Concurrent data structures have found increasingly widespread use in both multicore and distributed computing environments, thereby escalating the priority for verifying their correctness. The thread safe behavior of these concurrent objects is often described using formal semantics known as linearizability, which requires that  every operation in a concurrent object appears to take effect between its invocation and response. Quasi linearizability is a quantitative relaxation of linearizability to allow more implementation freedom for performance optimization.  However, ensuring the quantitative aspects of this new correctness condition is an arduous task. We propose the first method for formally verifying quasi linearizability of the implementation model of a concurrent data structure. The method is based on checking the refinement relation between the implementation model and a specification model via explicit state model checking. It can directly handle multi-threaded programs where each thread can make infinitely many method calls, without requiring the user to manually annotate for the linearization points. We have implemented and evaluated our method in the PAT model checking toolkit.  Our experiments show that the method is effective in verifying quasi linearizability and in detecting its violations. / Master of Science

Our reliance on software has been growing fast over the past decades as the pervasive use of computer and software penetrated not only our daily life but also many critical applications. As the computational power of multi-core processors and other parallel hardware keeps increasing, concurrent software that exploit these parallel computing hardware become crucial for achieving high performance. However, developing correct and efficient concurrent software is a difficult task for programmers due to the inherent nondeterminism in their executions. As a result, concurrency related software bugs are among the most troublesome in practice and have caused severe problems in recent years. In this dissertation, I propose a series of new and fully automated methods for verifying and debugging concurrent software. They cover the detection, prevention, classification, and repair of some important types of bugs in the implementation of concurrent data structures and client-side web applications. These methods can be adopted at various stages of the software development life cycle, to help programmers write concurrent software correctly as well as efficiently. / Ph. D.