org.apache.commons.math3.ode

## Class ContinuousOutputModel

- java.lang.Object
- - org.apache.commons.math3.ode.ContinuousOutputModel

- All Implemented Interfaces:
    Serializable, StepHandler

      public class ContinuousOutputModel
      extends Object
      implements StepHandler, 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 `setInterpolatedTime` and `getInterpolatedState` to retrieve this information at any time. It is important to wait for the integration to be over before attempting to call `setInterpolatedTime` 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 ContinuousOutputModel 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 ContinuousOutputModel 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`).

  Since:
    1.2
  Version:
    $Id: ContinuousOutputModel.java 1416643 2012-12-03 19:37:14Z tn $
  See Also:
    `StepHandler`, `StepInterpolator`, Serialized Form

- - ### Field Summary

    Fields
    Modifier and Type | Field and Description
    --- | ---
    `private double` | `finalTime` Final integration time.
    `private boolean` | `forward` Integration direction indicator.
    `private int` | `index` Current interpolator index.
    `private double` | `initialTime` Initial integration time.
    `private static long` | `serialVersionUID` Serializable version identifier
    `private List<StepInterpolator>` | `steps` Steps table.

  - ### Constructor Summary

    Constructors
    Constructor and Description
    `ContinuousOutputModel()` Simple constructor.

  - ### Method Summary

    Methods
    Modifier and Type | Method and Description
    --- | ---
    `void` | `append(ContinuousOutputModel model)` Append another model at the end of the instance.
    `double` | `getFinalTime()` Get the final integration time.
    `double` | `getInitialTime()` Get the initial integration time.
    `double[]` | `getInterpolatedState()` Get the state vector of the interpolated point.
    `double` | `getInterpolatedTime()` Get the time of the interpolated point.
    `void` | `handleStep(StepInterpolator interpolator, boolean isLast)` Handle the last accepted step.
    `void` | `init(double t0, double[] y0, double t)` Initialize step handler at the start of an ODE integration.
    `private int` | `locatePoint(double time, StepInterpolator interval)` Compare a step interval and a double.
    `void` | `setInterpolatedTime(double time)` Set the time of the interpolated point.

    - ### Methods inherited from class java.lang.Object

      `clone, equals, finalize, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait`

- - ### Field Detail

    - #### serialVersionUID

          private static final long serialVersionUID

      Serializable version identifier
      See Also:
        Constant Field Values

    - #### initialTime

          private double initialTime

      Initial integration time.

    - #### finalTime

          private double finalTime

      Final integration time.

    - #### forward

          private boolean forward

      Integration direction indicator.

    - #### index

          private int index

      Current interpolator index.

    - #### steps

          private List<StepInterpolator> steps

      Steps table.

  - ### Constructor Detail

    - #### ContinuousOutputModel

          public ContinuousOutputModel()

      Simple constructor. Build an empty continuous output model.

  - ### Method Detail

    - #### append

          public void append(ContinuousOutputModel model)
                      throws MathIllegalArgumentException,
                             MaxCountExceededException

      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)
        `MaxCountExceededException` - if the number of functions evaluations is exceeded during step finalization

    - #### init

          public void init(double t0,
                  double[] y0,
                  double t)

      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.

      Specified by:
        `init` in interface `StepHandler`
      Parameters:
        `t0` - start value of the independent time variable
        `y0` - array containing the start value of the state vector
        `t` - target time for the integration

    - #### handleStep

          public void handleStep(StepInterpolator interpolator,
                        boolean isLast)
                          throws MaxCountExceededException

      Handle the last accepted step. A copy of the information provided by the last step is stored in the instance for later use.
      Specified by:
        `handleStep` in interface `StepHandler`
      Parameters:
        `interpolator` - interpolator for the last accepted step.
        `isLast` - true if the step is the last one
      Throws:
        `MaxCountExceededException` - if the number of functions evaluations is exceeded during step finalization

    - #### 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

    - #### getInterpolatedTime

          public double getInterpolatedTime()

      Get the time of the interpolated point. If `setInterpolatedTime(double)` has not been called, it returns the final integration time.
      Returns:
        interpolation point time

    - #### setInterpolatedTime

          public void setInterpolatedTime(double time)

      Set the time of the interpolated point.

      This method should not be called before the integration is over because some internal variables are set only once the last step has been handled.

      Setting the time outside of the integration interval is now allowed (it was not allowed up to version 5.9 of Mantissa), but should be used with care since the accuracy of the interpolator will probably be very poor far from this interval. This allowance has been added to simplify implementation of search algorithms near the interval endpoints.

      Parameters:
        `time` - time of the interpolated point

    - #### getInterpolatedState

          public double[] getInterpolatedState()
                                        throws MaxCountExceededException

      Get the state vector of the interpolated point.
      Returns:
        state vector at time `getInterpolatedTime()`
      Throws:
        `MaxCountExceededException` - if the number of functions evaluations is exceeded

    - #### locatePoint

          private int locatePoint(double time,
                        StepInterpolator interval)

      Compare a step interval and a double.
      Parameters:
        `time` - point to locate
        `interval` - step interval
      Returns:
        -1 if the double is before the interval, 0 if it is in the interval, and +1 if it is after the interval, according to the interval direction

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