Hannu Peltola: Towards Faster String Matching

Opponent: Ph.D. Juha Kärkkäinen, University of Helsinki

Supervisor: Professor Jorma Tarhio, Aalto University, Department of Computer Science and Engineering.

M.Sc. Hannu Peltola will defend the dissertation “Towards Faster String Matching” on 10th of May. Exact string matching is a much studied and popular problem. The task is to find the occurrences of a string pattern in a long text. We introduce several new algorithms for online exact string matching and study their experimental performance and compare them with some earlier algorithms. Moreover, we give examples of anomalies caused by repetitive texts, and present algorithms for that kind of data. Specialized algorithms for long patterns (longer than about 50 characters) are also studied. In addition, we discuss the principles of fair testing of string matching algorithms.

More information: http://sci.aalto.fi/en/current/events/vaitos_peltola_hannu/

Welcome!

Abstract

Pattern matching is a basic text-processing problem and its complexity seems well understood when we are given an explicit representation of the input.  With the recent explosion in the amount of digital data we need to process, however, we should aim to develop solutions that work directly with compressed input.  For example, we should try to come up with pattern-matching algorithms that work with compressed representations of both the pattern and the text.  I will present some ideas behind a linear-time solution of this problem for LZW-like compression methods (from STACS 2012), starting with a simpler variant where the pattern is given explicitly (from SODA 2011).

Biography

Pawel Gawrychowski received his PhD from the University of Wroclaw in October 2011 and is now a post-doctoral researcher at the Max Planck Institute in Saarbruecken.  He has authored or co-authored over a dozen academic papers, winning the Best Paper Award at CIAA 2011 and Best Student Paper Awards at IWOCA 2009, MFCS 2009 and ESA 2011.  He has been a finalist in the ACM International Collegiate Programming Contest twice, receiving the silver medal in 2005, and a Top Coder finalist five times, earning third place in 2007.  His PhD thesis was on pattern-matching in Lempel-Ziv-compressed texts, as were his solo papers at SODA 2011, ESA 2011 and STACS 2012.

Contact: Travis Gagie travis.gagie@aalto.fi