用生成模型解决图优化问题,能学出最优解且计算更可扩展。
Exploration through Generation: Applying GFlowNets to Structured Search
- 用流生成网络逐步构建图解,按奖励比例采样
- 在不同规模实例上生成解,均达到经典算法最优结果
- 训练后可快速推理,适合大规模难解问题
本文将生成流网络(GFlowNets)应用于三个图优化问题:旅行商问题、最小生成树和最短路径。GFlowNets是生成模型,通过轨迹平衡损失学习按奖励函数比例采样解,依次选择边构建生成树、节点构成路径、城市组成环路。在不同规模的基准实例上实验表明,该方法能学习到最优解。对每类问题,测试了多种节点数的图配置。生成解与经典算法结果一致:最短路径使用Dijkstra,最小生成树采用Kruskal,旅行商问题使用精确求解器。训练收敛速度依赖问题复杂度,随着图规模增大,损失稳定所需迭代次数增加。一旦训练收敛,生成解在所有测试实例中均匹配经典算法的已知最优解。结果表明,生成模型可通过学习策略求解组合优化问题。主要优势在于计算可扩展性:传统算法每实例复杂度固定,而GFlowNets通过训练分摊计算开销。在足够算力下,该框架有望扩展至经典精确方法失效的大规模实例。
原文摘要 · Abstract (English)
This work applies Generative Flow Networks (GFlowNets) to three graph optimization problems: the Traveling Salesperson Problem, Minimum Spanning Tree, and Shortest Path. GFlowNets are generative models that learn to sample solutions proportionally to a reward function. The models are trained using the Trajectory Balance loss to build solutions sequentially, selecting edges for spanning trees, nodes for paths, and cities for tours. Experiments on benchmark instances of varying sizes show that GFlowNets learn to find optimal solutions. For each problem type, multiple graph configurations with different numbers of nodes were tested. The generated solutions match those from classical algorithms (Dijkstra for shortest path, Kruskal for spanning trees, and exact solvers for TSP). Training convergence depends on problem complexity, with the number of episodes required for loss stabilization increasing as graph size grows. Once training converges, the generated solutions match known optima from classical algorithms across the tested instances. This work demonstrates that generative models can solve combinatorial optimization problems through learned policies. The main advantage of this learning-based approach is computational scalability: while classical algorithms have fixed complexity per instance, GFlowNets amortize computation through training. With sufficient computational resources, the framework could potentially scale to larger problem instances where classical exact methods become infeasible.
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