In this paper, we propose a fast convergence parallel iteration proces
s for solving a low-order implicit Runge-Kutta-Nystrom method. The res
ulting scheme can be regarded as a parallel singly diagonally implicit
Runge-Kutta-Nystrom (PDIRKN) method. On a two-processor computer, thi
s parallel method requires effectively two sequential implicit stages
per step. By numerical experiments applied to initial-boundary-value p
roblems for semi-discrete pai tial differential equations (PDEs), we c
ompare this method with some sequential DIRKN methods from the literat
ure, and show its efficiency in a low-accuracy range which is realisti
c for these problems.