include/Geant4/G4RKG3_Stepper.hh

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0025 //
0026 // G4RKG3_Stepper
0027 //
0028 // Class description:
0029 //
0030 // Runga-Kutta integrator stepper from Geant3.
0031
0032 // Created: J.Apostolakis, V.Grichine - 30.01.1997
0033 // -------------------------------------------------------------------
0034 #ifndef G4RKG3_STEPPER_HH
0035 #define G4RKG3_STEPPER_HH
0036
0037 #include "G4Types.hh"
0038 #include "G4MagIntegratorStepper.hh"
0039 #include "G4ThreeVector.hh"
0040
0041 class G4Mag_EqRhs;
0042
0043 class G4RKG3_Stepper : public G4MagIntegratorStepper
0044 {
0045   public:
0046
0047     G4RKG3_Stepper(G4Mag_EqRhs* EqRhs);
0048       // Integrate over 6 variables only:  position & velocity.
0049       // Not implemented yet !
0050
0051     ~G4RKG3_Stepper() override;
0052
0053     void Stepper( const G4double yIn[],
0054                   const G4double dydx[],
0055                         G4double h,
0056                         G4double yOut[],
0057                         G4double yErr[] ) override;
0058       // The method which must be provided, even if less efficient.
0059
0060     G4double  DistChord() const override ;
0061
0062     void StepNoErr( const G4double tIn[8],
0063                     const G4double dydx[6],
0064                           G4double Step,
0065                           G4double tOut[8],
0066                           G4double B[3] );
0067       // Integrator RK Stepper from G3 with only two field evaluation per
0068       // Step. It is used in propagation initial Step by small substeps
0069       // after solution error and delta geometry considerations.
0070       // B[3] is magnetic field which is passed from substep to substep.
0071
0072     void StepWithEst( const G4double  tIn[8],
0073                       const G4double dydx[6],
0074                             G4double Step,
0075                             G4double tOut[8],
0076                             G4double& alpha2,
0077                             G4double& beta2,
0078                       const G4double B1[3],
0079                             G4double B2[3] );
0080       // Integrator for RK from G3 with evaluation of error in solution and
0081       // delta geometry based on naive similarity with the case of uniform
0082       // magnetic field.
0083       // B1[3] is input  and is the first magnetic field values
0084       // B2[3] is output and is the final magnetic field values.
0085
0086     inline G4int IntegratorOrder() const override { return 4; }
0087
0088   private:
0089
0090     G4ThreeVector fyInitial,
0091                   fyMidPoint,
0092                   fyFinal;
0093     G4ThreeVector fpInitial;
0094     G4ThreeVector BfldIn;
0095     G4double      hStep = 0.0;
0096 };
0097
0098 #endif