Computer Sciences Commons^™

An Analysis Of Product Metrics In Terms Of Qualitative And Formal Metric Properties, Tuliz Dengi, George Zobrist

Computer Science Technical Reports

In recent years, the increased concern for developing reliable, cost-efficient software systems has been accompanied by a higher need to analyze and measure software complexity. Numerous metrics have been proposed to measure software complexity and functionality. Yet, testing the validity of these metrics has been a difficult and long process. As an initial test of metric validity, some researchers have suggested the use of formal metric properties so that metrics without a sound theoretical base are rejected right away. This approach has the additional advantage of allowing a reasonable and fair comparison of software metrics.

In this study, a discussion …

An Object-Oriented Approach To Data Exchange Applications: Development Of A Class Library For The Spatial Data Transfer Standard, Phyllis Altheida, John Prater

Computer Science Technical Reports

The object-orienced paradigm embodies a set of concepts that differentiates it from process-oriented and data-oriented methods. Among che commonly included principles are object, class, encapsulation, inheritance and polymorphism. The synergism of the concepts creates a powerful and new perspective that can be applied to all phases of systems development. Application developers need to try out the object-oriented languages, methodologies and development tools to help define its niche. The problem domain of data transfer standards is used to test the applicability of object-oriented techniques. Data transfer standards have three levels of abstraction: conceptual, logical, and format. The Spatial Data Transfer Standard …

An Animation System For Shift Reduce Parsers, M. S. Mandl, T. J. Sager, D. C. St. Clair

Computer Science Technical Reports

This paper presents the design and implementation of the Parse Display Utility (POU) system. This system introduces a mechanism to augment traditional methods of exploring parsing theory by providing a PRESENTATION scheme which allows a user to view the operation of a shift-reduce parser.

The overall operation of the tool revolves around an LALR (LookAhead LR) parser/parser generator and is managed by a Graphical User-Interface (GUI) developed using Borland's Turbo Vision product. The GUI allows access to a facility which draws derivation trees in Turbo Pascal graphics. This parse tree facility utilizes an algorithm which can easily be ported to …

Effect Of The X² Test On Construction Of Id3 Decision Trees, Mayank Thakore, Daniel C. St. Clair

Computer Science Technical Reports

Inductive machine learning algorithms are knowledge-based learning algorithms which take training instances as input and produce knowledge as output. One popular induction algorithm is Quinlan's ID3 [1986]. This algorithm produces knowledge in the form of a decision tree. Each path in the tree can be interpreted as a rule with the leaves representing rule conclusions. Selected attributes which describe the training instances form the interior nodes of the tree.

The ID3 algorithm is extremely sensitive to noisy training data. In an effort to reduce the effects of noise on tree construction, Quinlan used the X² test to identify noisy …

Formal Generation Of Executable Assertions For Application-Oriented Fault Tolerance, Hanan Lutfiyya, Martina Schollmeyer, Bruce M. Mcmillin

Computer Science Technical Reports

Executable assertions embedded into a distributed computing system can provide run-time assurance by ensuring that the program state, in the actual run-time environment, is consistent with the logical stage specified in the assertions; if not, then an error has occurred and a reliable communication of this diagnostic information is provided to the system such that reconfiguration and recovery can take place. Application- oriented fault tolerance is a method that provides fault detection using executable assertions based on the natural constraints of the application.

This paper focuses on giving application-oriented fault tolerance a theoretical foundation by providing a mathematical model for …

Fault Tolerance In Concurrent Systems Through Formal Methods, H. Lutfiyya, B. M. Mcmillin

Computer Science Technical Reports

An important aspect which is often overlooked in the software design cycle is the question of assurance. Many methodologies in the past have attempted to provide assurance efficiently, but have never been sucessful at eliminating explicit time and space redundancy. One approach is the Application-Oriented Fault Tolerance Paradigm, which provides assurance by examining the behavior and propenies of the application and deriving executable assertions for the detection of faults. Previous work has demonstrated the feasibility of the application-oriented fault tolerance paradigm for various applications. However, the executable assertions were guided by the natural constraints of the problem. This work focuses …

Parallel Computer Needs At Dartmouth College, David Kotz, Fillia Makedon, Matt Bishop, Scot Drysdale, Don Johnson, Takis Metaxas

Computer Science Technical Reports

To determine the need for a parallel computer on campus, a committee of the Graduate Program in Computer Science surveyed selected Dartmouth College faculty and students in December, 1991, and January, 1992. We hope that the information in this report can be used by many groups on campus, including the Computer Science graduate program and DAGS summer institute, Kiewit's NH Supercomputer Initiative, and by numerous researchers hoping to collaborate with people in other disciplines.

We found significant interest in parallel supercomputing on campus. An on-campus parallel supercomputing facility would not only support numerous courses and research projects, but would provide …

Effects Of Nonsymmetric Release Times On Rate Monotonic Scheduling, R. G. Karl, T. L. Lo, D. C. St. Clair

Computer Science Technical Reports

This paper discusses problems associated with scheduling periodic tasks in a hard, real-time processing or computing environment using a static-priority, preemptive-resume operating system . The scheduling problems associated with a task set containing a single periodic task which has two fixed release periods of unequal length are examined. Some real-world applications may require task release times which are periodic, but whose tasking periods are not symmetric. A scheduling algorithm for task sets with a single nonsymmetric task has been developed for staticpriority, preemptive-resume operating systems. The nonsymmetric scheduling algorithm is based on the rate monotonic scheduling algorithm which assigns higher …

Design Of Backpropagation Neural Network Architectures Using A Decision Tree Classifier, B. M. Van Horn, D. C. St. Clair

Computer Science Technical Reports

The backpropagation neural network algorithm is a popular machine learning methodology. One difficulty with using the algorithm is that the network architecture must be designed before learning can occur. This includes deciding the number of layers, the number of nodes in each layer, and the number of connections. Traditionally this problem is solved by heuristics gained by an expert through experience.

This paper presents an algorithm for using ID3 decision trees to design the network architecture. Previous approaches rely on binary decision trees. The proposed technique utilizes n-ary trees. These trees are easier to understand, are better suited for continuous-valued …

Optimizing Accuracy And Generalization In Numeric Classification Systems, M. D. Walters, D. C. St. Clair

Computer Science Technical Reports

Classifier systems are knowledge-based learning algorithms that take training instances as input and produce a set of rules as output. The classifier systems focused on in this paper represent the knowledge they learn in the form of decision trees, and are built upon Quinlan's [ 1986] inductive algorithm ID3.

The ID3 algorithm suffers from the inability to easily and effectively handle domains with numeric-valued attributes. Numeric attributes are those whose values are taken from a continuous domain or from a domain with a large number of discrete values. A number of approaches have been developed for extending ID3 to handle …

The Identification And Processing Of Don't-Care Attribute Values In Id3 Decision Tree Construction, P. D. Dorr, D. C. St. Clair

Computer Science Technical Reports

ID3 is most successful when used with sets of training and testing data that contain no missing attribute values. Many times, however, real-world domains have attributes with missing values. Sometimes these attribute values may not be needed to classify an instance. Such attribute values are called don't-care attribute values. In other cases, the values are needed but are unavailable. These values are called unknown attribute values. This paper describes the difference between unknown and don't-care attribute values and discusses several ways of identifying don't-care attribute values in ID3. Numerical results are described which validate the practicality of these approaches.

Network Key Management In A Large Distributed Environment, J. J. Stapleton, D. C. St. Clair

Computer Science Technical Reports

The technique of using encryption for protecting information in a network environment involves managing encryption keys within that same network. In large distributed networks the goal of achieving a secure environment requires a secure method of performing network key management. Network security, system security, and application security by means of data encryption rely on encryption keys remaining secret.

Both international and domestic standards organizations such as the International Organization for Standardization (ISO), the American National Standards Institute (ANSI), and the National Institute of Standards and Technology (NIST) address the issues of encryption through various standards. However, these standards discuss methods …

An Enhanced Reconfigurable Embedding Scheme For Rings In Hypercubes, Junlin Liu, Bruce M. Mcmillin

Computer Science Technical Reports

In this paper we present an enhanced version of a reported reconfigurable embedding scheme (i.e., DC scheme) that based on the idea of divide and conquer to efficiently embed even length rings in hypercubes. It was shown that the system with the DC scheme is 3-step recoverable and needs an average of 1.3 steps to recover one single fault. Here, we show that the system with the enhanced embedding scheme will be 2-step recoverable when the dimensions of hypercubes are ~ 5, and the system is able to recover any single fault in an average of 1.1 steps.

Relaxing Synchronization In Distributed Simulated Annealing, Chul-Eui Hong, Bruce M. Mcmillin

Computer Science Technical Reports

Simulated annealing is an attractive, but expensive, heuristic for approximating the solution to combinatorial optimization problems. Attempts to parallelize simulated annealing, particularly on distributed memory multicomputers, are hampered by the algorithm's requirement of a globally consistent system state. In a multicomputer, maintaining the global state S Involves explicit message traffic and is a critical performance bottleneck. To mitigate this bottleneck, it becomes necessary to amortize the overhead of these state updates over as many parallel state changes as possible. By using this technique, errors in the actual cost C(S) of a particular state S will be introduced into the annealing …

A Visualization System For Correctness Proofs Of Graph Algorithms, Peter A. Gloor, Donald B. Johnson, Fillia Makedon, Panagiotis Metaxas

Computer Science Technical Reports

In this paper we describe a system for visualizing correctness proofs of graph algorithms. The system has been demonstrated for a greedy algorithm. Prim's algorithm for finding a minimum spanning tree of an undirected, weighted graph. We believe that our system is particularly appropriate for greedy algorithms, though much of what we discuss can guide visualization of proofs in other contexts. While an example is not a proof, our system provides concrete examples to illustrate the operation of the algorithm. These examples can be referred to by the user interactively and alternatively with the visualization of the proof where the …

An Algorithm For Generating Executable Assertions For Fault Tolerance, Martina Schollmeyer, Hanan Lutfiyya, Bruce M. Mcmillin

Computer Science Technical Reports

This paper presents an algorithm for deriving executable assertions that can be evaluated in a faulty distributed environment. A transformation from the global auxiliary variable approach into a new proof system based on the history of the auxiliary variables is introduced. This transformation, which matches the operational distributed environment more closely than the global auxiliary variable system, is then shown to retain the properties of this system such as noninterference, satisfaction, soundness, and completeness. An example is presented in which a model problem is transformed from one system into the other.

Multiprocessor File System Interfaces, David Kotz

Computer Science Technical Reports

Increasingly, file systems for multiprocessors are designed with parallel access to multiple disks, to keep I/O from becoming a serious bottleneck for parallel applications. Although file system software can transparently provide high-performance access to parallel disks, a new file system interface is needed to facilitate parallel access to a file from a parallel application. We describe the difficulties faced when using the conventional (Unix-like) interface in parallel applications, and then outline ways to extend the conventional interface to provide convenient access to the file for parallel programs, while retaining the traditional interface for programs that have no need for explicitly …

Fault-Tolerant Distributed Database Lock Managers Formally Derived From Program Verification, Hanan Lutfiyya, Martina Schollmeyer, Bruce M. Mcmillin

Computer Science Technical Reports

This paper presents a system for formally deriving executable assertions that can be evaluated in the faulty distributed computing environment. Since executable assertions for fault tolerance need to show that a program meets its specification and, since program verification is the process of formally showing that a program satisfies some particular properties with respect to its specification, we use program verification as a basis for derivation. It is well known that in the sequential computing environment the assertions from a program verification proof outline may be translated directly into executable assertions. However, due to the lack of global state information …

Fault-Tolerant Concurrent Branch And Bound Algorithm Derived From Program Verification, Hanan Lutfiyya, Aggie Sun, Bruce M. Mcmillin

Computer Science Technical Reports

The process of showing that a program satisfies some particular properties with respect to its specification is called program verification. Axiomatic semantics is a verification method that makes assertions describing properties about the states of the program. There exists a transformation from the assertions of the verification proof of a program to executable assertions. These executable assertions may be embedded in the program to create a fault-tolerant program. While this approach has been applied to the sequential programming environment, the distributed programming environment presents special challenges. This paper focuses on applying concurrent programming axiomatic proof systems to generate executable assertions …

A Divide And Conquer Ring Embedding Scheme On Hypercubes With Efficient Recovery Ability, Junlin Liu, Bruce M. Mcmillin

Computer Science Technical Reports

The hypercube architecture has been considered a useful host to simulate many networks. However, when processors on hypercubes become faulty, the simulated topologies may no longer be valid and, thus, the system needs to invoke some reconfiguration algorithm to recover the topology. The efficiency of this reconfiguration depends heavily on the initial embedding method. This paper proposes a general scheme based on the idea of divide and conquer that efficiently embeds even length rings on hypercubes with small expansion and recovery cost. It is shown that the average expansion for the proposed scheme is 1.58, and the average number of …

How To Encrypt /Usr/Dict/Words In About A Second, Peter Su, Matt Bishop

Computer Science Technical Reports

We present an implementation of the Data Encryption Standard on the Connection Machine architecture. The DES encryption algorithm is ideally suited to the Connection Machine because it consists of bit serial operations, and thousands of encryptions can be done in parallel, independently of one another. Thus, our code encrypts passwords about ten times faster than the fastest competition that we know about. In addition, the nature of the Connection Machine's architecture is such that some of the optimizations that make DES run much faster on conventional architectures have no effect on the performance of the Connection Machine. Our comparison of …

Concurrent Local Search For Fast Proximity Algorithms On Parallel And Vector Architectures, Peter Su

Computer Science Technical Reports

This paper presents a fast algorithm for solving the all-nearest-neighbors problem. The algorithm uses a data parallel style of programming which can be efficiently utilized on a variety of parallel and vector architectures [4,21,26]. I have implemented the algorithm in C on one such architecture, the Cray Y-MP. On one Cray CPU, the implementation is about 19 times faster than a fast sequential algorithm running on a Sparc workstation. The main idea in the algorithm is to divide the plane up into a fixed grid of cells, or buckets. When the points are well distributed, the algorithm processes each query …

On The De Bruijn Torus Problem, Glenn Hurlbert, Garth Isaak

Computer Science Technical Reports

A (kn;n)k-de Bruijn Cycle is a cyclic k-ary sequence with the property that every k-ary n-tuple appears exactly once contiguously on the cycle. A (kr, ks; m, n)k-de Bruijn Torus is a k-ary krXks toroidal array with the property that every k-ary m x n matrix appears exactly once contiguously on the torus. As is the case with de Bruijn cycles, the 2-dimensional version has many interesting applications, from coding and communications to pseudo-random arrays, spectral imaging, and robot self-location. J.C. Cock proved the existence of such tori for all m, n, and k, and Chung, Diaconis, and Graham asked …

Optimal Algorithms For Multipacket Routing Problems On Rings, Fillia Makedon, Antonios Symvonis

Computer Science Technical Reports

We study multipacket routing problems. We divide the multipacket routing problem into two classes, namely, distance limited and bisection limited routing problems. Then, we concentrate on rings of processors. We prove a new lower bound of 2n/ 3 routing steps for the case of distance limited routing problems. We also give an algorithm that tightens this lower bound. For bisection limited problems the lower bound is kn/ 4,k >2, where k is the number of packets per processor. The trivial algorithm needs in the worst case k | n /2| steps to terminate. An algorithm that completes the routing in …

Effects Of Replication On The Duration Of Failure In Distributed Databases, Donald B. Johnson, Larry Raab

Computer Science Technical Reports

Replicating data objects has been suggested as a means of increasing the performance of a distributed database system in a network subject to link and site failures. Since a network may partition as a consequence of such failures, a data object may become unavailable from a given site for some period of time. In this paper we study duration failure, which we define as the length of time, once the object becomes unavailable from a particular site, that the object remains unavailable. We show that, for networks composed of highly-reliable components, replication does not substantially reduce the duration of failure. …

Availability Issues In Data Replication In Distributed Database, Donald B. Johnson, Larry Raab

Computer Science Technical Reports

Replication of data at more than one site in a distributed database has been reported to increase the availability in data in systems where sites and links are subject to failure. We have shown in results summarized in this paper that in many interesting cases the advantage is slight. A well-placed single copy is available to transactions almost as much of the time as is correct replicated data no matter how ingeniously it is managed. We explain these findings in terms of the behavior of the partitions that form in networks where components fail. We also show that known and …

An Lr(L) Testing Algorithm, Thomas J. Ssager

Computer Science Technical Reports

A grammar is LR{1} if it can be parsed deterministically from left to right while looking ahead no more than one symbol. Because of the difficulty in generating full LR{l) parsers, many parser generators such as YACC limit themselves to LALR(1} grammars which are a subset of the LR{l) grammars.

Unlike other algorithms in the literature for testing whether a grammar is LR{l), the algorithm presented here uses only the characteristic finite state machine and other structures necessary for creating an LALR{l) parser. Thus, if a parser generator finds that a grammar is not LALR{l), with little additional work the …

The Minlrl Algorithm For Generating Small Lr(L) Parsers, Thomas J. Sager

Computer Science Technical Reports

The MINLRl algorithm for finding minimal deterministic parsers for LR(1) grammars is presented. MINLRl also detects whether a grammar is LR(l) with little more work than building the grammar's LALR(l) parser. MINLRl starts by building the characteristic finite state machine, CFSM, for the input grammar and then checks for LR(l)ness. If the input grammar is LR(l), MINLRl transforms the CFSM into a minimal LR(l) parser by creating extra copies of certain states of the CFSM as necessary. The complexity of the algorithm is O(n³l²v²) where n is the number of states in the parser, …

Complexity Of Network Reliability And Optimal Database Placement Problems, Donald B. Johnson, Larry Raab

Computer Science Technical Reports

A fundamental problem of distributed database design in an existing network where components can fail is finding an optimal location at which to place the database in a centralized system or copies of each data item in a decentralized or replicated system. In this paper it is proved for the first time exactly how hard this placement problem is under the measure of data availability. Specifically, we show that the optimal placement problem for availability is #P- complete, a measure of intractability at least as severe as NP-completeness. Given the anticipated computational difficulty of finding an exact solution, we go …

Formal Generation Of Executable Assertions For A Fault-Tolerant Parallel Matrix Relaxation, Hanan Lutfiyya, Bruce M. Mcmillin

Computer Science Technical Reports

No abstract provided.