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arXiv 2404.00527cs.DScs.GT
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带取消成本的先知不等式

Prophet Inequalities with Cancellation Costs

Booth School of Business, University of Chicago(芝加哥大学布斯商学院);Department of Mathematics, Stanford University(斯坦福大学数学系)

Farbod Ekbatani, Rad Niazadeh, Pranav Nuti, Jan Vondrak

AI总结:

针对收益管理中可取消决策场景,提出带线性取消成本(回购模型)的先知不等式问题,通过微分方程刻画最优竞争比并设计多项式时间随机自适应策略,该策略与到达顺序无关。

摘要:

收益管理中的在线算法文献大多关注不可撤销决策的设置,即一旦在新输入到达时做出决策,之后便无法取消。受现代应用(如云现货市场、横幅广告销售或在线酒店预订)的启发,我们在线性取消成本(即回购模型)下引入并研究了“带取消的先知不等式”。在经典先知不等式问题中,一个由具有已知分布的独立随机变量 $X_1, X_2, \ldots$ 组成的序列被逐一揭示,决策者必须决定何时停止并接受当前变量,以最大化其选择的期望值。在我们的模型中,在接受 $X_j$ 之后,可以稍后丢弃 $X_j$ 并以成本 $f \times X_j$ 接受另一个 $X_i$,其中 $f\geq 0$ 是一个参数。目标是最大化期望净收益:最终接受的变量值减去总取消成本。我们旨在设计能够与最优离线基准竞争的在线策略。\n\n我们的第一个主要结果是针对所有参数 $f \ge 0$ 的最优先知不等式。我们通过某个微分方程(我们为其提供了构造性解)的解,完整刻画了最优在线策略相对于最优离线的最坏情况竞争比。我们的第二个主要结果是设计并分析一个简单且多项式时间的随机自适应策略,该策略达到这一最优竞争比。重要的是,我们的策略是顺序无关的(à la [Samuel-Cahn, 1984]),因为它只需要分布集合,而不需要它们的到达顺序。这些结果是通过与因子揭示LP和广义流、约化为微分方程以及将问题实例嵌入特定泊松点过程相关的新技术获得的。

英文摘要:

Most of the literature on online algorithms and sequential decision-making in revenue management focuses on settings with irrevocable decisions. Motivated by modern applications such as cloud spot markets, selling banner ads, and online hotel booking, we study "prophet inequalities with cancellations" under linear cancellation costs (the buyback model). A sequence of independent random variables $X_1, X_2, \ldots$ with known distributions is revealed one by one. After accepting $X_j$, a decision-maker may later discard it and accept another variable at a cost of $f \times X_j$, where $f \ge 0$. The goal is to maximize the expected net reward: the value of the final accepted variable minus the total cancellation cost. We compare online policies with an omniscient optimal offline "prophet" benchmark. Our first main result is an optimal prophet inequality for all parameters $f \ge 0$. We fully characterize the worst-case competitive ratio of the optimal online policy against the optimal offline benchmark via a differential equation, for which we provide a constructive solution. Our second main result is a simple polynomial-time randomized adaptive policy that achieves this optimal competitive ratio. Our policy is order-agnostic (in the sense of Samuel-Cahn (1984)): it only needs to know the set of distributions and not their arrival order. These results follow from reductions to a continuous "generalized flow problem," viewed as the dual to a factor-revealing LP for the worst-case competitive ratio. Our techniques include a geometric interpretation of its solution via a differential equation and the embedding of random variables into specific Poisson point processes. We also use these building blocks to construct lower-bound instances and to design and analyze our

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。

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