Constructor Detail

• RungeKuttaFieldIntegrator

  protected RungeKuttaFieldIntegrator(Field<T> field,
                           String name,
                           T step)

  Simple constructor. Build a Runge-Kutta integrator with the given step. The default step handler does nothing.

  Parameters:

  field - field to which the time and state vector elements belong

  name - name of the method

  step - integration step

Method Detail

• fraction

  protected T fraction(int p,
           int q)

  Create a fraction.

  Parameters:

  p - numerator

  q - denominator

  Returns:

  p/q computed in the instance field

• createInterpolator

  protected abstract org.apache.commons.math3.ode.nonstiff.RungeKuttaFieldStepInterpolator<T> createInterpolator(boolean forward,
                                                                                            T[][] yDotK,
                                                                                            FieldODEStateAndDerivative<T> globalPreviousState,
                                                                                            FieldODEStateAndDerivative<T> globalCurrentState,
                                                                                            FieldEquationsMapper<T> mapper)

  Create an interpolator.

  Parameters:

  forward - integration direction indicator

  yDotK - slopes at the intermediate points

  globalPreviousState - start of the global step

  globalCurrentState - end of the global step

  mapper - equations mapper for the all equations

  Returns:

  external weights for the high order method from Butcher array

• integrate

  public FieldODEStateAndDerivative<T> integrate(FieldExpandableODE<T> equations,
                                        FieldODEState<T> initialState,
                                        T finalTime)
                                                                      throws NumberIsTooSmallException,
                                                                             DimensionMismatchException,
                                                                             MaxCountExceededException,
                                                                             NoBracketingException

  Integrate the differential equations up to the given time.

  This method solves an Initial Value Problem (IVP).

  Since this method stores some internal state variables made available in its public interface during integration (FirstOrderFieldIntegrator.getCurrentSignedStepsize()), it is not thread-safe.

  Specified by:

  integrate in interface FirstOrderFieldIntegrator<T extends RealFieldElement<T>>

  Parameters:

  equations - differential equations to integrate

  initialState - initial state (time, primary and secondary state vectors)

  finalTime - target time for the integration (can be set to a value smaller than t0 for backward integration)

  Returns:

  final state, its time will be the same as finalTime if integration reached its target, but may be different if some FieldEventHandler stops it at some point.

  Throws:

  NumberIsTooSmallException - if integration step is too small

  MaxCountExceededException - if the number of functions evaluations is exceeded

  NoBracketingException - if the location of an event cannot be bracketed

  DimensionMismatchException

• singleStep

  public T[] singleStep(FirstOrderFieldDifferentialEquations<T> equations,
               T t0,
               T[] y0,
               T t)

  Fast computation of a single step of ODE integration.

  This method is intended for the limited use case of very fast computation of only one step without using any of the rich features of general integrators that may take some time to set up (i.e. no step handlers, no events handlers, no additional states, no interpolators, no error control, no evaluations count, no sanity checks ...). It handles the strict minimum of computation, so it can be embedded in outer loops.

  This method is not used at all by the integrate(FieldExpandableODE, FieldODEState, RealFieldElement) method. It also completely ignores the step set at construction time, and uses only a single step to go from t0 to t.

  As this method does not use any of the state-dependent features of the integrator, it should be reasonably thread-safe if and only if the provided differential equations are themselves thread-safe.

  Parameters:

  equations - differential equations to integrate

  t0 - initial time

  y0 - initial value of the state vector at t0

  t - target time for the integration (can be set to a value smaller than t0 for backward integration)

  Returns:

  state vector at t