Neural Coarsening Process for Multi-level Graph Combinatorial Optimization

Combinatorial optimization (CO) is applicable to various industrial fields, but solving CO problems is usually NP-hard. Thus, previous studies have focused on designing heuristics to solve CO within a reasonable time. Recent advances in deep learning show the potential to automate the designing process of CO solvers by leveraging the powerful representation capability of deep neural networks. Practically, solving CO is often cast as a multi-level process; the lower-level CO problems are solved repeatedly so as to solve the upper-level CO problem. In this case, the number of iterations within the lower-level process can dramatically impact the overall process. This paper proposes a new graph learning method, Neural Coarsening Process (NCP), to reduce the number of graph neural network inferences for lower-level CO problems. Experimental results show that NCP effectively reduces the number of inferences as compared to fully sequential decision-making. Furthermore, NCP outperforms competitive heuristics on CVRP-CapacityCut, a subproblem of the cutting plane method for the capacitated vehicle routing problem (CVRP).