LAcc: Exploiting Lookup Table-based Fast and Accurate Vector Multiplication in DRAM-based CNN Accelerator.

PIM (Processing-in-memory)-based CNN (Convolutional neural network) accelerators leverage the characteristics of basic memory cells to enable simple logic and arithmetic operations so that the bandwidth constraint can be effectively alleviated. However, it remains a major challenge to support multiplication operations efficiently on PIM accelerators, in particular, DRAM-based PIM accelerators. This has prevented PIM-based accelerators from being immediately adopted for accurate CNN inference. In this paper, we propose LAcc, a DRAM-based PIM accelerator to support LUT- (lookup table) based fast and accurate multiplication. By enabling LUT based vector multiplication in DRAM, LAcc effectively decreases LUT size and improve its reuse. LAcc further adopts a hybrid mapping of weights and inputs to improve the hardware utilization rate. LAcc achieves 95 FPS at 5.3 W for Alexnet and 6.3 × efficiency improvement over the state-of-the-art.