leff@smu.UUCP (Laurence Leff) (05/11/89)
DEPARTMENT OF COMPUTER SCIENCES TECHNICAL REPORT CENTER TAYLOR HALL 2.124 THE UNIVERSITY OF TEXAS AT AUSTIN AUSTIN, TEXAS 78712-1188 (512) 471-9595 ELECTRONIC MAIL ADDRESS: trcenter@cs.utexas.edu TECHNICAL REPORTS, JANUARY 1989 - APRIL 1989 PREPAYMENT IS REQUIRED. Please make U.S. bank checks or international money orders payable to "The University of Texas." [] TR-88-23 (Revision) $1.50 [] TR-89-01 $1.50 [] TR-89-06 $1.50 [] TR-89-02 $1.50 [] TR-89-07 $1.50 [] TR-89-03 $1.50 [] TR-89-08 $1.50 [] TR-89-04 $3.00 [] TR-89-09 $1.50 [] TR-89-05 $1.50 [] TR-89-10 $1.50 [] TR-89-11 $2.00 --------------------------------------------------------------------------- TR-88-23 A NEW EXPLANATION OF THE GLITCH PHENOMENON James H. Anderson and Mohamed G. Gouda March 1989 (Revision) 18 pages ABSTRACT: We consider a discrete model for asynchronous cir- cuits and show that, under very mild restrictions, this model excludes the existence of glitch-free arbiters. This result contradicts a long standing conjecture that the nonexistence of glitch-free arbiters is due to the continuous nature of such circuits. Keywords: arbiter, asynchronous circuit, atomicity, glitch, history, interleaving semantics, metastability, nondeterminism, waiting. TR-89-01 ILLUMINATION NETWORKS: FAST REALISTIC RENDERING WITH ARBITRARY REFLECTANCE FUNCTIONS Chris Buckalew and Donald Fussell January 1989 8 pages ABSTRACT: We present a technique for modeling global illumina- tion which allows a wide variety of reflectance functions. Scene coherence is exploited in a preprocessing step in which the geometry is analyzed using iterative techniques. Memory is traded for speed, in anticipation of the high memory capacities of workstations of the future. The algorithm operates well over a wide range of time and image quality constraints: real- istic results may be produced very quickly while very accurate results may be produced given more time and space. The method can be extended for animation and parallelization. Keywords: Computer Graphics, Picture/Image generation - display algorithms, three-dimensional graphics and realism, global illumination, radiosity, ray tracing, memory, specular, dif- fuse, data structure, incremental, ray space. TR-89-02 BLOCK ACKNOWLEDGEMENT: REDESIGNING THE WINDOW PROTOCOL G. M. Brown, M. G. Gouda, and R. E. Miller March 1989 16 pages ABSTRACT: We describe a new version of the window protocol where message sequence numbers are taken from a finite domain and where both message disorder and loss can be tolerated. Most existing window protocols achieve only one of these two goals. Our protocol is based on a new method of acknowledge- ment, called block acknowledgement, where each acknowledgement message has two numbers m and n to acknowledge the reception of all data messages with sequence numbers ranging from m to n. Using this method of acknowledgement, the proposed protocol achieves the two goals while maintaining the same data transmission capability of the traditional window protocol. Keywords: Computer networks, communication protocols, window protocol, protocol verification, message sequence numbers, transmission errors. TR-89-03 TOPOLOGICAL TESTING Miroslaw Malek, Antoine Mourad, and Mihir Pandya March 1989 22 pages ABSTRACT: A concept of topological testing is introduced and its applications are presented. Topological testing uses graph theoretic optimization methods such as the Traveling Salesman Problem, the Chinese Postman Problem, path covering and parti- tioning to minimize the test time. The topological testing techniques can be applied to each level of system hierarchy, namely, circuit, logic, register transfer, instruction and processor-memory-switch levels. Specifically, the topological testing approach is demonstrated by developing tests for the multistage interconnection network and the hypercube network. Time optimization for the testing of these networks gives very promising results by taking advantage of inherent parallelism and removing test redundancy. Three orders of magnitude improvement is achieved by applying topological testing tech- niques to the testing of an existing multistage interconnection network. Keywords: Testing, graph theory, optimization methods, multis- tage interconnection networks, hypercube. TR-89-04 DISTRIBUTED FILE SYSTEMS Eliezer Levy and Abraham Silberschatz March 1989 54 pages ABSTRACT: Distributed File Systems are essential for sharing of data and storage space in a distributed system. A viewpoint that emphasizes the dispersed structure and decentralization of both data and control in the design of such systems is esta- blished. The concepts of location transparency, fault tolerance and scalability are defined and discussed in the context of Distributed File Systems. It is claimed that the principle of distributed operation is fundamental for a fault tolerant and scalable Distributed File System. Alternatives for the seman- tics of sharing and methods for providing access to remote files are also presented. A survey of current systems, namely Unix United, Locus, Sprite, Sun's Network File System, and ITC's Andrew, illustrates the discussed concepts and demon- strates various implementations and design alternatives. Based on the assessment of these systems, a point is made that a departure from the approach of extending centralized file sys- tems over the network is necessary to accomplish sound Distri- buted File System design. Keywords: Distributed systems, networks, file systems, fault tolerance, scalability. TR-89-05 A FRAMEWORK FOR THE PARALLEL PROCESSING OF DATALOG QUERIES Sumit Ganguly, Avi Silberschatz, and Shalom Tsur March 1989 17 pages ABSTRACT: This paper presents several schemas for the parallel, bottom-up evaluation of a class of Datalog queries. Our method is presented in three steps: A rewrite step that renders an equivalent program to the original one, explicitly amenable to parallel execution; an assignment step that assigns the rules and data of the rewritten program to processors and an execu- tion step that performs the computation, either with or without processor intercommunication. The schemas obtained demonstrate trade-offs between redundancy (duplication of computation by processors) and interprocessor- communication. We introduce the notion of a discriminating predicate by which the computation is partitioned among the processors and parallelism is achieved. Keywords: Parallelization, datalog, bottom-up evaluation. TR-89-06 A HYBRID ALGORITHM TECHNIQUE Miroslaw Malek, Mohan Guruswamy, Howard Owens, and Mihir Pandya March 1989 27 pages ABSTRACT: A new hybrid algorithm technique (HAT) based on the idea of mixing two or more algorithms is proposed. Though the algorithm is general and may be applied to the majority of optimization problems, a hybrid algorithm search technique (HAST) is the focus of this paper. As an example of HAST, this paper describes mixing of simulated annealing and tabu search algorithms into a new hybrid search algorithm applied to the traveling salesman problem. A brief introduction to the simu- lated annealing and tabu search algorithms is given followed by a description of how we mixed these algorithms to form a new parallel hybrid search technique. Comparison of our algorithm mixer with simulated annealing and tabu search indicates con- sistently better results. Examples include 33, 42, 50, 57, 75, and 100 city problems from the literature. Solutions for the 50 and 75 city problems outperform best known published to date results. Keywords: Algorithm, search techniques, simulated annealing, tabu search, traveling salesman problem. TR-89-07 A SYSTOLIC PROGRAM FOR GAUSS-JORDAN ELIMINATION Duncan Hudson and Christian Lengauer March 1989 14 pages ABSTRACT: A scheme for the compilation of imperative or func- tional programs into systolic programs is used to derive an occam program for Gauss-Jordan elimination from a Pascal-like program. The correctness of the output program is guaranteed by the correctness of the input program and of the compilation scheme. The novelty of this example is that the compilation scheme has been applied for the first time to a systolic array that is described by piecewise linear, not linear distribution functions. Keywords: Algebraic Path Problem, code generation, compilation, Gauss-Jordan elimination, occam, systolic array. TR-89-08 MECHANICAL THEOREM PROVING IN DIFFERENTIAL GEOMETRY Shang-Ching Chou and Xiao-Shan Gao March 1989 29 pages ABSTRACT: With an improved version of Ritt-Wu's zero decomposi- tion algorithm for differential polynomials, we present two approaches to mechanical proving of geometry theorems in dif- ferential geometry. The first approach can be used to prove a theorem when nondegenerate conditions are given explicitly. The second approach can be used to prove a statement to be generically true. More than fifty nontrivial theorems in the space curve theory have been proved mechanically by our pro- gram, in particular, the properties of the Bertrand curves are studied in full detail. Keywords: Mechanical theorem proving, Wu's method, differential polynomial, Ritt-Wu's decomposition algorithm, main component, differential geometry, the space curve theore, the Bertrand curves. TR-89-09 RITT WU'S DECOMPOSITION ALGORITHM AND GEOMETRY THEOREM PROVING Shang-Ching Chou and Xiao-Shan Gao March 1989 23 pages ABSTRACT: An improved Ritt-Wu's decomposition (of an algebraic set into the union of irreducible varieties) algorithm is given. The algorithm has been used to prove geometric theorems that Wu's original method addresses. Unlike Wu's original approach, nondegenerate conditions are given explicitly at the beginning, not generated during the proof process. A program based on this improved version of the algorithm proved more than 500 theorems, including Morley's trisector theorem. Keywords: Wu's method, mechanical theorem proving, prover, ele- mentary geometry, degenerate conditions, Ritt-Wu's principle, algebraic variety, nondegenerate component, ideal, ascending chain, the dimension theorem, Morley's trisector theorem. TR-89-10 USING (N-1)-PROCESS ELECTION TO SOLVE N-PROCESS ELECTION James H. Anderson March 1989 8 pages ABSTRACT: We present a solution strategy for N-process election in which a leader is chosen based upon the results of a number of (N-1)-process elections. We show that the existence of such a solution depends on the constraints that are placed on the (N-1)-process elections. Keywords: election primitives, impossibility proof, leader election, knowledge-based reasoning, program composition, ran- dom assignment. TR-89-11 AUTOMATED REASONING IN MECHANICS USING RITT-WU'S METHOD Shang-Ching Chou and Xiao-Shan Gao April 1989 33 pages ABSTRACT: Methods of automated reasoning in mechanics have been presented and implemented on computers. The paper consists of two parts. In part I, a mechanical method developed by W.T. Wu on the basis of the work of J. F. Ritt has been used to prove theorems in mechanics. In particular, a mechanical study of the complete logical relationship between Kepler's laws and Newton's gravitational laws has been given. Wu's work on the same topic has been extended in several ways. Many other exam- ples from mechanics are also given. In part II, a method of mechanical derivation of formulas from a set of differential polynomials has been presented. The method has been used successfully to some problems in mechanics. In particular, a mechanical derivation of Newton's gravitational laws from Kepler's laws has been given without knowing Newton's Laws in advance. Keywords: Mechanical theorem proving, mechanical derivation of formulas, Wu's method, differential polynomial, Ritt-Wu's decomposition algorithm, mechanics, Newton's gravitational laws, Kepler's laws.