An OpenMP* Barrier Using SIMD Instructions for Intel® Xeon PhiTM Coprocessor.

Barrier synchronisation is a widely-studied topic since the supercomputer era due to its significant impact on the overall performance of parallel applications. With the current shift to many-core architectures, such as the Intel® Many Integrated Core Architecture, software barriers need to be revisited from an on-chip point of view to exploit their new specific resources. In this paper, we propose a tree-based barrier that takes advantage of SIMD instructions and the inter-thread cache locality provided by the 4-way SMT of the Intel® Xeon PhiTM coprocessor. Our SIMD approach shows a speed-up of up to 2.84x over the default Intel OpenMP* barrier in the EPCC barrier microbenchmark. It also improves by up to 60% and 21% the Livermore Loop kernel number six and the NAS MG benchmark, respectively.