VPNBody: Integration Methods
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The following integration methods are available in VPNBody. The table provides the common name of the method, along the keyword you need in the input file (as the argument to the METHOD keyword) to invoke that method.
| Method | Keyword | Symplectic? | Order |
| Euler | EULER | No | 1st |
| Euler-Cromer | EULER_CROMER | Yes | 2nd |
| Runge-Kutta | RK4 | No | 4th |
| Verlet (leapfrog) | VERLET | Yes | 2nd |
| Yoshida Composition | YOSHIDA_4 | Yes | 4th |
| Yoshida Composition | YOSHIDA_6 | Yes | 6th |
| Yoshida Composition | YOSHIDA_8 | Yes | 8th |
| Ruth | RUTH | Yes | 3rd |
| Forest-Ruth | FOREST_RUTH | Yes | 4th |
| Position-extended Forest Ruth | PEFRL | Yes | 4th |
| Candy-Rozmus | CANDY_ROZMUS | Yes | 4th |
| Optimized Candy-Rozmus (McLachlan and Atela) | CRO | Yes | 4th |
| Chin-Chen Forward Integrator* | CHIN_CHEN | Yes | 4th |
| Gauss' f and g functions | KEPLER | ** | ** |
*The Chin-Chen forward symplectic integrator produces larger than expected relative energy errors. There is probably a bug in the code, but I can't track it down. Please contact me if you find it.
**Gauss' method advances each particle along its keplerian orbit, ignoring the pairwise interactions (i.e., the orbits do not evolve).