High-Speed Serial and Semi-Parallel IMPLY-based Approximate Adders through Memristors for In-Memory Computing

This paper introduces three memristive approximate adder designs using Material Implication (IMPLY) logic. Two designs follow a serial approach, while the third adopts a semi-parallel technique. The proposed design achieves the approximate output in just 2 steps, utilizing only 3 memristors, in contrast to the 8 steps and 5 memristors required by the best competing IMPLY-based approximate adder. Furthermore, when integrated into an 8-bit Ripple Carry Adder (RCA), the proposed designs enhance latency by 4% to 28% compared to the existing IMPLY-based approximate design. Compared to exact serial and semi-parallel adders in literature, latency is improved by 27% to 56.8%. Similarly, an improvement in the range of 4% to 42% is achieved for energy consumption. The performance of the proposed approximate adder designs is then evaluated in image processing applications, specifically Image Masking and RGB to Grayscale conversion. The results demonstrate better Peak Signal-to-Noise Ratio (PSNR) and Structural Similarity Index Measure (SSIM) values compared to the existing approximate IMPLY design.