Large linear systems of saddle point type arise in a wide variety of applications throughout
computational science and engineering. Due to their indefiniteness and often poor spectral …

Preconditioners are often conceived as approximate inverses. For nonsingular indefinite
matrices of saddle-point (or KKT) form, we show how preconditioners incorporating an exact …

We provide a general framework for the understanding of inexact Krylov subspace methods
for the solution of symmetric and nonsymmetric linear systems of equations, as well as for …

Iterative methods are currently the solvers of choice for large sparse linear systems of
equations. However, it is well known that the key factor for accelerating, or even allowing for …

We consider 2× 2 block indefinite linear systems whose (2, 2) block is zero. Such systems
arise in many applications. We discuss two techniques that are based on modifying the (1, 1) …

We are interested in the numerical solution of large structured indefinite symmetric linear
systems arising in mixed finite element approximations of the magnetostatic problem; in …

Mixed finite element formulations give rise to large, sparse, block linear systems of
equations, the solution of which is often sought via a preconditioned iterative technique. In …

The solution of quadratic or locally quadratic extremum problems subject to linear (ized)
constraints gives rise to linear systems in saddle point form. This is true whether in the …

In this paper we analyze the null-space projection (constraint) indefinite preconditioner
applied to the solution of large-scale saddle point problems. Nonsymmetric Krylov subspace …

The conventional electric field integral equation (EFIE) is augmented by including charge as
the extra unknown, so that the contributions of the vector potential and the scalar potential …