IMA Journal of Numerical Analysis Advance Access originally published online on January 22, 2008
IMA Journal of Numerical Analysis 2008 28(3):598-618; doi:10.1093/imanum/drm039
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Block preconditioning of real-valued iterative algorithms for complex linear systems

Department of Mathematics and Computer Science, Emory University, Atlanta, GA 30322, USA

Dipartimento di Matematica, Università di Roma "Tor Vergata", 00133 Roma, Italy
Corresponding author. Email: benzi{at}mathcs.emory.edu
Email: bertaccini{at}mat.uniroma2.it
Received on 16 October 2006. Revised on 7 September 2007.
| Abstract |
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We revisit real-valued preconditioned iterative methods for the solution of complex linear systems, with an emphasis on symmetric (non-Hermitian) problems. Different choices of the real equivalent formulation are discussed, as well as different types of block preconditioners for Krylov subspace methods. We argue that if either the real or the symmetric part of the coefficient matrix is positive semidefinite, block preconditioners for real equivalent formulations may be a useful alternative to preconditioners for the original complex formulation. Numerical experiments illustrating the performance of the various approaches are presented.
Key Words: complex symmetric systems; Krylov subspace methods; block preconditioners; Schur complement; Helmholtz equation