OBSD: On-The-Fly Block-Wise Sparse Distillation Accelerating SpGEMMs in DNN Applications

The mainstream deep neural networks (DNNs) widely adopt pruning techniques to alleviate network overfitting and computational complexity. Simultaneously, the weight and activation data exhibit increasingly noticeable block-wise sparsity. Current DNN-specific accelerators mainly focus on element-wise while neglecting sparse features of block granularity. Meanwhile, one of the state-of-the-art work, HIRAC, combining matrix tiling with the fast packing algorithm, SorPack, to achieve effective acceleration of Sparse General Matrix Multiplications (SpGEMMs). However, the SorPack algorithm executes on the host CPU, and its runtime lies on the critical path of the overall execution. In this work, a specific SpGEMM accelerator named OBSD is proposed which achieves high performance and energy efficiency. An on-the-fly block-wise distillation approach is proposed for leveraging the block-wise sparsity in both weight and activation data, which is implemented during the data loading process, consuming minimal additional time. Moreover, a data-flow architecture is devised to improve efficiency of data exchange among data processing elements (DPs) with investigating the relationship for different partition sizes, block-wise sparsity, and block-wise distance. The evaluation results demonstrate that: (1) OBSD achieves average of 1.89× speedup as compared to HIRAC for representative matrices in DNN workloads. (2) An end-to-end evaluation on a DNN model shows a 2.41× speedup and energy efficiency improvement of 1.99× over the HIRAC. (3) OBSD possesses a power consumption 12.9W with 56.6mm² area @28nm TSMC.