A note on rounding fractional matchings with constant-factor strong negative correlation
关于具有常数因子强负相关的分数匹配取整的注记
David G. Harris
AI总结 针对二分图提出新的依赖取整算法,将分数匹配转化为整数解,实现强负相关性质,常数因子改进至0.79751。
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我们描述了二分图的新依赖取整算法。给定图 $G = (U \cup V, E)$ 的分数匹配 $x$,算法返回一个整数解 $X$,使得每个右节点 $v \in V$ 最多有一条边,并且变量 $X_e$ 还满足广泛的非正相关性质。特别地,对于共享左节点 $u \in U$ 的任意边 $e_1, e_2$,变量 $X_{e_1}, X_{e_2}$ 具有强负相关性,即 $X_{e_1} X_{e_2}$ 的期望显著低于 $x_{e_1} x_{e_2}$。具有这些性质的依赖取整方案已用于无关机器上最小化加权完成时间的作业调度近似算法等应用中。我们的新算法相比先前算法实现了更简单且定性更强的界。特别地,我们实现了负相关性质 $$ \E[X_{e_1} X_{e_2}] \leq 0.79751 \\ x_{e_1} x_{e_2}, $$ 这是对 Baveja, Qu & Srinivasan (2023) 的显著常数因子改进。
We describe new dependent-rounding algorithms for bipartite graphs. Given a fractional matching $x$ of graph $G = (U \cup V, E)$, the algorithms return an integral solution $X$ such that each right-node $v \in V$ has at most one edge, and where the variables $X_e$ also satisfy broad non-positive correlation properties. In particular, for any edges $e_1, e_2$ sharing a left-node $u \in U$, the variables $X_{e_1}, X_{e_2}$ have \emph{strong} negative-correlation, i.e. the expectation of $X_{e_1} X_{e_2}$ is significantly below $x_{e_1} x_{e_2}$. Dependent rounding schemes with these properties have been used for a approximation algorithms for job-scheduling on unrelated machines to minimize weighted completion times, among other applications. Our new algorithm achieves simpler and qualitatively stronger bounds compared to prior algorithms. In particular, we achieve a negative-correlation property $$ \E[X_{e_1} X_{e_2}] \leq 0.79751 \ x_{e_1} x_{e_2}, $$ which is a significant constant-factor improvement over Baveja, Qu & Srinivasan (2023).