org.apache.commons.math3.ode.sampling

## Class StepNormalizer

- java.lang.Object
- - org.apache.commons.math3.ode.sampling.StepNormalizer

- All Implemented Interfaces:
    StepHandler

      public class StepNormalizer
      extends Object
      implements StepHandler

  This class wraps an object implementing `FixedStepHandler` into a `StepHandler`.

  This wrapper allows to use fixed step handlers with general integrators which cannot guaranty their integration steps will remain constant and therefore only accept general step handlers.

  The stepsize used is selected at construction time. The `handleStep` method of the underlying `FixedStepHandler` object is called at normalized times. The normalized times can be influenced by the `StepNormalizerMode` and `StepNormalizerBounds`.

  There is no constraint on the integrator, it can use any time step it needs (time steps longer or shorter than the fixed time step and non-integer ratios are all allowed).

  Examples (step size = 0.5)
  Start time | End time | Direction | `Mode` | `Bounds` | Output
  0.3 | 3.1 | forward | `INCREMENT` | `NEITHER` | 0.8, 1.3, 1.8, 2.3, 2.8
  0.3 | 3.1 | forward | `INCREMENT` | `FIRST` | 0.3, 0.8, 1.3, 1.8, 2.3, 2.8
  0.3 | 3.1 | forward | `INCREMENT` | `LAST` | 0.8, 1.3, 1.8, 2.3, 2.8, 3.1
  0.3 | 3.1 | forward | `INCREMENT` | `BOTH` | 0.3, 0.8, 1.3, 1.8, 2.3, 2.8, 3.1
  0.3 | 3.1 | forward | `MULTIPLES` | `NEITHER` | 0.5, 1.0, 1.5, 2.0, 2.5, 3.0
  0.3 | 3.1 | forward | `MULTIPLES` | `FIRST` | 0.3, 0.5, 1.0, 1.5, 2.0, 2.5, 3.0
  0.3 | 3.1 | forward | `MULTIPLES` | `LAST` | 0.5, 1.0, 1.5, 2.0, 2.5, 3.0, 3.1
  0.3 | 3.1 | forward | `MULTIPLES` | `BOTH` | 0.3, 0.5, 1.0, 1.5, 2.0, 2.5, 3.0, 3.1
  0.0 | 3.0 | forward | `INCREMENT` | `NEITHER` | 0.5, 1.0, 1.5, 2.0, 2.5, 3.0
  0.0 | 3.0 | forward | `INCREMENT` | `FIRST` | 0.0, 0.5, 1.0, 1.5, 2.0, 2.5, 3.0
  0.0 | 3.0 | forward | `INCREMENT` | `LAST` | 0.5, 1.0, 1.5, 2.0, 2.5, 3.0
  0.0 | 3.0 | forward | `INCREMENT` | `BOTH` | 0.0, 0.5, 1.0, 1.5, 2.0, 2.5, 3.0
  0.0 | 3.0 | forward | `MULTIPLES` | `NEITHER` | 0.5, 1.0, 1.5, 2.0, 2.5, 3.0
  0.0 | 3.0 | forward | `MULTIPLES` | `FIRST` | 0.0, 0.5, 1.0, 1.5, 2.0, 2.5, 3.0
  0.0 | 3.0 | forward | `MULTIPLES` | `LAST` | 0.5, 1.0, 1.5, 2.0, 2.5, 3.0
  0.0 | 3.0 | forward | `MULTIPLES` | `BOTH` | 0.0, 0.5, 1.0, 1.5, 2.0, 2.5, 3.0
  3.1 | 0.3 | backward | `INCREMENT` | `NEITHER` | 2.6, 2.1, 1.6, 1.1, 0.6
  3.1 | 0.3 | backward | `INCREMENT` | `FIRST` | 3.1, 2.6, 2.1, 1.6, 1.1, 0.6
  3.1 | 0.3 | backward | `INCREMENT` | `LAST` | 2.6, 2.1, 1.6, 1.1, 0.6, 0.3
  3.1 | 0.3 | backward | `INCREMENT` | `BOTH` | 3.1, 2.6, 2.1, 1.6, 1.1, 0.6, 0.3
  3.1 | 0.3 | backward | `MULTIPLES` | `NEITHER` | 3.0, 2.5, 2.0, 1.5, 1.0, 0.5
  3.1 | 0.3 | backward | `MULTIPLES` | `FIRST` | 3.1, 3.0, 2.5, 2.0, 1.5, 1.0, 0.5
  3.1 | 0.3 | backward | `MULTIPLES` | `LAST` | 3.0, 2.5, 2.0, 1.5, 1.0, 0.5, 0.3
  3.1 | 0.3 | backward | `MULTIPLES` | `BOTH` | 3.1, 3.0, 2.5, 2.0, 1.5, 1.0, 0.5, 0.3
  3.0 | 0.0 | backward | `INCREMENT` | `NEITHER` | 2.5, 2.0, 1.5, 1.0, 0.5, 0.0
  3.0 | 0.0 | backward | `INCREMENT` | `FIRST` | 3.0, 2.5, 2.0, 1.5, 1.0, 0.5, 0.0
  3.0 | 0.0 | backward | `INCREMENT` | `LAST` | 2.5, 2.0, 1.5, 1.0, 0.5, 0.0
  3.0 | 0.0 | backward | `INCREMENT` | `BOTH` | 3.0, 2.5, 2.0, 1.5, 1.0, 0.5, 0.0
  3.0 | 0.0 | backward | `MULTIPLES` | `NEITHER` | 2.5, 2.0, 1.5, 1.0, 0.5, 0.0
  3.0 | 0.0 | backward | `MULTIPLES` | `FIRST` | 3.0, 2.5, 2.0, 1.5, 1.0, 0.5, 0.0
  3.0 | 0.0 | backward | `MULTIPLES` | `LAST` | 2.5, 2.0, 1.5, 1.0, 0.5, 0.0
  3.0 | 0.0 | backward | `MULTIPLES` | `BOTH` | 3.0, 2.5, 2.0, 1.5, 1.0, 0.5, 0.0

  Since:
    1.2
  See Also:
    `StepHandler`, `FixedStepHandler`, `StepNormalizerMode`, `StepNormalizerBounds`

- - ### Constructor Summary

    Constructors
    Constructor and Description
    `StepNormalizer(double h, FixedStepHandler handler)` Simple constructor.
    `StepNormalizer(double h, FixedStepHandler handler, StepNormalizerBounds bounds)` Simple constructor.
    `StepNormalizer(double h, FixedStepHandler handler, StepNormalizerMode mode)` Simple constructor.
    `StepNormalizer(double h, FixedStepHandler handler, StepNormalizerMode mode, StepNormalizerBounds bounds)` Simple constructor.

  - ### Method Summary

    Methods
    Modifier and Type | Method and Description
    --- | ---
    `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.

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

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

- - ### Constructor Detail

    - #### StepNormalizer

          public StepNormalizer(double h,
                        FixedStepHandler handler)

      Simple constructor. Uses `INCREMENT` mode, and `FIRST` bounds setting, for backwards compatibility.
      Parameters:
        `h` - fixed time step (sign is not used)
        `handler` - fixed time step handler to wrap

    - #### StepNormalizer

          public StepNormalizer(double h,
                        FixedStepHandler handler,
                        StepNormalizerMode mode)

      Simple constructor. Uses `FIRST` bounds setting.
      Parameters:
        `h` - fixed time step (sign is not used)
        `handler` - fixed time step handler to wrap
        `mode` - step normalizer mode to use
      Since:
        3.0

    - #### StepNormalizer

          public StepNormalizer(double h,
                        FixedStepHandler handler,
                        StepNormalizerBounds bounds)

      Simple constructor. Uses `INCREMENT` mode.
      Parameters:
        `h` - fixed time step (sign is not used)
        `handler` - fixed time step handler to wrap
        `bounds` - step normalizer bounds setting to use
      Since:
        3.0

    - #### StepNormalizer

          public StepNormalizer(double h,
                        FixedStepHandler handler,
                        StepNormalizerMode mode,
                        StepNormalizerBounds bounds)

      Simple constructor.
      Parameters:
        `h` - fixed time step (sign is not used)
        `handler` - fixed time step handler to wrap
        `mode` - step normalizer mode to use
        `bounds` - step normalizer bounds setting to use
      Since:
        3.0

  - ### Method Detail

    - #### 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
      Specified by:
        `handleStep` in interface `StepHandler`
      Parameters:
        `interpolator` - interpolator for the last accepted step. For efficiency purposes, the various integrators reuse the same object on each call, so if the instance wants to keep it across all calls (for example to provide at the end of the integration a continuous model valid throughout the integration range), it should build a local copy using the clone method and store this copy.
        `isLast` - true if the step is the last one
      Throws:
        `MaxCountExceededException` - if the interpolator throws one because the number of functions evaluations is exceeded

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