gFCT: A 2D-FCT code for solving bounded continuity equations with gravity

A modification ot the FCT time-splitting algorithm of Boris and Book is presented that takes into account gravitational effects. The modifications concern: (a) a 5 point guard for fine extrapolation of the gravitational force into the ghost cells: (b) a storage rearrangement that saves computational time and message-passing time. The code runs in both serial and parallel mode using MPI. Parallel scaling falls 7% short of the theoretical linear scaling using MPICH-2 with 10/100 Ethernet cards.