Free BDD based CAD of Compact Memristor Crossbars for in-Memory Computing

The demise of Moore's law, breakdown of Dennard Scaling, dark silicon phenomenon, process variation, leakage currents and quantum tunneling are some of the hurdles faced in the further advancement of computing systems today. As a result, there is a renewed interest in alternate computing paradigms using emerging nanoelectronic devices. This work uses free binary decision diagrams (FBDDs) for computer-aided design (CAD) of compact memristive crossbars for sneak-path based in-memory computing. The absence of a fixed variable ordering makes FBDDs more compact than their ordered counterpart called reduced ordered binary decision diagrams (ROBDDs). Our design has used the size of the circuit-representation of Boolean functions for selecting different variable orderings along different paths which results in compact FBDDs. We have demonstrated our approach by designing compact crossbars for a four-bit multiplier and other RevLib benchmarks. Our synthesis process yields a 50.1% reduction in area over the previous FBDD-based synthesis for the fourth-output-bit of the multiplier. Overall, our approach has reduced the multiplier area by 20.1%.