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package org.apache.commons.math3.ode;

import org.apache.commons.math3.RealFieldElement;
import org.apache.commons.math3.exception.DimensionMismatchException;
import org.apache.commons.math3.exception.MaxCountExceededException;

This interface allows users to add secondary differential equations to a primary
set of differential equations.

In some cases users may need to integrate some problem-specific 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 FieldExpandableODE.addSecondaryEquations(FieldSecondaryEquations) method. 
Type parameters:
<T> – the type of the field elements
See Also:
FirstOrderFieldDifferentialEquations
FieldExpandableODE
Since:
3.6/**
 * This interface allows users to add secondary differential equations to a primary
 * set of differential equations.
 * <p>
 * In some cases users may need to integrate some problem-specific 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.
 * </p>
 * <p>
 * This interface allows users to add such equations to a primary set of {@link
 * FirstOrderFieldDifferentialEquations first order differential equations}
 * thanks to the {@link FieldExpandableODE#addSecondaryEquations(FieldSecondaryEquations)}
 * method.
 * </p>
 * @see FirstOrderFieldDifferentialEquations
 * @see FieldExpandableODE
 * @param <T> the type of the field elements
 * @since 3.6
 */
public interface FieldSecondaryEquations<T extends RealFieldElement<T>> {

    
Get the dimension of the secondary state parameters.
Returns:
dimension of the secondary state parameters/** Get the dimension of the secondary state parameters.
     * @return dimension of the secondary state parameters
     */
    int getDimension();

    
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.

Params:
t0 – value of the independent time variable at integration start
primary0 – array containing the value of the primary state vector at integration start
secondary0 – array containing the value of the secondary state vector at integration start
finalTime – target time for the integration/** Initialize equations at the start of an ODE integration.
     * <p>
     * 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.
     * </p>
     * @param t0 value of the independent <I>time</I> variable at integration start
     * @param primary0 array containing the value of the primary state vector at integration start
     * @param secondary0 array containing the value of the secondary state vector at integration start
     * @param finalTime target time for the integration
     */
    void init(T t0, T[] primary0, T[] secondary0, T finalTime);

    
Compute the derivatives related to the secondary state parameters.
Params:
t – current value of the independent time variable
primary – array containing the current value of the primary state vector
primaryDot – array containing the derivative of the primary state vector
secondary – array containing the current value of the secondary state vector
Throws:
MaxCountExceededException – if the number of functions evaluations is exceeded
DimensionMismatchException – if arrays dimensions do not match equations settings
Returns:
derivative of the secondary state vector/** Compute the derivatives related to the secondary state parameters.
     * @param t current value of the independent <I>time</I> variable
     * @param primary array containing the current value of the primary state vector
     * @param primaryDot array containing the derivative of the primary state vector
     * @param secondary array containing the current value of the secondary state vector
     * @return derivative of the secondary state vector
     * @exception MaxCountExceededException if the number of functions evaluations is exceeded
     * @exception DimensionMismatchException if arrays dimensions do not match equations settings
     */
    T[] computeDerivatives(T t, T[] primary, T[] primaryDot, T[] secondary)
        throws MaxCountExceededException, DimensionMismatchException;

}