Subject: Hermitian and skew-Hermitian Solvers and Preconditioners: Application to Symmetric and Indefinite Problems
treated by: Lilya Ghazaryan
Supervisor: O.Univ.-Prof. Dr. Dipl.-Ing. Ulrich Langer
sketch of FETI methods

The aim of the master thesis is to apply the Hermitian and skew-Hermitian (HSS) iterative method and its inexact version to the solution of linear algebraic systems, arising in different applications, with symmetric, but indefinite system matrices. In particular, we consider saddle-point problems coming from a reformulation of the well-known domain decomposition Finite Element Tearing and Interconnecting method as a saddle-point problem with both primal and dual variables as unknowns. This is an alternative, hopefully better, approach to the existing methods, namely block-structured preconditioners combined with suitable Krylov subspace methods or Schur-complement conjugate gradient methods. The convergence of HSS method is studied numerically. The numerical experiments show that the use of the HSS method as a preconditioner in a Krylov subspace method is very efficient.

spectrum of the iteration matrix for optimal value of alpha
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