1 | // |
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2 | // ******************************************************************** |
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3 | // * License and Disclaimer * |
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4 | // * * |
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6 | // * the Geant4 Collaboration. It is provided under the terms and * |
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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 | // $Id: G4NystromRK4.hh,v 1.3 2009/11/12 15:01:36 japost Exp $ |
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27 | // GEANT4 tag $Name: $ |
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28 | // |
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29 | // class G4NystromRK4 |
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30 | // |
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31 | // Class description: |
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32 | // |
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33 | // Integrate the equations of the motion of a particle in a magnetic field |
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34 | // using 4th Runge-Kutta-Nystrom method with errors estimation |
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35 | // (ATL-SOFT-PUB-2009-01) |
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36 | // Current form can be used only for 'pure' magnetic field. |
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37 | // Notes: 1) field must be time-independent. |
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38 | // 2) time is not integrated |
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39 | // |
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40 | // History: |
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41 | // - Created: I.Gavrilenko 15.05.2009 (as G4AtlasRK4) |
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42 | // - Adaptations: J. Apostolakis May-Nov 2009 |
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43 | // ------------------------------------------------------------------- |
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44 | |
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45 | #ifndef G4NYSTROMRK4_HH |
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46 | #define G4NYSTROMRK4_HH |
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47 | |
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48 | #include "globals.hh" |
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49 | #include "G4MagIntegratorStepper.hh" |
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50 | #include "G4Mag_EqRhs.hh" |
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51 | |
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52 | class G4NystromRK4 : public G4MagIntegratorStepper |
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53 | { |
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54 | public: |
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55 | G4NystromRK4(G4Mag_EqRhs *EquationMotion, G4double distanceConstField=0.0); |
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56 | // Can be used only for Magnetic Fields - and for 6 variables (x,p) |
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57 | |
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58 | ~G4NystromRK4() ; |
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59 | |
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60 | void Stepper(const G4double P [], |
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61 | const G4double dPdS[], |
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62 | G4double step , |
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63 | G4double Po [], |
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64 | G4double Err []); |
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65 | // Single call for integration result and error |
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66 | // - Provides Error via analytical method |
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67 | |
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68 | virtual void ComputeRightHandSide(const double P[],double dPdS[]); |
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69 | // Must compute RHS - and does caches result |
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70 | |
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71 | void SetDistanceForConstantField( G4double length ); |
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72 | G4double GetDistanceForConstantField() const; |
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73 | |
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74 | G4int IntegratorOrder() const {return 4;} |
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75 | G4double DistChord() const; |
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76 | |
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77 | private: |
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78 | |
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79 | inline void getField (const G4double P[4]); |
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80 | |
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81 | //////////////////////////////////////////////////////////////// |
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82 | // Private data |
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83 | //////////////////////////////////////////////////////////////// |
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84 | |
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85 | G4Mag_EqRhs* m_fEq; |
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86 | G4double m_lastField[3]; |
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87 | G4double m_fldPosition[4]; |
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88 | G4double m_magdistance ; |
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89 | G4double m_magdistance2; |
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90 | G4double m_cof ; |
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91 | G4double m_mom ; |
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92 | G4double m_imom ; |
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93 | G4bool m_cachedMom ; |
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94 | G4double m_iPoint [3]; |
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95 | G4double m_mPoint [3]; |
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96 | G4double m_fPoint [3]; |
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97 | |
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98 | }; |
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99 | |
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100 | ///////////////////////////////////////////////////////////////////////////////// |
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101 | // Inline methods |
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102 | ///////////////////////////////////////////////////////////////////////////////// |
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103 | inline void G4NystromRK4::SetDistanceForConstantField( G4double length ) |
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104 | { |
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105 | m_magdistance= length; |
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106 | m_magdistance2 = length*length; |
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107 | } |
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108 | |
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109 | inline G4double G4NystromRK4::GetDistanceForConstantField() const |
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110 | { |
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111 | return m_magdistance; |
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112 | } |
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113 | |
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114 | ///////////////////////////////////////////////////////////////////////////////// |
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115 | // Get value of magnetic field while checking distance from last stored call |
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116 | ///////////////////////////////////////////////////////////////////////////////// |
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117 | |
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118 | inline void G4NystromRK4::getField (const G4double P[4]) |
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119 | { |
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120 | |
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121 | G4double dx = P[0]-m_fldPosition[0]; |
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122 | G4double dy = P[1]-m_fldPosition[1]; |
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123 | G4double dz = P[2]-m_fldPosition[2]; |
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124 | |
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125 | if((dx*dx+dy*dy+dz*dz) > m_magdistance2) { |
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126 | |
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127 | m_fldPosition[0] = P[0]; |
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128 | m_fldPosition[1] = P[1]; |
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129 | m_fldPosition[2] = P[2]; |
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130 | m_fldPosition[3] = P[3]; // Generally it is P[7] - changed convention !! |
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131 | m_fEq->GetFieldValue(m_fldPosition, m_lastField); |
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132 | } |
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133 | } |
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134 | #endif // G4NYSTROMRK4 |
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