A burden of wonder

The Post-Proceedings of this Festschrift will be formally published in The South African Computer Journal number 41

Sensitivity analysis of voronoi-based sensor deployment and reconfiguration algorithms

This study examines the effects of location inaccuracies on two movement-assisted Voronoi-based sensor deployment and reconfiguration algorithms, VEC and VOR, due to Wang et al. For the purposes of examining the extent to which the deployment and reconfiguration algorithms are capable of reducing coverage holes, a simulator environment was set up, using a custom-designed simulation tool. By integrating the environment with that of a GIS application, real-world distance and scaling can be applied, allowing the assessment of the algorithms to be performed in a virtual world mimicking that of a real-world deployment. The simulation results suggest the VOR algorithm is reasonably robust if the location inaccuracies are somewhat lower than the sensing distance, and also if a high degree of inaccuracy is limited to a relatively small percentage of the nodes. The VEC algorithm is considerably less robust, but prevents nodes from drifting beyond the boundaries in the case of large inaccuracies

A comparison of simulated traffic conditioner performance

In this paper, the simulated performance of a number of differentiated services traffic conditioners is studied under a range of synthetic traffic conditions. The traffic conditioners are compared using two performance measures which are defined and justified in the paper. In the initial simulation the traffic conditioner performance differed in one measure but not the other. Further experimentation showed that one could get all the conditioners to have similar performance by setting carefully the configuration parameters of the conditioners

A Concurrent Specification of Brzozowski’s DFA Construction Algorithm

Abstract. In this paper two concurrent versions of Brzozowski’s deterministic finite automaton (DFA) construction algorithm are developed from first principles, the one being a slight refinement of the other. We rely on Hoare’s CSP as our notation. The specifications that are proposed of the Brzozowski algorithm are in terms of the concurrent composition of a number of top-level processes, each participating process itself composed of several other concurrent processes. After considering a number of alternatives, this particular overall architectural structure seemed like a natural and elegant mapping from the sequential algorithm’s structure. While we have carefully argued the reasons for constructing the concurrent versions as proposed in the paper, there are of course, a large range of alternative design choices that could be made. There might also be scope for a more fine-grained approach to updating sets or checking for similarity of regular expressions. At this stage, we have chosen to abstract away from these considerations, and leave their exploration to future research

A process-oriented implementation of Brzozowski's DFA construction algorithm

A process-algebraic description of Brzozowski's deterministic finite automaton construction algorithm, slightly adapted from a previous version, shows how the algorithm can be structured as a set of communicating processes. This description was used to guide a process-oriented implementation of the algorithm. The performance of the process-oriented algorithm is then compared against the sequential version for a statistically significant number of randomly generated regular expressions. It is shown that the concurrent version of the algorithm outperforms the sequential version both on a multi-processor machine as well as on a single-processor multi-core machine. This is despite the fact that processor allocation and process scheduling cannot be user-optimised but are, instead, determined by the operating system

Empirically assessing algorithm performance

The timing performance data of ten related algorithms (solving the single keyword pattern matching problem) executing under a wide variety of operating conditions, was gathered and analysed. Using the resulting 15 million items of timing data, various metrics to estimate algorithm performance were computed and compared. An assessment is made of whether and how various changes in the operating environment affect the measurements