Projects per year
Abstract
We consider dynamic and online variants of 2D pattern matching between an m x m pattern and an n x n text. All the algorithms we give are randomised and give correct outputs with at least constant probability.
- For dynamic 2D exact matching where updates change individual symbols in the text, we show updates can be performed in O(log2 n) time and queries in O(log2 m) time.
- We then consider a model where an update is a new 2D pattern and a query is a location in the text. For this setting we show that Hamming distance queries can be answered in O(log m + H) time, where H is the relevant Hamming distance.
- Extending this work to allow approximation, we give an efficient algorithm which returns a (1 + E) approximation of the Hamming distance at a given location in O("􀀀2 log2 m log log n) time. Finally, we consider a different setting inspired by previous work on locality sensitive hashing (LSH). Given a threshold k and after building the 2D text index and receiving a 2D query pattern, we must output a location where the Hamming distance is at most (1+")k as long as there
exists a location where the Hamming distance is at most k.
- For our LSH inspired 2D indexing problem, the text can be pre-processed in O(n2(4=3+1=(1+")) log3 n) time into a data structure of size
O(n2(1+1=(1+"))) with query time O(n2(1=(1+"))m2).
- For dynamic 2D exact matching where updates change individual symbols in the text, we show updates can be performed in O(log2 n) time and queries in O(log2 m) time.
- We then consider a model where an update is a new 2D pattern and a query is a location in the text. For this setting we show that Hamming distance queries can be answered in O(log m + H) time, where H is the relevant Hamming distance.
- Extending this work to allow approximation, we give an efficient algorithm which returns a (1 + E) approximation of the Hamming distance at a given location in O("􀀀2 log2 m log log n) time. Finally, we consider a different setting inspired by previous work on locality sensitive hashing (LSH). Given a threshold k and after building the 2D text index and receiving a 2D query pattern, we must output a location where the Hamming distance is at most (1+")k as long as there
exists a location where the Hamming distance is at most k.
- For our LSH inspired 2D indexing problem, the text can be pre-processed in O(n2(4=3+1=(1+")) log3 n) time into a data structure of size
O(n2(1+1=(1+"))) with query time O(n2(1=(1+"))m2).
Original language | English |
---|---|
Title of host publication | String Processing and Information Retrieval |
Subtitle of host publication | 23rd International Symposium, SPIRE 2016, Beppu, Japan, October 18-20, 2016, Proceedings |
Editors | Shunsuke Inenaga, Kunihiko Sadakane, Tetsuya Sakai |
Publisher | Springer Verlag |
Pages | 133-144 |
Number of pages | 11 |
ISBN (Print) | 9783319460499 |
DOIs | |
Publication status | Published - 2016 |
Event | SPIRE 2016: 23rd International Symposium on String Processing and Information Retrieval - Beppu, Oita Prefecture, Beppu, Japan Duration: 18 Oct 2016 → 20 Oct 2016 |
Publication series
Name | Lecture Notes in Computer Science |
---|---|
Publisher | Springer-Verlag |
Volume | 9954 |
ISSN (Print) | 0302-9743 |
Conference
Conference | SPIRE 2016 |
---|---|
Country/Territory | Japan |
City | Beppu |
Period | 18/10/16 → 20/10/16 |
Fingerprint
Dive into the research topics of 'Dynamic and approximate pattern matching in 2D'. Together they form a unique fingerprint.Projects
- 1 Finished
-
Next generation pattern matching
Clifford, R. (Principal Investigator)
1/01/13 → 14/01/19
Project: Research
Profiles
-
Dr Raphael Clifford
- School of Computer Science - Reader in Algorithm Design
- Intelligent Systems Laboratory
- Algorithms and Complexity
Person: Academic , Member, Group lead