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Atomicity violations are a major source of bugs in concurrent programs. Empirical studies have shown that the majority of atomicity violations are instances of the three-access pattern, where two accesses to a shared variable by a thread are interleaved by an access to the same variable by another thread. This article describes two advancements in atomicity violation detection. First, we describe a new technique that directs the execution of a dynamic analysis tool towards three-access pattern (TAP) instances. The directed search is based on constraint solving and concolic execution. We implemented this technique in a tool called AtomChase. Using 27 benchmarks comprising 5.4 million lines of... 

To enhance performance, common processors feature relaxed memory models that reorder instructions. However, the correctness of concurrent programs is often dependent on the preservation of the program order of certain instructions. Thus, the instruction set architectures offer memory fences. Using fences is a subtle task with performance and correctness implications: using too few can compromise correctness and using too many can hinder performance. Thus, fence insertion algorithms that given the required program orders can automatically find the optimum fencing can enhance the ease of programming, reliability, and performance of concurrent programs. In this paper, we consider the class of... 

One of the most important issues discussed in multi-agent systems, is communication between agents. Usually, a predefined communication protocol is used, but predefining a protocol between agents causes some problems; for example it is possible that agents recognize a subject that is not defined in their protocol so they can't express anything about it. In this paper we propose a new method for evolution of a communication protocol between intelligent agents by using natural selection mechanism. Experimental results will be discussed in detail. © 2006 IEEE