Table clearly shows the superior performance of SAS, followed by the implicit variable-step methods -ODE23s and ODE15s -and the other explicit fixed-step methods (Euler, Ralston, Heun, Runge-Kutta of 3 rd , 4 th , and 5 th order). Notably, SAS was able to integrate for all tested SRs. Also, the implicit variable step methods -ODE23s and ODE15s -stand out for solving very stiff systems, with SR = 10 ?n . ODE23s is a single-step and implicit solver based on the modified Rosenbrock formula of order 2, designed for moderately stiff ODEs. On the other hand, ODE15s is a multi-step and implicit solver based on the variableorder backward differentiation formula (BDF) method, designed for stiff ODEs and differential-algebraic system of equations.