Information retrieval on an SCI-based PC cluster

This article presents an efficient parallel information retrieval (IR) system which provides fast information service for the Internet users on low-cost high-performance PC-NOW environment. The IR system is implemented on a PC cluster based on the scalable coherent interface (SCI), a powerful interconnecting mechanism for both shared memory models and message-passing models. In the IR system, the inverted-index file (IIF) is partitioned into pieces using a greedy declustering algorithm and distributed to the cluster nodes to be stored on each node's hard disk. For each incoming user's query with multiple terms, terms are sent to the corresponding nodes which contain the relevant pieces of the IIF to be evaluated in parallel. The IR system is developed using a distributed-shared memory (DSM) programming technique based on the SCI. According to the experiments, the IR system outperforms an MPI-based IR system using Fast Ethernet as an interconnect. Speed-up of up to 5.0 was obtained with an 8-node cluster in processing each query on a 500,000-document IIF.