Conjugate gradient type methods are discussed for unsymmetric and inconsistent system of equations. For unsymmetric problems, besides conjugate gradient methods based on the normal equations, we also present a (modified) minimal residual (least square) method, which converges for systems with matrices that have a positive definite symmetric part. For inconsistent problems, for completeness we discuss briefly various (well-known) versions of the conjugate gradient method. Preconditioning and rate of convergence are also discussed. © 1980.
Axelsson, O. (1980). Conjugate gradient type methods for unsymmetric and inconsistent systems of linear equations. Linear Algebra and Its Applications, 29(C), 1–16. https://doi.org/10.1016/0024-3795(80)90226-8