B. Commentz-Walter. A string matching algorithm fast on the average. In Proc. ICALP'79, LNCS v. 6, pages 118--132, 1979.  Home/Search   Document Not in Database   Summary   Related Articles   Check

....matching. For example, Watson [28, chapter 5] presented an algorithm that determines the minimum length of a string matching the regular expression and forms a trie with all the prefixes of that length of strings matching the regular expression. A multipattern search algorithm like Commentz Walter [8] is run over those prefixes as a filter to detect text areas where a complete occurrence may start. Another technique of this kind is used in Gnu Grep 2.0, which extracts a set of strings which must appear in any match. This string is searched for and the neighborhoods of its occurrences are ....

B. Commentz-Walter. A string matching algorithm fast on the average. In Proc. ICALP'79, LNCS v. 6, pages 118--132, 1979.

....of Technology P.O. Box 513, 5600 MB Eindhoven, The Netherlands email: watson win.tue.nl or wsinswan win.tue.nl April 21, 1995 Abstract This paper presents a taxonomy of sublinear keyword pattern matching algorithms related to the Boyer Moore algorithm [BM77] and the Commentz Walter algorithm [CW79a, CW79b]. The taxonomy includes, amongst others, the multiple keyword generalization of the single keyword Boyer Moore algorithm and an algorithm by Fan and Su [FS93, FS94] The corresponding precomputation algorithms are presented as well. The taxonomy is based on the idea of ordering algorithms ....

....matching problem has been extensively studied and a multitude of diverse solutions algorithms exists. Single keyword algorithms are for instance described by Knuth, Morris, and Pratt [KMP77] and Boyer and Moore [BM77] multiple keyword algorithms by Aho and Corasick [AC75] by Commentz Walter [CW79a, CW79b], and by Fan and Su [FS93, FS94] An overview of keyword pattern matching algorithms can be found in [Aho90] Due to the diversity of the algorithms and their descriptions that tend to be rather involved and verbal it is hard to get a good overview and to make a sound comparison between ....

[Article contains additional citation context not shown here]

Beate Commentz-Walter. A string matching algorithm fast on the average. Technical Report TR 79.09.007, IBM-Germany, Scientific Center Heidelberg, September 1979.

....of Technology P.O. Box 513, 5600 MB Eindhoven, The Netherlands email: watson win.tue.nl or wsinswan win.tue.nl April 21, 1995 Abstract This paper presents a taxonomy of sublinear keyword pattern matching algorithms related to the Boyer Moore algorithm [BM77] and the Commentz Walter algorithm [CW79a, CW79b]. The taxonomy includes, amongst others, the multiple keyword generalization of the single keyword Boyer Moore algorithm and an algorithm by Fan and Su [FS93, FS94] The corresponding precomputation algorithms are presented as well. The taxonomy is based on the idea of ordering algorithms ....

....matching problem has been extensively studied and a multitude of diverse solutions algorithms exists. Single keyword algorithms are for instance described by Knuth, Morris, and Pratt [KMP77] and Boyer and Moore [BM77] multiple keyword algorithms by Aho and Corasick [AC75] by Commentz Walter [CW79a, CW79b], and by Fan and Su [FS93, FS94] An overview of keyword pattern matching algorithms can be found in [Aho90] Due to the diversity of the algorithms and their descriptions that tend to be rather involved and verbal it is hard to get a good overview and to make a sound comparison between ....

[Article contains additional citation context not shown here]

Beate Commentz-Walter. A string matching algorithm fast on the average. In H.A. Maurer, editor, Proceedings 6th International Colloquium on Automata, Languages and Programming, volume 71 of Lecture Notes in Computer Science, pages 118--132. Springer, July 1979.

....structure to represent Delta such that any changes of Delta can be processed efficiently and, given any text string t, the occurrences of the patterns of Delta in t can be reported efficiently. For the static case in which no insertion or deletion is supported, optimal solutions already exist [1, 5]. These solutions each can build a data structure representing Delta in O(n) time and search a text t in Research supported in part by Hong Kong RGC Grant 338 065 0027 O(jtj tocc) time, where n denotes the total length of patterns in Delta and tocc is the total number of occurrences of the ....

B. Commentz-Walter. A string matching algorithm fast on the average. In Proceedings of the Sixth International Colloquium on Automata Languages and Programming, pages 118-- 132, 1979.

....Each time a piece is found, it uses dynamic programming over an area of length m 2k where the approximate occurrence can be found. The multipattern search can be carried out in O(n) worst case search time by using an Aho Corasick machine [1] or in O(n=m) best case time using Commentz Walter [11] or another Boyer Moore type algorithm adapted to multipattern search. The total cost of verifications keeps below O(n) time provided k=m 1= 3 log oe m) Two dimensional string matching was first considered by Bird and Baker [10, 9] who obtain O(n 2 ) worst case time. Good average results are ....

B. Commentz-Walter. A string matching algorithm fast on the average. In Proc. ICALP'79, number 6 in LNCS, pages 118--132. Springer-Verlag, 1979.

....their longest necessary string, which is used as a filter and searched as a simple string. In fact, grep is able to extract a necessary set of strings, i.e. such that one of the strings in the set has to appear in every match. This set is searched as a filter using a Commentz Walter like algorithm [7], which is a kind of multipattern Boyer Moore. As we will see, this extension makes grep very powerful and closer to our goal of a smooth degradation in efficiency as the pattern gets more complex. The experiments were carried out over 100 Mb of English text extracted from Wall Street Journal ....

B. Commentz-Walter. A string matching algorithm fast on the average. In Proc. ICALP'79, LNCS v. 6, pages 118--132, 1979.

....strings. The two famous algorithms for this string matching problem are the Boyer Moore algorithm [BM77] and the Knuth Morris Pratt algorithm [KMP77] The basic problem has been extended to include more complicated patterns, including a set of strings (Aho and Corasick [AC75] and Commentz Walter [CW79]) strings with don t care symbols (Fischer and Paterson [FP74] and strings with don t care and complement symbols (Pinter [Pin85] Abrahamson [Abr87] studied the complexity of several matching problems and presented algorithms for strings with classes, which are sets of characters, but ....

Commentz-Walter, B, "A string matching algorithm fast on the average," Proc. 6th International Colloquium on Automata, Languages, and Programming, (1979), pp. 118-132.

....algorithm (KMP algorithm) KMP 77] designed for a single pattern. As for one pattern, the Boyer Moore algorithm (BM algorithm) BM 77] has a better behavior in practice than the KMP algorithm, CommentzWalter developed an algorithm combining the ideas of AC and BM algorithms ( Co 79a,Co 79b] A complete version can be found in [Ah 90] Later, Uratani [Ur 88] and Baeza Yates and R egnier [BR 90] developed similar algorithms. In this paper, we show how to use the power of directed acyclic word graphs (DAWG s) for finding a finite set of patterns. Such graphs are used to represent ....

B. Commentz-Walter, A string matching algorithm fast on the average, in: H.A. Maurer, ed., Proceedings of the 6th International Colloquim on Automata, Languages and Programming, Lecture Notes in Computer Science, (SpringerVerlag, Berlin, 1979) 118--132.

....Knuth Morris Pratt algorithm (KMP algorithm) KMP 77] designed for a single pattern. As for one pattern, the Boyer Moore algorithm (BM algorithm) BM 77] has a better behavior in practice than the KMP algorithm, CommentzWalter developed an algorithm combining the ideas of AC and BM algorithms ( Co 79a,Co 79b] A complete version can be found in [Ah 90] Later, Uratani [Ur 88] and Baeza Yates and R egnier [BR 90] developed similar algorithms. In this paper, we show how to use the power of directed acyclic word graphs (DAWG s) for finding a finite set of patterns. Such graphs are used to ....

B. Commentz-Walter, A string matching algorithm fast on the average, Technical Report 79.09.007, I.B.M. Heidelberg Scientific Center, Germany, 1979.

....of input patterns. Clearly a better solution to this problem can be devised. Desirable solutions would be to find all pattern occurrences by scanning T only once regardless of the number of input patterns. A lot of research on the multiple string pattern matching can be found in the literature [1, 5, 6, 13]. The state of the art algorithms can quickly find all pattern occurrences by scanning T only once even for a very large number of patterns; for example, Wu and Manber s algorithm [13] can find all occurrences of 10,000 input patterns in 15.8M text about 10 seconds Partially supported by the ....

Commentz-Walter, B., "A string matching algorithm fast on the average," Proc. 6th International Colloquium on Automata, Languages, and Programming, 1979

....the Knuth Morris Pratt algorithm (KMP) 11] designed for a single pattern. Since for one pattern the BoyerMoore algorithm [6] has a better behavior in practice, several algorithms have been elaborated to extend this idea to multi pattern matching. Among them, the first is Commentz Walter algorithm [7]. It uses a trie of the reverse patterns (i.e. read from right to left) A shift is associated to each node in a preprocessing E mail: raffinot monge.univ mlv.fr Institut Gaspard Monge, Universit e de Marne la Vall ee, 2 rue de la Butte Verte, 93160 Noisy le Grand, France phase to skip ....

....two improvements) with the following algorithms. Commentz Walter.We use two different versions of this algorithm, CWBM (for Commentz Walter weak Boyer Moore) and CWN (for Commentz Walter Normalized) Details on these two versions, which are quite similar, of the Commentz Walter algorithm [7] are given in the taxonomy [12] Note that in the tests we performed the results obtained with both are the same. Dawg Match. The Dawg Match algorithm can be found in [9] MultiBDM algorithm is inspired on it. Multipat. Multipat is a Boyer Moore algorithm with an Horspool Sunday heuristic ....

B. Commentz-Walter. A string matching algorithm fast on the average. In H. A. Maurer, editor, 6th, number 71 in Lecture Notes in Computer Science, pages 118-- 132, 1979.

....5] a multipattern search algorithm is generalized to regular expression searching, in order to take advantage of this fact. The resulting algorithm finds all suffixes (of a predetermined length) of words in the language denoted by the regular expression and uses the Commentz Walter algorithm [7] to search them. Another technique of this kind is used in Gnu Grep v2.0, which extracts a single string (the longest) which must appear in any match. This string is searched for and the neighborhoods of its occurrences are checked for complete matches using a lazy deterministic automaton. Note ....

B. Commentz-Walter. A string matching algorithm fast on the average. In Proc. ICALP'79, number 6 in LNCS, pages 118--132. Springer-Verlag, 1979.

....this case is a very unlikely one in satellite imagery, the problem of finding an algorithm with a linear performance even in the worst case remains open. However, average runtime could be improved further by replacing the multiple string matching machine from Aho Corasick with the Commentz Walter [7] method. Also using [4] instead of Bird s 2D algorithm is possible, although this would increase the row and column calculations using checkpoints for setting up in the compressed image for the checkmatch procedure described in [4] In the course of this algorithm, we have studied the details of ....

B. Commentz-Walter. A string matching algorithm fast on the average. In Proc. of the 6th International Colloquium on Automata, Languages and Programming ICALP, volume 71 of Lecture Notes in Computer Science, pages 118--132, Berlin, 1979. Springer-Verlag.

....O(n) 3.4 Improvements The Aho and Corasick [AC75] multi string searching algorithm runs in time O(n m L) using O(m L) extra space, for L strings of size m and a text of length n. Using the Boyer Moore [BM77] string matching idea of searching from right to left in the string, Commentz Walter [CW79] proposed a faster algorithm on the average. Variations on this algorithm are proposed by Sridhar [Sri86] and Baeza Yates and Regnier [BYR90] By using a multiple string searching based on Boyer Moore s ideas, we improve the searching phase, achieving O(ff(m; q)n 2 =m) time where ff(m; q) ....

B. Commentz-Walter. A string matching algorithm fast on the average. In ICALP, volume 6 of Lecture Notes in Computer Science, pages 118--132. Springer-Verlag, 1979.

....string matching problem is to find all substrings in the text that match at least one of the patterns in the set. The first efficient algorithm for solving this problem is by Aho and Corasick [AC75] which solves the problem in linear time. This algorithm is the basis of fgrep. Commentz Walter [CW79] presented an algorithm which combines the Boyer Moore technique with the Aho Corasick algorithm. The Commentz Walter Algorithm is substantially faster than the Aho Corasick algorithm when the number of patterns is not too big. The pattern matching tool gre [Hu91] which covers almost all ....

Commentz-Walter, B, "A string matching algorithm fast on the average," Proc. 6th International Colloquium on Automata, Languages, and Programming (1979), pp. 118-132.

....et al. 1977] used in string matching to multipattern matching. The complexity of the construction of the automaton required in AC is linear in time and space in the sum of the lengths of all patterns, more precisely in O(log jAj Delta P n i=1 jP i j) where A is the alphabet of the patterns. Commentz Walter [1979] gave an algorithm which is the extension of the Boyer Moore algorithm [Boyer and Moore 1977] to the case of a finite set of strings. The complexity of her algorithm is quadratic though more efficient in practice than AC for shorts strings [Aho 1990] Crochemore et al. 1993] gave a linear time ....

Commentz-Walter, B. 1979. A String Matching Algorithm Fast on the Average. Automata, Languages and Programming Lecture Notes in Computer Science, SpringerVerlag, Berlin, 118--132.

....0, then the text scanning step requires at least Omega Gamma nd) 6= comparisons. This bounds is achieved by the Aho Corasick algorithm and also by the naive algorithm that matches each pattern separately. When the text is shorter, it is possible to modify the text scanning Commentz Walter [22, 23] and Crochemore et al. 24] gave other dictionary matching algorithms that are based on ideas from the Boyer Moore [17] string matching algorithm. These algorithms achieve faster average running times by matching the patterns from their end towards their start. Recently, the dictionary matching ....

....dynamically changing without having to recompute the dictionary preprocessing information from scratch [7, 8, 9, 10, 11, 29] The main contribution of this paper is a new approach to the dictionary matching problem with uniform length patterns on ordered alphabets. Similarly to the Commentz Walter [22, 23] algorithm, the new algorithm tries to match the dictionary patterns from their end towards their start. However, our motivation is entirely different. While the CommentzWalter algorithm matches the patterns from their end to start hoping to skip parts of the text, our algorithm does so since this ....

B. Commentz-Walter. A string matching algorithm fast on the average. Technical Report 79.09.007, IBM Wissenschaftliches Zentrum, Heidelberg, Germany, 1979.

....0, then the text scanning step requires at least Omega Gamma nd) 6= comparisons. This bounds is achieved by the Aho Corasick algorithm and also by the naive algorithm that matches each pattern separately. When the text is shorter, it is possible to modify the text scanning Commentz Walter [22, 23] and Crochemore et al. 24] gave other dictionary matching algorithms that are based on ideas from the Boyer Moore [17] string matching algorithm. These algorithms achieve faster average running times by matching the patterns from their end towards their start. Recently, the dictionary matching ....

....dynamically changing without having to recompute the dictionary preprocessing information from scratch [7, 8, 9, 10, 11, 29] The main contribution of this paper is a new approach to the dictionary matching problem with uniform length patterns on ordered alphabets. Similarly to the Commentz Walter [22, 23] algorithm, the new algorithm tries to match the dictionary patterns from their end towards their start. However, our motivation is entirely different. While the CommentzWalter algorithm matches the patterns from their end to start hoping to skip parts of the text, our algorithm does so since this ....

B. Commentz-Walter. A string matching algorithm fast on the average. In H. A. Maurer, editor, Proc. 6th International Colloquium on Automata, Languages, and Programming, pages 118--132. Springer-Verlag, Berlin, Germany, 1979.

....of the pattern in the text. For the static dictionary matching problem, two algorithms are known: one due to Aho and Corasick [AC75] AC for short) which can be seen as a generalization of the Knuth Morris Pratt string matching algorithm [KMP77] and the other one due to Commentz Walter [C79] (CW for short) which can be seen as a generalization of the Boyer Moore algorithm [BM77] Both AC and CW have preprocessing phases in which graphs are built from the dictionary D for later use, and search phases in which text positions are checked in increasing order for occurrences of ....

B. Commentz-Walter, A string matching algorithm fast on the average, Proc. 6th ICALP (1979), 118--132.

.... cannot handle more than 500 patterns) even though egrep does not allow errors This implementation is not competitive, however, with very fast multiple string matching without errors, such as the ones used in agrep [WM92] or in Gnu grep [Ha93] which uses an algorithm based on Commentz Walter [CW79]) We cannot hope to compete with string matching without errors, but we can hope to come close, which we did. Next, we will show how to improve this basic scheme. We call this basic algorithm Algorithm 00. 3. Better and Faster Hash Functions The choice of a hash function is a critical choice in ....

Commentz-Walter, B, "A string matching algorithm fast on the average, " Proc. 6th International Colloquium on Automata, Languages, and Programming (1979), pp. 118-132.

....m = 31 and k = 0: 30 (right) our algorithm is the fastest for small k (up to 30 of the pattern length) For larger k, Chang s and Wu, Manber and Myers s algorithms are the fastest. We can improve the searching phase by using multiple string searching algorithms based on the Boyer Moore algorithm [10, 25, 6] or the shift or algorithm [3, 31] This improvement is significant when the number of blocks found is small (or in other words, when the alphabet is large) To improve the check phase, we need to decrease the number of potential matches. Two possible solutions are: ffl Select the blocks to be ....

B. Commentz-Walter. A string matching algorithm fast on the average. In ICALP, volume 6 of Lecture Notes in Computer Science, pages 118--132. Springer-Verlag, 1979.

.... In the same year, Baeza Yates and Perleberg [BYP96] suggested that better algorithms could be used for the multipattern search: at least an Aho Corasick machine [AC75] to guarantee O(n) search time (excluding verifications) or even a Boyer Moore algorithm adapted to multipattern search, such as [CW79] However, no more attention was paid to this idea until this thesis. In 1996, we resumed the work on this filter. First, we adapted to multipattern exact search a simple variation of the Boyer Moore Sunday algorithm [Sun90] an algorithm for exact string matching) The adaptation uses a trie for ....

B. Commentz-Walter. A string matching algorithm fast on the average. In Proc. ICALP'79, number 6 in LNCS, pages 118--132. Springer-Verlag, 1979.

....in this section, the problem of string matching with classes for more than one pattern at a time. To denote the union symbol we use , for example p 1 p 2 matches the pattern p 1 or the pattern p 2 . The KMP algorithm and the BM algorithm have been extended already to this case (see [2] and [13] respectively) achieving a worst case time of O(n m) where m is the total length of the set of patterns. If we have to search for p 1 Delta Delta Delta p , and we keep one vector state per pattern, we have an immediate O(d mmax w e n) time algorithm for a set of patterns, where m max ....

B. Commentz-Walter. A string matching algorithm fast on the average. In ICALP, volume 6 of Lecture Notes in Computer Science, pages 118--132. Springer-Verlag, 1979.

.... Pratt algorithm (KMP algorithm) KMP 77] designed for a single pattern. As for one pattern, the Boyer Moore algorithm (BM algorithm) BM 77] has a better behavior in practice than the KMP algorithm Commentz Walter developed an algorithm combining the ideas of AC and BM algorithms ( Co 79a, Co 79b] A complete version can be found in [Ah 90] Later, Uratani [Ur 88] and Baeza Yates and R egnier [BR 90] developed similar algorithms. In this paper, we show how to use the power of directed acyclic word graphs (DAWG s) for finding a finite set of patterns. Such graphs are used to represent ....

B. Commentz-Walter, A string matching algorithm fast on the average, In :(Proceedings of the 6th International Colloquim on Automata, Languages and Programming, Lecture Notes in Computer Science, SpringerVerlag, Berlin, 1979) 118--132.

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B. Commentz-Walter. "A String Matching Algorithm Fast on the Average." In Proc. 6th Int. Colloq. Automata, Lang., and Prog. (July 1979), 118--132.

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