Graph Neural Networks for Reasoning 2-Quantified Boolean Formulas

Fei Wang, Zhanfu Yang, Ziliang Chen, Guannan Wei, Tiark Rompf

Keywords: Graph Neural Networks, 2-Quantified Boolean Formula, Symbolic Reasoning

TL;DR: Learn GNN-based 2QBF solvers and GNN-based 2QBF heuristics

Abstract:

It is valuable yet remains challenging to apply neural networks in logical reasoning tasks. Despite some successes witnessed in learning SAT (Boolean Satisfiability) solvers for propositional logic via Graph Neural Networks (GNN), there haven't been any successes in learning solvers for more complex predicate logic. In this paper, we target the QBF (Quantified Boolean Formula) satisfiability problem, the complexity of which is in-between propositional logic and predicate logic, and investigate the feasibility of learning GNN-based solvers and GNN-based heuristics for the cases with a universal-existential quantifier alternation (so-called 2QBF problems).

We conjecture, with empirical support, that GNNs have certain limitations in learning 2QBF solvers, primarily due to the inability to reason about a set of assignments. Then we show the potential of GNN-based heuristics in CEGAR-based solvers and explore the interesting challenges to generalize them to larger problem instances. In summary, this paper provides a comprehensive surveying view of applying GNN-based embeddings to 2QBF problems and aims to offer insights in applying machine learning tools to more complicated symbolic reasoning problems.