Code Generation and Run-time Support For Multi-Level Parallelism . . .

In this paper we describe the main components of the NanosCompiler, an OpenMP compiler whose implementation is oriented towards the efficient exploitation of nested parallelism. Program parallelization relies both on the automatic parallelization capabilities of the base compiler and the information obtained from user--supplied directives. The compiler uses a hierarchical internal representation that unifies both sources of parallelism, proceeds with a task identification phase that adapts the granularity of the final tasks to the target architecture and then generates parallel code. The paper also presents an analysis of the special support needed from the threads library level to support this kind of parallelism. These requirements are analyzed in our current implementation named NthLib