An Automated Approximation Methodology for Arithmetic Circuits

Arithmetic circuits like adders and multipliers are key workforces of many error resilient applications. Prior efforts on approximating these arithmetic circuits mainly focused on manual circuit level functional modifications. These manual approaches need high design time and effort. Due to this only a limited no. of approximate design points can be generated from the original circuit leading to a sparsely occupied pareto front. This work proposes an automated approximation methodology for arithmetic circuits. Proposed method approximates the gate level standard cell library and uses these approximate standard cells to modify the netlist of the original circuit. A heuristic design space exploration methodology is proposed to speed-up the design process. We integrate this methodology with traditional ASIC flow and validate our results using adders and multipliers of different bitwidths. We show that our methodology improves on existing state-of-the-art manual as well as automated design techniques by generating non-dominant pareto-fronts. An application case study (sobel edge detection) is shown using approximate arithmetic circuits generated by our methodology. In case of sobel edge detector, we show upto 50% energy improvements for hardly any quality degradation (PSNR ≥ 20dB).