swSpTRSV: A Fast Sparse Triangular Solve with Sparse Level Tile Layout on Sunway Architectures

Sparse triangular solve (SpTRSV) is one of the most important kernels in many real-world applications. Currently, much research on parallel SpTRSV focuses on level-set construction for reducing the number of inter-level synchronizations. However, the out-of-control data reuse and high cost for global memory or shared cache access in inter-level synchronization have been largely neglected in existing work. In this paper, we propose a novel data layout called Sparse Level Tile to make all data reuse under control, and design a Producer-Consumer pairing method to make any inter-level synchronization only happen in very fast register communication. We implement our data layout and algorithms on an SW26010 many-core processor, which is the main building-block of the current world fastest supercomputer Sunway Taihulight. The experimental results of testing all 2057 square matrices from the Florida Matrix Collection show that our method achieves an average speedup of 6.9 and the best speedup of 38.5 over parallel level-set method. Our method also outperforms the latest methods on a KNC many-core processor in 1856 matrices and the latest methods on a K80 GPU in 1672 matrices, respectively