Fast Packed String Matching for Short Patterns

TL;DR

This paper introduces fast string matching algorithms optimized for short patterns using SIMD instructions, significantly improving average-case performance despite quadratic worst-case complexity.

Contribution

It presents novel SIMD-based algorithms for short pattern string matching, leveraging packed string instructions to achieve superior average performance.

Findings

Algorithms outperform existing methods on short patterns

Significant speed-up observed in experimental results

Effective despite quadratic worst-case complexity

Abstract

Searching for all occurrences of a pattern in a text is a fundamental problem in computer science with applications in many other fields, like natural language processing, information retrieval and computational biology. In the last two decades a general trend has appeared trying to exploit the power of the word RAM model to speed-up the performances of classical string matching algorithms. In this model an algorithm operates on words of length w, grouping blocks of characters, and arithmetic and logic operations on the words take one unit of time. In this paper we use specialized word-size packed string matching instructions, based on the Intel streaming SIMD extensions (SSE) technology, to design very fast string matching algorithms in the case of short patterns. From our experimental results it turns out that, despite their quadratic worst case time complexity, the new presented algorithms become the clear winners on the average for short patterns, when compared against the most effective algorithms known in literature.