— Approximate computing has recently emerged as a promising approach to energy-efficient design of digital systems. Approximate computing relies on the ability of many systems and applications to tolerate some loss of quality or optimality in the computed result. By relaxing the need for fully precise or completely deterministic operations, approximate computing techniques allow substantially improved energy efficiency. This paper reviews recent progress in the area, including design of approximate arithmetic blocks, pertinent error and quality measures, and algorithm-level techniques for approximate computing. Keywords—approximate computing, probabilistic computing, stochastic computation, adder, multiplier, low-energy design I. IMPRECISION TOLERANCE AND ENERGY REDUCTION Energy-efficiency has become the paramount concern in design of computing systems. At the same time, as the computing systems become increasingly embedded and mobile, computational tasks include a growing set of a...