Title:Fast matrix rank algorithms and applications
Abstract: We consider the problem of computing the rank of an mxn matrix A over a field. We present a randomized algorithm to find a set of r =rank(A) linearly independent columns in O(|A| + r^w) field operations, where |A| denotes the number of nonzero entries in A and w < 2.38 is the matrix multiplication exponent. Previously the best known algorithm to find a set of r linearly independent columns is by Gaussian elimination, with running time O(mnr^{w-2}). Our algorithm is considerably faster when r <<max{m,n}, for instance when the matrix is rectangular. We also consider the problem of computing the rank of a matrix dynamically, supporting the operations of rank one updates and additions and deletions of rows and columns. We present an algorithm that updates the rank in O(mn) field operations. We show that these algorithms can be used to obtain faster algorithms for various problems in numerical linear algebra, combinatorial optimization and dynamic data structure.

Joint work with Ho Yee Chung and Tsz Chiu Kwok.