arXivDaily arXiv每日学术速递 周一至周五更新
arXiv 2510.20153cs.DS
收藏

两阶段二分图匹配的最优舍入

Optimal Rounding for Two-Stage Bipartite Matching

Stanford University(斯坦福大学)

Tristan Pollner, Amin Saberi, Anders Wikum

AI总结:

针对两阶段二分图匹配,提出基于负关联的舍入算法,实现顶点加权7/8、边加权0.828的近似比,并扩展到样本访问场景。

摘要:

我们研究两阶段二分图匹配问题,其中二分图顶点集为$(B_1 \cup B_2, I)$的边分两批揭示。在第一阶段,必须从已揭示的边$E \subseteq B_1 \times I$中选择一个匹配。在第二阶段,边$E^θ\subseteq B_2 \times I$从已知分布中采样,并且必须在$B_2$与$I$中未匹配的顶点之间选择第二个匹配。目标是最大化组合匹配的总权重。我们设计了最优在线算法的多项式时间近似,在任意分布下,对于顶点加权图达到$7/8$的保证,对于边加权图达到$2\sqrt{2}-2 \approx 0.828$的保证。两个近似比都匹配了自然分数松弛的积分间隙的已知上界,改进了Feng、Niazadeh和Saberi对于第二批由独立到达节点组成的无权图的最佳已知近似0.767。\n我们的结果通过一种算法获得,该算法对两阶段揭示的分数匹配进行舍入,旨在以与其分数权重成比例的概率匹配离线节点(或边),损失一个常数因子。我们利用离线节点可用性之间的负关联(NA)——这是由依赖舍入引起的性质——来推导随机图中最大权重匹配期望大小的新下界,其中一侧通过NA二元随机变量实现。此外,我们将这些结果扩展到仅能对分布进行样本访问的设置。特别地,$\text{poly}(n,ε^{-1})$个样本足以在顶点加权问题的近似比中获得$ε$的加性损失;对于边加权问题,类似界限成立,但额外依赖于边权重的尺度(这是不可避免的)。

英文摘要:

We study two-stage bipartite matching, in which the edges of a bipartite graph on vertices $(B_1 \cup B_2, I)$ are revealed in two batches. In stage one, a matching must be selected from among revealed edges $E \subseteq B_1 \times I$. In stage two, edges $E^θ\subseteq B_2 \times I$ are sampled from a known distribution, and a second matching must be selected between $B_2$ and unmatched vertices in $I$. The objective is to maximize the total weight of the combined matching. We design polynomial-time approximations to the optimum online algorithm, achieving guarantees of $7/8$ for vertex-weighted graphs and $2\sqrt{2}-2 \approx 0.828$ for edge-weighted graphs under arbitrary distributions. Both approximation ratios match known upper bounds on the integrality gap of the natural fractional relaxation, improving upon the best-known approximation of 0.767 by Feng, Niazadeh, and Saberi for unweighted graphs whose second batch consists of independently arriving nodes. Our results are obtained via an algorithm that rounds a fractional matching revealed in two stages, aiming to match offline nodes (respectively, edges) with probability proportional to their fractional weights, up to a constant-factor loss. We leverage negative association (NA) among offline node availabilities -- a property induced by dependent rounding -- to derive new lower bounds on the expected size of the maximum weight matching in random graphs where one side is realized via NA binary random variables. Moreover, we extend these results to settings where we have only sample access to the distribution. In particular, $\text{poly}(n,ε^{-1})$ samples suffice to obtain an additive loss of $ε$ in the approximation ratio for the vertex-weighted problem; a similar bound holds for the edge-weighted problem with an additional (unavoidable) dependence on the scale of edge weights.

机构、总结、中文摘要均由AI分析而来,可能存在错误,请以论文正文为准。

↑