  We investigate the robustness of the discovery of the perfect fluid through
comparison of hydrodynamic calculations with the elliptic flow coefficient v_2
at midrapidity in Au+Au collisions at sqrt{s_{NN}}=200 GeV. Employing the
Glauber model for initial entropy density distributions, the centrality
dependence of v_2 is reasonably reproduced by using an ideal fluid description
of the early QGP stage followed by a hadronic cascade in the late hadronic
stage. On the other hand, initial conditions based on the Colour Glass
Condensate model are found to generate larger elliptic flow due to larger
initial eccentricity epsilon. We further predict v_2/epsilon at a fixed impact
parameter as a function of collision energy sqrt{s_{NN}} up to the LHC energy.
