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geant4/source/geometry/magneticfield/include/G4DoLoMcPriRK34.hh
2025-12-05 08:54:02 +01:00

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// G4DoLoMcPriRK34
//
// Class description:
//
// Dormand-Lockyer-McGorrigan-Prince-6-3-4 non-FSAL method
// ( 6 stage, 3rd & 4th order embedded RK method )
// Author: Somnath Banerjee (CERN, Google Summer of Code 2015), 07.07.2015
// Supervision: John Apostolakis (CERN)
// --------------------------------------------------------------------
#ifndef DOLO_MCPRI_RK34_HH
#define DOLO_MCPRI_RK34_HH
#include "G4MagIntegratorStepper.hh"
/**
* @brief G4DoLoMcPriRK34 implements the Dormand-Lockyer-McGorrigan-Prince-6-3-4
* non-FSAL method ( 6 stage, 3rd & 4th order embedded Runge-Kutta method ).
*/
class G4DoLoMcPriRK34 : public G4MagIntegratorStepper
{
public:
/**
* Constructor for G4DoLoMcPriRK34.
* @param[in] EqRhs Pointer to the provided equation of motion.
* @param[in] numberOfVariables The number of integration variables.
* @param[in] primary Flag for initialisation of the auxiliary stepper.
*/
G4DoLoMcPriRK34( G4EquationOfMotion* EqRhs,
G4int numberOfVariables = 6,
G4bool primary = true );
/**
* Destructor.
*/
~G4DoLoMcPriRK34() override;
/**
* Copy constructor and assignment operator not allowed.
*/
G4DoLoMcPriRK34(const G4DoLoMcPriRK34&) = delete;
G4DoLoMcPriRK34& operator=(const G4DoLoMcPriRK34&) = delete;
/**
* The stepper for the Runge Kutta integration.
* The stepsize is fixed, with the step size given by 'h'.
* Integrates ODE starting values y[0 to 6].
* Outputs yout[] and its estimated error yerr[].
* @param[in] y Starting values array of integration variables.
* @param[in] dydx Derivatives array.
* @param[in] h The given step size.
* @param[out] yout Integration output.
* @param[out] yerr The estimated error.
*/
void Stepper( const G4double y[],
const G4double dydx[],
G4double h,
G4double yout[],
G4double yerr[] ) override ;
/**
* Interface method for interpolation setup. Does nothing here.
*/
inline void SetupInterpolation() {}
/**
* Calculates the output at the tau fraction of Step.
* @param[in] yInput Starting values array of integration variables.
* @param[in] dydx Derivatives array.
* @param[in] Step The given step size.
* @param[out] yOut Interpolation output.
* @param[out] tau Fraction of step.
*/
void Interpolate( const G4double yInput[],
const G4double dydx[],
const G4double Step,
G4double yOut[],
G4double tau );
void Interpolate( G4double tau,
G4double yOut[]);
/**
* Returns the distance from chord line.
*/
G4double DistChord() const override;
/**
* Returns the order, 3, of integration.
*/
inline G4int IntegratorOrder() const override { return 3; }
/**
* Returns the stepper type-ID, "kDoLoMcPriRK34".
*/
inline G4StepperType StepperType() const override { return kDoLoMcPriRK34; }
private :
G4double *ak2, *ak3, *ak4, *ak5, *ak6, *yTemp, *yIn;
G4double fLastStepLength = -1.0;
/** For DistChord calculations. */
G4double *fLastInitialVector, *fLastFinalVector,
*fLastDyDx, *fMidVector, *fMidError;
G4DoLoMcPriRK34* fAuxStepper = nullptr;
};
#endif