[PAST EVENT] Mathematics Colloquium - Ren-Cang Li (Univ of Texas - Arlington)

March 22, 2024
2pm - 3pm
Jones Hall, Room 302
200 Ukrop Way
Williamsburg, VA 23185Map this location
Access & Features
  • Free food
  • Open to the public
Jones Hall

Title: Optimizing Convex Compositions of Matrix Traces on the Stiefel Manifold

Abstract: The NEPv approach has been increasingly used lately for optimization on the Stiefel manifold arising from machine learning. General speaking, the approach first turns the first order optimality condition, also known as the KKT condition, into a nonlinear eigenvalue problem with eigenvector dependency (NEPv) or a nonlinear polar decomposition problem with orthogonal factor dependency (NPDo) and then solve the nonlinear problem via some variations of the self-consistent-field (SCF) iteration. The difficulty, however, lies in designing a proper SCF iteration so that a maximizer is found at the end. Currently, each use of the approach is very much individualized, especially in its convergence analysis to show that the approach does work or otherwise. In this talk, a unifying framework is established. The framework is built upon some basic assumptions. If the basic assumptions are satisfied, globally convergence is guaranteed to a stationary point and during the SCF iterative process that leads to the stationary point, the objective function increases monotonically. Also a notion of atomic functions is proposed, which include commonly used matrix traces of linear and quadratic forms as special ones. It is shown that the basic assumptions are satisfied by atomic functions and by convex compositions of atomic functions. Together they provide a large collection of objectives for which the NEPv approach is guaranteed to work.

Sponsored by: Mathematics


Chi-Kwong Li