Algorithms to solve large sparse eigenvalue problems are considered. A new class of algorithms which is based on rational functions of the matrix is described. The Lanczos method, the Arnoldi method, the spectral transformation Lanczos method, and Rayleigh quotient iteration all are special cases, but there are also new algorithms which correspond to rational functions with several poles. In the simplest case a basis of a rational Krylov subspace is found in which the matrix eigenvalue problem is formulated as a linear matrix pencil with a pair of Hessenberg matrices. © 1984.
Ruhe, A. (1984). Rational Krylov sequence methods for eigenvalue computation. Linear Algebra and Its Applications, 58(C), 391–405. https://doi.org/10.1016/0024-3795(84)90221-0