How a DDE compares to an ODE
Differences in how you specify the problem
A so-called initial-value problem for an ordinary differential equation (ODE) is completely determined by the equation itself:
With this information, the solvers can proceed to find the numerical solution of the ODE.
But, for a delay differential equation (DDE), the problem requires the equation:
We call these values in EJS, the pre-initial conditions.
Differences in how the solvers work
There are also differences in how the solvers proceed to step the solution of an DDE in time. In particular, one must take care in propagating correctly in time the discontinuities of the pre-initial conditions. EJS takes care of all these subtleties and requires only the minimum information that must be provided by you.