[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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