| Summary: | As one of the most promising energy-efficient emerging paradigms for designing digital systems, approximate computing has attracted a significant attention in recent years. Applications utilizing approximate computing (AxC) can tolerate some loss of quality in the computed results for attaining high performance. Approximate arithmetic circuits have been extensively studied; however, their application at system level has not been extensively pursued. Furthermore, when approximate arithmetic circuits are applied at system level, error-accumulation effects and a convergence problem may occur in computation. Multiple approximate components can interact in a typical datapath, hence benefiting from each other. Many applications require more complex datapaths than a single multiplication. In this paper, a hardware/software co-design methodology for adaptive approximate computing is proposed. It makes use of feature constraints to guide the approximate computation at various accuracy levels in each iteration of the learning process in Artificial Neural Networks (ANNs). The proposed adaptive methodology also considers the input operand distribution and the hybrid approximation. Compared with a baseline design, the proposed method significantly reduces the power-delay product while incurring in only a small loss of accuracy. Simulation and a case study of image segmentation validate the effectiveness of the proposed methodology.
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