Optimizing massively parallel sparse matrix computing on ARM many-core processor

Abstract

Sparse matrix multiplication is ubiquitous in many applications such as graph processing and numerical simulation. In recent years, numerous efficient sparse matrix multiplication algorithms and computational libraries have been proposed. However, most of them are oriented to x86 or GPU platforms, while the optimization on ARM many-core platforms has not been well investigated. Our experiments show that existing sparse matrix multiplication libraries for ARM many-core CPU cannot achieve expected parallel performance. Compared with traditional multi-core CPU, ARM many-core CPU has far more cores and often adopts NUMA techniques to scale the memory bandwidth. Its parallel efficiency tends to be restricted by NUMA configuration, memory bandwidth cache contention, etc.

In this paper, we propose optimized implementations for sparse matrix computing on ARM many-core CPU. We propose various optimization techniques for several routines of sparse matrix multiplication to ensure coalesced access of matrix elements in the memory. In detail, the optimization techniques include a fine-tuned CSR-based format for ARM architecture, co-optimization of Gustavson’s algorithm with hierarchical cache and dense array strategy to mitigate performance loss caused by handling compressed storage formats. We exploit the coarse-grained NUMA-aware strategy for inter-node parallelism and the fine-grained cache-aware strategy for intra-node parallelism to improve the parallel efficiency of sparse matrix multiplication. The evaluation shows that our implementation consistently outperforms the existing library on ARM many-core processor.