ApproxLUT: A novel approximate lookup table-based accelerator

Computing with memory, which stores function responses of some input patterns into lookup tables offline and retrieves their values when encountering similar patterns (instead of performing online calculation), is a promising energy-efficient computing technique. No doubt to say, with a given lookup table size, the efficiency of this technique depends on which function responses are stored and how they are organized. In this paper, we propose a novel adaptive approximate lookup table based accelerator, wherein we store function responses in a hierarchical manner with increasing fine-grained granularity and accuracy. In addition, the proposed accelerator provides lightweight compensation on output results at different precision levels according to input patterns and output quality requirements. Moreover, our accelerator conducts adaptive lookup table search by exploiting input locality. Experimental results on various computation kernels show significant energy savings of the proposed accelerator over prior solutions.