Package org.hipparchus.ode

Class DenseOutputModel

java.lang.Object
org.hipparchus.ode.DenseOutputModel
All Implemented Interfaces:
Serializable, ODEStepHandler
public class DenseOutputModel extends Object implements ODEStepHandler, Serializable
This class stores all information provided by an ODE integrator during the integration process and build a continuous model of the solution from this.

This class act as a step handler from the integrator point of view. It is called iteratively during the integration process and stores a copy of all steps information in a sorted collection for later use. Once the integration process is over, the user can use the getInterpolatedState method to retrieve this information at any time. It is important to wait for the integration to be over before attempting to call getInterpolatedState because some internal variables are set only once the last step has been handled.

This is useful for example if the main loop of the user application should remain independent from the integration process or if one needs to mimic the behaviour of an analytical model despite a numerical model is used (i.e. one needs the ability to get the model value at any time or to navigate through the data).

If problem modeling is done with several separate integration phases for contiguous intervals, the same DenseOutputModel can be used as step handler for all integration phases as long as they are performed in order and in the same direction. As an example, one can extrapolate the trajectory of a satellite with one model (i.e. one set of differential equations) up to the beginning of a maneuver, use another more complex model including thrusters modeling and accurate attitude control during the maneuver, and revert to the first model after the end of the maneuver. If the same continuous output model handles the steps of all integration phases, the user do not need to bother when the maneuver begins or ends, he has all the data available in a transparent manner.

An important feature of this class is that it implements the Serializable interface. This means that the result of an integration can be serialized and reused later (if stored into a persistent medium like a filesystem or a database) or elsewhere (if sent to another application). Only the result of the integration is stored, there is no reference to the integrated problem by itself.

One should be aware that the amount of data stored in a DenseOutputModel instance can be important if the state vector is large, if the integration interval is long or if the steps are small (which can result from small tolerance settings in adaptive step size integrators).

See Also:

  • Constructor Details

    • DenseOutputModel

      public DenseOutputModel()
      Simple constructor. Build an empty continuous output model.

  • Method Details

    • append

      public void append(DenseOutputModel model) throws MathIllegalArgumentException, MathIllegalStateException
      Append another model at the end of the instance.
      Parameters:
      model - model to add at the end of the instance
      Throws:
      MathIllegalArgumentException - if the model to append is not compatible with the instance (dimension of the state vector, propagation direction, hole between the dates)
      MathIllegalStateException - if the number of functions evaluations is exceeded during step finalization

    • init

      public void init(ODEStateAndDerivative initialState, double targetTime)
      Initialize step 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 handler to initialize some internal data if needed.

      The default implementation does nothing

      Specified by:
      init in interface ODEStepHandler
      Parameters:
      initialState - initial time, state vector and derivative
      targetTime - target time for the integration

    • handleStep

      public void handleStep(ODEStateInterpolator interpolator)
      Handle the last accepted step.
      Specified by:
      handleStep in interface ODEStepHandler
      Parameters:
      interpolator - interpolator for the last accepted step

    • finish

      public void finish(ODEStateAndDerivative finalState)
      Finalize integration.
      Specified by:
      finish in interface ODEStepHandler
      Parameters:
      finalState - state at integration end

    • getInitialTime

      public double getInitialTime()
      Get the initial integration time.
      Returns:
      initial integration time

    • getFinalTime

      public double getFinalTime()
      Get the final integration time.
      Returns:
      final integration time

    • getInterpolatedState

      public ODEStateAndDerivative getInterpolatedState(double time)
      Get the state at interpolated time.
      Parameters:
      time - time of the interpolated point
      Returns:
      state at interpolated time