Chennai Mathematical Institute


2:00 pm, Lecture Hall 5
Fast algorithms for computational statistics and elliptic partial differential equations

Sivaram Ambikasaran
Courant Institute, New York, U.S.A.


Large-dense matrices arise in numerous applications: covariance matrices in statistics, boundary integral formulation for elliptic partial differential equations, inverse problems, radial basis function interpolation, multi frontal solvers for sparse linear systems, etc. As the problem size increases, large memory requirements, scaling as O(N^2), and extensive computational time to perform matrix algebra, scaling as O(N^2) or O(N^3), make computations impractical. I will discuss some novel methods for handling these computationally intense problems. In the first half of the talk, I will discuss my contributions to some of the new developments in handling large dense covariance matrices in the context of computational statistics. More specifically, I will be discussing how fast dense linear algebra (O(N) algorithms for inversion, determinant computation, symmetric factorisation, etc.) enables us to handle large scale Gaussian processes. In the second half of the talk, I will discuss a new algorithm termed Inverse Fast Multipole Method, which permits solving singular integral equations arising out of elliptic PDE's at a computational cost of O(N).