“…Simple discretizations, such as Euler's method (1.1), do not typically respect such invariants, giving approximate solutions that drift from the manifold. Invariant-preserving alternatives (see, e.g., [18,26]) generally require significantly more computation per step (though a tractable method for the unpreconditioned, Hermitian case has been proposed by Nakamura, Kajiwara, and Shiotani [28]). Our goal is to explain the relationship between convergence and stability of the continuous and discrete dynamical systems.…”