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geant4/source/geometry/magneticfield/include/G4HelixImplicitEuler.hh
2025-12-05 08:54:02 +01:00

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// G4HelixImplicitEuler
//
// Class description:
//
// Helix Implicit Euler stepper for magnetic field:
// x_1 = x_0 + 1/2 * ( helix(h,t_0,x_0)
// + helix(h,t_0+h,x_0+helix(h,t0,x0) ) )
// Second order solver.
// Take the current derivative and add it to the current position.
// Take the output and its derivative. Add the mean of both derivatives
// to form the final output.
// Author: W.Wander (MIT), 03.11.1998
// -------------------------------------------------------------------
#ifndef G4HELIXIMPLICITEULER_HH
#define G4HELIXIMPLICITEULER_HH
#include "G4MagHelicalStepper.hh"
/**
* @brief G4HelixImplicitEuler implements a helix implicit Euler
* stepper for magnetic field with 2nd order solver.
*/
class G4HelixImplicitEuler : public G4MagHelicalStepper
{
public:
/**
* Constructor for G4HelixImplicitEuler.
* @param[in] EqRhs Pointer to the provided equation of motion.
*/
G4HelixImplicitEuler(G4Mag_EqRhs* EqRhs);
/**
* Default Destructor.
*/
~G4HelixImplicitEuler() override = default;
/**
* The stepper function for the integration.
* @param[in] y Starting values array of integration variables.
* @param[in] Bfld Derivatives array.
* @param[in] h The given step size.
* @param[out] yout Integration output.
*/
void DumbStepper( const G4double y[],
G4ThreeVector Bfld,
G4double h,
G4double yout[] ) override;
/**
* Returns the order, 2, of integration.
*/
inline G4int IntegratorOrder() const override { return 2; }
/**
* Returns the stepper type-ID, "kHelixImplicitEuler".
*/
inline G4StepperType StepperType() const override { return kHelixImplicitEuler; }
};
#endif