Package org.hipparchus.ode.events

Interface ODEStepEndHandler

  • public interface ODEStepEndHandler
    This interface represents a handler for discrete events triggered during ODE integration at each step end.
    Since:
    3.0
    See Also:
    org.hipparchus.ode.events

    • Method Detail

      • init

        default void init​(ODEStateAndDerivative initialState,
                  double finalTime)
        Initialize step end handler at the start of an ODE integration.

        This method is called once at the start of the integration. It may be used by the step end handler to initialize some internal data if needed.

        The default implementation does nothing

        Parameters:
        initialState - initial time, state vector and derivative
        finalTime - target time for the integration

      • stepEndOccurred

        Action stepEndOccurred​(ODEStateAndDerivative state,
                       boolean forward)
        Handle an event and choose what to do next.

        This method is called when the integrator has accepted a step ending exactly on step end, just after the step handler itself is called (see below for scheduling). It allows the user to update his internal data to acknowledge the fact the event has been handled (for example setting a flag in the differential equations to switch the derivatives computation in case of discontinuity), or to direct the integrator to either stop or continue integration, possibly with a reset state or derivatives.

        • if Action.STOP is returned, the integration will be stopped,
        • if Action.RESET_STATE is returned, the resetState method will be called once the step handler has finished its task, and the integrator will also recompute the derivatives,
        • if Action.RESET_DERIVATIVES is returned, the integrator will recompute the derivatives,
        • if Action.RESET_EVENTS is returned, the integrator will recheck all event handlers,
        • if Action.CONTINUE is returned, no specific action will be taken (apart from having called this method) and integration will continue.

        The scheduling between this method and the ODEStepHandler method handleStep(interpolator) is to call handleStep first and this method afterwards. This scheduling allows user code called by this method and user code called by step handlers to get values of the independent time variable consistent with integration direction.

        Parameters:
        state - current value of the independent time variable, state vector and derivative at step end
        forward - if true, propagation is forward
        Returns:
        indication of what the integrator should do next, this value must be one of Action.STOP, Action.RESET_STATE, Action.RESET_DERIVATIVES, Action.RESET_EVENTS, or Action.CONTINUE

      • resetState

        default ODEState resetState​(ODEStateAndDerivative state)
        Reset the state prior to continue the integration.

        This method is called after the step handler has returned and before the next step is started, but only when ODEEventHandler.eventOccurred(ODEStateAndDerivative, ODEEventDetector, boolean) has itself returned the Action.RESET_STATE indicator. It allows the user to reset the state vector for the next step, without perturbing the step handler of the finishing step.

        The default implementation returns its argument.

        Parameters:
        state - current value of the independent time variable, state vector and derivative at step end
        Returns:
        reset state (note that it does not include the derivatives, they will be added automatically by the integrator afterwards)