This special issue of Data Mining and Knowledge Discovery addresses the issue of scaling data mining algorithms, applications and systems to massive data sets by applying high performance computing technology. With the commoditization of high performance computing using clusters of workstations and related technologies, it is becoming more and more common to have the necessary infrastructure for high performance data mining. On the other hand, many of the commonly used data mining algorithms do not scale to large data sets. Two fundamental challenges are: to develop scalable versions of the commonly used data mining algorithms and to develop new algorithms for mining very large data sets. In other words, today it is easy to spin a terabyte of disk, but difficult to analyze and mine a terabyte of data.
Developing algorithms which scale takes time. As an example, consider the successful scale up and parallelization of linear algebra algorithms during the past two decades. This success was due to several factors, including: a) developing versions of some standard algorithms which exploit the specialized structure of some linear systems, such as blockstructured systems, symmetric systems, or Toeplitz systems; b) developing new algorithms such as the Wierderman and Lancos algorithms for solving sparse systems; and c) developing software tools providing high performance implementations of linear algebra primitives, such as Linpack, LA Pack, and PVM.
In some sense, the state of the art for scalable and high performance algorithms for data mining is in the same position that linear algebra was in two decades ago. We suspect that strategies a)–c) will work in data mining also.
High performance data mining is still a very new subject with challenges. Roughly speaking, some data mining algorithms can be characterised as a heuristic search process involving many scans of the data. Thus, irregularity in computation, large numbers of data access, and non-deterministic search strategies make efficient parallelization of a data mining algorithms a difficult task. Research in this area will not only contribute to large scale data mining applications but also enrich high performance computing technology itself. This was part of the motivation for this special issue.