Lock-free Parallel Access Collections

All new computers have multicore processors. To exploit this hardware parallelism for improved performance, the predominant approach today is multithreading using shared variables and locks. This approach has potential data races that can create a nondeterministic program. This paper presents a promising new approach to parallel programming that is both lock-free and deterministic. The standard forall primitive for parallel execution of for-loop iterations is extended into a more highly structured primitive called a Parallel Operation (POP). Each parallel process created by a POP may read shared variables (or shared collections) freely. Shared collections modified by a POP must be selected from a special set of predefined Parallel Access Collections (PAC). Each PAC has several Write Modes that govern parallel updates in a deterministic way. This paper presents an overview of a Prototype Library that implements this POP-PAC approach for the C++ language, including performance results for two benchmark parallel programs.