G4HelixExplicitEuler.hh

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// G4HelixExplicitEuler
//
// Class description:
//
// Helix Explicit Euler: x_1 = x_0 + helix(h)
// with helix(h) being a helix piece of length h.
// A simple approach for solving linear differential equations.
// Take the current derivative and add it to the current position.
 
// Author: W.Wander (MIT), 12.09.1997
// -------------------------------------------------------------------
#ifndef G4HELIXEXPLICITEULER_HH
#define G4HELIXEXPLICITEULER_HH
 
#include "G4MagHelicalStepper.hh"
 
/**
 * @brief G4HelixExplicitEuler implements an Explicit Euler stepper for
 * magnetic field: x_1 = x_0 + helix(h), with helix(h) being a helix piece
 * of length h. A simple approach for solving linear differential equations.
 * Takes the current derivative and adds it to the current position.
 */
 
class G4HelixExplicitEuler : public G4MagHelicalStepper
{
  public:
 
    /**
     * Constructor for G4HelixExplicitEuler.
     *  @param[in] EqRhs Pointer to the provided equation of motion.
     */
    G4HelixExplicitEuler(G4Mag_EqRhs* EqRhs);
 
    /**
     * Default Destructor.
     */
    ~G4HelixExplicitEuler() override = default;
 
    /**
     * The stepper function for the integration.
     *  @param[in] y Starting values array of integration variables.
     *  @param[in] na Not used.
     *  @param[in] h The given step size.
     *  @param[out] yout Integration output.
     *  @param[out] yerr Integration error.
     */
    void Stepper( const G4double y[],
                  const G4double* na,
                        G4double h,
                        G4double yout[],
                        G4double yerr[]  ) override; 
 
    /**
     * 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 distance from chord line.
     */
    G4double DistChord() const override;
 
    /**
     * Returns the order, 1, of integration.
     */
    inline G4int IntegratorOrder() const override { return 1; }
 
    /**
     * Returns the stepper type-ID, "kHelixExplicitEuler".
     */
    inline G4StepperType StepperType() const override { return kHelixExplicitEuler; }
};
 
#endif