Endogenous role assignment and team performance

We study how the mechanism used for assigning roles within teams affects team performance. Subjects play the takeover game in buyer-seller teams. Understanding optimal play is demanding for buyers and trivial for sellers, so teams should perform better if the buyer is the abler teammate. When teammates are allowed to jointly choose their roles, abler teammates tend to become buyers, but this is more than offset by disruptions to the learning process. We examine two potential sources for the latter effect, and find that endogenous role assignment has a negative psychological and emotional effect on buyers

Mapping polygons to the grid with small Hausdorff and Fréchet distance

We show how to represent a simple polygon P by a (pixel-based) grid polygon Q that is simple and whose Hausdorff or Fréchet distance to P is small. For any simple polygon P, a grid polygon exists with constant Hausdorff distance between their boundaries and their interiors. Moreover, we show that with a realistic input assumption we can also realize constant Fréchet distance between the boundaries. We present algorithms accompanying these constructions, heuristics to improve their output while keeping the distance bounds, and experiments to assess the output

Practical synthesis from real-world oracles

As software systems become increasingly heterogeneous, the ability of compilers to reason about an entire system has decreased. When components of a system are not implemented as traditional programs, but rather as specialised hardware, optimised architecture-specific libraries, or network services, the compiler is unable to cross these abstraction barriers and analyse the system as a whole. If these components could be modelled or understood as programs, then the compiler would be able to reason about their behaviour without concern for their internal implementation details: a homogeneous view of the entire system would be afforded. However, it is not often the case that such components ever corresponded to an original program. This means that to facilitate this homogenenous analysis, programmatic models of component behaviour must be learned or constructed automatically. Constructing these models is an inductive program synthesis problem, albeit a challenging one that is largely beyond the ability of existing implementations. In order for the problem to be made tractable, information provided by the underlying context (i.e. the real component behaviour to be matched) must be integrated. This thesis presents three program synthesis approaches that integrate contextual information to synthesise programmatic models for real, existing components. The first, Annote, exploits informally-encoded information about a component's interface (e.g. from documentation) by weaving that information into an extended type-and-attribute system for component interfaces. The second, Presyn, learns a pair of cooperating probabilistic models from prior syntheses, that aim to predict likely program structure based on a component's interface. Finally, Haze uses observations of common side-effects of component executions to bias the search for programs. These approaches are each evaluated against comparable synthesisers from the literature, on a set of benchmark problems derived from real components. Learning models for component behaviour is only a partial solution; the compiler must also have some mechanism to use those models for program analysis and transformation. This thesis additionally proposes a novel mechanism for context-sensitive automatic API migration based on synthesised programmatic models, and evaluates the effectiveness of doing so on real application code. In summary, this thesis proposes a new framing for program synthesis problems that target the behaviour of real components, and demonstrates three different potential approaches to synthesis in this spirit. The success of these approaches is evaluated against implementations from the literature, and their results used to drive a novel API migration technique

The response of structures to acoustic excitation with special reference to the sonic boom

The research reported in this thesis is concerned with the response of mechanical structures to the excitation of acoustic fields. Both the vibration of the structure itself (sonic boom studies) and the secondary sound field which this vibration produces (transmission loss studies) are investigated. In measuring the airborne transmission loss of a high loss partition an important limitation of the University's experimental suite was discovered. Attempts at an indirect measurement of transmission loss using vibration transducers illustrate a fallacious assumption of most transmission loss theories. These findings impose a considerable limitation upon the accelerometer method of transmission loss measurement. The study of structural vibration was extended to sonic boom response. In particular the effects of a cavity behind a panel upon the panel's dynamic properties is studied both experimentally and theoretically. This model is comparable with a window-room system and so is of current interest in the evaluation of the possibility of sonic boom damage