FQMR: A Flexible Quasi-Minimal Residual Method with Inexact Preconditioning
FQMR: A Flexible Quasi-Minimal Residual Method with Inexact Preconditioning
A flexible version of the QMR algorithm is presented which allows for the use of a different preconditioner at each step of the algorithm. In particular, inexact solutions of the preconditioned equations are allowed, as well as the use of an (inner) iterative method as a preconditioner. Several theorems are …