CPU time for the HO method. Left: dependence of the initialization CPU time on the particle number of a realization of the Hernquist model. The red, blue, green, and black lines are the results for the spherical, oblate, prolate, and triaxial models, respectively. The blue, green, and black lines are slightly shifted along the x-axis. Right: dependence of the subsequent CPU time on the number of the expansion coefficients. The subsequent CPU time is estimated by the forces at 10 000 positions.