Demand Queries with Preprocessing
Demand Queries with Preprocessing
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带预处理的需求查询
DOI：
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发表时间：
2014
期刊：
影响因子：
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通讯作者：
Shlomo Jozeph
中科院分区：
文献类型：
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作者：
U. Feige;Shlomo Jozeph
给定一组项目和一组situction函数f，该函数确定项目每个子集的价值，需求查询将价格分配给项目，所需的答案是使利润最大化的一组项目，即价值，即S减去需求查询的使用是在组合拍卖的情况下的动机。需求查询可以帮助以后在多项式时间内回答需求查询。 NP⊂p/poly。
Given a set of items and a submodular set-function f that determines the value of every subset of items, a demand query assigns prices to the items, and the desired answer is a set S of items that maximizes the profit, namely, the value of S minus its price. The use of demand queries is well motivated in the context of combinatorial auctions. However, answering a demand query (even approximately) is NP-hard. We consider the question of whether exponential time preprocessing of f prior to receiving the demand query can help in later answering demand queries in polynomial time. We design a preprocessing algorithm that leads to approximation ratios that are NP-hard to achieve without preprocessing. We also prove that there are limitations to the approximation ratios achievable after preprocessing, unless NP ⊂ P/poly.