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Full-Text Articles in Computer Engineering

Distributed Computing Systems And Checkpointing, Ken Wong, Mark Franklin Jan 1993

Distributed Computing Systems And Checkpointing, Ken Wong, Mark Franklin

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This paper examines the performance of synchronous checkpointing in a distributed computing environment with and without load redistribution. Performance models are developed, and optimum checkpoint intervals are determined. The analysis extends earlier work by allowing for multiple nodes, state dependent checkpoint intervals, and a performance metric which is coupled with failure-free performance and the speedup functions associated with implementation of parallel algorithms. Expressions for the optimum checkpoint intervals for synchronous checkpointing with and without load redistribution are derived and the results are then used to determine when load redistribution is advantageous.


Dna Mapping Algorithms: Synchronized Double Digest Mapping, Jim Daues, Will Gillett Jan 1993

Dna Mapping Algorithms: Synchronized Double Digest Mapping, Jim Daues, Will Gillett

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A technique called Synchronized Double Digest Mapping (SDDM) is presented; it combines classical Double Digest Mapping (DDM) and Multiple-Restriction-Enzyme Mapping (MREM). Classical DDM is a technique for determining the order of restriction fragments in a clone given three digestions of the clone: a digestion by enzyme1, a digestion by enzyme2, and a digestion by enzyme1 and enzyme2 combined. All algorithms for applying this technique are exponential (in the number of fragments present in the clone) in nature. MREM is an extension of classical high-resolution restriction-fragment mapping of a YAC or a genome, in which the overlaps among a set of …


Exact Dominance Without Search In Decision Trees, Nilesh L. Jain, Ronald P. Loui Dec 1992

Exact Dominance Without Search In Decision Trees, Nilesh L. Jain, Ronald P. Loui

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In order to improve understanding of how planning and decision analysis relate, we propose a hybrid model containing concepts from both. This model is comparable to [Hartman90], with slightly more detail. Dominance is simple concept in decision theory. In a restricted version of our model, we give conditions under which dominance can be detected without search: that is, it can be used as a pruning strategy to avoid growing large trees. This investigation follows the lead of [Wellman87]. The conditions seem hard to meet, but may nevertheless be useful in forward-chaining situations without focus, such as [Breese87]. It may be …


Efficient Accommodation Of May-Alias Information In Ssa Form, Ron Cytron, Reid Gershbein Dec 1992

Efficient Accommodation Of May-Alias Information In Ssa Form, Ron Cytron, Reid Gershbein

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We present an algorithm for incrementally including may-alias information into Static Single Assignment form by computing a sequence of increasingly precise (and correspondingly larger) partial SSA forms. Our experiments show significant speedup of our method over exhaustive use of may-alias information, as optimization problems converge well before most may-aliases are needed.


The Programmers' Playground: I/O Abstraction For Heterogeneous Distributed Systems, Kenneth J. Goldman, Michael D. Anderson Nov 1992

The Programmers' Playground: I/O Abstraction For Heterogeneous Distributed Systems, Kenneth J. Goldman, Michael D. Anderson

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A new high-level approach to interprocess communication in heterogeneous distributed systems in introduced, This approach, called I/O Abstraction, allows one to write each functional component of a distributed system as an encapsulated program that acts upon a set of local data structures, some of which may be published for external use. The functional components are separately configured by establishing logical connections among the published data structures. In order to illustrate this approach, we describe the The Programmers' Playground, a high-level language "veneer" and protocol designed to support I/O abstraction in heterogeneous computing environment. Support for communication among programs written in …


Computing Specificity, Ronald Loui, J. Norman, K. Stiefvater, A. Merrill, A. Costello, J. Olson Nov 1992

Computing Specificity, Ronald Loui, J. Norman, K. Stiefvater, A. Merrill, A. Costello, J. Olson

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This note reports on an effort to implement a version of Poole's rule for specificity. Relatively, efficient implementation relies on correcting and improving a pruning lemma of Simari-Loui [92]. This in turn requires revision of Poole's specificity concept. The resulting system is a usable knowledge representation system with first-order-language and defeasible reasoning. Sample input and output are included in an appendix. It is a good candidate for multiple inheritance applications; it is useful for planning, but limited by the underlying search for plans.


Process And Policy: Resource-Bounded Non-Demonstrative Reasoning, Ronald P. Loui Oct 1992

Process And Policy: Resource-Bounded Non-Demonstrative Reasoning, Ronald P. Loui

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This paper investigates the appropriateness of formal dialectics as a basis for non-monotonic and defeasible reasoning that takes computational limits seriously. Rules that can come into conflict should be regarded as policies, which are inputs to deliberative processes. Dialectical protocols are appropriate for such deliberations when resources are bounded and search is serial. AI, it is claimed here, is now perfectly positioned to correct many misconceptions about reasoning that have resulted from mathematical logic's enormous success in this century: among them (1) that all reasons are demonstrative, (2) that rational belief is constrained, not constructed, (3) that process and disputation …


Separating Structure From Function In The Specification And Design Of Distributed Systems, Kenneth J. Goldman Sep 1992

Separating Structure From Function In The Specification And Design Of Distributed Systems, Kenneth J. Goldman

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A distributed system is viewed as a collection of functional components and a unifying structure that defines relationships among the components. In the paper, we advocate a particular approach to distributed system specification and design in which the structure of a distributed system is specified separately from the functional components. This permits one to reason about individual functional components in isolation, and encourages one to make explicit not only the input/output behavior of the functional components but also the logical placement of these components within the overall structure of the system. We describe a new software tool for the specification, …


Dna Mapping Algorithms: Strategies For Single Restriction Enzyme And Multiple Restriction Enzyme Mapping, Will Gillett Aug 1992

Dna Mapping Algorithms: Strategies For Single Restriction Enzyme And Multiple Restriction Enzyme Mapping, Will Gillett

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An approach to high-resolution restriction-fragment DNA mapping, known as Multiple-Restriction-Enzyme mapping (MRE mapping), is present. This approach significantly reduces the uncertainty of clone placement by using clone ends to synchronize the position in of clones within different maps, each map being constructed from fragment-length data produced by digestion of each clone with a specific restriction enzyme. Maps containing both fragments-length data and clone-end data are maintained for each restriction enzyme, and synchronization between two such maps is achieved by requiring them to have "compatible" clone-end map projections. Basic definitions of different kinds of maps, such as restriction sites maps, restriction …


Can Pac Learning Algorithms Tolerate Random Attribute Noise?, Sally A. Goldman, Robert H. Sloane Jul 1992

Can Pac Learning Algorithms Tolerate Random Attribute Noise?, Sally A. Goldman, Robert H. Sloane

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This paper studies the robustness of pac learning algorithms when the instances space is {0,1}n, and the examples are corrupted by purely random noise affecting only the instances (and not the labels). In the past, conflicting results on this subject have been obtained -- the "best agreement" rule can only tolerate small amounts of noise, yet in some cases large amounts of noise can be tolerated. We show that the truth lies somewhere in between these two alternatives. For uniform attribute noise, in which each attribute is flipped independently at random with the same probability, we present an algorithm that …


The 3-Tier Structured Access Protocol To Control Unfairness In Dqdb Mans, Lakshmana N. Kumar, Andreas D. Bovopoulos Jun 1992

The 3-Tier Structured Access Protocol To Control Unfairness In Dqdb Mans, Lakshmana N. Kumar, Andreas D. Bovopoulos

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This paper addresses the unfairness problem appearing in 802.6-based DQDB MANs. Traffic load demand is characterized as low (below 0.4 of the channel capacity), normal (from 0.4 to 0.9 of the channel capacity) or heavy (greater than 0.9 of the channel capacity). At low loads the 802.6 protocol is acceptably fair. At normal loads, however, the protocol performance is markedly unfair. The unfairness is related to the latency in transporting a request. At heavy loads the unfairness is both latency-related and flooding-related. In this paper, both types of unfairness are carefully analyzed. As a control measure, a 3-Tier Structured Access …


Energy-Related Feature Abstraction For Handwritten Digit Recognition, Thomas H. Fuller Jr. Jan 1992

Energy-Related Feature Abstraction For Handwritten Digit Recognition, Thomas H. Fuller Jr.

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Most handwritten character recognizers use either graphical (static) or first-order dynamic data. Our research speculates that the mental signal to write a digit might be partially encoded as an energy profile. We used artificial neural networks (ANN) to analyze energy-related features (first and second time derivatives) of handwritten digits of 20 subjects and later 40 subjects. An experimenal environment was developed on a NeXTstation with a real-time link to a pen-based GO computer. Although such an experiment cannot confirm an energy profile encoded in the writer, it did indicate the usefulness of energy-related features by recognizing 94.5% of the 600 …


Dna Mapping Algorithms: Clone Sequencing, Judith H. Lewis, Will Gillett Oct 1991

Dna Mapping Algorithms: Clone Sequencing, Judith H. Lewis, Will Gillett

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The DNA restriction mapping problem can be abstracted to the Shortest Common Matching String problem by viewing the restriction fragment lengths as symbols and the clones as bags. The Shortest Common Matching String problem can be decomposed into the Bag Sequencing problem and the Symbol Sequencing problem. All three of these problems have bene shown to be NP-hard. Rhee has proposed a family of greedy algorithms to compute polynomial time approximations to the Bag Sequencing problem, which produced surprisingly good performance results on abstracted data. In the test data generated by Rhee for pragmatic analysis, the symbols in bags represented …


Converting Binary Thresholds Networks Into Equivalent Symmetric Networks, Gadi Pinkas Jul 1991

Converting Binary Thresholds Networks Into Equivalent Symmetric Networks, Gadi Pinkas

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We give algorithms to convert any network of binary threshold units (that does not oscillate) into an equivalent network with symmetric weight matrix (like Hopfield networks [Hopfield 82] or Boltzmann machines [Hinton, Sejnowski 88]). The motivation for the transformation is dual: a) to demonstrate the expressive power of symmetric networks; i.e. binary threshold networks (that do not oscillate) are subsumed in the energy minimization paradigm; 2) to use network modules (developed for the spreading activation paradigm for example), within the energy minimization paradigm. Thus optimization [Tank, Hopfield 88] and approximation of hard problems can be combined with efficient modules, that …


Composition, Superposition, And Encapsulation In The Formal Specification Of Distributed Systems, Kenneth J. Goldman Jul 1991

Composition, Superposition, And Encapsulation In The Formal Specification Of Distributed Systems, Kenneth J. Goldman

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Composition, superposition, and encapsulation are important techniques that work well together for designing large distributed software systems. Composition is a symmetric operator that allows system components to communicate with each other across module boundaries. Superposition is an asymmetric relationship that allows one system component to observe the state of another. Encapsulation is the ability to define the reason about the behavior of a module in terms of a well-defined boundary between that module and its environment, while hiding the internal operations of that module. In this paper, the I/O automation model of Lynch and Tuttle is extended to permit superposition …


The Spectrum Simulation System: A Formal Approach To Distributed Algorithm Development Tools, Kenneth J. Goldman Jul 1991

The Spectrum Simulation System: A Formal Approach To Distributed Algorithm Development Tools, Kenneth J. Goldman

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We present the Spectrum Simulation System, a new research tool for the design and study of distributed algorithms. Based on the formal Input/Output Automation model of Lynch and Tuttle, Spectrum allows one to express distributed algorithms as collections of I/O automata and simulate them directly in terms of the semantics of that model. This permits integration of algorithm specification, design, debugging, analysis, and proof of correctness within a single formal framework that is natural for describing distributed algorithms. Spectrum provides a language for expressing algorithms as I/O automata, a simulator for generating algorithm executions, and a graphics interface for constructing …


An Access Protection Solution For Heavy Load Unfairness In Dqdb, Lakshmana N. Kumar, Andreas D. Bovopoulos Jul 1991

An Access Protection Solution For Heavy Load Unfairness In Dqdb, Lakshmana N. Kumar, Andreas D. Bovopoulos

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This paper discusses the unfairness issue arising in a 802.6 DQDB network at high loads-- when the traffic demand to a bus exceeds the capacity of that bus. As per the 802.6 protocol, at heavy loads, the end nodes along a bus experience longer delays than the other nodes. The origin and remedy of this heavy load unfairness is discussed. An access control scheme is proposed as a solution. The comparison of the proposed scheme with 802.6 protocol is presented. The simulation results and performance characteristics are discussed under several types of loads. With symmetric load conditions under the proposed …


Rapid Display Of Radiographic Images, Jerome R. Cox Jr., Stephen M. Moore, Robert A. Whitman, G. James Blaine, R. Gilbert Jost, L. Magnus Karlsson, Thomas L. Monsees, Gregory L. Hansen, Timothy C. David Jul 1991

Rapid Display Of Radiographic Images, Jerome R. Cox Jr., Stephen M. Moore, Robert A. Whitman, G. James Blaine, R. Gilbert Jost, L. Magnus Karlsson, Thomas L. Monsees, Gregory L. Hansen, Timothy C. David

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The requirements for the rapid display of radiographic images exceed the capabilities of widely available display, computer and communication technologies. Computed radiography captures data with a resolution of about four megapixels. Large format displays are available that can present over four megapixels. One megapixel displays are practical for use in combination with large format displays and in areas where the viewing task does not require primary diagnosis. This paper describes an electronic radiology system that approximates the highest quality systems, but through the use of several interesting techniques allows the possibility of its widespread installation throughout hospitals. The techniques uses …


Dna Mapping Algorithms: Abstract Data Types - Concepts And Implementation, Will Gillett, Liz Hanks Jun 1991

Dna Mapping Algorithms: Abstract Data Types - Concepts And Implementation, Will Gillett, Liz Hanks

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The conceptual aspects of and the implementation details of a set of self-identifying abstract data types (ADT) are described. Each of the ADTs constitutes a specific class of object, upon which a set of well-defined access functions is available. The intent of these ADTs is to supply a paradigm in which a class of object is available for manipulation, but in which the underlying implementation is hidden from the application programmer. Specific ADTs are the described in some detail. The tagged architecture used to achieve the self-identifying property of the ADTs is presented, and a set of required system-backbone access …


The Difficulty Of Random Attribute Noise, Sally A. Goldman, Robert H. Sloan Jun 1991

The Difficulty Of Random Attribute Noise, Sally A. Goldman, Robert H. Sloan

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This paper studies the robustness of pac learning algorithms when the instance space is {0,1}n, and the examples are corrupted by purely random noise affecting only the instances (and not the labels). In the past, conflicting results on this subject have been obtained-- the "best agreement" rule can only tolerate small amounts of noise, yet in some cases large amounts of noise can be tolerated. We show the truth lies somewhere between the two alternatives. For uniform attribute noise, in which each attribute is flipped independently at random with the same probability, we present an algorithm that pac learns monomial …


Computational Learning Theory Lecture Notes For Cs 582 Spring Semester, 1991, Sally A. Goldman Jun 1991

Computational Learning Theory Lecture Notes For Cs 582 Spring Semester, 1991, Sally A. Goldman

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This manuscript is a compilation of lecture notes from the graduate level course CS 582, "Computational Learning Theory," I taught at Washington University in the spring of 1991. Students taking the course were assumed to have background in the design and analysis of algorithms as well as good mathematical background. Given that there is no text available on this subject, the course material was drawn from recent research papers. I selected the first twelve topics and the remainder were selected by the students from a list of provided topics. This list of topics is given at the end of these …


Applying Formal Verification Methods To Pure Rule-Based Programs, Rose F. Gamble, Gruia-Catalin Roman, William E. Ball, H. Conrad Cunningham May 1991

Applying Formal Verification Methods To Pure Rule-Based Programs, Rose F. Gamble, Gruia-Catalin Roman, William E. Ball, H. Conrad Cunningham

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Reliability, defined as the guarantee that a program satisfies its specifications, is an important aspect of many applications for which rule-based expert systems are suited. Verification refer to the process used to determine the reliability of the rule-based program. Because past approaches to verification are informal, guarantees of reliability cannot fully be made without severely restricting the system. On the other hand, by constructing formal specifications for a program and showing the program satisfies those specifications, guarantees of reliability can be made. This paper presents an assertional approach to the verification of rule-based programs. The proof logical needed for verification …


Dna Mapping Algorithms: Topological Mapping, Kenneth Moorman, Paul Poulosky, Will Gillett Mar 1991

Dna Mapping Algorithms: Topological Mapping, Kenneth Moorman, Paul Poulosky, Will Gillett

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There are several basic approaches that can be used in attempting to produce high-resolution DNA restriction maps. A standard approach is the match/merge approach in which first the topology of the map units being mapped together is suppressed and lists of potential matches between fragments are generated, and second the topology is introduced to eliminate matchlists which are inconsistent with the topology. This technical report documents a different approach to DNA mapping, known as topological mapping. In topological mapping the precedence of the two criteria are reversed, i.e., the topology of the two map units is used as the primary …


Performance Evaluation Of A Traffic Control Mechanism For Atm Networks, Andreas D. Bovopoulos Feb 1991

Performance Evaluation Of A Traffic Control Mechanism For Atm Networks, Andreas D. Bovopoulos

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Future ATM networks will be required to support a plethora of services, transaction types and cell sequence behaviors with performance guarantees. Before this goal can be realized, however, some basically problems related to bandwidth allocation and traffic control in the ATM layer must be resolve. Such problems will in all likelihood defy solution as long as they studied in isolation without a unifying traffic characterization and traffic control framework. This work presented in this paper is part of an ongoing effort directed at the development of an integrated traffic characterization and control infrastructure for ATM networks. In this paper a …


Saam: The Strategic Asset Allocation Model, Judy Lewis, Todd Gamble, John Tai Feb 1991

Saam: The Strategic Asset Allocation Model, Judy Lewis, Todd Gamble, John Tai

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Asset Allocation has become a dominant factor for investment strategies in recent years. It has found that by holding a strategically diversified portfolio, a high total return on investments can be maintained while, at the same time, reducing portfolio volatility. With recent federal regulations mandating pension investment responsibilities, appropriate asset allocation has become more important than ever. SAAM is a software package specifically designed to be used as a tool to aid the investment professional in determining pension portfolio allocations. SAAM uses the expect system shell CLIPS, has a user-friendly interface, displays output graphically, and runs within the confines of …


Performance Analysis Of The Ethernet Under Conditions Of Bursty Traffic, Tony Y. Mazraani, Gurudatta M. Parulkar Feb 1991

Performance Analysis Of The Ethernet Under Conditions Of Bursty Traffic, Tony Y. Mazraani, Gurudatta M. Parulkar

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In this paper we present a simulation study of the Ethernet performance under conditions of bursty traffic. This study is motivated by two observations: Ethernet will continue to be a widely used Local Area Network (LAN), especially as an access LAN for future high speed internet (or Broadband ISDN); and future high speed applications can best be modeled as bursty sources. Bursty traffic in this study is specified using three parameters: peak bandwidth, average bandwidth, and burst factor. The simulation study shows that the inherent behavior of the Ethernet does not change with bursty traffic. That is, as long as …


Transforming A Rule-Based Program, Rose F. Gamble Jan 1991

Transforming A Rule-Based Program, Rose F. Gamble

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Conflict resolution is a form of global control used in production systems to achieve an efficient sequential execution of a rule-based program. This type of control is not used to parallel production system models [6,13]. Instead, only those programs that make no assumptions regarding conflict resolution are executed in parallel. Therefore, the initial sequential rule-based programs are either executed in parallel without their conflict resolution strategy, which normally results in incorrect behavior, or the programs are transformed in an ad hoc manner to execute on an particular parallel production system model. As a result, these programs do not exhibit the …


A Multi-Scale Approach For Recognizing Complex Annotations In Engineering Documents., Andrew Francis Laine, William Ball, Arun Kumar Dec 1990

A Multi-Scale Approach For Recognizing Complex Annotations In Engineering Documents., Andrew Francis Laine, William Ball, Arun Kumar

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This paper describes a novel method of character recognition targeted for extracting complex annotations found in engineering documents. The results of this work will make it possible to capture the information contained in documents used to support facilities management and manufacturing. The recognition problem is made difficult in part because characters and text may be expressed in arbitrary fonts and orientations. Our approach includes a novel incremental strategy based on the multi-scale representation of wavelet decompositions. Our approach is motivated by biological mechanisms of the human visual systems. Using wavelets as a set of basis functions, we may decompose an …


Segment Streaming For Efficient Pipelined Televisualization, Fengmin Gong Nov 1990

Segment Streaming For Efficient Pipelined Televisualization, Fengmin Gong

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The importance of scientific visualization for both science and engineering endeavors has been well recognized. Televisualization becomes necessary because of the physical distribution of data, computation resources, and users involved in the visualization process. However, televisualization poses a number of challenges to the designers of communication protocols. A pipelined televisualization (PTV) model is proposed for efficient implementation of a class of visualization applications. Central to the proposed research is the development of a segment of streaming IPC (interprocess communication) mechanism in support of efficient pipelining across very high speed internetworks. This requires exploration of special issues arising from extending a …


Highly Concurrent Logically Synchronous Multicast, Kenneth J. Goldman Oct 1990

Highly Concurrent Logically Synchronous Multicast, Kenneth J. Goldman

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We define the logically synchronous multicast problem, which imposes a natural and useful structure on message delivery order in an asynchronous system. In this problem, a computation proceeds by a sequence of multicasts, in which a process sends a message to some arbitrary subset of the processes, including itself. A logically synchronously multicast protocol must make it appear to every process as if each multicast occurs simultaneously at all participants of that multicast (sender plus receivers). Furthermore, if a process continually wishes to sends a message, it must eventually be permitted to do so. We present a highly concurrent solution …