org.apache.commons.math3.ode

## Class AbstractFieldIntegrator<T extends RealFieldElement<T>>

- java.lang.Object
- - org.apache.commons.math3.ode.AbstractFieldIntegrator<T>

- Type Parameters:
    `T` - the type of the field elements
  All Implemented Interfaces:
    FirstOrderFieldIntegrator<T>
  Direct Known Subclasses:
    AdaptiveStepsizeFieldIntegrator, RungeKuttaFieldIntegrator

      public abstract class AbstractFieldIntegrator<T extends RealFieldElement<T>>
      extends Object
      implements FirstOrderFieldIntegrator<T>

  Base class managing common boilerplate for all integrators.
  Since:
    3.6

- - ### Constructor Summary

    Constructors
    Modifier | Constructor and Description
    --- | ---
    `protected` | `AbstractFieldIntegrator(Field<T> field, String name)` Build an instance.

  - ### Method Summary

    Methods
    Modifier and Type | Method and Description
    --- | ---
    `protected FieldODEStateAndDerivative<T>` | `acceptStep(AbstractFieldStepInterpolator<T> interpolator, T tEnd)` Accept a step, triggering events and step handlers.
    `void` | `addEventHandler(FieldEventHandler<T> handler, double maxCheckInterval, double convergence, int maxIterationCount)` Add an event handler to the integrator.
    `void` | `addEventHandler(FieldEventHandler<T> handler, double maxCheckInterval, double convergence, int maxIterationCount, BracketedRealFieldUnivariateSolver<T> solver)` Add an event handler to the integrator.
    `void` | `addStepHandler(FieldStepHandler<T> handler)` Add a step handler to this integrator.
    `void` | `clearEventHandlers()` Remove all the event handlers that have been added to the integrator.
    `void` | `clearStepHandlers()` Remove all the step handlers that have been added to the integrator.
    `T[]` | `computeDerivatives(T t, T[] y)` Compute the derivatives and check the number of evaluations.
    `T` | `getCurrentSignedStepsize()` Get the current signed value of the integration stepsize.
    `FieldODEStateAndDerivative<T>` | `getCurrentStepStart()` Get the current value of the step start time ti.
    `protected FieldExpandableODE<T>` | `getEquations()` Get the differential equations to integrate.
    `int` | `getEvaluations()` Get the number of evaluations of the differential equations function.
    `protected IntegerSequence.Incrementor` | `getEvaluationsCounter()` Get the evaluations counter.
    `Collection<FieldEventHandler<T>>` | `getEventHandlers()` Get all the event handlers that have been added to the integrator.
    `Field<T>` | `getField()` Get the field to which state vector elements belong.
    `int` | `getMaxEvaluations()` Get the maximal number of functions evaluations.
    `String` | `getName()` Get the name of the method.
    `Collection<FieldStepHandler<T>>` | `getStepHandlers()` Get all the step handlers that have been added to the integrator.
    `protected T` | `getStepSize()` Get the current step size.
    `protected FieldODEStateAndDerivative<T>` | `getStepStart()` Getcurrent step start.
    `protected FieldODEStateAndDerivative<T>` | `initIntegration(FieldExpandableODE<T> eqn, T t0, T[] y0, T t)` Prepare the start of an integration.
    `protected boolean` | `isLastStep()` Check if this step is the last one.
    `protected boolean` | `resetOccurred()` Check if a reset occurred while last step was accepted.
    `protected void` | `sanityChecks(FieldODEState<T> eqn, T t)` Check the integration span.
    `protected void` | `setIsLastStep(boolean isLastStep)` Set the last state flag.
    `void` | `setMaxEvaluations(int maxEvaluations)` Set the maximal number of differential equations function evaluations.
    `protected void` | `setStateInitialized(boolean stateInitialized)` Set the stateInitialized flag.
    `protected void` | `setStepSize(T stepSize)` Set the current step size.
    `protected void` | `setStepStart(FieldODEStateAndDerivative<T> stepStart)` Set current step start.

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

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

    - ### Methods inherited from interface org.apache.commons.math3.ode.FirstOrderFieldIntegrator

      `integrate`

- - ### Constructor Detail

    - #### AbstractFieldIntegrator

          protected AbstractFieldIntegrator(Field<T> field,
                                 String name)

      Build an instance.
      Parameters:
        `field` - field to which the time and state vector elements belong
        `name` - name of the method

  - ### Method Detail

    - #### getField

          public Field<T> getField()

      Get the field to which state vector elements belong.
      Returns:
        field to which state vector elements belong

    - #### getName

          public String getName()

      Get the name of the method.
      Specified by:
        `getName` in interface `FirstOrderFieldIntegrator<T extends RealFieldElement<T>>`
      Returns:
        name of the method

    - #### addStepHandler

          public void addStepHandler(FieldStepHandler<T> handler)

      Add a step handler to this integrator.

      The handler will be called by the integrator for each accepted step.

      Specified by:
        `addStepHandler` in interface `FirstOrderFieldIntegrator<T extends RealFieldElement<T>>`
      Parameters:
        `handler` - handler for the accepted steps
      See Also:
        `FirstOrderFieldIntegrator.getStepHandlers()`, `FirstOrderFieldIntegrator.clearStepHandlers()`

    - #### getStepHandlers

          public Collection<FieldStepHandler<T>> getStepHandlers()

      Get all the step handlers that have been added to the integrator.
      Specified by:
        `getStepHandlers` in interface `FirstOrderFieldIntegrator<T extends RealFieldElement<T>>`
      Returns:
        an unmodifiable collection of the added events handlers
      See Also:
        `FirstOrderFieldIntegrator.addStepHandler(FieldStepHandler)`, `FirstOrderFieldIntegrator.clearStepHandlers()`

    - #### clearStepHandlers

          public void clearStepHandlers()

      Remove all the step handlers that have been added to the integrator.
      Specified by:
        `clearStepHandlers` in interface `FirstOrderFieldIntegrator<T extends RealFieldElement<T>>`
      See Also:
        `FirstOrderFieldIntegrator.addStepHandler(FieldStepHandler)`, `FirstOrderFieldIntegrator.getStepHandlers()`

    - #### addEventHandler

          public void addEventHandler(FieldEventHandler<T> handler,
                             double maxCheckInterval,
                             double convergence,
                             int maxIterationCount)

      Add an event handler to the integrator.

      The default solver is a 5th order `FieldBracketingNthOrderBrentSolver`.

      Specified by:
        `addEventHandler` in interface `FirstOrderFieldIntegrator<T extends RealFieldElement<T>>`
      Parameters:
        `handler` - event handler
        `maxCheckInterval` - maximal time interval between switching function checks (this interval prevents missing sign changes in case the integration steps becomes very large)
        `convergence` - convergence threshold in the event time search
        `maxIterationCount` - upper limit of the iteration count in the event time search events.
      See Also:
        `FirstOrderFieldIntegrator.addEventHandler(FieldEventHandler, double, double, int, org.apache.commons.math3.analysis.solvers.BracketedRealFieldUnivariateSolver)`, `FirstOrderFieldIntegrator.getEventHandlers()`, `FirstOrderFieldIntegrator.clearEventHandlers()`

    - #### addEventHandler

          public void addEventHandler(FieldEventHandler<T> handler,
                             double maxCheckInterval,
                             double convergence,
                             int maxIterationCount,
                             BracketedRealFieldUnivariateSolver<T> solver)

      Add an event handler to the integrator.
      Specified by:
        `addEventHandler` in interface `FirstOrderFieldIntegrator<T extends RealFieldElement<T>>`
      Parameters:
        `handler` - event handler
        `maxCheckInterval` - maximal time interval between switching function checks (this interval prevents missing sign changes in case the integration steps becomes very large)
        `convergence` - convergence threshold in the event time search
        `maxIterationCount` - upper limit of the iteration count in the event time search events.
        `solver` - solver to use to locate the event
      See Also:
        `FirstOrderFieldIntegrator.addEventHandler(FieldEventHandler, double, double, int)`, `FirstOrderFieldIntegrator.getEventHandlers()`, `FirstOrderFieldIntegrator.clearEventHandlers()`

    - #### getEventHandlers

          public Collection<FieldEventHandler<T>> getEventHandlers()

      Get all the event handlers that have been added to the integrator.
      Specified by:
        `getEventHandlers` in interface `FirstOrderFieldIntegrator<T extends RealFieldElement<T>>`
      Returns:
        an unmodifiable collection of the added events handlers
      See Also:
        `FirstOrderFieldIntegrator.addEventHandler(FieldEventHandler, double, double, int)`, `FirstOrderFieldIntegrator.clearEventHandlers()`

    - #### clearEventHandlers

          public void clearEventHandlers()

      Remove all the event handlers that have been added to the integrator.
      Specified by:
        `clearEventHandlers` in interface `FirstOrderFieldIntegrator<T extends RealFieldElement<T>>`
      See Also:
        `FirstOrderFieldIntegrator.addEventHandler(FieldEventHandler, double, double, int)`, `FirstOrderFieldIntegrator.getEventHandlers()`

    - #### getCurrentStepStart

          public FieldODEStateAndDerivative<T> getCurrentStepStart()

      Get the current value of the step start time ti.

      This method can be called during integration (typically by the object implementing the `differential equations` problem) if the value of the current step that is attempted is needed.

      The result is undefined if the method is called outside of calls to `integrate`.

      Specified by:
        `getCurrentStepStart` in interface `FirstOrderFieldIntegrator<T extends RealFieldElement<T>>`
      Returns:
        current value of the state at step start time ti

    - #### getCurrentSignedStepsize

          public T getCurrentSignedStepsize()

      Get the current signed value of the integration stepsize.

      This method can be called during integration (typically by the object implementing the `differential equations` problem) if the signed value of the current stepsize that is tried is needed.

      The result is undefined if the method is called outside of calls to `integrate`.

      Specified by:
        `getCurrentSignedStepsize` in interface `FirstOrderFieldIntegrator<T extends RealFieldElement<T>>`
      Returns:
        current signed value of the stepsize

    - #### setMaxEvaluations

          public void setMaxEvaluations(int maxEvaluations)

      Set the maximal number of differential equations function evaluations.

      The purpose of this method is to avoid infinite loops which can occur for example when stringent error constraints are set or when lots of discrete events are triggered, thus leading to many rejected steps.

      Specified by:
        `setMaxEvaluations` in interface `FirstOrderFieldIntegrator<T extends RealFieldElement<T>>`
      Parameters:
        `maxEvaluations` - maximal number of function evaluations (negative values are silently converted to maximal integer value, thus representing almost unlimited evaluations)

    - #### getMaxEvaluations

          public int getMaxEvaluations()

      Get the maximal number of functions evaluations.
      Specified by:
        `getMaxEvaluations` in interface `FirstOrderFieldIntegrator<T extends RealFieldElement<T>>`
      Returns:
        maximal number of functions evaluations

    - #### getEvaluations

          public int getEvaluations()

      Get the number of evaluations of the differential equations function.

      The number of evaluations corresponds to the last call to the `integrate` method. It is 0 if the method has not been called yet.

      Specified by:
        `getEvaluations` in interface `FirstOrderFieldIntegrator<T extends RealFieldElement<T>>`
      Returns:
        number of evaluations of the differential equations function

    - #### initIntegration

          protected FieldODEStateAndDerivative<T> initIntegration(FieldExpandableODE<T> eqn,
                                                      T t0,
                                                      T[] y0,
                                                      T t)

      Prepare the start of an integration.
      Parameters:
        `eqn` - equations to integrate
        `t0` - start value of the independent time variable
        `y0` - array containing the start value of the state vector
        `t` - target time for the integration
      Returns:
        initial state with derivatives added

    - #### getEquations

          protected FieldExpandableODE<T> getEquations()

      Get the differential equations to integrate.
      Returns:
        differential equations to integrate

    - #### getEvaluationsCounter

          protected IntegerSequence.Incrementor getEvaluationsCounter()

      Get the evaluations counter.
      Returns:
        evaluations counter

    - #### computeDerivatives

          public T[] computeDerivatives(T t,
                               T[] y)
                                                             throws DimensionMismatchException,
                                                                    MaxCountExceededException,
                                                                    NullPointerException

      Compute the derivatives and check the number of evaluations.
      Parameters:
        `t` - current value of the independent time variable
        `y` - array containing the current value of the state vector
      Returns:
        state completed with derivatives
      Throws:
        `DimensionMismatchException` - if arrays dimensions do not match equations settings
        `MaxCountExceededException` - if the number of functions evaluations is exceeded
        `NullPointerException` - if the ODE equations have not been set (i.e. if this method is called outside of a call to `integrate`

    - #### setStateInitialized

          protected void setStateInitialized(boolean stateInitialized)

      Set the stateInitialized flag.

      This method must be called by integrators with the value `false` before they start integration, so a proper lazy initialization is done automatically on the first step.

      Parameters:
        `stateInitialized` - new value for the flag

    - #### acceptStep

          protected FieldODEStateAndDerivative<T> acceptStep(AbstractFieldStepInterpolator<T> interpolator,
                                                 T tEnd)
                                                                                  throws MaxCountExceededException,
                                                                                         DimensionMismatchException,
                                                                                         NoBracketingException

      Accept a step, triggering events and step handlers.
      Parameters:
        `interpolator` - step interpolator
        `tEnd` - final integration time
      Returns:
        state at end of step
      Throws:
        `MaxCountExceededException` - if the interpolator throws one because the number of functions evaluations is exceeded
        `NoBracketingException` - if the location of an event cannot be bracketed
        `DimensionMismatchException` - if arrays dimensions do not match equations settings

    - #### sanityChecks

          protected void sanityChecks(FieldODEState<T> eqn,
                          T t)
                               throws NumberIsTooSmallException,
                                      DimensionMismatchException

      Check the integration span.
      Parameters:
        `eqn` - set of differential equations
        `t` - target time for the integration
      Throws:
        `NumberIsTooSmallException` - if integration span is too small
        `DimensionMismatchException` - if adaptive step size integrators tolerance arrays dimensions are not compatible with equations settings

    - #### resetOccurred

          protected boolean resetOccurred()

      Check if a reset occurred while last step was accepted.
      Returns:
        true if a reset occurred while last step was accepted

    - #### setStepSize

          protected void setStepSize(T stepSize)

      Set the current step size.
      Parameters:
        `stepSize` - step size to set

    - #### getStepSize

          protected T getStepSize()

      Get the current step size.
      Returns:
        current step size

    - #### setStepStart

          protected void setStepStart(FieldODEStateAndDerivative<T> stepStart)

      Set current step start.
      Parameters:
        `stepStart` - step start

    - #### getStepStart

          protected FieldODEStateAndDerivative<T> getStepStart()

      Getcurrent step start.
      Returns:
        current step start

    - #### setIsLastStep

          protected void setIsLastStep(boolean isLastStep)

      Set the last state flag.
      Parameters:
        `isLastStep` - if true, this step is the last one

    - #### isLastStep

          protected boolean isLastStep()

      Check if this step is the last one.
      Returns:
        true if this step is the last one

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