Open Access. Powered by Scholars. Published by Universities.®

Computer Engineering Commons

Open Access. Powered by Scholars. Published by Universities.®

Washington University in St. Louis

Discipline
Keyword
Publication Year
Publication
Publication Type

Articles 571 - 600 of 733

Full-Text Articles in Computer Engineering

Formal Specification Of A Dynamically Configurable Distributed System, Ram Sethuraman, Kenneth J. Goldman Jan 1995

Formal Specification Of A Dynamically Configurable Distributed System, Ram Sethuraman, Kenneth J. Goldman

All Computer Science and Engineering Research

The Programmers' Playground is a programming environment that supports end-user construction of distributed multimedia applications. The system implements a new programming model that is based, in part, upon ideas from the formal I/O automaton model of Lynch and Tuttle. Important features of The Programmers' Playground are a separation of communication and computation and graphical support for dynamic reconfiguration. This paper provides a formal specification of the Playground programming model and runtime system in terms of the I/O automaton model on which it is based. Exploiting the compositionality properties of the I/O automaton model, the formal specification is describd as a …


Error Control For Continuous Media And Multipoint Applications, Christos Papadopoulos, Guru Parulkar Jan 1995

Error Control For Continuous Media And Multipoint Applications, Christos Papadopoulos, Guru Parulkar

All Computer Science and Engineering Research

High-bandwidth multimedia applications pose new challenges to error control. These include the support of error control for Continuous Media (CM) streams and the scalable support of error control in multipoint applications where the number of participants is large. Current error control mechanisms provide no support for the above applications. In this report we present new error control mechanisms that provide the required support. Continuous media applications have strict timing requirements which greatly affect recovery. To support continuous media applications we have designed and implemented a point-to-point error control mechanism which features the following: (1) selective repeat retransmission, (2) conditional retransmission, …


User Interface Applications Of A Multi-Way Constraint Solver, T. Paul Mccartney Jan 1995

User Interface Applications Of A Multi-Way Constraint Solver, T. Paul Mccartney

All Computer Science and Engineering Research

Constraints are widely recognized as a useful tool for user interface constructino. Through constraints, relationships among user interface components can be defined declaratively, leaving the task of relationship management to a constraint solver. Multi-way constraint solvers supporting constraint hierarchies provide a means to specify preferential constraint relationships with a dynamically changing computation flow, making them especially well suited to interactive user interfaces. However, previous such constraint solvers lack the ability to enforce inequalities or to effectively handle cyclic constraint relationships. These deficiencies limit the problems that could be solved using a constraint-based approach. This paper presents a new algorithm called …


Reliable Fifo Load Balancing Over Multiple Fifo Channels, Hari Adieseshu, Gurudatta M. Parulkar, George Varghese Jan 1995

Reliable Fifo Load Balancing Over Multiple Fifo Channels, Hari Adieseshu, Gurudatta M. Parulkar, George Varghese

All Computer Science and Engineering Research

Link striping algorithms are often used to overcome transmission bottlenecks in computer networks. However, traidtional striping algorithms suffer from two major disadvantages. They provide inadequate load sharing in the presence of variable length packets, and may result in non-FIFO delivery of data. We describe a new family of link striping algorithms that solve both problems. Our scheme applies to packets at any layer (physical, data, link, network, and transport) that work over multiple FIFO channels. We deal with variable sized packets by showing how a class of fair queueing algorithms can be converted into load sharing algorithms. Our transformation results …


An Efficient Signaling Structure For Atm Networks, Dakang Wu Jan 1995

An Efficient Signaling Structure For Atm Networks, Dakang Wu

All Computer Science and Engineering Research

As ATM becomes widely accepted as the communication standard for high speed networks, the signaling system structure and protocols that support ATM become more and more important. To support existing, future and unknown applications, the signalign system has to be very flexible and efficient. In this paper we define the signaling problem, present several possible signaling system structures, compare the advantages and disadvantages of these systems, and then we propose a new signaling system structure. The fundamental idea of the new signaling system is the logical separation of the signaling system structure from the underlying communication network, even though they …


Can Declared Strategy Voting Be An Effective Instrument For Group Decision-Making?, Lorrie Faith Cranor Jan 1995

Can Declared Strategy Voting Be An Effective Instrument For Group Decision-Making?, Lorrie Faith Cranor

All Computer Science and Engineering Research

The goal of this research is to determine whether declared strategy voting can be an effective tool for group decision-making. Declared strategy voting is a novel group decision-making procedure in which preference is specified using voting strategies - first-order mathematical functions that specify a choice in terms of zero or more parameters. This research will focus on refining the declared strategy voting concept, developing an accessible implementation of declared strategy voting that can be used for mock elections, assessing the potential impacts of declared strategy voting, and evaluating the effectiveness of declared strategy voting for group decision-making. This proposal describes …


An Oo Encapsulation Of Lightweight Os Concurrency Mechanisms In The Ace Toolkit, Douglas C. Schmidt Jan 1995

An Oo Encapsulation Of Lightweight Os Concurrency Mechanisms In The Ace Toolkit, Douglas C. Schmidt

All Computer Science and Engineering Research

This paper describes the design of the ACE object-oriented thread encapsulation class library. The architecture of this class library is presented from an end-user and internal design perspective and several key design issues are discussed. Readers should gain an understanding of the overall design approach as well as the tradeoffs between various software quality factors such as performance, portability, and extensibility.


Strategies For The Parallel Training Of Simple Recurrent Neural Networks, Peter J. Mccann, Barry L. Kalman Jan 1994

Strategies For The Parallel Training Of Simple Recurrent Neural Networks, Peter J. Mccann, Barry L. Kalman

All Computer Science and Engineering Research

Two concurrent implementations of the method of conjugate gradients for training Elman networks are discussed. The parallelism is obtained in the computation of the error gradient and the method is therefore applicable to any gradient descent training technique for this form of network. The experimental results were obtained on a Sun Sparc Center 2000 multiprocessor. The Sparc 2000 is a shared memory machine well suited to coarse-grained distributed computations, but the concurrency could be extended to other architectures as well.


Congestion Control In Atm Networks, Apostolos Dailianas, Andreas Bovopoulos Jan 1994

Congestion Control In Atm Networks, Apostolos Dailianas, Andreas Bovopoulos

All Computer Science and Engineering Research

No abstract provided.


Efficient Quality Of Service Support In Multimedia Computer Operating Systems, Raman Gopalakrishna, Guru M. Parulkar Jan 1994

Efficient Quality Of Service Support In Multimedia Computer Operating Systems, Raman Gopalakrishna, Guru M. Parulkar

All Computer Science and Engineering Research

This report describes our approach towards providing quality of service (QoS) guarantees for network communication within the endsystems to support multimedia applications. We first address the problem of QoS specification by identifying a set of application classes and their QoS parameters that cover the communication requirements of most applications. We then describe the QoS mapping problem, and show how requirements for resources (such as the CPU, the network interface adaptor and network connections) can be automatically derived from the application QoS parameters. We then deal with the QoS enforcement issue in which we describe techniques for scheduling protocol processing threads …


Distributed Data Layout, Scheduling And Playout Control In A Large Scale Multimedia Storage Server, Milind M. Buddhikot, Guru Parulkar Jan 1994

Distributed Data Layout, Scheduling And Playout Control In A Large Scale Multimedia Storage Server, Milind M. Buddhikot, Guru Parulkar

All Computer Science and Engineering Research

No abstract provided.


Production Quality Video Over Broadband Networks: A Description Of The System And Two Interactive Applications, William D. Richard, Jerome R. Cox Jr., A. Maynard Engebretson, Jason Fritts And Brian L. Gottlieb And Craig Horn Jan 1994

Production Quality Video Over Broadband Networks: A Description Of The System And Two Interactive Applications, William D. Richard, Jerome R. Cox Jr., A. Maynard Engebretson, Jason Fritts And Brian L. Gottlieb And Craig Horn

All Computer Science and Engineering Research

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 can be supported via an ATM extension port on the MMX. The major components of the MMX are an ATMizer and three multimedia channels. The ATMizer implements the host interface, the interface to the ATM network, and hte interface to the three multimdeia channels. This paper describes the architecture of the MMX, the software used …


Practical Methods For Approximating Shortest Paths On A Convex Polytope In R3, John Hershberger, Subhash Suri Jan 1994

Practical Methods For Approximating Shortest Paths On A Convex Polytope In R3, John Hershberger, Subhash Suri

All Computer Science and Engineering Research

We propose a n extremely simple approximation scheme for computing shortest paths on the surface of a convex polytope in three dimensions. Given a convex polytope P with n vertices and two points p,q on its surface, let dp (p,q) denote the shortest path distance between p and q on the surface of P. Our algorithm produces a path of length at most 2 × dp(p,q) in time O(n). Extending this results, we can also compute ana pproximation of the shortest path tree rooted at an arbitrary point χ Є P in time O(n log n). In the approximate tree, …


An Evaluation Of The Pavane Visualization System, Kenneth C. Cox, Gruia-Catalin Roman Jan 1994

An Evaluation Of The Pavane Visualization System, Kenneth C. Cox, Gruia-Catalin Roman

All Computer Science and Engineering Research

The Pavane program visualization system is an implementation of the declarative paradigm of visualization. After a brief report on the status of the Pavane implementation, we present the results of an evaluation of the usability of Pavane. This evaluation is based on the use of Pavane by its developers to construct program visualizations, on its use in a classroom setting as a tool for examining executing programs, and on its application to some simple scientific visualizations.


Visual Specification Of Interprocess And Intraprocess Communication, T. Paul Mccartney, Kenneth J. Goldman Jan 1994

Visual Specification Of Interprocess And Intraprocess Communication, T. Paul Mccartney, Kenneth J. Goldman

All Computer Science and Engineering Research

We present a visual specification language for constructing distributed applications and their direct manipulation graphical user interfaces. Each distributed application consists of a collection of independent modules and a configuration of logical connections that define communication among the data interfaces of the modules. Our specification language uses a single visual mechanism that allows end-users to define interprocess communication among distributed modules and to define intraprocess communication among objects within a module. This seamless specification provides a general encapsulation/abstraction mechanism and is designed to support dynamic change to the communication structure. User interfaces are completely decoupled from the module(s) they control.


Pipelined And Superscalar Architectures In Clocked And Asynchronous Environments, Mark A. Franklin, Tienyo Pan Jan 1994

Pipelined And Superscalar Architectures In Clocked And Asynchronous Environments, Mark A. Franklin, Tienyo Pan

All Computer Science and Engineering Research

In this paper, a set of simple, general, yet practical performance models for RISC architectures are developed. These models apply to a wide range of systems that include both pipelined and superscalar systems operating in either clocked or asynchronous environments. The models permit quantitative evaluation of various design choices (e.g., the number of pipelines in the system, the pipeline depth, and the choice between clocked and asynchronous methodologies) as functions of technology parameters, environmental operating parameters, and pipeline function characteristics. Design curves are presented indicating optimal pipeline depth and number of pipelines to employ under various conditions.


Self-Stabilization By Counter Flushing, George Varghese Jan 1994

Self-Stabilization By Counter Flushing, George Varghese

All Computer Science and Engineering Research

A useful way to design simple and robust protocols is to make them self-stabilitizing. We describe a simple technique for self-stabilization called counter flushign which is applicable to a number of distributed algorithms. A randomized version of counter flushing is shown to have extremely small expected stabilization time. We show how our technique helps to crisply understand and improve some previous distributed algorithms. Then we apply it to a variety of total algorithms for deadlock detection, propagation of information with feedback, resets and snapshots. Our stabilizing snapshot protocol has much better complexity than the previous stabilizing non-blocking snapshot protocol. Hence …


Reasoning About Places, Times, And Actions In The Presence Of Mobility, C. Donald Wilcox, Gruia-Catalin Roman Jan 1994

Reasoning About Places, Times, And Actions In The Presence Of Mobility, C. Donald Wilcox, Gruia-Catalin Roman

All Computer Science and Engineering Research

The current trend toward portable computing systems (e.g., cellular phones, laptop computers) brings with it the need for a new paradigm for thinking about designing distributed applications. We introduce the term mobile to refer to distributed systems that include moving, autonomous agents which loosely cooperate to accomplish a tastk. The fluid nature of hte interconnections between components in a mobile system provides new challenges and new opportunities for the research community. While we do not propsoe to have fully grasped the consequences of these systems, we believe that the notions of place, time, and action will be central in any …


High-Performance Training Of Feedforward & Simple Recurrent Networks, Barry L. Kalman, Stan C. Kwasny Jan 1994

High-Performance Training Of Feedforward & Simple Recurrent Networks, Barry L. Kalman, Stan C. Kwasny

All Computer Science and Engineering Research

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 …


Learning And Teaching Of Boolean And Geometric Classes, H. David Mathias Jan 1994

Learning And Teaching Of Boolean And Geometric Classes, H. David Mathias

All Computer Science and Engineering Research

We consider the concept classes of DNF formulas and unions of discretized, axis-parallel d-dimensional boxes in discretized d-dimensional space with respect to several different learning models. In the model of learning with queries we present an algorithm to learn unions of boxes. We introduce a model of teaching that prevents illicit communication between the teacher and the leaner but that captures the intuitive aspect of teaching: a learner should perform at least as well with a cooperative teacher as with an adversarial teacher. We propose the study of teaching of DNF formulas and unions of boxes in this model. We …


Trading Packet Headers For Packet Processing, George Varghese Jan 1994

Trading Packet Headers For Packet Processing, George Varghese

All Computer Science and Engineering Research

In high speed networks, packet processing is relatively expensive while bandwidth is cheap. This begs the question: what fields can be added to packets to make packet processing easier? By exploring this question, we device a number of novel mechanisms to speed up packet processing. With the advent of new standards for hte Data Link, Network, and Transport lyaers, we believe there is an opportunity to apply these techniques to improve the performance of real protocols. First, we suggest adding a data manipulation header to an easily accessible portion of each packet. This header contains pointers to fields (in various …


Rationales And Argument Moves, R. P. Loui, Jeff Norman Jan 1994

Rationales And Argument Moves, R. P. Loui, Jeff Norman

All Computer Science and Engineering Research

No abstract provided.


Learning From A Consistently Ignorant Teacher, Michael Frazier, Sally Goldman, Nina Mishra, Leonard Pitt Jan 1994

Learning From A Consistently Ignorant Teacher, Michael Frazier, Sally Goldman, Nina Mishra, Leonard Pitt

All Computer Science and Engineering Research

One view of computational learning theory is that of a learner acquiring the knowledge of a teacher. We introduce a formal model of learning capturing the idea that teachers may have gaps in their knowledge. The goal of the learner is still to acquire the knowledge of the teacher, but now the learner must also identify the gaps. This is the notion of learning from a consistently ignorant teacher. We consider the impact of knowledge gaps on learning, for example, monoton DNF and d-dimensional boxes, and show that leraning is still possible. Negatively, we show that knowledge gaps make learning …


Cell Tracking Using A Distributed Algorithm For 3d Image Segmentation, Vikas Awasthi, Keith W. Doolittle, Guru Parulkar, James G. Mcnally Jan 1994

Cell Tracking Using A Distributed Algorithm For 3d Image Segmentation, Vikas Awasthi, Keith W. Doolittle, Guru Parulkar, James G. Mcnally

All Computer Science and Engineering Research

We have developed and tested an automated method for simultaneous 3D tracking of numerous, flourescently-tagged cells. The procedure uses multiple thresholding to segment individual cells at a starting timepoint, and then iteratively applies a template-matching algorithm to locate a particular cell's position at subsequent time points. To speed up the method, we have developed a distributed implementation in which template matching is carried out in parallel on several different server machines. The distributed implementation showed a monotonic decrease in response time with increasing number of servers (up to 15 tested), demonstrating that the tracking algorithm is well suited to parallelization, …


Design Of A Large Scale Multimedia Server, Milind M. Buddhikot, Guru Parulkar, Jerome R. Cox Jr. Jan 1994

Design Of A Large Scale Multimedia Server, Milind M. Buddhikot, Guru Parulkar, Jerome R. Cox Jr.

All Computer Science and Engineering Research

Large scale multimedia storage servers will be an integral part of the emerging distributed multimedia computing infrastructure. However, given the modest rate of improvements in storage transfer rates, designing servers that meet the demands of multimedia applications is a challenging task that needs significant architectural innovation. Our research project, called Massively-parallel And Real-time Storage (MARS) architecture, is aimed at the design and prototype implementation of a large scale multimedia storage server. It uses some of the well-known techniques in parallel I/O, such as data striping and Redundant Arrays of Inexpensive Disks (RAID) and an innovative ATM based interconnect inside the …


Learning One-Dimensional Geometric Patterns Under One-Sided Random Misclassification Noise, Paul W. Goldberg, Sally A. Goldman Jan 1994

Learning One-Dimensional Geometric Patterns Under One-Sided Random Misclassification Noise, Paul W. Goldberg, Sally A. Goldman

All Computer Science and Engineering Research

Developing the ability to recognize a landmark from a visual image of a robot's current location is a fundamental problem in robotics. We consider the problem of PAC-learning the concept class of geometric patterns where the target geometric pattern is a configuration of k points on the real line. Each instance is a configuration of n points on the real line, where it is labeled according to whether or not it visually resembles the target pattern. To capture the notion of visual resemblance we use the Hausdorff metric. Informally, two geometric patterns P and Q resemble each othe runder the …


Catching Up With The Networks: Host I/O At Gigabit Rates, Zubin D. Dittia, Jerome R. Cox Jr., Guru M. Parulkar Jan 1994

Catching Up With The Networks: Host I/O At Gigabit Rates, Zubin D. Dittia, Jerome R. Cox Jr., Guru M. Parulkar

All Computer Science and Engineering Research

The last few years have seen network data rates skyrocket from a few Mbps to a Gbps or more. However, a lack of integration of the host-netowrk interface, the operating system, and network protocols has resulted in end-applications seeing only a small fraction of this total bandwidth being available for data transfer. The emergence of demanding applications in the realms of multimedia and virtual reality provides further impetus in the drive to overcome this problem. In this paper, we present the design of a high performance ATM host-network interface for workstations and servers that can support a bidirecitonal sustained data …


Boxgraph: A Two-Dimensional Visual Computation Model, Takayuki Dan Kimura, Timothy B. Brown Jan 1994

Boxgraph: A Two-Dimensional Visual Computation Model, Takayuki Dan Kimura, Timothy B. Brown

All Computer Science and Engineering Research

Traditional computation models such as Turing machines, lambda-calculus, Markov's normal algorithms, are not suitable models for visual programming languages because they are all based on one-dimensional text strings and visual programming uses two-dimensional graphic diagrams. We propose a two-dimensional computation model, called Boxgraph, that requires no text. The syntax of the model consists of nested boxes connected by arrows, and the semantics consists of dataflow and the concept of consistency. The expressive power of the model is demonstrated by constructing representations of a binary full adder, the Fibonacci function, and the GCD function. The model, with a small extension to …


Visual Presentation Of Software Specifications And Designs, Gruia-Catalin Roman, Delbert Hart, Charles Calkins Jan 1994

Visual Presentation Of Software Specifications And Designs, Gruia-Catalin Roman, Delbert Hart, Charles Calkins

All Computer Science and Engineering Research

Formal methods hold the promise for high dependability in the design of critical software. However, software engineers who employ formal methods need to communicate their design decisions to users, customers, managers, and collegues who may not be in a position to acquire a full understanding of the formal notation being used. Visualizations derived from formal specifications and designs must be able to convey the required information precisely and reliably without the use of formal notation. This paper discusses a design methodology which attempts to integrate a design methodology based upon specification and program refinement with a state-of-the-art approach to rapid …


Speculative Computation: Overcoming Communication Delays In Parallel Algorithms, Vasudha Govindan, Mark A. Franklin Jan 1994

Speculative Computation: Overcoming Communication Delays In Parallel Algorithms, Vasudha Govindan, Mark A. Franklin

All Computer Science and Engineering Research

Communication latencies and delays are a major source of performance degradation in parallel computing systems. It is importnat to "mask" these communication delays by overlapping them with useful computation in order to obtain good parallel performance. This paper proposes speculative computation as a technique to mask communication latencies. Speculative computation is discussed in the context of synchronous iterative algorithms. Processors speculate the contents of messages that are not hyet received and perform computation based on the speculated values. When the messages are received, they are compared with the speculated values and, if the error is unacceptable, the resulitng computation is …