Symplectic numerical methods in dynamics of nonlinear waves

The symplectic integrator of the Gauss-Legendre type is tested on the nonlinear Schrodinger equation. Preservation of high integrals (up to 10 or more) and quasiperiodic motion have been detected for dynamics on both stable soliton and homoclinic manifolds, which indicate applicability of symplectic integrators for adequate simulation of integrable equation. The tested integrator is applied to the problem of long-time stability of the solitons in higher-derivative nonlinear Schrodinger equation. The slow logarithmic-type depletion of the soliton amplitude with time has been detected.