Computer Sciences Commons^™

Direct Finite First-Order Model Generation With Negative Constraint Propagation Heuristic, Olga Shumsky, Ralph W. Wilkerson, Fikret Ercal, William W. Mccune

Computer Science Faculty Research & Creative Works

An Automated Finite First-Order Model Generator Has Been Developed. the Problem is Viewed as a First-Order Satisfiability Problem. Most Existing Model Generators Reduce the Problem to Propositional Satisfiability by Converting the Input First-Order Clauses into Propositional Clauses. This Generator, Unlike Others, Stores the Input First-Order Clauses and Solves the Problem Directly. It Uses an Exhaustive Backtracking Algorithm with Weight-Based Splitting. a Negative Constraint Propagation is Implemented to Reduce the Number of Decision Points and Thus to Speed Up the Search. © 1997 ACM.

User Defined Prewrites For Increasing Concurrency In Design Databases, Sanjay Kumar Madria, A. Embong

Computer Science Faculty Research & Creative Works

We introduce a prewrite operation before a write operation is performed on design databases, a database that consists of objects as engineering designs. A prewrite operation does not actually make a design but it only makes available the model of the design that the transaction will produce in future. Once the prewrite design by a transaction is announced, the transaction executes a pre-commit operation. After the pre-commit, read operations can access the prewrite design even before the pre-committed transaction has finally made the design and committed. Therefore, our algorithm increases the potential concurrency as compared to the algorithms that permit …

Evolutionary Computation Applied To Adaptive Information Filtering, Daniel R. Tauritz, Ida G. Sprinkhuizen-Kuyper, Joost N. Kok

Computer Science Faculty Research & Creative Works

Information Filtering is concerned with filtering data streams in such a way as to leave only pertinent data (information) to be perused. When the data streams are produced in a changing environment the filtering has to adapt too in order to remain effective. Adaptive Information Filtering is concerned with filtering in changing environments. The changes may occur both on the transmission side (the nature of the streams can change), and on the reception side (the interest of a user can change). Weighted trigram analysis is a quick and flexible technique for describing the contents of a document. A novel application …

A Fast Algorithm For Complete Subcube Recognition, Fikret Erçal, H. J. Burch

Computer Science Faculty Research & Creative Works

The complete subcube recognition problem is defined as, given a collection of available processors on an n-dimensional hypercube, locate a subcube of dimension k that consists entirely of available processors, if one exists. Despite many algorithms proposed so far on this subject, improving the time complexity of this problem remains a challenge. Efficiency limits that can be reached have not been exhausted yet. This paper proposes a novel algorithm to recognize all the overlapping subcubes available on an n-dimensional hypercube whose processors are partially allocated. Given P=2n, as the total number of processors in the hypercube, the new algorithm runs …

A Concurrency Control Algorithm For An Open And Safe Nested Transaction Model, Sanjay Kumar Madria

Computer Science Faculty Research & Creative Works

We present a concurrency control algorithm for an open and safe nested transaction model. We use prewrite operations in our model to increase the concurrency. Prewrite operations are modeled as subtransactions in the nested transaction tree. The subtransaction which initiates prewrite subtransactions are modelled as recovery point subtransaction. The recovery point subtransaction can release their locks before its ancestors commit. Thus, our model increases the concurrency in comparison to other nested transaction models. Our model is useful an environment of long-running transactions common in object oriented databases, computer aided design and in the software development process

Timestamp-Based Approach For The Detection And Resolution Of Mutual Conflicts In Distributed Systems, Sanjay Kumar Madria

Computer Science Faculty Research & Creative Works

We present a timestamp based algorithm for the detection of both write-write and read-write conflicts for a single file in distributed systems during network partitions. Our algorithm allows operations to occur in different network partitions simultaneously. When the sites from different partitions merge, the algorithm detects and resolves both read-write and write-write conflicts without taking into account the semantics of the transactions. Once the conflicts have been detected some reconciliation steps for the resolution of conflicts have also been proposed. Our algorithm will be useful in real-time systems where timeliness of operations is more important than response time (delayed commit)

Efficient Parallel Algorithms On Reconfigurable Mesh Architectures, His-Chieh Lee, Fikret Ercal

Computer Science Technical Reports

This dissertation describes a number of novel parallel algorithms for solving maze-routing problems and string matching problems on a proposed reconfigurable mesh architecture.

Section I reviews the field of reconfigurable parallel computing. This includes an introduction to a number of reconfigurable architectures proposed in the literature and a list of references to the current literature on algorithms in the field of reconfigurable computing.

Section II presents a number of time-efficient algorithms to solve the mazerouting problem. Maze-routing algorithms are used in VLSI routing and robot path planning. In that section, definitions for absolute shortest path (ASP), shortest duplex-path (SDP), shortest …

Parallel Fast Multipole Algorithms For N-Body Simulations, Jui-Lin Lu, Daniel Okunbor

Computer Science Technical Reports

The computer simulation of N-Body problems has a wide range of applications. It is known that simulations can take years to complete. This can be greatly improved by using efficient algorithms in force calculations and in applying the computing power of parallel computers to the problem. A tremendous amount of work has been devoted to parallelization of the fast multipole algorithm (FMA) which is one of the fastest algorithms in force calculations. However, most parallel implementations target a specific machine. We developed an efficient communication scheme for parallel FMA in a message passing environment and implemented it by using Message …

Run-Time Security Evaluation: Can We Afford It?, Cristina Serban, Bruce M. Mcmillin

Computer Science Faculty Research & Creative Works

The use of the run-time security evaluation (RTSE) method for a distributed application takes a toll in overall application performance. The associated overhead and its major sources are discussed, along with possible solutions for improvements, and questions that remain still open.

A Declarative Approach To Understanding Program Behavior Through Program Visualization, Aggie Yee-Chun Sun, Bruce M. Mcmillin

Computer Science Technical Reports

A method is proposed to analyze the behavior of sequential algorithms. Most current methodologies are in the form of semantic analysis, domain decomposition or fixed point approximation. These tools, though useful in design, verification and testing, are not general enough to characterize the behavior at run-time without the aid of a correct set of specifications. In addition, a thorough understanding of the program and of the mathematical notations are necessary to use these tools effectively. The methodology described in this thesis is a general purpose tool which addresses and alleviates the problem of having to be an applications expert by …

Efficient String Matching Algorithms On Reconfigurable Mesh Architectures, His-Chieh Lee, Fikret Ercal

Computer Science Technical Reports

String matching problem received much attention over the years due to its importance in various applications such as text/file comparison, DNA sequencing, search engines, and spelling correction. Especially with the introduction of search engines dealing with tremendous amount of textual information presented on the world wide web and the research on DNA sequencing, this problem deserves special attention and any algorithmic or hardware improvements to speed up the process will benefit these important applications.

In this paper, we present three algorithms for string matching on reconfigurable mesh architectures. Given a text T of length n and a pattern P of …

Fast Algorithms For Maze Routing On An Rmesh, Fikret Ercal, H. C. Lee

Computer Science Technical Reports

The routing problem is one of the most widely studied problems in VLSI design. Mazerouting algorithms are used in VLSI routing and robot path planning. Efficiency of the parallel maze routing algorithms which were mostly based on Lee's algorithm is poor. In this paper, we propose time-efficient algorithms to solve the maze-routing problem on a reconfigurable mesh architecture. The constant-time algorithms presented include: (i) testing the existence of specific types of paths between two terminals, (ii) finding an absolute shortest path (ASP) and a shortest duplex-path (SDP). In addition, fast algorithms are presented for finding the shortest triplex-path (STP) and …

Run Time Security Evaluation For Distributed Applications, Cristina Serban, Bruce M. Mcmillin

Computer Science Technical Reports

Formal security specifications for a distributed application can be checked for compliance at run-time, during the execution of the application. We propose the RunTime Security Evaluation (RTSE) method which makes use of executable security assertions, histories/traces of events, and operational evaluation in the distributed environment to ensure the security specifications regarding the confidentiality and integrity requirements for the application are fulfilled at run-time. A model problem is used to aid in developing the security requirements formally, and assessment of the RTSE method is given based on the results obtained for the implementation of the model problem. The elements necessary for …

New Methods In Finite First-Order Model Search, Olga Shumsky, Fikret Ercal, Ralph W. Wilkerson

Computer Science Technical Reports

An automated first-order theorem prover, armed with appropriate strategies, will find a proof of a true conjecture, but will, in theory, run indefinitely if no proof exists. In reality, if no proof exists, the execution will be terminated by user-defined constraints, such as running time or memory usage limit. In this case the the question of validity of the conjecture remains unanswered. An automated first-order model generator gives one the ability to find counterexamples, if any exist, showing that the conjecture is invalid. A model generator also helps find the illustrations of previously proved theorems. It can be viewed as …

Application Of Neural Networks To The Non-Destructive Testing Of Aluminum Cans, B. Balasubramaniam, Daniel .. Clair

Computer Science Technical Reports

Neural Networks are used to c lassify aluminum beverage containers as acceptable or non acceptable, depending upon their wall thicknesses. For each can, the thickness of the wall of the can at different points is measured using a non-destructive, ultra-sound technique. These measureI\}ents are then applied as inputs to the networks and the classification is provided as the output Three architectures, one unsupervised and two supervised, are tested. Their performances are analyzed and compared and the paradigm best suited to the problem is selected.

Computer Assisted Control Of Robotic Rock Drilling Equipment Using Rock Face Image Mapping, William Robert Macneil, Peter (C. Y.)(Chung You) Ho

Computer Science Technical Reports

Use of a totally unmanned mining robot is an ideal solution in removing humans from the dangerous underground mining environment. However, a complete autonomous system is a long way from reality. In the meantime, steps towards that goal can be made and integrated into current mining technology to take away some of the risk and stress from the miner making him more alert and the environment safer for those that do have to be undergroμnd. For our purposes here, the machine will be an automated robotic platform with the intelligence necessary for accurate placement of the drill tip on an …

Wheels: An Automated Program Analysis Tool, Aggie Sun, Bruce Mcmillin

Computer Science Technical Reports

The understanding of program behavior is becoming vitally more important now that software is becoming an integral part of industry and everyday life. However, even the best documented code is often not sufficient enough to completely and correctly relay the actual program behavior. The problem lies beyond being familiar with the programming language and is hidden in the complex mathematics which govern the program's behavior. This behavior is not easily detected and varies from one program to the next. We propose a method for describing program behavior using two general properties of iterative programs: feasibility and progress. This method can …

R-By-C Crozzle: An Np-Hard Problem, Michelle Gower, Ralph W. Wilkerson

Computer Science Faculty Research & Creative Works

In an Australian Magazine, a Monetary Prize is Awarded to the Person with the Best Answer to a Word Puzzle Called a Crozzle. the Placement of Words into a Ten by Fifteen Grid Obtaining the Highest Score is the Best Answer. Various Search Techniques Have Been Employed to Solve This Problem, Yet No One Has Shown Whether There is a Polynomial-Time Algorithm to Find the Best Crozzle. This Paper Creates a Similar Word Puzzle, Called R-By-C Crozzle, by Lifting the Constraint on the Grid Size. R-By-C Crozzle is Not in NP, But There Exists a Polynomial Reduction to It from …

Near Perfect Hash Table For Image Databases, Sanjiv K. Bhatia, Chaman Sabharwal

Computer Science Faculty Research & Creative Works

In image database systems, a perfect hash table can be used to enhance the efficiency and effectiveness of the image retrieval process. In our earlier work, we have proposed heuristic algorithms to compute the minimal perfect hash table from symbolic picture objects. The hash table thus computed cannot be modified easily, limiting its application to fixed databases like the ones on CD-ROMs. In this paper, we propose a new data structure to allow for insertion and deletion in the hash table. The new data structure, the near-perfect hash table, allows a limited number of collisions on some of the hash …

Data Parallel Implementation Of Surface-To-Surface Intersection, Terence M. Burke, Chaman Sabharwal

Computer Science Faculty Research & Creative Works

The sequential surface-to-surface intersection algorithm has been extensively studied in the past decade. With the advent of parallel processing machines, it is desirable to parallelize this algorithm to gain extra computation speed for real time applications. An earlier attempt to parallelize this algorithm was on shared memory parallel computer due to the highly shared model of data structure [Chang 1991). A shared memory machine is not available at every location. Instead, we have implemented it on distributed parallel computer iPSC/860 with 32 processors. The initial development was done using PVM software in heterogeneous environment consisting of Sun workstations and 486's …

Optimization Of The Discriminatory Power Of A Trigram Based Document Clustering Algorithm Using Evolutionary Computation, Daniel R. Tauritz

Computer Science Faculty Research & Creative Works

No abstract provided.

Frequency Coordination Between Adjacent Carriers Of Two Cdma Operators, Seung Jong Park, Hun Bum Ha, Jong Tai Chung, Yoon Sub Shim, Do Young Lee

Computer Science Faculty Research & Creative Works

Frequency coordination is the process that assigns frequency bands to neighboring or coexisting systems to minimize interference. This interference is caused by unwanted signals from adjacent frequency bands. Especially, interference is maximized by the spatial near-far problem which occurs in case two different cellular systems serve. This critical case happens when different cellular operators using the adjacent carriers do not collocate their base stations (BS). In this paper, we investigate the frequency coordination when two CDMA operators using adjacent CDMA carriers don't collocate their BS. In order to lessen the unwanted interference, we put the guard band which separates adjacent …

A Systematic Tradeoff Methodology For Acquiring And Validating Imprecise Requirements, J. Yen, Xiaoqing Frank Liu, W. A. Tiao

Computer Science Faculty Research & Creative Works

Requirement analysis is one of the most important phases in a software development process. Existing requirement methodologies are limited in specifying requirements that are usually vague and imprecise, and in supporting tradeoff analysis between the conflicting requirements. In this paper, the elasticity of imprecise requirements is captured using fuzzy logic to facilitate tradeoffs between conflicting requirements. Based on the marginal rate of substitution in decision science, we have developed a systematic approach to elicit the structures and the parameters of imprecise requirements, to validate the scheme for aggregating requirements, and to assess relative priorities of conflicting requirements.

Adaptive Information Filtering As A Means To Overcome Information Overload, Daniel R. Tauritz

Computer Science Faculty Research & Creative Works

Information Filtering is concerned with filtering data streams in such a way as to leave only pertinent data (information) to be perused. When the data streams are produced in a changing environment (as most if not all are) the filtering has to adapt too in order to remain effective. Adaptive Information Filtering (AIF) is concerned with filtering in changing environments. The changes may occur both on the transmission side (the nature of the streams can change), and on the reception side (the interest of a user can change). The thesis research described in this paper combines trigram analysis, clustering, and …

Concepts Of Adaptive Information Filtering, Daniel R. Tauritz

Computer Science Faculty Research & Creative Works

This paper was written for the project study “Adaptive Information Filtering” at the Department of Computer Science, Leiden University, The Netherlands. The assignment was to write an introduction to Adaptive Information Filtering (AIF), based on the author’s ideas for his M.Sc. thesis, and with as large an audience as possible in mind. In addition to a simple introduction to AIF, this paper should also provide easy introductions to clustering algorithms, evolutionary computation, and n-gram analysis. (Preface, page 2)

A User Interface For The Visualization And Manipulation Of Arrays, Jennifer Leopold, A. Ambler

Computer Science Faculty Research & Creative Works

The success of spreadsheets has shown that a visual representation of a 2D array greatly facilitates solving certain problems. However, spreadsheets are not general-purpose programming environments and are not suited to many problems that might naturally be solved using multi-dimensional arrays. Furthermore, spreadsheets employ a textual notation for cell references in formulas. This notation, which adds to the programmer''s burden by distinguishing between relative and absolute addressing, can be difficult to understand and is error-prone even for the most experienced users. In this paper, we present a user interface for multi-dimensional arrays within Formulate, a form-based visual programming language. This …

Tuning Numeric Parameters To Troubleshoot A Telephone-Network Loop, Christopher J. Merz, M. J. Pazzani, A. P. Danyluk

Computer Science Faculty Research & Creative Works

The Nynex Max expert system analyzes the result of an automated electric test on a telephone line and determines the type of problem. However, tuning the system's parameter values can be difficult. The Opti-Max system can automatically set these parameters by analyzing decisions made by experts who troubleshoot problems

Automatic Pcb Inspection Algorithms: A Survey, Madhav Moganti, Fikret Ercal, Cihan H. Dagli, Shou Tsunekawa

Computer Science Faculty Research & Creative Works

The importance of the inspection process has been magnified by the requirements of the modern manufacturing environment. In electronics mass-production manufacturing facilities, an attempt is often made to achieve 100% quality assurance of all parts, subassemblies, and finished goods. A variety of approaches for automated visual inspection of printed circuits have been reported over the past two decades. In this survey, algorithms and techniques for the automated inspection of printed circuit boards are examined. A classification tree for these algorithms is presented and the algorithms are grouped according to this classification. This survey concentrates mainly on image analysis and fault …

Formal Methods: How, When, And Why They Are Used, Beth Arrowsmith, Bruce Mcmillin, Ralph Wilkerson

Computer Science Technical Reports

Formal methods, theoretically a wonderful concept for ensuring a program's correctness, are not widely used in practice. This dichotomy between what theory advocates and practice might be due to programmers' lack of experience with formal methods. To determine if this was the case, a module on Formal Methods was introduced into a graduate course on distributed systems. This module first introduced the students to the theory of formal methods and then required students to program a distributed problem in CCSP, a subset of CSP, using formal methods. The results were abysmal. Students avoided using formal methods. When they did use …

Matching And Indexing Techniques In Rules, Madhav Moganti

Computer Science Technical Reports

Rules are widely used in present-day intelligent systems for modeling intelligent behavior, building expert systems, database rule systems, and advanced document retrieval systems. Most rule-based system programs are extremely computation-intensive and run quite slowly. This problem may get still worse when a rulebase does not fit into primary memory completely. This article reviews currently existing rule matching and indexing techniques. This report is organized into two parts. Part I presents the well known rule matching algorithms, Rete and TREAT, along with their performance evaluations. Part II presents rule indexing techniques for large scale rulebases. Here two sources of indexing are …