ABSTRACT
The term “preconditioning” dates back to Turing in 1948, meaning the transformation of a problem to a form that is more easily solved, cf. Golub and O’Leary [193]. The use of this term in conjunction with iterative methods can be traced back to the late 1960s and early 1970s. One important contribution to the early development of preconditioning techniques is the general exposition of the Pcg algorithm provided by Concus et al. [119] in 1976. Today, this setup is adapted to a large number of Krylov methods.
