  In this work we explore the combination of metaheuristics and learned neural
network solvers for combinatorial optimization. We do this in the context of
the transit network design problem, a uniquely challenging combinatorial
optimization problem with real-world importance. We train a neural network
policy to perform single-shot planning of individual transit routes, and then
incorporate it as one of several sub-heuristics in a modified Bee Colony
Optimization (BCO) metaheuristic algorithm. Our experimental results
demonstrate that this hybrid algorithm outperforms the learned policy alone by
up to 20% and the original BCO algorithm by up to 53% on realistic problem
instances. We perform a set of ablations to study the impact of each component
of the modified algorithm.

Neural and Evolutionary Computing;Machine Learning