Particles with zero mass are called test particles and they are assumed not to influence each other and the particles with nonzero mass. A modified Cowell-Stormer integrator, with modifications by W. I. Newman and his students. A symplectic mapping with Kinetic-Potential energy splitting. This is included for the sake of completeness. It can be compiled with a single command and should run on all platforms.
More information is provided in the code.
Click here for the code. Click here for a sample input file. Hierarchical Wisdom-Holman mapping. Click here for another sample input file.