5,289 Works

Two Computer Graphics Systems for the Visualization of Pressure Distributions and Airflow in Wind Tunnel Experimentation

Jack Davidson, David Whalley, Carol Luan & Worthy Martin

On Determining Performance of A Localnet 20 Network

Nancy Schult

Performance Analysis of a Software Implementation of the Xpress Transfer Protocol

Timothy Hartrick
In this thesis we present a survey of a group of influential Transport Layer protocols, including the Transmission Control Protocol (TCP), ISO Transport Protocol Class 4 (TP4), the Versatile Message Transaction Protocol (VMTP) and the Xpress Transfer Protocol (XTP). A variety of features of each protocol are examined in detail. These features include packet formats, communication syntax, error and sequencing control and multicast capabilities. Next, we describe an implementation of XTP version 3.5 which was...

Heuristics for Backplane Ordering

James Cohoon & Sartaj Sahni
The Board Permutation Problem, a backplane ordering problem, has been previously shown to be NP - hard. We develop here several heuristics for the Board Permutation Problem. These heuristics produce solutions that are locally optimal with respect to some nontrivial transforms. The heuristics are analytically shown to be m/3- approximate, where m is the number of nets in a problem instance. The heuristics have been shown experimentally to have quite acceptable behavior. Several of the...

A Retargetable Instruction Reorganizer

Jack Davidson
Extant peephole optimizers can perform many optimizations that are handled by higher - 1eve1 optimizers. This paper describes a retargetable instruction reorganizer that performs targeting and evaluation order determination by applying a well known algorithm for optimal code generation for expressions to object code. The reorganize: fits well into the framework of an existing peephole optimizer. By rearranging computations and instructions, it minimizes the number of registers and temporaries required to compile expressions. For some...

A Distributed System for Analyzing Time Varying Multi-Resolution Imager

C Tan & Worthy Martin
A distributed system for analyzing time varying, mu1ti~resolution imagery is described in this paper. A pipelined pyramid structure is constructed in the system by continually converging incoming images into successive levels of decreasing resolutions. A set of processes work concurrently and asynchronously on subimages at different levels of the pyramid. These processes initially watch for interesting features in the coarsest resolution rendition of the scene. Processes working on promising areas individually but cooperatively proceed to...

An Investigation of Models of Concurrent Programs

David OHallaron & Paul Reynolds
Reynolds has proposed an interesting new approach to verifying concurrent programs, called static incremental deadlock detection, where deadlock potential is automatically detected during the interactive construction of a concurrent program, before the program is ever run. In order to perform efl"ective static incremental deadlock detection. we will require accurate models that can be analyzed efficiently. Towards this end. we investigate three existing classes of models: algebraic models, geometric models, and Petri net models. We report...

Shipboard Network Analysis

Alfred Weaver

Recognizing Shapes Via Random Chord Samplings

R Hashim & Worthy Martin
A brief introduction to various methods of two dimensional shape recognition is given. A procedure for image-plane rotation and translation invariant object recognition is described. The method is based on sampling random chords from the greylevel image of an object and using the texture information associated with these chords to recognize the object. A voting scheme based on a generalized Hough transform performs the recognition. Schemes for organizing random chord shape descriptions and for matching...

Perceptually Guided Simplification of Lit, Textured Meshes

David Luebke, Jonathan Cohen, Nathaniel Williams, Mike Kelley & Brenden Schubert
We present a new algorithm for best-effort simplification of polygonal meshes based on principles of visual perception. Building on previous work, we use a simple model of low-level human vision to estimate the perceptibility of local simplification operations in a view-dependent Multi-Triangulation structure. Our algorithm improves on prior perceptual simplification approaches by accounting for textured models and dynamic lighting effects. We also model more accurately the scale of visual changes resulting from simplification, using parametric...

On the Implementation and Use of Ada on Fault-Tolerant Distributed Systems

John Knight & John Urquhart

Performance Analysis of the Manufacturing Automation Protocol

Timothy Strayer

Performance Analysis of the FDDI Token Ring

Randall Simonson

An Optimal Steiner Tree Algorithm for a Net Whose Terminals Lie on the Perimeter of a Rectangle

James Cohoon, Dana Richards & J Salowe
Given a set of input points, the rectilinear Steiner tree problem is to find a minimal length tree consisting of vertical and horizontal line segments that Connects the input points, where it is possible to add new points to minimize the length of the tree. The restricted Steiner tree problem in which all the input points lie on the boundary of a rectangle frequently occurs in VLSI physical design. Since the fastest published algorithm is...

Tailor: Creating Custom User Interfaces Based on Gesture

Randy Pausch & Ronald Williams
Physical controls for most devices are either "one size fits all" or require custom hardware for each user. Cost often prohibits custom design, and each user must adapt to the standard device interface, typically with a loss of precision and efficiency. When user abilities vary widely, such as in the disabled community, devices often become unusable. Our goal is to create a system that will track user gestures and interpret them as control signals for...

Experimental Evaluation of a Concurrent Checkpointing Algorithm

Sang Son & ShiChin Chiang
The goal of checkpointing in database management systems is to save database states on a separate secure device so that the database can be recovered when errors and failures occur. Recently. non‘ interfering checkpointing algorithms which allow user transactions to be processed ooncimently with the checkpointing process have been proposed [4, 7]. This property of non-interference is highly desirable to real-time applications, where restricting transaction activity during the checkpointing operation is in many cases not...

Gate - A Genetic Algorithm for Compacting Randomly Generated Test Sets

J Aylor, J Cohoon, E Feldhousen & B Johnson
A new technique. named GATE. is presented for the generation of compact test sets. GATE combines a previously proven method for random test pattern generation with the adaptive searching capabilities of genetic algorithms to produce very high quality test sets. A series of experiments demonstrated that our technique performed consistently better than the traditional method with respect to both fault coverage and test set size. 1‘ This research was supported in part by the Virginia...

A Global Object Code Optimizer

Manuel Benitez
_A global object code optimizer performs optimizations at the machine level. It uses infonnation at the procedure level as well as knowledge about the specific capabilities of the target machine to produce high quality code. It takes many months, even years, of development effort to produce these optimizers. Performing optimizations at the machine level has traditionally been accomplished by machine-dependent algorithms. Retargeting to a new machine requires large portions of the optimizer to be re...

The IEEE Local Area Network Standards

Alfred Weaver

Distributed Checkpointing for Globally Consistent States of Databases

Sang Son
The goal of cheokpointing in database management systems is to save database states on a separate secure device so that the database can be recovered when errors and failures occur. Recently, the possibility of having a checkpointing mechanism which does not interfere with the transaction processing has been studied[4, 7]. Users are allowed to submit transactions while the checkpointing is in progress. and the transactions are performed in the system concurrently with the checkpointing process....

Simplifying Code Generation Through Peephole Optimizations

Jack Davidson
Producing compilers that generate good object code is difficult. The early phase of the compiler, syntactical and lexical analysis, have been automated. The latter phases, code generation and optimization, are more difficult because of the wide range of machine architectures. This dissertation describes a technique for the rapid implementation of production-quality compilers through the use of a machine-independent retargetable peephole optimizer, P0. P0 is retargeted by providing a description of the new machine. PO simplifies...

Beaver: A Computational Geometry-Based Tool for Switchbox Routing

James Cohoon & P Heck
A new fast switchbox router, BEAVER is presented. BEAVER combines a delayed layering scheme with computational geometry techniques to heuristically produce a switchbox solution that minimizes both via usage and wire length, and maximizes the use of a preferred routing layer. Other important features are its use of priority queues to determine the order that nets are routed and its prioritized control of individual track and column usage to prevent routing conflicts. BEAVER consists of...

The Effect of Instruction Set Complexity on Program Size and Memory Performance

Jack Davidson & Richard Vaughan

A Real-time Messaging System for Token Ring Networks

Alfred Weaver & M Colvin

The WM Computer Architecture Definition and Rationale

William Wulf

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