Scalable Parallel Data Mining for Association Rules

One of the important problems in data mining is discovering association rules from databases of transactions where each transaction consists of a set of items. The most time consuming operation in this discovery process is the computation of the frequency of the occurrences of interesting subset of items (called candidates) in the database of transactions. To prune the exponentially large space of candidates, most existing algorithms, consider only those candidates that have a user difined minimum support. Even with the pruning, the task of finding all association rules requires a lot of computation power and time. Parallel computers offer a potential solution to the computation requirement of this task, provided efficient and scalable parallel algorithms can be designed. In this paper, we present two new parallel algorithms for mining association rules. The Intelligent Data Distribution algorithm efficiently uses aggregate memory of the parallel computer by employing intelligent candicate partitioning scheme and uses efficient communication mechanism to move data among the processors. The Hybrid Distribution algorithm further improves upon the Intelligent Data Distribution algorithm by dynamically partitioning the candidate set to maintain good load balance. The experimental results on a Cray T3D parallel computer show that the Hybrid Distribution algorithm scales linearly and exploits the aggregate memory better and can generate more association rules with a single scan of database per pass.