Physical Sciences and Mathematics Commons^™

The N-Body Problem: Distributed System Load Balancing And Performance Evaluation, Vasudha Govindan, Mark A. Franklin

All Computer Science and Engineering Research

In this paper, the N-body simulation problem is considered, its parallel implementation described, its execution time performance is modeled and compared with measured results, and two alternative load balancing algorithms for enhancing performance investigated. Parallel N-body techniques are widely applied in various fields and possess characteristics that challenge the computation and communication capabilities of parallel computing systems and are therefore good candidates for use as parallel benchmarks. Performance models may be used to estimate the performance of an algorithm on a given system, identify performance bottlenecks and study the performance implications of several algorithm are system enhancements. In this paper, …

Clinical Decision-Support Systems In Radiation Therapy, Nilesh L. Jain, Michael G. Kahn

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Computers have been used in radiation therapy since the early 1960s to perform dose calculations. In the last decade, researchers have developed computer-based clinical decision-support systems for assisting in different decision-making tasks in radiation therapy. This paper reviews eleven prototype systems developed for target volume delineation, treatment planning, treatment plan evaluation, and treatment machine diagnosis. The advent of three-dimensional (3D) conformal radiation therapy (CRT) provides radiation oncologists with the opportunity to consider innovative beam arrangements which were not possible in two-dimensional class solutions. The difficulty of manually generating the thousands of clinically plausible 3D treatment plans calls for the use …

The Study Of Computer Science Concepts Through Game Play, Benjamin M. Weber

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No abstract provided.

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

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I/O abstraction is offered as a new high-level approach to interprocess communication. Functional components of a concurrent system are written as encapsulated modules that act upon local data structures, some of which may be published for external use. Relationships among modules are specified by logical connections among their published data structures. Whenever a module updates published data, I/O takes place implicitly according to the configuration of logical connections. The Programmer's Playground, a software library and run-time system supporting I/O abstraction, is described. Design goals include high-level communication among programs written in multiple programming languages and the uniform treatment of discrete …

A Unified Model For Shared-Memory And Message-Passing Systems, Kenneth Goldman, Katherine Yelick

All Computer Science and Engineering Research

A unified model of distributed systems that accomodates both shared-memory and message-passing communication is proposed. An extension of the I/O automaton model of Lynch and Tuttle, the model provides a full range of types of atomic accesses to shared memory, from basic reads and writes to read-modify-write. In addition to supporting the specification and verification of shared memory algorithms, the unified model is particularly helpful for proving correspondences between atomic shared objects and invocation-response systems and for proving the correctness of systems that contain both message passing and shared memory (such as a network of shared-memory multiprocessors or a distributed …

Human And Machine Cognition Workshop Papers 1989, 1991, 1993, R. P. Loui

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No abstract provided.

A Design For Reasoning With Policies, Prrecedents And Rationales, Ronald P. Loui, Jeff Norman, Jon Olson, Andrew Merrill

All Computer Science and Engineering Research

No abstract provided.

Reasoning About Synchrony Illustrated On Three Models Of Concurrency, Gruia-Catalin Roman, Jerome Plun

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This paper presents a model of concurrency (Dynamic Synchrony) whose distinctive feature is a novel formal treatment of synchronization. Synchrony is defined as the coordinated execution of two or more actions. The dynamic aspect comes from the fact that the definition of which actions must be executed synchronously can change freely during the execution of the program. This unique modeling capability comes with a UNITY-stype assertional logic that can be applied to program verification and derivation. This paper shows that the proposed proof logic can be used to verify programs expressed using other models of foncurrency without having to translate …

The Washington University Multimedia System, William D. Richard, Jerome R. Cox Jr., Brian Gottlieb, Ken Krieger

All Computer Science and Engineering Research

The Washington University Multimedia System (MMS) is a complete multimedia system capable of transmitting and receiving video, audio, and radiological images, in addition to normal network traffic, over the Washingon University broadband ATM network. The MMS consists of an ATMizer and three multimedia subsystems. The ATMizer implements the host interface, the interface to the ATM network, and the interface to the three multimedia subsystems. The video sybsystem encodes and decodes JPEG compressed video using two hardware compression engines. The audio subsystem encodes and decodes CD-quality stereo audio. The high-speed radiological image subsystem reformats radiological image data transmitted by a dedicated …

A Fault Tolerant Connectionist Architecture For Construction Of Logic Proofs, Gadi Pinkas

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This chapter considers the problems of expressing logic and constructing proofs in fault tolerant connectionist networks that are based on energy minimalism. Given a first-order-logic knowledge base and a bound k, a symmetric network is constructed (like a Boltzman machine or a Hopfield network) that searches for a proof for a given query. If a resolution-based proof of length no longer than k exists, then the global minima of the energy function that is associated with the network represent such proofs. If no proof exist then the global minima indicate the lack of a proof. The network that is generated …

Research Proposal: Preference Acquisition Through Reconciliation Of Inconsistencies, Nilesh L. Jain

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The quality of performance of a decision-support system (or an expert system) is determined to a large extent by its underlying preference model (or knowledge base). The difficulties in preference and knowledge acquisition make them a major focus of current research in decision-support and expert systems. Researchers have used various concepts to develop promising acquisition techniques. One of the concepts used is knowledge maintenence where the knowledge base is changed in response to incorrect or inadequate performance by the expert system. This dissertation investigates a preference acquisition technique based on the reconciliation of inconsistencies between the preference model and the …

Objective Evaluation Of Radiation Treatment Plans, Nilesh L. Jain, Michael G. Kahn

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The evaluation of radiation treatment plans involves making trade-offs among doses delivered to the tumor volumes and nearby normal tissues. Evaluating state-of-the-art three-dimensional (3D) plans is a difficult task because of the huge amount of planning data that needs to be deciphered. Multiattribute utility theory provides a methodology for specifying trade-offs and selecting the optimal plan from many competing lans. Using multiattribute utility theory, we are developing a clinically meaningful objective plan-evaluation model for 3D radiation treatment plans. Our model incorporates three of the factors involved in radiation treatment evaluation - treatment preferences of the radiation oncologist, clinical condition of …

Supervised Competitive Learning With Backpropagation Network And Fuzzy Logic, Takayuki Dan Kimura, Thomas H. Fuller Jr., Ce Wang

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SCL assembles a set of learning modules into a supervised learning system to address the stability-plasticity dilemma. Each learning module acts as a similarity detector for a prototype, and includes prototype resetting (akin to that of ART) to respond to new prototypes. Here (Part I) we report SCL results using back-propagation networks as the learning modules. We used two feature extractors: about 30 energy-based features, and a combination of energy-based and graphical features (about 60). ACL recognized 96% (energy) and 99% (energy/graphical) of test digits, and 91% (energy) and 96% (energy/graphical) of test letters. In the accompanying paper (Part II), …

Teaching A Smarter Learner, Sally A. Goldman, H. David Mathias

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We introduce a formal model of teaching in which the teacher is tailored to a particular learner, yet the teaching protocol is designed so that no collusion is possible. Not surprisingly, such a model remedies the non-intuitive aspects of otehr models in which the teacher must successfully teach any consistent learner. We prove that any class that can be exactly identified by a deterministic polynomial-time algorithm with access to a very rich set of example-based queries is teachable by a computationally unbounded teacher and a polynomial-time learner. In addition, we present other general results relating this model of teaching to …

Improving The Speed Of A Distributed Checkpointing Algorithm, Sachin Garg, Kenneth F. Wong

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This paper shows how Koo and Toueg's distributed checkpointing algorithm can be modified so as to substantially reduce the average message volume. It attempts to avoid O(n{squared}) messages by using dependency knowledge to reduce the number of checkpoint request messages. Lemmas on consistency and termination are also included.

Trainrec: A System For Training Feedforward & Simple Recurrent Networks Efficiently And Correctly, Barry L. Kalman, Stan C. Kwasny

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TRAINREC is a system for training feedforward and recurrent neural networks that incorporates several ideas. It uses the conjugate-gradient method which is demonstrably more efficient than traditional backward error propagation. We assume epoch-based training and derive a new error function having several desirable properties absent from the traditional sum-of-squared-error function. We argue for skip (shortcut) connections where appropriate and the preference for a sigmoidal yielding values over the [-1,1] interval. The input feature space is often over-analyzed, but by using singular value decomposition, input patterns can be conditioned for better learning often with a reduced number of input units. Recurrent …

A Characterization Of The Computational Power Of Rule-Based Visualization, Kenneth C. Cox, Gruia-Catalin Roman

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Declarative visualization is a paradigm in which the process of visualization is treated as a mapping from some domain (typically a program) to an image. One means of declaring such mappings is through the use of rules which specify the relationship between the domain and the image. This paper examines the computational power of such rule-based mappings. Computational power is measure using three separate criteria. The first of these uses the Chomsky hierarchy, in which computational power is treated as string-acceptance; with this criterion we are able to show that certain rule-based models are equivalent in power to Turing machines. …

Logical Interference In Symmetric Connectionist Networks, Gadi Pinkas

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This work delineates the relation between logic and symmetric neural networks. The motivation is two-fold: 1) to study the capabilities and limitations of connectionist networks with respect to knowledge representatoin; and 2) to develop a new kind of inference negine that is expressive, massively parallel, capable of coping with nonmonotonic or noisy knowledge and capable of learning. The thesis shows that propositional logic can be implemented efficiently in networks where hidden units allow the representation of arbitrary constraints. An inference engine is constructed which can obtain its knowledge either by compiling symbolic rules or by learning them inductively from examples. …

A Comparison Study Of The Pen And The Mouse In Editing Graphic Diagrams, Ajay Apte, Takayuki Dan Kimura

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We report the results of an experiment comparing the merits of the pen and the mouse as drawing devices. For this study a pen-based graphic diagram editor equipped with a shape recognition algorithm was developed on GO's PenPoint operating system. A commercially available drawing program on NeXT was used for mouse-based editing. Twelve CS students were chosen as subjects and asked to draw four different diagrams of similar complexity: two with a pen and the other two with a mouse. The diagrams are chosen from the categories of dataflow visual language, Petri nets, flowcharts, and state diagrams. The results indicate …

A Taxonomy Of Program Visualization Systems, Gruia-Catalin Roman, Kenneth C. Cox

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Program visualization may be viewed as a mapping from programs to graphical representations. This simple idea provides a formal framework for a new taxonomy of program visualization systems. The taxonomy is compared briefly against previous attempts to organize the program visualization field. The taxonomic principles and their motivation are explained in detail with reference to a number of existing systems, especially Balsa, Tango, and Pavane.

Asking Questions To Minimize Errors, Nader H. Bshouty, Sally A. Goldman, Thomas R. Hancock, Sleiman Matar

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A number of efficient learning algorithms achieve exact identification of an unknown function from some clas using membership and equivalence queries. Using a standard transformation such algorithms can easily be converted to on-line learning algorithms that use membership queries. Under such a transformation the number of equivalence queries made by the query algorithm directly corresponds to the number of mistakes made by the on-line algorithm. In this paper we consider several of the natural classes known to be learnable in this setting, and investigate the minimum number of equivalence queries with accompanying counterexamples (or equivalently the minimum number of mistakes …

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 …

Fril - A Fractal Intermediate Language, Ron Cytron, David Shields

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This document describes the motivation, language description, and experience using FrIL, an intermediate language for a compiler's "middle-end." FrIL has subbessfully supported a two-semester compiler construction sequence, where the first semester included code generation from a C-like language and the second semester included advanced data flow analysis and program transformation.

The Pessimism Behind Optimistic Simulation, George Varghese, Roger D. Chamberlain, William E. Weihl

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In this paper we make an analogy between the time that storage must be maintained in an optimistic simulation and the blocking time in a conservative simulation. By exploring this analogy, we design two new Global Virtual Time (GVT) protocols for Time Warp systems. The first simple protocol is based on the null message scheme proposed for clock advancement in some conservative approaches; this yields what we call Local Guaranteed Time. Our main contribution is a second new protocol that is inspired by Misra's circulating marker scheme for deadlock recovery in conservative simulations, and appears to have advantages over previous …

The Washington University Multimedia Explorer, William D. Richard, Jerome R. Cox Jr., A. Maynard Engebretson, Jason Fritts, Craig Horn

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The Washington University MultiMedia eXplorer (MMX) is a complete, host-independent multimedia system capable of transmitting and receiving JPEG-compressed video, CD-quality audio, and high-resolution radiographic images over the Washington University broadband ATM network. If the host is equipped with an ATM interface card, normal network traffic is supported via "T" and "Y" connections. The MMX consists of an ATMizer and three multimedia subsystems. The ATMizer implements the host interface, the interface to the ATM network, and the interface to the three multimdeia channels. This paper describes the architecture of the MMX, the software used with the system, and the applications which …

Rule-Maker's And Rule-Follower's Meaning, R. P. Loui

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No abstract provided.

An Integration Of Case-Based And Model-Based Reasoning And Its Application To Physical System Faults, Stamos T. Karamouzis

Dissertations, Theses, and Masters Projects

Case-Based Reasoning (CBR) systems solve new problems by finding stored instances of problems similar to the current one, and by adapting previous solutions to fit the current problem, taking into consideration any differences between the current and previous situations. CBR has been proposed as a more robust and plausible model of expert reasoning than the better-known rule-based systems.;Current CBR systems have been used in planning, engineering design, and memory organization. There has been minimal work, however, in the area of reasoning about physical systems. This type of reasoning is a difficult task, and every attempt to automate the process must …

Fourier Analysis Of Frequency Domain Discrete Event Simulation Experiments, Mousumi Mitra Hazra

Dissertations, Theses, and Masters Projects

Frequency Domain Experiments (FDEs) were first used in discrete-event simulation to perform system parameter sensitivity analysis for factor screening in stochastic system simulations. FDEs are based on the intuitive assertion that if one or more system parameters are oscillated at fixed frequencies throughout a simulation run, then oscillations at the same frequencies will be induced in the system's response. Spectral (Fourier) analysis of these induced oscillations is then used to characterize and analyze the system. Since their introduction 12 years ago, significant work has been done to extend the applicability of FDEs to regression analysis, simulation optimization and gradient estimation. …

Digital Information In The Peel-Harvey Catchment Area, Dennis Van Gool

Agriculture reports

This paper presents a summary of the main features of the digital mapping data available in the Peel-Harvey Catchment area. This type of information is essential for Geographic Information System (GIS) users to assess projects involving the use of digital data such as plotting of mapped themes, topological overlays, area calculations and reporting.

X.500 Directory Service Support For Electronic Mail, Mihai G. Sirbu

Masters Theses

"One of the difficult problems on the Internet is finding the electronic mail addresses of users. In practice, there are some indirect ways of finding these addresses such as the finger program in UNIX, but almost all of these methods require the user to know the exact host name of the destination. What is most desirable is an automated mechanism which provides the e-mail addresses of users if some minimal information about the destination site is known.

This thesis describes the design of such a directory service support system, based on the X.500 Series of CCITT Recommendation, for the elm …