Hash array mapped trie

Hash array mapped trie

A hash array mapped trie [Bagwell, P. (2001) [http://lampwww.epfl.ch/papers/idealhashtrees.pdf Ideal Hash Trees] . Technical Report, 2001.] (HAMT) is an implementation of an associative array that combines the characteristics of a hash table and an array mapped trie [Bagwell, P. (2000) [http://citeseer.ist.psu.edu/rd/61998956%2C282572%2C1%2C0.25%2CDownload/http%3AqSqqSqlampwww.epfl.chqSqpapersqSqtriesearches.pdf.gz Fast And Space Efficient Trie Searches] . Technical Report, 2000.] .

Advantages of HAMTs

Problems with HAMTs

Implementation of a HAMT involves the use of the "CTPOP" function, which counts the number of ones in the binary representation of a number. This operation is available in many instruction set architectures, but it is not commonly available in high-level languages. Although CTPOP can be implemented in software in O(1) time using a series of shift and add instructions, doing so results in a significant performance penalty.

References


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