  The evaluation of the performance of adiabatic annealers is hindered by lack
of efficient algorithms for simulating their behaviour. We exploit the
analyticity of the standard model for the adiabatic quantum process to develop
an efficient recursive method for its numerical simulation in case of both
unitary and non-unitary evolution. Numerical simulations show distinctly
different distributions for the most important figure of merit of adiabatic
quantum computing --- the success probability --- in these two cases.
