  Fast ion instability has been observed in the early commissioning and
operation of the Shanghai Synchrotron Radiation Facility (SSRF) storage ring.
In this paper, a weak-strong code is used to simulate the fast ion instability
in SSRF storage ring. Various fill patterns and gas pressures are investigated.
The results show that the mini-train fill patterns are very effective to
suppress the growth of the fast ion instability.
