27th Conference of the International Linear Algebra Society (ILAS 2026)

A BFBt Preconditioner for Double Saddle-Point Systems

May 19, 2026, 11:00 AM

25m

McBryde Hall 129 (Virginia Tech)

Minisymposium Talk Advanced Acceleration and Convergence Techniques for Solving Linear and Nonlinear Systems Advanced Acceleration and Convergence Techniques for Solving Linear and Nonlinear Systems

Speaker

Chen Greif (The Department of Computer Science)

Description

We consider nonsymmetric double saddle-point systems. Given the 3-by-3 block structure of the matrix, the associated block LU decomposition features two Schur complements. A theoretical question we explore is what happens when one of the Schur complements is inverted exactly and the second, nested one, is approximated. Eigenvalue analysis sheds some light on the effect of this type of inexactness on the speed of convergence of minimum residual iterative solvers. Specific analytical and computational observations are made for the case where the nested Schur complement is approximated using the BFBt method.