Author(s)

Shoji Itoh¹, Masaaki Sugihara²

¹Division of Science, School of Science and Engineering, Tokyo Denki University, Saitama, Japan.
²Department of Physics and Mathematics, College of Science and Engineering, Aoyama Gakuin University, Kanagawa, Japan.

In this paper, we propose an improved preconditioned algorithm for the conjugate gradient squared method (improved PCGS) for the solution of linear equations. Further, the logical structures underlying the formation of this preconditioned algorithm are demonstrated via a number of theorems. This improved PCGS algorithm retains some mathematical properties that are associated with the CGS derivation from the bi-conjugate gradient method under a non-preconditioned system. A series of numerical comparisons with the conventional PCGS illustrate the enhanced effectiveness of our improved scheme with a variety of preconditioners. This logical structure underlying the formation of the improved PCGS brings a spillover effect from various bi-Lanczos-type algorithms with minimal residual operations, because these algorithms were constructed by adopting the idea behind the derivation of CGS. These bi-Lanczos-type algorithms are very important because they are often adopted to solve the systems of linear equations that arise from large-scale numerical simulations.

Linear Systems, Krylov Subspace Method, Bi-Lanczos Algorithm, Preconditioned System, PCGS

Itoh, S. and Sugihara, M. (2015) Formulation of a Preconditioned Algorithm for the Conjugate Gradient Squared Method in Accordance with Its Logical Structure. Applied Mathematics, 6, 1389-1406. doi: 10.4236/am.2015.68131.