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geant4/source/geometry/magneticfield/include/G4SimpleRunge.hh
2025-12-05 08:54:02 +01:00

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//
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// G4SimpleRunge
//
// Class description:
//
// Simple Runge:
//
// x_1 = x_0 + h * ( dx( t_0+h/2, x_0 + h/2 * dx( t_0, x_0) ) )
//
// Second order solver.
// Takes the derivative at a position to be assumed at the middle of the
// Step and adds it to the current position.
// Author: W.Wander (MIT), 12.09.1997
// -------------------------------------------------------------------
#ifndef G4SIMPLERUNGE_HH
#define G4SIMPLERUNGE_HH
#include "G4MagErrorStepper.hh"
/**
* @brief G4SimpleRunge implements a simple Runge stepper for magnetic field
* with 2nd order solver.
*/
class G4SimpleRunge : public G4MagErrorStepper
{
public:
/**
* Constructor for G4SimpleRunge.
* @param[in] EquationRhs Pointer to the provided equation of motion.
* @param[in] numberOfVariables The number of integration variables.
*/
G4SimpleRunge(G4EquationOfMotion* EquationRhs,
G4int numberOfVariables = 6);
/**
* Destructor.
*/
~G4SimpleRunge() override;
/**
* Copy constructor and assignment operator not allowed.
*/
G4SimpleRunge(const G4SimpleRunge&) = delete;
G4SimpleRunge& operator=(const G4SimpleRunge&) = delete;
/**
* The stepper for the Runge Kutta integration, but performing a 'dump' step
* without error calculation.
* @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.
*/
void DumbStepper( const G4double y[],
const G4double dydx[],
G4double h,
G4double yout[] ) override;
/**
* Returns the order, 2, of integration.
*/
inline G4int IntegratorOrder() const override { return 2; }
/**
* Returns the stepper type-ID, "kSimpleRunge".
*/
inline G4StepperType StepperType() const override { return kSimpleRunge; }
private:
G4int fNumberOfVariables = 0;
G4double* dydxTemp = nullptr;
G4double* yTemp = nullptr;
};
#endif