Accelerating Graph Similarity Search through Integer Linear Programming

The Graph Edit Distance ({GED}) is an important metric for measuring the similarity between two (labeled) graphs. It is defined as the minimum cost required to convert one graph into another through a series of (elementary) edit operations. Its effectiveness in assessing the similarity of large graphs is limited by the complexity of its exact calculation, which is {NP}-hard theoretically and computationally challenging in practice. The latter can be mitigated by switching to the Graph Similarity Search under {GED} constraints, which determines whether the edit distance between two graphs is below a given threshold. A popular framework for solving Graph Similarity Search under {GED} constraints in a graph database for a query graph is the filter-and-verification framework. Filtering discards unpromising graphs, while the verification step certifies the similarity between the filtered graphs and the query graph. To improve the filtering step, we define a lower bound based on an integer linear programming formulation. We prove that this lower bound dominates the effective branch match-based lower bound and can also be computed efficiently. Consequently, we propose a graph similarity search algorithm that uses a hierarchy of lower bound algorithms and solves a novel integer programming formulation that exploits the threshold parameter. An extensive computational experience on a well-assessed test bed shows that our approach significantly outperforms the state-of-the-art algorithm on most of the examined thresholds.