Complementing user-level coarsegrain parallelism with implicit speculative parallelism

Multi-core and many-core systems are the norm in contem-porary processor technology and are expected to remain so for the foreseeable future. Programs using parallel program-ming primitives like PThreads or OpenMP often exploit coarse-grain parallelism, because it offers a good trade-off between programming effort versus performance gain. Some parallel applications show limited or no scaling beyond a number of cores. Given the abundant number of cores ex-pected in future many-cores, several cores would remain idle in such cases while execution performance stagnates. This paper proposes using cores that do not contribute to per-formance improvement for running implicit fine-grain spec-ulative threads. In particular, we present a many-core ar-chitecture and protocol that allow applications with coarse