As confirmed by a recent survey conducted among developers of the Apache, Eclipse, and Mozilla projects, two extremely challenging tasks during maintenance are reproducing and debugging field failures--failures that occur on user machines after release. In my PhD study, I have developed several techniques to address and mitigate the problems of reproducing and debugging field failures. In this defense, I will present an overview of my work and describe in detail four different techniques: BugRedux, F3, Clause Weighting (CW), and On-demand Formula Computation (OFC). BugRedux is a general technique for reproducing field failures that collects dynamic data about failing executions in the field and uses this data to synthesize executions that mimic the observed field failures. F3 leverages the executions generated by BugRedux to perform automated debugging using a set of suitably optimized fault-localization techniques. OFC and CW improves the overall effectiveness and efficiency of state-of-the-art formula-based debugging. In addition to the presentation of these techniques, I will also present an empirical evaluation of the techniques on a set of real-world programs and field failures. The results of the evaluation are promising in that, for all the failures considered, my approach was able to (1) synthesize failing executions that mimicked the observed field failures, (2) synthesize passing executions similar to the failing ones, and (3) use the synthesized executions successfully to perform fault localization with accurate results.

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published_or_final_version / Physics / Doctoral / Doctor of Philosophy

Today’s farmers gut feeling and Fingerspitzengefühl comes from a learning by doing. By year 2025 farmers will have less know-how than today. Foretell supports the farmers in developing their gut feeling and lead more efficient farms. By visualising data, the system provides a comprehensive overview of the farm, both in the tractor, the barn, at the field and in the office. In the transition from running a family farm to become an entrepreneur with an own company has resulted in that the farmers need to supervise the farm’s production but also have control of external conditions. Future farmers needs to quicker become experts. Through research and user studies the system Foretell have been created. Foretell connects the data available today and displays it where it is needed and when it is suitable. The mobile application shows information on the go. While the desktop version gives the user better planning tools. A new precision farming input is added in form of a near-infra-red camera that detects the plants health. With all pieces together Foretell is bringing gut feeling to farmers!

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The General theory of Relativity (GR) brought gravity into accord with the principles of locality and relativity. Since its discovery it has been preeminent, recognized as the most accurate description of gravity on the many scales where it has been tested. During this period, seemingly radical predictions like the existence of black holes and the expansion of the Universe have been verified and testify to the great leap of insight that GR represented in our understanding of space and time. However not all precision observations of astrophysical systems have yielded easily to interpretation within GR, and with the discovery of cosmic acceleration, there is genuine concern that General Relativity may be incomplete when describing the Universe on the largest sizes imaginable. In this uncertainty, many theoretical models have been proposed. In this thesis we shall first outline the motivation behind a certain subset of these models and the known issues that arise in interpreting these models as alternative theories of gravity. Then focus on one variety of theory the f(R) modifications to gravity. Demonstrating that many of the known instabilities have a common origin and that they are avoided when treating these theories via perturbative constraints. In the second part of this work we examine the astrophysical impact of modifications to gravity, first in the case of high mass neutron stars, then subsequently on corrections to the line profile of neutral hydrogen from violations of the equivalence principle. Finally we explore the phenomenology of modifications to gravity that produce late-Universe acceleration. In particular, what solutions are allowed and what range of accelerations are predicted as a result. Furthermore we explore how a correction to gravity at large scales would impact the growth and evolution of cosmological perturbations.

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No description available.