FAST UPDATING ALGORITHMS FOR LATENT SEMANTIC INDEXING∗ EUGENE VECHARYNSKI † AND YOUSEF SAAD‡

Abstract. This paper discusses a few algorithms for updating the approximate Singular Value Decomposition (SVD) in the context of information retrieval by Latent Semantic Indexing (LSI) methods. A unifying framework is considered which is based on Rayleigh-Ritz projection methods. First, a Rayleigh-Ritz approach for the SVD is discussed and it is then used to interpret the Zha-Simon algorithms [SIAM J. Scient. Comput. vol. 21 (1999), pp. 782-791]. This viewpoint leads to a few alternatives whose goal is to reduce computational cost and storage requirement by projection techniques that utilize subspaces of much smaller dimension. Numerical experiments show that the proposed algorithms yield accuracies comparable or better than those obtained from standard ones at a much lower computational cost