Subspace sampling and relative-error matrix approximation: column-row-based methods

  • Authors:
  • Petros Drineas;Michael W. Mahoney;S. Muthukrishnan

  • Affiliations:
  • Department of Computer Science, RPI;Yahoo Research Labs;Department of Computer Science, Rutgers University

  • Venue:
  • ESA'06 Proceedings of the 14th conference on Annual European Symposium - Volume 14
  • Year:
  • 2006

Quantified Score

Hi-index 0.00

Visualization

Abstract

Much recent work in the theoretical computer science, linear algebra, and machine learning has considered matrix decompositions of the following form: given an m × n matrix A, decompose it as a product of three matrices, C, U, and R, where C consists of a small number of columns of A, R consists of a small number of rows of A, and U is a small carefully constructed matrix that guarantees that the product CUR is "close" to A. Applications of such decompositions include the computation of matrix "sketches", speeding up kernel-based statistical learning, preserving sparsity in low-rank matrix representation, and improved interpretability of data analysis methods. Our main result is a randomized, polynomial algorithm which, given as input an m × n matrix A, returns as output matrices C, U, R such that ||A-CUR||F ≤ (1+ε)|| A-Ak||F with probability at least 1-δ. Here, Ak is the "best" rank-k approximation (provided by truncating the Singular Value Decomposition of A), and ||X||F is the Frobenius norm of the matrix X. The number of columns in C and rows in R is a low-degree polynomial in k, 1/ε, and log(1/δ). Our main result is obtained by an extension of our recent relative error approximation algorithm for l2 regression from overconstrained problems to general l2 regression problems. Our algorithm is simple, and it takes time of the order of the time needed to compute the top k right singular vectors of A. In addition, it samples the columns and rows of A via the method of "subspace sampling," so-named since the sampling probabilities depend on the lengths of the rows of the top singular vectors, and since they ensure that we capture entirely a certain subspace of interest.