TASCEL: Task Scheduling Library. TASCEL (pronounced ”tassel”) is a framework to study the design of algorithms to address the challenges associated with programming abstractions supporting finer-grained concurrency. It uses an active message framework built on MPI. MPI allows quick prototyping and evaluation on various platforms with minimal porting effort. The active message framework enables the design of supporting algorithms that are concurrent with ongoing execution (e.g., load balancing or fault recovery concurrent with application execution). TASCEL supports various threading modes, progress semantics, together with SPMD and non-SPMD execution, so as to be representative of a variety of useful execution environments.