Fast and powerful hashing using tabulation
Fast and powerful hashing using tabulation
复制标题
使用表格进行快速而强大的散列
DOI：
10.1145/3068772
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发表时间：
2015
影响因子：
22.7
通讯作者：
M. Thorup
中科院分区：
文献类型：
--
作者：
M. Thorup
随机算法通常是为了简单性而享受，但是在这里，用于产生所需的概率保证的功能通常是太复杂了，我们在此调查了最新的结果，这些结果是基于制表的简单哈希计划，这是如何出乎意料的。威斯康星州被视为C字符，我们的字符表H1。通常通过较高的独立性，我们考虑一个简单的分布型，我们考虑了一个扭曲的表格考虑我们构成两个简单的表函数，将一个功能应用于另一个成绩，表明这在Wegman和Carter的经典框架中产生了很高的独立性。所有这些都易于实施和使用，它们的分析不是。
Randomized algorithms are often enjoyed for their simplicity, but the hash functions employed to yield the desired probabilistic guarantees are often too complicated to be practical. Here, we survey recent results on how simple hashing schemes based on tabulation provide unexpectedly strong guarantees. Simple tabulation hashing dates back to Zobrist (A new hashing method with application for game playing. Technical Report 88, Computer Sciences Department, University of Wisconsin). Keys are viewed as consisting of c characters and we have precomputed character tables h1, . . ., hc mapping characters to random hash values. A key x = (x1, . . ., xc) is hashed to h1[x1] ⊕ h2[x2]..... ⊕ hc[xc] This schemes is very fast with character tables in cache. Although simple tabulation is not even four-independent, it does provide many of the guarantees that are normally obtained via higher independence, for example, linear probing and Cuckoo hashing. Next, we consider twisted tabulation where one input character is "twisted" in a simple way. The resulting hash function has powerful distributional properties: Chernoff-style tail bounds and a very small bias for minwise hashing. This is also yields an extremely fast pseudorandom number generator that is provably good for many classic randomized algorithms and data-structures. Finally, we consider double tabulation where we compose two simple tabulation functions, applying one to the output of the other, and show that this yields very high independence in the classic framework of Wegman and Carter. In fact, w.h.p., for a given set of size proportional to that of the space consumed, double tabulation gives fully random hashing. We also mention some more elaborate tabulation schemes getting near-optimal independence for given time and space. Although these tabulation schemes are all easy to implement and use, their analysis is not.
关于使用带有简单通用哈希类的布谷鸟哈希的风险
DOI：
10.1137/1.9781611973068.87
发表时间：
2009
期刊：
影响因子：
--
作者：
Martin Dietzfelbinger;Ulf Schellbach
通讯作者：
Ulf Schellbach