3. The method of claim 1 , wherein providing the nonlinear constitutive relations comprises: identifying respective nonlinear constitutive relations of a current source and a charge source of the DUT as respective functions of the first dynamical variables and the calculated values of the second dynamical variables; and training artificial neural networks (ANNs) to learn the identified nonlinear constitutive relations of the current source and the charge source.
4. The method of claim 3 , wherein training the ANNs to learn the identified nonlinear constitutive relations of the current source and the charge source comprises: defining neural network internal parameters corresponding to the nonlinear constitutive relations of the current source and the charge source, respectively; and adjusting the neural network internal parameters to minimize an error function.