RUCA: RUntime Configurable Approximate Circuits with Self-Correcting Capability

Approximate computing is an emerging computing paradigm that offers improved power consumption by relaxing the requirement for full accuracy. Since the requirements for accuracy may vary according to specific real-world applications, one trend of approximate computing is to design quality-configurable circuits, which are able to switch at runtime among different accuracy modes with different power and delay. In this paper, we present a novel framework RUCA which aims to synthesize runtime configurable approximate circuits based on arbitrary input circuits. By decomposing the truth table, our approach aims to approximate and separate the input circuit into multiple configuration blocks which support different accuracy levels, including a corrector circuit to restore full accuracy. Power gating is used to activate different blocks, such that the approximate circuit is able to operate at different accuracy-power configurations. To improve the scalability of our algorithm, we also provide a design space exploration scheme with circuit partitioning. We evaluate our methodology on a comprehensive set of benchmarks. For 3-level designs, RUCA saves power consumption by 43.71% within 2% error and by 30.15% within 1% error on average.