CSR --- PDOS: Monitoring and Controlling Multithreaded Distributed Software

计算机故障或消息的意外顺序会导致分布式程序中出现微妙的错误。这个项目正在研究监视和控制多线程分布式计算的算法和实现问题。这个项目中的技术对于测试分布式Java程序和执行过程中的容错非常有用。该项目正在研究四个领域的技术：切片、依赖跟踪、全局谓词检测和控制计算。计算切片在减少需要分析的计算量方面很有用。该项目正在开发用于切片的在线和分布式算法。依赖项跟踪是在线监视全局谓词所必需的，目前使用的矢量时钟的维度等于系统中进程和线程的数量。该项目正在研究一种称为链时钟的技术，即使对于大型系统，也可以以可扩展的方式跟踪依赖关系。在测试或运行时期间，需要全局谓词检测来检测错误。该项目正在研究在计算的全局状态格上解释的时间逻辑谓词的检测。在测试阶段控制计算是很有用的，它可以使计算指向软件错误，在操作阶段控制计算远离任何现有的软件错误。该项目正在用Java实现一个框架，它将在并发程序的监控和测试方面取得理论和实践上的进步。该项目有望显著提高分布式软件的质量和容错性。

Failures of computers or an unexpected order of messages leads to subtle bugs in distributed programs. This project is investigating algorithmic and implementation issues in monitoring and controlling multithreaded distributed computations. The techniques in this project are useful for testing distributed Java programs and for fault-tolerance during their execution. The project is investigating techniques in four areas: slicing, dependency tracking, global predicate detection and controlling a computation. Computation slicing is useful in reducing the size of the computation that needs to be analyzed. The project is developing online and distributed algorithms for slicing. Dependency tracking is required for online monitoring of global predicates and is currently done using vector clocks of dimension equal to the number of processes and threads in the system. The project is investigating a technique calledchain clocks that can track dependency in a scalable way even for a large-scale system. Global predicate detection is required to detect bugs during testing or runtime. The project is investigating detection of temporal logic predicates interpreted over the lattice of global states of a computation. Controlling a computation is useful during the testing phase to steer the computation toward software bugs and during the operation phase to steer it away from any existing software bugs.The project is implementing a framework in Java and it will result in theoretical and practical advances in monitoring and testing of concurrent programs. The project is expected to significantly improve the quality and fault-tolerance of distributed software.