UPC Performance and Potential: A NPB Experimental Study

UPC, or Unified Parallel C, is a parallel extension of ANSI C. UPC follows a distributed shared memory programming model aimed at leveraging the ease of programming of the shared memory paradigm, while enabling the exploitation of data locality. UPC incorporates constructs that allow placing data near the threads that manipulate them to minimize remote accesses. This paper gives an overview of the concepts and features of UPC and establishes, through extensive performance measurements of NPB workloads, the viability of the UPC programming language compared to the other popular paradigms. Further, through performance measurements we identify the challenges, the remaining steps and the priorities for UPC. It will be shown that with proper hand tuning and optimized collective operations libraries, UPC performance will be comparable to that of MPI. Furthermore, by incorporating such improvements into automatic compiler optimizations, UPC will compare quite favorably to message passing in ease of programming.