Java programs perform many synchronization operations on data structures. Some of these synchronization are unnecessary; in particular, if an object is reachable only by a single thread, concurrent access is impossible and no synchronization is needed. We describe an interprocedural, flow- and context-insensitive dataflow analysis that finds such situations. A global optimizing transformation then eliminates synchronizations on these objects. For every program in our suite of ten Java benchmarks consisting of SPECjvm98 and others, our system optimizes over 90% of the alias sets containing at least one synchronized object. As a result, the dynamic frequency of synchronizations is reduced by up to 99%. For two benchmarks that perform synchronizations very frequently, this optimization leads to speedups of 36% and 20%.

KLYDE is a software workbench that helps students study issues related to the design, implementation, and empirical analysis of algorithms. Using the system's graphical user interface students can design and conduct experiments to study the efficiency of a variety of algorithms and their underlying implementations. The data generated by these experiments can be studied directly, or imported into speadsheet and presented graphically. This paper gives an overview of the KLYDE system and illustrates how the system can be used in a variety of undergraduate computer science courses.