  Theoretical estimates for the cutoff errors in the Ewald summation method for
dipolar systems are derived. Absolute errors in the total energy, forces and
torques, both for the real and reciprocal space parts, are considered. The
applicability of the estimates is tested and confirmed in several numerical
examples. We demonstrate that these estimates can be used easily in determining
the optimal parameters of the dipolar Ewald summation in the sense that they
minimize the computation time for a predefined, user set, accuracy.
