A Study of Concurrency Bugs and Advanced Development Support for Actor-based Programs

The actor model is an attractive foundation for developing concurrent applications because actors are isolated concurrent entities that communicate through asynchronous messages and do not share state. Thereby, they avoid concurrency bugs such as data races, but are not immune to concurrency bugs in general. This study taxonomizes concurrency bugs in actor-based programs reported in literature. Furthermore, it analyzes the bugs to identify the patterns causing them as well as their observable behavior. Based on this taxonomy, we further analyze the literature and find that current approaches to static analysis and testing focus on communication deadlocks and message protocol violations. However, they do not provide solutions to identify livelocks and behavioral deadlocks. The insights obtained in this study can be used to improve debugging support for actor-based programs with new debugging techniques to identify the root cause of complex concurrency bugs.Comment: - Submitted for review - Removed section 6 "Research Roadmap for Debuggers", its content was summarized in the Future Work section - Added references for section 1, section 3, section 4.3 and section 5.1 - Updated citation

Inappropriate stereotypical inferences? An adversarial collaboration in experimental ordinary language philosophy

This paper trials new experimental methods for the analysis of natural language reasoning and the (re)development of critical ordinary language philosophy in the wake of J.L. Austin. Philosophical arguments and thought experiments are strongly shaped by default pragmatic inferences, including stereotypical inferences. Austin suggested that contextually inappropriate stereotypical inferences are at the root of some philosophical paradoxes and problems, and that these can be resolved by exposing those verbal fallacies. This paper builds on recent efforts to empirically document inappropriate stereotypical inferences that may drive philosophical arguments. We demonstrate that previously employed questionnaire-based output measures do not suffice to exclude relevant confounds. We then report an experiment that combines reading time measurements with plausibility ratings. The study seeks to provide evidence of inappropriate stereotypical inferences from appearance verbs that have been suggested to lie at the root of the influential ‘argument from illusion’. Our findings support a diagnostic reconstruction of this argument. They provide the missing component for proof of concept for an experimental implementation of critical ordinary language philosophy that is in line with the ambitions of current ‘evidential’ experimental philosophy

Static safety analysis for non-uniform service availability in Actors

This paper presents a safe static analysis which detects all safety orphan messages in actor-based programs. This result extends previous work derived from sequential object-oriented languages type systems to non-uniform behaviors. Most of the type systems designed for concurrent objects rely on the uniform behavior assumption : an object is a) always able to handle requests to the same set of methods, and b) always accessible (each method can be handled any number of times). This hypothesis allows the use of type systems designed for sequential object-oriented languages (either kind-based ones as proposed by Vasconcelos and Tokoro [VT93] and by Kobayashi and Yonezawa [KY94], or subtype-based ones as advocated by the authors in [CPS97b]). In the case of objects with non-uniform behavior (i.e. short lifetime objects or behavior changing actors), an object may be able to handle a request to one of its method at a given time and not be able to handle it at some other time. If the request cannot be handled, the associated message is called a "safety orphan". The previous type systems could only detect rather trivial safety orphan messages. The system described in this paper extends our subtype-based previous work in order to catch all potential safety orphans in actor-based programs. 1 In this purpose, a new safe type-based abstraction of an actor possible behaviors is proposed. We extend a Primitive Actor Calculus introduced in the first section and defined in a previous paper ([CPS96, CPS97b]) in order to give a simple semantic characterisation of safety orphan messages. A sound type system based on the type abstraction is then presented. It rejects all the programs which may produce safety orphan messages. In conclusion, related works and possible extensions are discus..