论文标题
重复球的紧密界限
Tight Bounds for Repeated Balls-into-Bins
论文作者
论文摘要
我们研究了Becchetti,Clementi,Natale,Pasquale和Posta(2019)引入的重复球键过程。这个过程以$ m $球任意分布在$ n $ bins上。在每个回合$ t = 1,2,\ ldots $中,从每个非空箱中选择一个球,然后将其随机地将其独立和均匀地选中。我们证明了以下结果: $ \ Quad \ bullet $用于任何$ n \ leq m \ leq \ mathrm {poly}(n)$,我们在最大负载上证明了$ω(m/n \ cdot \ log n)$的下限。对于特殊情况$ m = n $,这与$ o(\ log n)$的上限相匹配,如[BCNPP19]所示。它还对[BCNPP19]中的猜想提供了一个积极的答案,即对于$ m = n $,最大负载为$ω(\ log n/ \ log \ log \ log \ log \ log n)$至少在多条件较大的时间间隔中至少一次。对于$ m \在[ω(n),n \ log n] $中,我们的新下限反驳了[bcnpp19]的猜想,即最大负载保留$ o(\ log n)$。 对于任何$ n \ leq m \ leq \ mathrm {poly}(n)$,$ \ quad \ bullet $ $ $ o(m/n \ cdot \ log n)$在最大值的所有步骤上,我们证明了$ o(m/n \ cdot \ log n)$的上限。这匹配了我们的下限与乘法常数。 对于任何$ M \ geq n $,$ \ quad \ bullet $,我们的分析也意味着$ O(m^2/n)$等待时间以$ O(M/N \ CDOT \ log M)$最大负载达到配置,即使对于最差的初始分布也是如此。 $ \ quad \ bullet $对于任何$ m \ geq n $,我们表明每个球都访问$ o(m \ log m)$ rounds中的每个垃圾箱。对于$ m = n $,这改善了[bcnpp19]中$ o(n \ log^2 n)$的上一个上限。我们还证明,对于任何$ n \ leq m \ leq \ mathrm {poly}(n)$,上限紧密到乘法常数。
We study the repeated balls-into-bins process introduced by Becchetti, Clementi, Natale, Pasquale and Posta (2019). This process starts with $m$ balls arbitrarily distributed across $n$ bins. At each round $t=1,2,\ldots$, one ball is selected from each non-empty bin, and then placed it into a bin chosen independently and uniformly at random. We prove the following results: $\quad \bullet$ For any $n \leq m \leq \mathrm{poly}(n)$, we prove a lower bound of $Ω(m/n \cdot \log n)$ on the maximum load. For the special case $m=n$, this matches the upper bound of $O(\log n)$, as shown in [BCNPP19]. It also provides a positive answer to the conjecture in [BCNPP19] that for $m=n$ the maximum load is $ω(\log n/ \log \log n)$ at least once in a polynomially large time interval. For $m\in [ω(n),n\log n]$, our new lower bound disproves the conjecture in [BCNPP19] that the maximum load remains $O(\log n)$. $\quad \bullet$ For any $n\leq m\leq\mathrm{poly}(n)$, we prove an upper bound of $O(m/n\cdot\log n)$ on the maximum load for all steps of a polynomially large time interval. This matches our lower bound up to multiplicative constants. $\quad \bullet$ For any $m\geq n$, our analysis also implies an $O(m^2/n)$ waiting time to reach a configuration with a $O(m/n\cdot\log m)$ maximum load, even for worst-case initial distributions. $\quad \bullet$ For any $m \geq n$, we show that every ball visits every bin in $O(m\log m)$ rounds. For $m = n$, this improves the previous upper bound of $O(n \log^2 n)$ in [BCNPP19]. We also prove that the upper bound is tight up to multiplicative constants for any $n \leq m \leq \mathrm{poly}(n)$.