arXiv:2502.08125cs.DScs.LG2025-02被引 6

用预测加速增量图的单源最短路径维护,性能随预测精度平滑下降。

Incremental Approximate Single-Source Shortest Paths with Predictions

  • 基于预测预热数据结构,动态更新近似最短路径。
  • 运行时间仅依赖于预测误差η,达(1+ε)近似精度。
  • 预测精准时接近离线最优,最坏情况也优于传统算法。

本文研究在算法-带预测模型下,增量图中维护单源近似最短路径这一基础数据结构问题。给定依次插入的边序列σ,目标是在每个时间步维持从源点到各顶点的近似最短路径。在边到来前,数据结构会收到对在线边序列的预测ˆσ,用于“预热”其状态。主要成果是设计了一种学习型算法,可在˜O(m η log W/ε)时间内维护(1+ε)近似最短路径,其中W为最大边权,η为预测误差。该方法可直接扩展至全源最短路径场景。当预测近乎完美时,算法表现接近离线最优;预测误差增大时,性能平滑退化;最坏情况下,仍比现有最优离线算法仅差对数因子。作为基础组件,本文还研究了离线增量近似最短路径问题:边序列σ已知,需高效输出前t条边构成的中间图Gt的最短路径长度。该离线问题本身在最坏情况下具有独立研究价值。

原文摘要 · Abstract (English)

The algorithms-with-predictions framework has been used extensively to develop online algorithms with improved beyond-worst-case competitive ratios. Recently, there is growing interest in leveraging predictions for designing data structures with improved beyond-worst-case running times. In this paper, we study the fundamental data structure problem of maintaining approximate shortest paths in incremental graphs in the algorithms-with-predictions model. Given a sequence $σ$ of edges that are inserted one at a time, the goal is to maintain approximate shortest paths from the source to each vertex in the graph at each time step. Before any edges arrive, the data structure is given a prediction of the online edge sequence $\hatσ$ which is used to ``warm start'' its state. As our main result, we design a learned algorithm that maintains $(1+ε)$-approximate single-source shortest paths, which runs in $\tilde{O}(m η\log W/ε)$ time, where $W$ is the weight of the heaviest edge and $η$ is the prediction error. We show these techniques immediately extend to the all-pairs shortest-path setting as well. Our algorithms are consistent (performing nearly as fast as the offline algorithm) when predictions are nearly perfect, have a smooth degradation in performance with respect to the prediction error and, in the worst case, match the best offline algorithm up to logarithmic factors. As a building block, we study the offline incremental approximate single-source shortest-paths problem. In this problem, the edge sequence $σ$ is known a priori and the goal is to efficiently return the length of the shortest paths in the intermediate graph $G_t$ consisting of the first $t$ edges, for all $t$. Note that the offline incremental problem is defined in the worst-case setting (without predictions) and is of independent interest.

最短路径增量算法预测驱动学习型数据结构

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