随机顺序流中的匹配:基于历史删除界
Matching in Random-Order Streams via Historical Deletion Bounds
Alireza Farhadi, Mohammadtaghi Hajiaghayi, Mohammad Mahdavi
AI 速读 基于摘要
针对固定图边以均匀随机顺序到达的场景,作者提出单遍流式最大匹配算法,在无权与加权图上均达到约0.713的近似比,核心工具是加权匹配的历史删除不等式。
cs.DS
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We study maximum matching when the edges of a fixed graph arrive in a uniformly random order. For any fixed $\varepsilon>0$, we give a one-pass algorithm that achieves, with high probability over the arrival order, approximation ratios of $0.71295$ for unweighted graphs and $0.71295-\varepsilon$ for weighted graphs, using near-linear space with an explicit charge for weight precision. Both approximation ratios hold for bipartite and general graphs. The algorithm does not require the stream length or the weight range in advance. The main structural ingredient is a historical deletion inequality for weighted matchings. The deletion price of a vertex set is the decrease in maximum matching weight when that set is removed. We bound the sum of these prices for pairwise disjoint vertex sets, even when each price is evaluated at a different stage as edges are added to the graph. Applied to the usual unfolding of integer weights, it transfers a bipartite cardinality certificate to an original weighted matching, even when the original graph is not bipartite. This transfer preserves the approximation coefficient. We combine this transfer with a refined analysis of fractional matchings in the two auxiliary graphs arising in the transfer theorem. An exact rational linear-programming certificate proves the stated constant for every feasible graph profile. The approximation guarantees and the new structural results are formally verified in Lean.