A compact static double-array keeping character codes

Oono, Masaki; Morita, Ken; Fuketa, Masao; Sumitomo, Toru; Aoe, Jun-ichi

doi:10.1016/j.ipm.2006.04.004

Cited by 22 publications

(27 citation statements)

References 14 publications

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“…1, character 'a' traces from state number 6 to state number 3. The child state number t is set to BASE [6]+CODE[a]=3, and then it is checked that t is equal to CHECK [3].…”

Section: Double Arraymentioning

confidence: 99%

“…Moreover, a compact double array proposed by Yata [6]. In this data structure, a character c of key is stored as a value of CHECK array.…”

Section: Double Arraymentioning

confidence: 99%

“…This method uses two arrays called BASE and CHECK, and combines the retrieval speed of the matrix form with compactness of the list form. As schemes reduce the dictionary size of the double array, a method that CHECK array keeps character codes are proposed [6]. This method is useful to make the double array compact and the retrieval speed is almost as fast as the original double array.…”

Section: Introductionmentioning

confidence: 99%

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Compression of double array structures for fixed length keywords

Fuketa¹,

Kitagawa²,

Ogawa³

et al. 2014

Information Processing & Management

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Abstract-Trie is one of the data structures for keyword matching. The trie is used in natural language processing, IP address routing, and so on. It is represented by the matrix form, the link form, the double array, and LOUDS. The double array combines retrieval speed of the matrix form with compactness of the list form. LOUDS is a succinct data structure using bit-string. Retrieval speed of LOUDS is not faster than that of double array, but the dictionary size is smaller. This paper proposes a compression data structure of the double array by dividing trie into each depth and removing the BASE array from that double array. From experimental results, the retrieval speed was almost the same as double array, and the size of the presented method was the most compact in other methods including LOUDS for a large set of keywords with fixed length.

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“…1, character 'a' traces from state number 6 to state number 3. The child state number t is set to BASE [6]+CODE[a]=3, and then it is checked that t is equal to CHECK [3].…”

Section: Double Arraymentioning

confidence: 99%

“…Moreover, a compact double array proposed by Yata [6]. In this data structure, a character c of key is stored as a value of CHECK array.…”

Section: Double Arraymentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

See 1 more Smart Citation

Compression of double array structures for fixed length keywords

Fuketa¹,

Kitagawa²,

Ogawa³

et al. 2014

Information Processing & Management

Self Cite

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show abstract

“…Most studies of static DA tries attempted to improve space efficiency and retrieval speed. [8][9][10][11][12] Static DA tries are typically used for dictionaries without frequent key updates (ie, insertions and deletions), such as Darts 13 and Darts-clone. 14 With respect to dynamic DA tries, there are 2 main objectives.…”

Section: Introductionmentioning

confidence: 99%

Practical rearrangement methods for dynamic double‐array dictionaries

et al. 2017

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SummaryDouble-array structures have been widely used to implement dictionaries with string keys. Although the space efficiency of dynamic double-array dictionaries tends to decrease with key updates, we can still maintain high efficiency using existing methods. However, these methods have practical problems of time and functionality. This paper presents several efficient rearrangement methods to solve these problems.Through experiments using real-world datasets, we demonstrate that the proposed rearrangement methods are much more practical than existing methods.

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“…However, because one state has only one parent state, the original double array can construct a trie but cannot construct DAWG and DFA. Moreover, the compact double array was proposed as a method to compress the double array [8]. This method reduces the space usage by storing traversed characters in CHECK.…”

mentioning

confidence: 99%

Comparisons of Efficient Implementations for DAWG

Fuketa¹,

Morita²,

Aoe³

2016

IJCTE

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Abstract-Key retrieval is very important in various applications. A trie and DAWG are data structures for key retrieval. The double array is one of methods to construct a trie and has both high speed and compactness. In this paper, a data structure of DAWG by the double array using BASE and CHECK is compared with that of DAWG by the double array using CHECK and NEXT, and the retrieval speed and the space usage are theoretically observed. When DAWG and DFA by the double array are constructed, it turns out that it is important to consider indexes for CHECK and NEXT arrays as edge numbers.Index Terms-Automaton, DAWG, double array, triple array. I. INTRODUCTIONKey retrieval is used in various applications [1]. A trie is one of data structures to retrieve keys and merge common prefixes of keys [2]. Moreover, Directed Acyclic Word Gragh (DAWG) is a data structure to reduce the number of trie states [3]. DAWG merges common parts of keys. As the trie and DAWG are kinds of Deterministic Finite Automaton (DFA), they can be traditionally represented by a matrix form (transition table) and a linked list.The triple array is a data structure to construct DFA [4]. This method uses three one-dimensional arrays called BASE, CHECK, and NEXT in order to compress the matrix form. It has high speed because keys of length k can be retrieved by O(k). There is also a method called the double array [5], which compresses the triple array. This method deletes a NEXT array from the triple array and consists of BASE and CHECK. The double array is used in various applications and fields because of its high speed [6], [7]. However, because one state has only one parent state, the original double array can construct a trie but cannot construct DAWG and DFA. Moreover, the compact double array was proposed as a method to compress the double array [8]. This method reduces the space usage by storing traversed characters in CHECK. A method to construct DAWG by the features of the compact double array was proposed [9]. This method has higher speed and less space usage than other methods such as the matrix form, linked list and TST [10]. Furthermore, a method to construct DFA with CHECK and NEXT by deleting a BASE array from the triple array was proposed [11].In this paper, a data structure of DAWG by the double array using BASE and CHECK(BC DAWG) is compared with that of DAWG by the double array using CHECK and NEXT(CN DAWG), and the retrieval speed and the space usage are theoretically observed. A construction algorithm of CN DAWG is proposed. Moreover, features of DAWG by the double array are discussed. II. DOUBLE ARRAY AND DAWGA. Trie A trie is a tree structure used for key retrieval in the field of natural language processing, and is a kind of DFA. Fig. 1 shows examples of the trie in key set K = {"aaa", "aba", "bbc", "cbc", "cc"}. Double circles show terminal states. The trie merges common prefixes of keys. Retrieval always starts from a root state (for example, state number 1 in Fig. 1), and traverses states by one-by-one character in the key....

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A compact static double-array keeping character codes

Cited by 22 publications

References 14 publications

Compression of double array structures for fixed length keywords

Compression of double array structures for fixed length keywords

Practical rearrangement methods for dynamic double‐array dictionaries

Comparisons of Efficient Implementations for DAWG

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