Descriptions: A problem is said to be stiff if the solution being sought varies slowly, but there are nearby solutions that vary rapidly, so the numerical method must take small steps to obtain satisfactory results. The flame model demonstrates stiffness. ODE solvers with names ending in “s”, such as ODE23s and ODE15s, employ implicit methods and are intended for stiff problems. These methods require more work per step, but take many fewer steps.
Instructor: Cleve Moler