Parallel mining of maximal sequential patterns using multiple samples
In this paper, we propose a new parallel algorithm, named PMSPX, which mines maximal frequent sequences by using multiple samples to exclude infrequent candidates effectively. A frequent sequence is maximal if none of its supersequences is frequent. Unlike the traditional single-sample methods developed for mining frequent itemsets, PMSPX uses multiple samples. Thus, it can avoid or alleviate some problems inherent in the single-sample methods. We theoretically analyzed how to increase the minimum support level to prevent misestimating infrequent candidates as frequent in the mining of samples. PMSPX is a parallel version of our sequential MSPX algorithm, and it is developed on a cluster of workstations. In PMSPX, each processing node uses MSPX to find a candidate set of local maximal frequent sequences first, independently from other processing nodes. Then, a top-down search is performed, starting with all the candidates, in a synchronous manner to identify real maximal frequent sequences. This asynchronous local mining followed by synchronous global mining approach minimizes the synchronization and communication among the processing nodes. Three database partitioning methods are proposed to distribute the database across the processing nodes, so that their workloads are balanced and the data skewness of the whole database is preserved in the data partition of each node. A comprehensive analysis was performed on PMSPX and existing parallel sequence mining algorithms, and extensive experiments were conducted on PMSPX. PMSPX demonstrates very good speedup and scaleup properties. It also requires less communication and synchronization than other parallel algorithms.
parallel mining sampling maximal frequent sequences data skewness data mining workload balance