Just Initialize speeds up large routing solutions by 70 times
Just Initialize: A Training-Free Initialization Component for Large-Scale Routing Optimization
Artificial Intelligence
Summary
Solving large routing problems like planning delivery routes or visiting many locations is very hard and slow because there are so many possibilities. The authors came up with a new way to start solving these problems that doesn’t need training and works with many existing solvers. Their method shrinks a big problem into a smaller one, solves that, and then turns it back into a good starting point for the full problem. This approach finds solutions as good as top methods but much faster, even for problems with tens or hundreds of thousands of stops.
What this means in practice
- •For logistics planners: Generate high-quality delivery routes quickly for large fleets and many destinations, reducing computational delays.
- •For transportation software engineers: Incorporate fast initialization to existing routing solvers to improve speed without retraining or extra model complexity.
Authors
Jiale Zhao, Sirui Mao, Zimu Chen, Wentao Yang, Zihan Wang, Xuefeng Huang, Junji Cheng, Liyuanjun Lai
Abstract
Large-scale routing problems are difficult to solve efficiently as their search spaces grow rapidly with problem size. Existing approaches primarily improve the optimization procedure itself, often at increasing computational cost. We instead shift the focus to a useful initialization that can be refined into a high-quality solution with limited downstream refinement. We propose Just Initialize, a training-free and solver-agnostic initialization component for large-scale routing optimization. Just Initialize compresses a large routing instance into a compact surrogate space, optimizes its global routing structure, and recovers the resulting solution as an optimization-friendly starting point in the original space. Extensive experiments on Traveling Salesman Problems (TSPs), Capacitated Vehicle Routing Problems (CVRPs), Vehicle Routing Problems with Time Windows (VRPTWs), and Prize-Collecting Traveling Salesman Problems (PCTSPs) demonstrate that Just Initialize achieves high-quality solutions comparable to or better than state-of-the-art methods while substantially reducing computational cost across instances ranging from 1K to 100K nodes, including an average speedup of approximately 70$\times$, sub-second runtimes on 10K-node instances, and runtimes within tens of seconds on 100K-node instances.