In the last years, there has been a great interest in machine-learning-based heuristics for solving NP-hard combinatorial optimization problems. The developed methods have shown potential on many optimization problems. In this paper, we present a learned heuristic for the reoptimization of a problem after a minor change in its data. We focus on the case of the capacited vehicle routing problem with static clients (i.e., same client locations) and changed demands. Given the edges of an original solution, the goal is to predict and fix the ones that have a high chance of remaining in an optimal solution after a change of client demands. This partial prediction of the solution reduces the complexity of the problem and speeds up its resolution, while yielding a good quality solution. The proposed approach resulted in solutions with an optimality gap ranging from 0\% to 1.7\% on different benchmark instances within a reasonable computing time.
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列生成是一种用于解决各种优化问题的迭代方法。它将问题分解为两部分:主问题,以及一个或多个定价问题(PP)。该方法采取的总计计算时间在这两个部分之间划分。在路由或调度应用程序中,问题主要在网络上定义,并且PP通常是具有资源约束的NP-难以最短的路径问题。在这项工作中,我们提出了一种基于机器学习的新的启发式定价算法。通过利用先前执行期间收集的数据,目标是减小网络的大小并加速PP,仅保持具有高机会的弧形成为线性松弛解决方案的一部分。该方法已应用于两个特定问题:在公共交通中的车辆和船员调度问题以及时间窗口的车辆路由问题。可以获得高达40%的计算时间的减少。
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