Profile-Based Output Error Compensation for Approximate Arithmetic Circuits
Ke Chen, Weiqiang Liu, Jie Han, Fabrizio Lombardi
Abstract
Truncation is one of the most commonly used approaches for circuit-level approximate computing. This paper proposes a scheme for error compensation of arithmetic circuits in which a so-called padding is utilized to compensate at the output for the truncated bits of the input operands. Compensation relies on adjusting the output results of an arithmetic circuit; the padding takes a value determined by utilizing statistical information based on profiling an arithmetic circuit to reduce the average signed difference between the inexact and exact values and so the mean square error. An extensive analysis and simulation-based evaluation of error metrics are performed on signed truncated adders, multipliers and dividers; an excellent agreement is found. Additional design metrics such as power consumption and circuit complexity are also assessed. Different applications of approximate arithmetic circuits with the proposed output error compensation scheme are presented. Matrix multiplication and image processing (changing detection) are investigated to show the effectiveness of the scheme proposed in this paper.