Comparison of scatter storage techniques using an analysis of variance model

An analysis of variance model is developed to determine if a significant difference exists between various scatter storage techniques. The model is a two-factor hierarchical mixed design with each combination of transformation and search method considered as a treatment. The data used in the analysis is obtained from a computer program which provides statistics on the number of probes needed to load the (k+l)st item into a table for the different treatments. An ANOVA table was then computed for various load factors. A significant difference among the treatments was detected for load factors above .4. Comparison of individual treatments using Tukey\u27s multiple range test shows that although some treatments are significantly inferior, most treatments are not significantly different in terms of the average number of probes needed to load an item --Abstract, page ii

Data structures for set manipulation- hash table, 1986

The most important issue addressed in this thesis is the efficient implementation of hash table methods. There are credential trade-offs in a desired implement ion. These are discussed in issues such as hash addressing, handling collision, hash table layout., and bucket overflow problems. The criteria of good hash function is providing even distribution. Collision is the major problem in hash table methods. Two major hashtable methods are discussed. Open Addressing Method places the synonymous items somewhere within the table. The Chaining Method, however, chains all synonymies and stores them somewhere outside the table called overflow area. Hash table is widely used by system software as an ideal data structure. Hash Table -applications canbe found in compiler's symbol table, database, directories of file organizations, as well as in problem-solving application programs

An experimental approach to the prediction of retrieval timme using inverted and sequential search techniques for files stored on the disk packs of an IBM OS/360 MOD 50

In the course of designing file organization systems, comparing packaged generalized file processing systems, or when evaluating alternative hardware/ soft/ware configurations, it is often desirable to have a good estimate of system performance before committing large expenditure a of money and manpower

Advanced Computer Program Models : A Talking Textbook Based on Three Languages

The purpose of this dissertation was to develop a learning instrument, to be used by programmers preparing for the Data Processing Management Association Test as a self study book, or by college business programming and computer science students who have completed a course in data processing and a course in programming a higher level language. The mathematical ability requirement was minimized by developing the algorithms in parallel with the programs. The learner should experience _emphasis in the following .areas: l. The type of activities required to pass the DPMA test (the programming part) 2. Data Structures 3. Fortran (at the level of the DPMA test) I 4. RPG (at the level of the DPMA test) 5. Flow chart reading and writing Fortran and RPG (Report Program Generator) languages were used, since their proficiency is required for the DPMA test; however a subset of IBM Basic Assembler language was used, because the author believed that a person who is more than superficially interested in computers should demonstrate a proficiency with a machine language. An important part of this method of presentation are the cassette recordings which allow the learner to progress outside the classroom. The recordings plus the hard copy of the actual programs, diminished in size, give the learner material which he can move to any location and study without the presence of the instructor

Indirect key derivation schemes for key management of access hierarchies

In this thesis, we study the problem of key management within an access hierarchy. Our contribution to the key management problem is an indirect key derivation approach we call the HMAC-method. It is called the HMAC-method, because it is based on hashed message authentication codes (HMACs) built from a fast, single, dedicated hash function (SHA-1). It is intended to provide an efficient indirect key management method for large access hierarchies resembling tree structures. We are able to achieve better tree traversals using a technique we created called path addressing. Our path addressing scheme allows us to efficiently calculate relationships between security classes, determine traversal paths, and improve the performance of indirect key derivation. We also present our cached key update scheme which is meant to improve the indirect key derivation schemes on tree hierarchies by delaying key updates when changes to the structure of the access hierarchy are necessary, but the re-calculation and re-assignment of keys would either be costly or inconvenient. For access hierarchies represented as weakly/strongly connected directed acyclic graphs, we suggest modifications to our path addressing and key derivation scheme which could allow our HMAC-method to be appplied to these types of hierarchies. Along the way, we discuss various current key management methods and discuss certain pragmatic issues that can arise which affect the applicability and implementation of a key management method

An investigation to study the feasibility of on-line bibliographic information retrieval system using an APP

This thesis was submitted for the degree of Doctor of Philosophy and was awarded by Brunel University.This thesis reports an investigation on the feasibility study of a searching mechanism using an APP suitable for an on-line bibliographic retrieval, operation, especially for retrospective searches. From the study of the searching methods used in the conventional systems it is seen that elaborate file- and data- structures are introduced to improve the response time of the system. These consequently lead to software and hardware redundancies. To mask these complexities of the system an expensive computer with higher capabilities and more powerful instruction set is commonly used. Thus the service of the systen becomes cost-ineffective. On the other hand the primitive operations of a searching mechanism, such as, association, domain selection, intersection and unions, are the intrinsic features of an associative parallel processor. Therefore it is important to establish the feasibility of an APP as a cost-effective searching mechanise. In this thesis a searching mechanism using an 'ON-THE-FLY' searching technique has been proposed. The parallel search unit uses a Byte-oriented VRL-APP for efficient character string processing. At the time of undertaking this work the specification for neither the retrieval systems nor the BO-VRL APP's were well established; hence a two-phase investigation was originated. In the Phase I of the work a bottom up approach was adopted to derive a formal and precise specification for the BO-VRL-APP. During the Phase II of the work a top-down approach was opted for the implementation of the searching mechanism. An experimental research vehicle has been developed to establish the feasibility of an APP as a cost-effective searching mechanism. Although rigorous proof of the feasibility has not been obtained, the thesis establishes that the APP is well suited for on-line bibligraphic information retrieval operations where substring searches including boolean selection and threshold weights are efficiently supported