Deflated Krylov subspace methods for nearly singular linear systems

This paper concerns the use of Krylov subspace methods for the solution of nearly singular nonsymmetric linear systems. We show that the incomplete orthogonalization methods (IOM) in conjunction with certain deflation techniques of Stewart, Chan, and Saad can be used to solve large nonsymmetric linear systems which are nearly singular.This work was supported by the National Science Foundation, Grants DMS-8403148 and DCR-81-16779, and by the Office of Naval Research, Contract N00014-85-K-0725.