A Spin Wave-Based Approximate 4:2 Compressor: Seeking the most energy-efficient digital computing paradigm

In this article, we propose an energy-efficient spin wave (SW)-based approximate 4:2 compressor including three- and five-input majority gates. We validate our proposal by means of micromagnetic simulations and assess and compare its performance with state-of-the-art SW 45-nm CMOS and spin-CMOS counterparts. The evaluation results indicate that the proposed compressor consumes 31.5% less energy than its accurate SW-design version. Furthermore, it has the same energy consumption and error rate as a directional coupler (DC)-based approximate compressor, but it exhibits a 3× shorter delay. In addition, it consumes 14% less energy while having a 17% lower average error rate than its approximate 45-nm CMOS counterpart. When compared with other emerging technologies, the proposed compressor outperforms the approximate spin-CMOS-based compressor by three orders of magnitude in terms of energy consumption while providing the same error rate. Finally, the proposed compressor requires the smallest chip real estate measured in terms of devices.