| [1059] | 1 | //
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| 2 | // ********************************************************************
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| 3 | // * License and Disclaimer *
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| 4 | // * *
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| 5 | // * The Geant4 software is copyright of the Copyright Holders of *
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| 6 | // * the Geant4 Collaboration. It is provided under the terms and *
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| 7 | // * conditions of the Geant4 Software License, included in the file *
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| 8 | // * LICENSE and available at http://cern.ch/geant4/license . These *
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| 9 | // * include a list of copyright holders. *
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| 10 | // * *
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| 11 | // * Neither the authors of this software system, nor their employing *
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| 12 | // * institutes,nor the agencies providing financial support for this *
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| 13 | // * work make any representation or warranty, express or implied, *
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| 14 | // * regarding this software system or assume any liability for its *
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| 15 | // * use. Please see the license in the file LICENSE and URL above *
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| 16 | // * for the full disclaimer and the limitation of liability. *
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| 17 | // * *
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| 18 | // * This code implementation is the result of the scientific and *
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| 19 | // * technical work of the GEANT4 collaboration. *
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| 20 | // * By using, copying, modifying or distributing the software (or *
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| 21 | // * any work based on the software) you agree to acknowledge its *
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| 22 | // * use in resulting scientific publications, and indicate your *
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| 23 | // * acceptance of all terms of the Geant4 Software license. *
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| 24 | // ********************************************************************
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| 25 | //
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| 26 | //
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| 27 | // $Id: G4ConstRK4.hh,v 1.2 2008/10/29 14:17:42 gcosmo Exp $
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| 28 | // GEANT4 tag $Name: geant4-09-02-cand-01 $
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| 29 | //
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| 30 | //
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| 31 | // Class G4ConstRK4
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| 32 | //
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| 33 | // class description:
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| 34 | //
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| 35 | // G4ConstRK4 performs the integration of one step with error calculation
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| 36 | // in constant magnetic field. The integration method is the same as in
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| 37 | // ClassicalRK4. The field value is assumed constant for the step.
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| 38 | // This field evaluation is called only once per step.
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| 39 | // G4ConstRK4 can be used only for magnetic fields.
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| 40 |
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| 41 | // History:
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| 42 | // - 18.09.2008 - J.Apostolakis, T.Nikitina - Created
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| 43 | // -------------------------------------------------------------------
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| 44 |
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| 45 | #ifndef G4CONSTRK4_HH
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| 46 | #define G4CONSTRK4_HH
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| 47 |
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| 48 | #include "G4MagErrorStepper.hh"
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| 49 | #include "G4EquationOfMotion.hh"
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| 50 | #include "G4Mag_EqRhs.hh"
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| 51 |
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| 52 | class G4ConstRK4 : public G4MagErrorStepper
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| 53 | {
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| 54 | public: // with description
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| 55 |
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| 56 | G4ConstRK4(G4Mag_EqRhs *EquationMotion, G4int numberOfVariables = 8);
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| 57 | ~G4ConstRK4();
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| 58 |
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| 59 | void Stepper( const G4double y[],
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| 60 | const G4double dydx[],
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| 61 | G4double h,
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| 62 | G4double yout[],
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| 63 | G4double yerr[] );
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| 64 | void DumbStepper( const G4double yIn[],
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| 65 | const G4double dydx[],
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| 66 | G4double h,
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| 67 | G4double yOut[] ) ;
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| 68 | G4double DistChord() const;
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| 69 |
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| 70 | inline void RightHandSideConst(const G4double y[],
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| 71 | G4double dydx[] ) const;
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| 72 |
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| 73 | inline void GetConstField(const G4double y[],G4double Field[]);
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| 74 |
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| 75 | public: // without description
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| 76 |
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| 77 | G4int IntegratorOrder() const { return 4; }
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| 78 |
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| 79 | private:
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| 80 |
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| 81 | G4ConstRK4(const G4ConstRK4&);
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| 82 | G4ConstRK4& operator=(const G4ConstRK4&);
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| 83 | // Private copy constructor and assignment operator.
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| 84 |
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| 85 | private:
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| 86 |
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| 87 | G4ThreeVector fInitialPoint, fMidPoint, fFinalPoint;
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| 88 | // Data stored in order to find the chord
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| 89 | G4double *dydxm, *dydxt, *yt; // scratch space - not state
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| 90 | G4double *yInitial, *yMiddle, *dydxMid, *yOneStep;
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| 91 | G4Mag_EqRhs *fEq;
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| 92 | G4double Field[3];
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| 93 | };
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| 94 |
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| 95 | // Inline methods
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| 96 |
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| 97 | inline void G4ConstRK4:: RightHandSideConst(const G4double y[],
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| 98 | G4double dydx[] ) const
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| 99 | {
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| 100 |
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| 101 | G4double momentum_mag_square = y[3]*y[3] + y[4]*y[4] + y[5]*y[5];
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| 102 | G4double inv_momentum_magnitude = 1.0 / std::sqrt( momentum_mag_square );
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| 103 |
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| 104 | G4double cof =fEq->FCof()*inv_momentum_magnitude;
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| 105 |
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| 106 | dydx[0] = y[3]*inv_momentum_magnitude; // (d/ds)x = Vx/V
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| 107 | dydx[1] = y[4]*inv_momentum_magnitude; // (d/ds)y = Vy/V
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| 108 | dydx[2] = y[5]*inv_momentum_magnitude; // (d/ds)z = Vz/V
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| 109 |
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| 110 | dydx[3] = cof*(y[4]*Field[2] - y[5]*Field[1]) ; // Ax = a*(Vy*Bz - Vz*By)
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| 111 | dydx[4] = cof*(y[5]*Field[0] - y[3]*Field[2]) ; // Ay = a*(Vz*Bx - Vx*Bz)
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| 112 | dydx[5] = cof*(y[3]*Field[1] - y[4]*Field[0]) ; // Az = a*(Vx*By - Vy*Bx)
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| 113 | }
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| 114 |
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| 115 | inline void G4ConstRK4::GetConstField(const G4double y[],G4double B[])
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| 116 | {
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| 117 | G4double PositionAndTime[4];
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| 118 |
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| 119 | PositionAndTime[0] = y[0];
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| 120 | PositionAndTime[1] = y[1];
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| 121 | PositionAndTime[2] = y[2];
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| 122 | // Global Time
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| 123 | PositionAndTime[3] = y[7];
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| 124 | fEq -> GetFieldValue(PositionAndTime, B) ;
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| 125 | }
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| 126 |
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| 127 | #endif // G4CONSTRK4_HH
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