations of graphs in a rich family known as cographs. From the parse tree representation of a cograph it is possible to compute in an efficient way many properties which are difficult for general graphs. The presented algorithm runs in O$(\log^{2} n)$ parallel time using O$(n^{3} / \log^{2} n)$ processors on a CREW PRAM.
Two Point Constraint Approximation in Structural Optimization
Authors: Robert T. Haftka, Joel A. Nachlas, Layne T. Watson, Thomas Rizzo, Rajendra Desai
Venue:  (1986)

The use of constraint approximations is recognized as a primary means of achieving computational efficiency in structural optimization. Existing approximation methods are based upon the value of the constraint function and its derivatives at a single point. The present paper explores the use of approximations based upon the value of the constraint and its derivative at two points. Several candidate approximations are suggested and tested for randomly generated rational constraint functions* Several of the approximations prove to be superior to the single point approximations.
CIRCUMSCRIPTION: A FORMALISM OF NONMONOTONIC REASONING
Authors: Madhavan Thirumalai
Venue:  (1990)

It is commonsense to conclude, in the absence of any statement to the contrary, that a particular instance of a certain class of objects is typical in that it has all the attributes of that class of objects. Later, one withdraws one''s conclusion if one learns that the object in question varies from the typical in some way. Such reasoning, called *Nonmonotonic Reasoning*, is beyond the realm of classical logic. In this thesis we explore *Circumscription*, one of the formalisms of nonmonotonic reasoning. 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
Image Segmentation Based on the Multiresolution Fourier Transform and Markov Random Fields
Authors: Guo Chen, Roland Wilson
Venue:  (1998)

In this work, the Multiresolution Fourier Transform (MFT) and Markov Random Fields (MRFs) are combined to produce as a tool for image segmentation. Firstly, a Laplacian Pyramid is used as a high-pass filter. Then, the MFT is applied in order to segment images based on the analysis of local properties in the spatial frequency domain. A methodology for edge detection in image segmentation in the Bayesian framework using Markov random field models is then developed. Stochastic Relaxation is also adopted to maximise the likelihood and find the globally minimum energy states using simulated annealing.
Atomic Semantics of Nonatomic Programs
Authors: James H. Anderson, Mohamed G. Gouda
Venue:  (1987)

We argue that it is possible, and sometimes useful, to reason about nonatomic programs within the conventional atomic model of concurrency.
Multimessage Multicasting: Complexity and Approximations
Authors: Teofilo F. Gonzalez
Venue:  (1996)

We consider Multimessage Multicasting over the $n$ processor complete (or fully connected) static network ($MM_{C}$). First we present a linear time algorithm that constructs for every degree $d$ problem instance a communication schedule with total communication time at most $d^2$, where $d$ is the maximum number of messages that each processor may send (receive). Then we present degree $d$ problem instances such that all their communication schedules have total communication time at least $d^2$. We observe that our lower bound applies when the fan-out (maximum number of processors receiving any given message) is huge, and thus the number of processors is also huge. Since this environment is not likely to arise in the near future, we turn our attention to the study of important subproblems that are likely to arise in practice. We show that when each message has fan-out $k=1$ the $MM_C$ problem corresponds to the Makespan Openshop Preemptive Scheduling problem which can be solved in polynomial time, and show that for $k \ge 2$ our problem is NP-complete. We present an algorithm to generate a communication schedule with total communication time $2d-1$ for any degree $d$ problem instance with fan-out $k=2$. Our main result is an $O(q \cdot d \cdot e)$ time algorithm, where $e \le nkd$ (the input length), with an approximation bound of $qd + k^{\frac{1}{q}}(d-1)$, for any integer $q$ such that $k < q <= 2$. Our algorithms are centralized and require all the communication information ahead of time. Applications where all of this information is readily available include iterative algorithms for solving linear equations, and most dynamic programming procedures. The Meiko CS-2 machine and in general computer systems with processors communicating via dynamic permutation networks whose basic switches can act as data replicators (e.g., $n$ by $n$ Benes network with 2 by 2 switches that can also act as data replicators) will also benefit from our results at the expense of doubling the number of communication phases.
User-System Interfaces: An Important Element of Information Systems Strategies
Authors: H. R Hartson
Venue:  (1988)

A successful human-computer interface is one that exhibits high usability. This paper discusses several key development issues involved in attaining high usability: dialogue independence; an evaluation-centered methodology and support tools for developing the interface, and rapid prototyping. It relates each of these issues to the critical cooperative work that must occur between the two major developer roles: computer scientists (and the software engineering role) and behavioral scientists (and the human factors role). In particular, it examines the need for human factorable human-computer interfaces, rather than ones that are simply human factored, and discusses how each of the key development issues can help achieve human factorable interfaces.
Contemplations of A Simulated Navel
Authors: Richard E. Nance
Venue:  (1988)

The Model Development Environment Project has the goal of defining the software utilities and the database support needed for creating, validating, and experimenting with complex simulation models. This project review, emphasizing the needs and explaining some of the guiding concepts and principles, serves to underscore key issues extending beyond discrete event simulation. An introspective summary presents an optimistic reaction to the fear that technically naive modelers might use the more sophisticated capabilities to produce catastrophic results.
FDT Tools For Protocol Development
Authors: A. A. F. Loureiro, Samuel T. Chanson, Song T. Vuong
Venue:  (1991)

FDT tools support protocol development by making certain activities feasible, easier to be performed, more reliable, and faster. This paper discusses the desirable properties of FDT tools and classifies them according to the different stages of the protocol development cycle. An assessment of the tools available so far and projections (or suggestions) of the tools to come are given. A list of the tools that have appeared since the mid 1980''s is also included.
Parallel and distributed data mining through parallel skeletons and distributed objects
Authors: Massimo Coppola, Marco Vanneschi
Venue: Data mining: opportunities and challenges (2003)

We consider the application of parallel programming environments to develop portable and efficient high performance data mining (DM) tools. We first assess the need of parallel and distributed DM applications, by pointing out the problems of scalability of some mining techniques and the need to mine large, eventually geographically distributed databases. We discuss the main issues of exploiting parallel and distributed computation for DM algorithms. A high-level programming language enhances the software engineering aspects of parallel DM, and it simplifies the problems of integration with existing sequential and parallel data management systems, thus leading to programming-efficient and high-performance implementations of applications. We describe a programming environment we have implemented that is based on the parallel skeleton model, and we examine the addition of object-like interfaces toward external libraries and system software layers. This kind of abstractions will be included in the forthcoming programming environment ASSIST. In the main part of the chapter, as a proof-of-concept we describe three well-known DM algorithms, Apriori, C4.5, and DBSCAN. For each problem, we explain the sequential algorithm and a structured parallel version, which is discussed and compared to parallel solutions found in the literature. We also discuss the potential gain in performance and expressiveness from the addition of external objects on the basis of the experiments we performed so far. We evaluate the approach with respect to performance results, design, and implementation considerations.
Partitioned Frame Networks for Multi-Level, Menu-Based Interaction
Authors: James D. Arthur
Venue:  (1987)

Menu-based systems have continued to flourish because they present a simple interaction format that is adaptable to many diverse applications. The continued integration of menu-based interaction with increasingly sophisticated software systems, however, is resulting in complex, monolithic frame networks with several undesirable characteristics. This paper presents a novel approach to frame network construction and menu-based interaction for application systems that support user task specifications. The approach is based on partitioning the conventional, monolithic frame network into a set of hierarchically structured, disjoint networks that preserves the original network topology while reducing its overall complexity and size. Moreover, by providing a menu-based interaction scheme that exploits this hierarchical structure, one can realize a system that supports a "top-down" approach to user task specification and user interaction at varying levels of sophistication. 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
A Mathematically Precise Two-Level Formal Hardware Verification Methodology*
Authors: Carl Seger, Jeffrey J. Joyce
Venue:  (1992)

Theorem-proving and symbolic trajectory evaluation are both described as methods for the \fIformal verification of hardware\fP. They are both used to achieve a common goal -- correctly designed hardware -- and both are intended to be an alternative to conventional methods based on non-exhaustive simulation. However, they have different strengths and weaknesses. The main significance of this paper is the description of a two-level approach to formal hardware verification, where the HOL theorem prover is combined with the Voss verification system. From symbolic trajectory evaluation we inherit a high degree of automation and accurate models of circuit behavior and timing. From interactive theorem-proving we gain access to powerful mathematical tools such as induction and abstraction. The interface between the HOL and Voss is, however, more than just an ad hoc translation of verification results obtained by one tool into input for the other tool. We have developed a ``mathematical'''' interface where the results of the Voss system is embedded in HOL. We have also prototyped a hybrid tool and used this tool to obtain verification results that could not be easily obtained with previously published techniques.
From Formal Verification to Silicon Compilation
Authors: Jeffrey J. Joyce, Liu, Rushby, Shankar, Suaya, Henke von
Venue:  (1990)

Formal verification is emerging as a viable method for increasing design assurance for VLSI circuits. Potential benefits include reduction in the time and costs associated with testing and redesign, improved documentation and ease of modification, and greater confidence in the quality of the final product. This paper reports on an experiment whose main purpose was to identify the difficulties of integrating formal verification with conventional VLSI CAD methodology. Our main conclusion is that the most effective use of formal hardware verification will be at the higher levels of VLSI system design, with lower levels best handled by conventional VLSI CAD tools.
On the Maximum Tolerable Noise for Reliable Computation by Formulas
Authors: William Evans, Nicholas Pippenger
Venue:  (1995)

It is shown that if a formula is constructed from noisy 2-input NAND gates, with each gate failing independently with probability e, then reliable computation can or cannot take place according as e is less than or greater than e_0 = (3-sqrt(7))/4 = 0.08856....
Logical Frameworks as a Basis for Verification Tools: A Case Study
Authors: Ina Kraan, Peter Baumann
Venue:  (1995)

Wide-spread acceptance and use of formal methods in software development hinges on the availability of powerful tools which are reliable and offer real assistance to the user. Logical frameworks are a suitable medium to build such tools, since they provide a means to show the faithfulness and adequacy of the implementation and have the flexibility needed to build sufficiently automated tools. We present Z- in a deep semantic embedding of the specification language Z and a deductive system for Z in the generic theorem prover Isabelle. We illustrate the use of Z-in-Isabelle with a data refinement proof. We assess to what extent such proofs need to and can be automated to make implementations in logical frameworks such as Z-in-Isabelle viable tools for reasoning about specifications.
Scheduling Real-Time Tasks for Dependability
Authors: Yingfeng Oh, Sang H. Son
Venue:  (1995)

Real-time systems are increasingly used in applications whose failure may result in large economic and human costs. Since many of the systems operate in environments that are non-deterministic, and even hazardous, it is extremely important that the systems must be dependable, i.e., the deadlines of tasks must be met even in the presence of certain failures. In order to enhance the dependability of a real-time system, we study the problem of scheduling a set of real-time tasks to meet their deadlines even in the presence of processor failures. We first prove that the problem of scheduling a set of non-preemptive tasks on more than two processors to tolerate one arbitrary processor failure is NP-complete even when the tasks share a common deadline. A heuristic algorithm is then proposed to solve the problem. The schedule generated by the heuristic algorithm can tolerate one arbitrary processor failure in the worst case. The analysis and experimental data show that the performance of the heuristic algorithm is near-optimal.
Analyzing Exception Flow in Java Programs
Authors: Martin P. Robillard, Gail C. Murphy
Venue:  (1999)

Exception handling mechanisms provided by programming languages are intended to ease the difficulty of developing robust software systems. Using these mechanisms, a software developer can describe the exceptional conditions a module might raise, and the response of the module to exceptional conditions that may occur as it is executing. Creating a robust system from such a localized view requires a developer to reason about the flow of exceptions across modules. The use of unchecked exceptions, and in object-oriented languages, subsumption, makes it difficult for a software developer to perform this reasoning manually. In this paper, we describe a tool called Jex that analyzes the flow of exceptions in Java code to produce views of the exception structure. We demonstrate how Jex can help a developer identify program points where exceptions are caught accidentally, where there is an opportunity to add finer-grained recovery code, and where error-handling policies are not being followed.
Probabilistic Horn abduction and Bayesian networks
Authors: David Poole
Venue:  (1992)

This paper presents a simple framework for Horn-clause abduction, with probabilities associated with hypotheses. The framework incorporates assumptions about the rule base and independence assumptions amongst hypotheses. It is shown how any probabilistic knowledge representable in a discrete Bayesian belief network can be represented in this framework. The main contribution is in finding a relationship between logical and probabilistic notions of evidential reasoning. This provides a useful representation language in its own right, providing a compromise between heuristic and epistemic adequacy. It also shows how Bayesian networks can be extended beyond a propositional language. This paper also shows how a language with only (unconditionally) independent hypotheses can represent any probabilistic knowledge, and argues that it is better to invent new hypotheses to explain dependence rather than having to worry about dependence in the language.