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Publications of SPCL
|Remote Memory Access Programming: Faster Parallel Computing Without Messages|
(Presentation - presented in San Diego, CA, USA, Jun. 2015, )
AbstractRemote memory access (RMA) or partitioned global address space programming offers abstractions to coordinate directly accessible distributed memory domains. The presentation will start with an analysis of established technologies (cache-coherence), continue to describe RMA programming abstractions and example codes, and conclude with proposals for the future of RMA. In the first part, we will use an intuitive performance model to briefly demonstrate the complexities of cache-coherent systems with regards to performance tuning. We will exemplify these findings with results on Intel's Xeon Phi and Sandy Bridge CPUs where we speed up communication algorithms by up to 4.3x. We continue by showing how RMA programming simplifies the design and tuning and introduce MPI-3's RMA semantics as a particuler example. We discuss our reference implementation for Cray machines foMPI and demonstrate results with up to half a million processes. We conclude the talk by addressing producer-consumer synchronizations in task-based runtime environments and the new proposal of notified access. Overall, we advocate RMA as a potential programming model for scalable systems ranging from single-die multicores to large-scale supercomputers.