Simplifier: A New Tool for Boolean Circuit Simplification

The Boolean circuit simplification problem involves finding a smaller circuit that computes the same function as a given Boolean circuit. This problem is closely related to several key areas with both theoretical and practical applications, such as logic synthesis, satisfiability, and verification. In this paper, we present Simplifier, a new open source tool for simplifying Boolean circuits. The tool optimizes subcircuits with three inputs and at most three outputs, seeking to improve each one. It is designed as a low-effort method that runs in just a few seconds for circuits of reasonable size. This efficiency is achieved by combining two key strategies. First, the tool utilizes a precomputed database of optimized circuits, generated with SAT solvers after carefully clustering Boolean functions with three inputs and up to three outputs. Second, we demonstrate that it is sufficient to check a linear number of subcircuits, relative to the size of the original circuit. This allows a single iteration of the tool to be executed in linear time. We evaluated the tool on a wide range of Boolean circuits, including both industrial and hand-crafted examples, in two popular formats: AIG and BENCH. For AIG circuits, after applying the state-of-the-art ABC framework, our tool achieved an additional 4% average reduction in size. For BENCH circuits, the tool reduced their size by an average of 30%.