BOLT

"BOLT targets a high-performing OpenMP implementation, especially specialized for fine-grain parallelism. Unlike other OpenMP implementations, BOLT utilizes a lightweight threading model for its underlying threading mechanism. It currently adopts Argobots, a new holistic, low-level threading and tasking runtime, in order to overcome shortcomings of conventional OS-level threads. Its runtime and compiler are based on the OpenMP runtime and Clang in LLVM, respectively."

http://www.mcs.anl.gov/bolt/

https://github.com/pmodels/bolt-runtime

https://github.com/pmodels/argobots

https://wiki.mpich.org/mpich/index.php/MPI%2BArgobots