  In this paper, we present a preconditioned variant of the generalized
successive overrelaxation (GSOR) iterative method for solving a broad class of
complex symmetric linear systems. We study conditions under which the spectral
radius of the iteration matrix of the preconditioned GSOR method is smaller
than that of the GSOR method and determine the optimal values of iteration
parameters. Numerical experiments are given to verify the validity of the
presented theoretical results and the effectiveness of the preconditioned GSOR
method.
