功显示。）
2.3 numerical method
we utilize a second-order wisdom–holman symplectic map as our main integration method (wisdom & holman 1991; kinoshita， yoshida & nakai 1991) with a special start-up procedure to reduce the uncation error of angle variables，‘warm start’(saha & tremaine 1992， 1994).
the stepsize for the numerical integrations is 8 d throughout all integrations of the nine planets (n±1，2，3)， which is about 1/11 of the orbital perio