Symplectic integrators

In DifferentialEquations do the symplectic integrators require separable Hamiltonians? I’ve tried using a couple algorithms like Yoshida6 or KahanLi6 with a non-separable system and haven’t gotten good results when comparing them to just integrating the equations of motion from Hamilton’s equations.

They don’t necessarily require separable, but there are limitations mentioned in:

http://docs.juliadiffeq.org/latest/solvers/dynamical_solve.html#Dynamical,-Hamiltonian,-and-2nd-Order-ODE-Solvers-1

FWIW, symplectic integrators only have an advantage in long time integrations.

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Got it, thanks for pointing out those limitations.