Noncooperatively Optimized Tolerance: Decentralized Strategic Optimization in Complex Systems

We introduce noncooperatively optimized tolerance (NOT), a generalization of highly optimized tolerance (HOT) that involves strategic (game theoretic) interactions between parties in a complex system. We illustrate our model in the forest fire (percolation) framework. As the number of players increases, our model retains features of HOT, such as robustness, high yield combined with high density, and self-dissimilar landscapes, but also develops features of self-organized criticality (SOC) when the number of players is large enough. For example, the forest landscape becomes increasingly homogeneous and protection from adverse events (lightning strikes) becomes less closely correlated with the spatial distribution of these events. While HOT is a special case of our model, the resemblance to SOC is only partial; for example, the distribution of cascades, while becoming increasingly heavy-tailed as the number of players increases, also deviates more significantly from a power law in this regime. Surprisingly, the system retains considerable robustness even as it becomes fractured, due in part to emergent cooperation between neighboring players. At the same time, increasing homogeneity promotes resilience against changes in the lightning distribution, giving rise to intermediate regimes where the system is robust to a particular distribution of adverse events, yet not very fragile to changes

Theorem-Proving Analysis of Digital Control Logic Interacting with Continuous Dynamics

AbstractThis work outlines an equation-based formulation of a digital control program and transducer interacting with a continuous physical process, and an approach using the Coq theorem prover for verifying the performance of the combined hybrid system. Considering thermal dynamics with linear dissipation for simplicity, we focus on a generalizable, physically consistent description of the interaction of the real-valued temperature and the digital program acting as a thermostat. Of interest in this work is the discovery and formal proof of bounds on the temperature, the degree of variation, and other performance characteristics. Our approach explicitly addresses the need to mathematically represent the decision problem inherent in an analog-to-digital converter, which for rare values can take an arbitrarily long time to produce a digital answer (the so-called Buridan's Principle); this constraint ineluctably manifests itself in the verification of thermostat performance. Furthermore, the temporal causality constraints in the thermal physics must be made explicit to obtain a consistent model for analysis. We discuss the significance of these findings toward the verification of digital control for more complex physical variables and fields

An empirical study of fault localization for end-user programmers

End users develop more software than any other group of programmers, using software authoring devices such as e-mail filtering editors, by-demonstration macro builders, and spreadsheet environments. Despite this, there has been little research on finding ways to help these programmers with the dependability of their software. We have been addressing this problem in several ways, one of which includes supporting end-user debugging activities through fault localization techniques. This paper presents the results of an empirical study conducted in an end-user programming environment to examine the impact of two separate factors in fault localization techniques that affect technique effectiveness. Our results shed new insights into fault localization techniques for end-user programmers and the factors that affect them, with significant implications for the evaluation of those techniques

Interactive, visual fault localization support for end-user programmers

End-user programmers are writing an unprecedented number of programs, primarily using languages and environments that incorporate a number of interactive and visual programming techniques. To help these users debug these programs, we have developed an entirely visual, interactive approach to fault localization. This paper presents the approach. We also present the results of a think-aloud study that examined the interactive, human-centric issues that arise in end-user debugging using a fault localization strategy. Our results provide insights into the contributions such strategies can make to the end-user debugging process.Keywords: visual fault localization, debugging, end-user software engineering, slicing, form-based visual programs, testing, end-user programmin

Experimental program analysis: A new paradigm for program analysis

Program analysis techniques are used by software engineers to deduce and infer targeted characteristics of software systems for tasks such as testing, debugging, maintenance, and program comprehension. Recently, some program analysis techniques have been designed to leverage characteristics of traditional experimentation in order to analyze software systems. We believe that the use of experimentation for program analysis constitutes a new program analysis paradigm: experimental program analysis. This research seeks to accomplish four goals: to precisely define experimental program analysis, to provide a means for classifying experimental program analysis techniques, to identify existing experimental program analysis techniques in the research literature, and to enhance the use of experimental program analysis by improving existing, and by creating new, experimental program analysis techniques

Interactive Fault Localization Techniques in a Spreadsheet Environment

End-user programmers develop more software than any other group of programmers, using software authoring devices such as multimedia simulation builders, e-mail filtering editors, by-demonstration macro builders, and spreadsheet environments. Despite this, there has been only a little research on finding ways to help these programmers with the dependability of the software they create. We have been working to address this problem in several ways, one of which includes supporting end-user debugging activities through interactive fault localization techniques. This paper investigates fault localization techniques in the spreadsheet domain, the most common type of end-user programming environment. We investigate a technique previously described in the research literature and two new techniques. We present the results of an empirical study to examine the impact of two individual factors on the effectiveness of fault localization techniques. Our results reveal several insights into the contributions such techniques can make to the end-user debugging process and highlight key issues of interest to researchers and practitioners who may design and evaluate future fault localization techniques

Experimental Program Analysis: A New Program Analysis Paradigm

Program analysis techniques analyze software systems to collect, deduce, or infer information about them, which can then be used in software-engineering related tasks. Recent research has suggested that a new form of program analysis technique might be created by incorporating characteristics of experimentation into analyses. This paper reports the results of research exploring this suggestion. Building on background in classical experimentation, we provide descriptive and operational definitions of experimental program analysis, illustrate them by examples, and describe several differences between experimental program analysis and classical experimentation. We present three studies that show how the use of the paradigm can help researchers identify limitations of analysis techniques, improve existing experimental program analysis techniques, and create new experimental program analysis techniques by adapting existing non-experimental techniques