Property directed reachability with word-level abstraction

Abstract

SAT-based Property Directed Reachability (PDR) has become the key algorithmic development for unbounded model checking of gate-level sequential circuits, but it can be inefficient when applied to word-level problems with heavy arithmetic logic. To address this issue, word-level abstraction is often performed by replacing a whole set of signals with unconstrained new primary inputs. This paper introduces PDR-WLA, a wordlevel abstraction-refinement algorithm integrated into a modified PDR implementation. The algorithm uses efficient refinement and re-uses reachability information across iterations of refinement. PDR-WLA was implemented in ABC and evaluated on a large set of industrial Verilog designs. Experimental results show significant speedups on hard problems compared to the original PDR and to a naive word-level abstraction-refinement method.