Parallel alogorithms for MIMD parallel computers

This thesis mainly covers the design and analysis of asynchronous parallel algorithms that can be run on MIMD (Multiple Instruction Multiple Data) parallel computers, in particular the NEPTUNE system at Loughborough University. Initially the fundamentals of parallel computer architectures are introduced with different parallel architectures being described and compared. The principles of parallel programming and the design of parallel algorithms are also outlined. Also the main characteristics of the 4 processor MIMD NEPTUNE system are presented, and performance indicators, i.e. the speed-up and the efficiency factors are defined for the measurement of parallelism in a given system. Both numerical and non-numerical algorithms are covered in the thesis. In the numerical solution of partial differential equations, a new parallel 9-point block iterative method is developed. Here, the organization of the blocks is done in such a way that each process contains its own group of 9 points on the network, therefore, they can be run in parallel. The parallel implementation of both 9-point and 4- point block iterative methods were programmed using natural and redblack ordering with synchronous and asynchronous approaches. The results obtained for these different implementations were compared and analysed. Next the parallel version of the A.G.E. (Alternating Group Explicit) method is developed in which the explicit nature of the difference equation is revealed and exploited when applied to derive the solution of both linear and non-linear 2-point boundary value problems. Two strategies have been used in the implementation of the parallel A.G.E. method using the synchronous and asynchronous approaches. The results from these implementations were compared. Also for comparison reasons the results obtained from the parallel A.G.E. were compared with the ~ corresponding results obtained from the parallel versions of the Jacobi, Gauss-Seidel and S.O.R. methods. Finally, a computational complexity analysis of the parallel A.G.E. algorithms is included. In the area of non-numeric algorithms, the problems of sorting and searching were studied. The sorting methods which were investigated was the shell and the digit sort methods. with each method different parallel strategies and approaches were used and compared to find the best results which can be obtained on the parallel machine. In the searching methods, the sequential search algorithm in an unordered table and the binary search algorithms were investigated and implemented in parallel with a presentation of the results. Finally, a complexity analysis of these methods is presented. The thesis concludes with a chapter summarizing the main results

Media agenda-building battles between Greenpeace and Shell : a rhetorical and discursive approach

The empirical focus of this research comprises the UK television news battles between Greenpeace (a highly media-aware International Non-Governmental Organisation (INGO)), and the oil company Shell (a multinational corporation (MNC)). Specifically, two such media battles are examined, both receiving international attention and intense media publicity during 1995:- The battle between Royal Dutch/Shell, particularly, its subsidiary Shell-UK, and Greenpeace over the deep-sea disposal of the Brent Spar oil platform;- The battle between Royal Dutch/Shell's Nigerian subsidiary, the Shell Petroleum Development Corporation (SPDC) (hereafter referred to as Shell-Nigeria), and Greenpeace (amongst others) over environmental pollution in Ogoniland, Nigeria.These two battles were chosen mainly because they share the same main protagonists - Greenpeace and Shell - providing rich material for a number of interesting questions regarding media agenda-building

Effectiveness of training on algorithms versus notation for indirect addressing comprehension

This study compared two units of instruction for overcoming difficulties of beginning programmers in understanding and implementing strategies of indirect addressing. One of the units emphasized the algorithms in which indirection was used, whereas the other unit emphasized indirect notation. Both instructional units were delivered by computer to two introduction to Pascal programming classes. Students in each class were randomly divided so that each student used one or the other of the two units;These units were used prior to and were supplementary to three lectures covering indirect notation. The effectiveness of the units were determined by two posttests. One posttest, requiring students to select subscripts at several levels of indirection, was administered by computer. This test was very similar to the activities in the notation unit. The second posttest was a paper pencil activity requiring the students to complete or modify sorting algorithms in which indirection was used;Because of the explorative nature of this study and the small sample size, the findings must be viewed as tentative. However, it would appear the notation of indirection by itself is not an important source of student problems in this area. In fact, there was little evidence to suggest that either unit made a sizeable difference in the student\u27s ability to deal with indirection within the context of programming. There was an indication extra study of algorithms encouraged students to attempt to solve more problems, but this finding may be a result of the experimental conditions and may not be generalizable

Visualization of Sorting Algorithms

The purpose of this thesis was to develop a graphical tooi for the visuaiization of a number of soning methods. The tool developed, called SortDisplay, not only gives the users the option to view various sorting methods in execution, but also gives other options to get infonnation about the perfonnance and complexity of the sorting algorithms in tenns of the number cf comparisons and exchanges needed. The tool also has various other options which help the user understand and analyze the sorting algorithms implemented. The tool was designed to be an educational tool running on the Oklahoma State University Computer Science Department's Sequent Symmetry S/81 computer running the Dynixlptx operating system. The tollowing topics, which were covered as background and context, put the thesis work in perspective: (1) sorting and sorting algorithms; (2) the concept of visualization and types of visualization; (3) the X window system, the X protocoi, and various software layers in X; (4) the OSFlMotiftoolkit; and (5) using Motif with C++. The programming part of the tool involved designing and implementing the class hierarchies, application framework, sorting methods, and user-interface. The program, coded in the C++ programming language using the Motif toolkit, Xt Intrinsics, and Xlib, has over 4500 lines ofuncommented code (over 5500 lines of documented code), 2 major class hierarchies, and 40 classes. The six sorting methods that were implemented include two Insertion sorts (Linear Insertion and Shellsort), three Exchange sorts (Bubblesort, Combsort, and Quicksort), and one Exchange sort (Straight Selection). SortDisplay was evaluated by various users of the Computer Science Department's Sequent Symmetry S/81 machine including faculty and staff members, and former and current graduate students. Most of the recommendations and suggestions of the evaluators were incorporated into the tool. A number of the ideas that were deemed beyond the scope of the present work were left for the future updates of the tool

An adaptive environment for personal information management

This thesis was submitted for the degree of Doctor of Philosophy and awarded by Brunel University.This dissertation reports the results of research into the provision of adaptive user interfaces to support individuals in the management of their personal information. Many individuals find that they have increased responsibility for managing aspects of their own lives, including the information associated with their jobs. In contrast with traditional approaches to information management, which are generally driven by organisational or business requirements, the requirements of personal information management systems tend to be less rigidly defined. This dissertation employs research from the areas of personal information management and adaptive user interfaces - systems which can monitor how they are used, and adapt on a personal level to their user - to address some of the particular requirements of personal information management systems. An adaptive user interface can be implemented using a variety of techniques, and this dissertation draws on research from the area of software agents to suggest that reactive software agents can be fruitfully applied to realise the required adaptivity. The reactive approach is then used in the specification and development of an adaptive interface which supports simple elements of personal information management tasks. The resulting application is evaluated by means of user trials and a usability inspection, and the theoretical architectures and techniques used in the specification and development of the software are critically appraised. The dissertation demonstrates an application of reactive software agents in adaptive systems design and shows how the behaviour of the system can be specified based on the analysis of some representative personal information management tasks.EPSRC (Award Reference Number 95700906