  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.
