Abstract
Recently, as a robust precondition of the CG method, RIC, RIC2S decompositions have been remarked and often used in a variety of analytic field. These decompositions outperform in both robustness and convergence rate of the CG method. The robustness causes increase of computation cost in the con-struction of preconditioner matrix and the number of parameters to be adjusted. In this paper, a concept of safety constant is introduced into the RIC2S decomposition. Through numerical experiments, we make clear relationship between test matrices and safety constant used in the revised RIC2S decomposition.
