Interface SecondaryODE
 All Known Subinterfaces:
SecondaryEquations
In some cases users may need to integrate some problemspecific equations along with a primary set of differential equations. One example is optimal control where adjoined parameters linked to the minimized hamiltonian must be integrated.
This interface allows users to add such equations to a primary set of first order differential equations
thanks to the ExpandableODE.addSecondaryEquations(SecondaryODE)
method.
 See Also:

Method Summary
Modifier and TypeMethodDescriptiondouble[]
computeDerivatives
(double t, double[] primary, double[] primaryDot, double[] secondary) Compute the derivatives related to the secondary state parameters.int
Get the dimension of the secondary state parameters.default void
init
(double t0, double[] primary0, double[] secondary0, double finalTime) Initialize equations at the start of an ODE integration.

Method Details

getDimension
int getDimension()Get the dimension of the secondary state parameters. Returns:
 dimension of the secondary state parameters

init
default void init(double t0, double[] primary0, double[] secondary0, double finalTime) Initialize equations at the start of an ODE integration.This method is called once at the start of the integration. It may be used by the equations to initialize some internal data if needed.
The default implementation does nothing.
 Parameters:
t0
 value of the independent time variable at integration startprimary0
 array containing the value of the primary state vector at integration startsecondary0
 array containing the value of the secondary state vector at integration startfinalTime
 target time for the integration

computeDerivatives
double[] computeDerivatives(double t, double[] primary, double[] primaryDot, double[] secondary) throws MathIllegalArgumentException, MathIllegalStateException Compute the derivatives related to the secondary state parameters.In some cases, additional equations can require to change the derivatives of the primary state (i.e. the content of the
primaryDot
array). One use case is optimal control, when the secondary equations handle costate, which changes control, and the control changes the primary state. In this case, the primary and secondary equations are not really independent from each other, so if possible it would be better to put state and costate and their equations all in the primary equations. As this is not always possible, this method explicitly allows to modify the content of theprimaryDot
array. This array will be used to evolve the primary state only after all secondary equations have computed their derivatives, hence allowing this side effect. Parameters:
t
 current value of the independent time variableprimary
 array containing the current value of the primary state vectorprimaryDot
 array containing the derivative of the primary state vector (the method is allowed to change the derivatives here, when the additional equations do have an effect on the primary equations)secondary
 array containing the current value of the secondary state vector Returns:
 derivative of the secondary state vector
 Throws:
MathIllegalStateException
 if the number of functions evaluations is exceededMathIllegalArgumentException
 if arrays dimensions do not match equations settings
