Recent advances in test automation have seen a host of new techniques for automated test generation, which traditionally has largely been a manual and expensive process. These techniques have enabled generation of much larger numbers of tests at a much reduced cost. When executed successfully, these tests enable a significant increase in our confidence in the program's correctness. However, as our ability to generate greater numbers of tests increases, we are faced with the problem of the likely high cost of executing all the tests in terms of the total execution time. This thesis presents a novel approach - clustered test execution - to address this problem. Instead of executing each test case separately, we execute parts of several tests using a single execution, which then forks into several directions as the behaviors of the tests differ. Our insight is that in a large test suite, several tests are likely to have common initial execution segments, which do not have to be executed over and over again; rather such a segment could be executed once and the execution result shared across all those tests. As an enabling technology we use the Java PathFinder(JPF) model checker, which is a popular explicit-state model checker for Java programs. Experimental results show that our clustering approach for test execution using JPF provides speed-ups over executing each test in turn from a test suite on the JPF java virtual machine. / text

Compiler optimizations in the context of traditional program execution is a well-studied research area, and modern compilers typically offer a suite of optimization options. This thesis reports the first study (to our knowledge) on how standard compiler optimizations influence symbolic execution. We study 33 optimization flags of the LLVM compiler infrastructure, which are used by the KLEE symbolic execution engine. Specifically, we study (1) how different optimizations influence the performance of KLEE for Unix Coreutils, (2) how the influence varies across two different program classes, and (3) how the influence varies across three different back-end constraint solvers. Some of our findings surprised us. For example, KLEE's setting for applying the 33 optimizations in a pre-defined order provides sub-optimal performance for a majority of the Coreutils when using the basic depth-first search; moreover, in our experimental setup, applying no optimization performs better for many of the Coreutils. / text

Symbolic execution is a powerful, systematic analysis that has received much visibility in the last decade. Scalability however remains a major challenge for symbolic execution. Compositional analysis is a well-known general purpose methodology for increasing scalability. This thesis introduces a new approach for compositional symbolic execution. Our key insight is that we can summarize each analyzed method as a memoization tree that captures the crucial elements of symbolic execution, and leverage these memoization trees to efficiently replay the symbolic execution of the corresponding methods with respect to their calling contexts. Memoization trees offer a natural way to compose in the presence of heap operations, which cannot be dealt with by previous work that uses logical formulas as summaries for composi- tional symbolic execution. Our approach also enables an efficient treatment of error traces by short-circuiting the execution of paths that lead to them. Our preliminary experimental evaluation based on a prototype implementation in Symbolic PathFinder shows promising results. / text

In dynamic domains, the state of the world may change in unexpected ways during the generation or execution of plans. Regardless of the cause of such changes, they raise the question of whether they interfere with ongoing planning efforts. Unexpected changes during plan generation may invalidate the current planning effort, while discrepancies between expected and actual state of the world during execution may render the executing plan invalid or sub-optimal, with respect to previously identified planning objectives. In this thesis we develop a general monitoring technique that can be used during both plan generation and plan execution to determine the relevance of unexpected changes and which supports recovery. This way, time intensive replanning from scratch in the new and unexpected state can often be avoided. The technique can be applied to a variety of objectives, including monitoring the optimality of plans, rather then just their validity. Intuitively, the technique operates in two steps: during planning the plan is annotated with additional information that is relevant to the achievement of the objective; then, when an unexpected change occurs, this information is used to determine the relevance of the discrepancy with respect to the objective. We substantiate the claim of broad applicability of this relevance-based technique by developing four concrete applications: generating optimal plans despite frequent, unexpected changes to the initial state of the world, monitoring plan optimality during execution, monitoring the execution of near-optimal policies in stochastic domains, and monitoring the generation and execution of plans with procedural hard constraints. In all cases, we use the formal notion of regression to identify what is relevant for achieving the objective. We prove the soundness of these concrete approaches and present empirical results demonstrating that in some contexts orders of magnitude speed-ups can be gained by our technique compared to replanning from scratch.

The issue of the death penalty is not just a matter of legal and political, but mainly social, ethical and moral. As other questions like abortion, euthanasia and gay adoption of children, this issue forces us to make up our own opinion and take an attitude. In addition, capital punishment is not only historical relic, but there are still lot of states that retained it in their legal system and also a lot of states that can perform it today. And it is not just a totalitarian or authoritarian states, as it might seem, but also a modern democratic society such as Japan or the United States of America. In the second chapter of his work, I focus on issue what is punishment and what kind of punishment and purpose exists. In the third chapter I try to outline the history and present of the death penalty, in the fourth chapter on methods of its execution. In the fifth chapter I introduce arguments of supporters and opponents of the death penalty, in next chapter I focus on public opinion. In the seventh chapter I work with international documents that deal with the death penalty. In the eighth chapter, I try to look at the death penalty from the perspective of Christian faith. The ninth chapter focuses on alternatives to the death penalty and the tenth deals with several well-known cases which have occurred in our...

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Execution time control is a technique that allows execution time budgets to be set and overruns to be handled dynamically to prevent deadline misses. This removes the need for the worst-case execution time (WCET) of tasks to be found by offline timing analysis – a problem that can be very hard to solve for modern computer architectures. Execution time control can also increase the processor utilization, as the WCET will often be much higher than the average execution time. This thesis describes how the GNU Ada Compiler and a bare-board Ravenscar run-time environment were ported to the Atmel AVR32 UC3 microcontroller series making the Ada programming language available on this architecture for the first time, and an implementation of Ada execution time control for this system that supports full execution time control for interrupt handling. Usage patterns for this brand new feature are demonstrated in Ada by extending the object-oriented real-time framework with execution time servers for interrupt handling, allowing the system to be protected against unexpected bursts of interrupts that could otherwise result in deadline misses. Separate execution time measurement for interrupt handling also improves the accuracy of measurement for tasks. As a direct result of the work presented in this thesis separate execution time measurement for interrupts will be included in the forthcoming ISO-standard for Ada 2012. While the implementation of execution time control is for the Ada programming language and the UC3 microcontroller series, the design and implementation should be portable to other architectures, and the principles of execution time control for interrupt handling applicable to other programming languages. Low run-time overhead is important for execution time control to be useful for real-time systems. Therefore a hardware Time Management Unit (TMU) was designed to reduce the overhead of execution time control. This design has been implemented for the UC3 and performance tests with the developed run-time environment shows that it gives a significant reduction of overhead. The memory-mapped design of the TMU also allows it to be implemented on other architectures.

Best execution obligations weigh on brokers when they execute orders to trade in shares for clients. These obligations have been seen as an outflow of general agency duties, and have been complemented by regulatory requirements related to best execution, dissemination of trading data, the handling of client orders and – in the United States – an obligation to execute at the best publicly available price or better (price protection). Here, different sets of real-world rules are analyzed with regard to transactional efficiency. Economic analyses are used to compare the effects of different rules, and are underpinned by a detailed analysis of relevant rules in the United States, the European Union, France, Sweden and England & Wales. Several normative conclusions can be drawn. Best execution rules that impose an agency duty on brokers do not seem to contribute in a discernible way to increased transactional efficiency. In contrast, disclosure rules that require both brokers and trading venues to provide ex post information about execution quality, and about how client orders have been routed, may contribute to mitigating the information asymmetry between brokers and clients. The compliance costs associated with such rules are outweighed by the positive effects on transactional efficiency. Lastly, a solution such as the US National Market System, which entails consolidated collection and dissemination of market data as well as price protection, can deliver significant efficiency gains through the virtual consolidation of trading venues. It also allows for more detailed regulations on different aspects of order execution, allow order execution regulations to function better, and is conducive to deeper integration of trading. However, creating such a system entails large initial investments. In the end, the choice whether to create a tightly-knit market system or not has wide-ranging implications for market structure, the design of regulatory rules and market integration.

A criminal is thrown from a high cliff into the sea. He has been covered in feathers, live birds attached to him to slow his fall. Fishermen wait below, hopeful of being able to carry him safely away. The people are punishing the criminal with death, yet simultaneously rooting for his survival. This startling image from Strabo, with its delicious ironic tension, is the center‐piece of “Civic Poetics.” The thesis consists of a cycle of poems imagining life in a city where this bizarre ritual is performed, coupled with a number of essays written for several Religious Studies courses on related themes. The interplay of poetry and essay aims to illuminate the experience of my own journey from criminal outsider to re‐integrated citizen. The lenses of (1) my own experiences in 21st century Atlanta and (2) poetic imaginative reconstruction of this ancient ritual reveal a startling picture: a criminal’s relations with the divine, as mediated by his state, and a state’s relations with the divine as mediated by its criminals.