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: G4NystromRK4.cc,v 1.9 2010/09/10 15:42:09 japost Exp $ |
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28 | // GEANT4 tag $Name: field-V09-03-03 $ |
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29 | // |
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30 | // History: |
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31 | // - Created: I.Gavrilenko 15.05.2009 (as G4AtlasRK4) |
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32 | // - Adaptations: J. Apostolakis May-Nov 2009 |
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33 | // ------------------------------------------------------------------- |
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34 | |
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35 | #include "G4NystromRK4.hh" |
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36 | #include <iostream> |
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37 | |
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38 | ////////////////////////////////////////////////////////////////// |
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39 | // Constructor - with optional distance ( has default value) |
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40 | ////////////////////////////////////////////////////////////////// |
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41 | |
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42 | G4NystromRK4::G4NystromRK4(G4Mag_EqRhs* magEqRhs, G4double distanceConstField) |
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43 | : G4MagIntegratorStepper(magEqRhs, 6), // number of variables |
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44 | m_fEq( magEqRhs ), |
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45 | m_magdistance( distanceConstField ), |
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46 | m_cof( 0.0 ), |
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47 | m_mom( 0.0 ), |
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48 | m_imom( 0.0 ), |
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49 | m_cachedMom( false ) |
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50 | { |
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51 | m_fldPosition[0] = m_iPoint[0] = m_fPoint[0] = m_mPoint[0] = 9.9999999e+99 ; |
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52 | m_fldPosition[1] = m_iPoint[1] = m_fPoint[1] = m_mPoint[1] = 9.9999999e+99 ; |
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53 | m_fldPosition[2] = m_iPoint[2] = m_fPoint[2] = m_mPoint[2] = 9.9999999e+99 ; |
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54 | m_fldPosition[3] = -9.9999999e+99; |
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55 | m_lastField[0] = m_lastField[1] = m_lastField[2] = 0.0; |
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56 | |
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57 | m_magdistance2 = distanceConstField*distanceConstField; |
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58 | } |
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59 | |
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60 | //////////////////////////////////////////////////////////////// |
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61 | // Destructor |
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62 | //////////////////////////////////////////////////////////////// |
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63 | |
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64 | G4NystromRK4::~G4NystromRK4() |
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65 | { |
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66 | } |
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67 | |
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68 | ///////////////////////////////////////////////////////////////////////////////// |
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69 | // Integration in one step |
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70 | ///////////////////////////////////////////////////////////////////////////////// |
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71 | |
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72 | void |
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73 | G4NystromRK4::Stepper |
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74 | (const G4double P[],const G4double dPdS[],G4double Step,G4double Po[],G4double Err[]) |
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75 | { |
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76 | G4double R[3] = { P[0], P[1] , P[2]}; |
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77 | G4double A[3] = {dPdS[0], dPdS[1], dPdS[2]}; |
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78 | |
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79 | m_iPoint[0]=R[0]; m_iPoint[1]=R[1]; m_iPoint[2]=R[2]; |
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80 | |
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81 | const G4double one_sixth= 1./6.; |
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82 | G4double S = Step ; |
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83 | G4double S5 = .5*Step ; |
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84 | G4double S4 = .25*Step ; |
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85 | G4double S6 = Step * one_sixth; // Step / 6.; |
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86 | |
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87 | |
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88 | // John A added, in order to emulate effect of call to changed/derived RHS |
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89 | // m_mom = sqrt(P[3]*P[3]+P[4]*P[4]+P[5]*P[5]); |
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90 | // m_imom = 1./m_mom; |
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91 | // m_cof = m_fEq->FCof()*m_imom; |
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92 | |
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93 | // Point 1 |
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94 | // |
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95 | G4double K1[3] = { m_imom*dPdS[3], m_imom*dPdS[4], m_imom*dPdS[5] }; |
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96 | |
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97 | // Point2 |
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98 | // |
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99 | G4double p[4] = {R[0]+S5*(A[0]+S4*K1[0]), |
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100 | R[1]+S5*(A[1]+S4*K1[1]), |
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101 | R[2]+S5*(A[2]+S4*K1[2]), |
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102 | P[7] }; |
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103 | getField(p); |
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104 | |
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105 | G4double A2[3] = {A[0]+S5*K1[0],A[1]+S5*K1[1],A[2]+S5*K1[2]}; |
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106 | G4double K2[3] = {(A2[1]*m_lastField[2]-A2[2]*m_lastField[1])*m_cof, |
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107 | (A2[2]*m_lastField[0]-A2[0]*m_lastField[2])*m_cof, |
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108 | (A2[0]*m_lastField[1]-A2[1]*m_lastField[0])*m_cof}; |
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109 | |
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110 | m_mPoint[0]=p[0]; m_mPoint[1]=p[1]; m_mPoint[2]=p[2]; |
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111 | |
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112 | // Point 3 with the same magnetic field |
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113 | // |
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114 | G4double A3[3] = {A[0]+S5*K2[0],A[1]+S5*K2[1],A[2]+S5*K2[2]}; |
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115 | G4double K3[3] = {(A3[1]*m_lastField[2]-A3[2]*m_lastField[1])*m_cof, |
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116 | (A3[2]*m_lastField[0]-A3[0]*m_lastField[2])*m_cof, |
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117 | (A3[0]*m_lastField[1]-A3[1]*m_lastField[0])*m_cof}; |
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118 | |
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119 | // Point 4 |
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120 | // |
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121 | p[0] = R[0]+S*(A[0]+S5*K3[0]); |
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122 | p[1] = R[1]+S*(A[1]+S5*K3[1]); |
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123 | p[2] = R[2]+S*(A[2]+S5*K3[2]); |
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124 | |
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125 | getField(p); |
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126 | |
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127 | G4double A4[3] = {A[0]+S*K3[0],A[1]+S*K3[1],A[2]+S*K3[2]}; |
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128 | G4double K4[3] = {(A4[1]*m_lastField[2]-A4[2]*m_lastField[1])*m_cof, |
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129 | (A4[2]*m_lastField[0]-A4[0]*m_lastField[2])*m_cof, |
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130 | (A4[0]*m_lastField[1]-A4[1]*m_lastField[0])*m_cof}; |
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131 | |
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132 | // New position |
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133 | // |
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134 | Po[0] = P[0]+S*(A[0]+S6*(K1[0]+K2[0]+K3[0])); |
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135 | Po[1] = P[1]+S*(A[1]+S6*(K1[1]+K2[1]+K3[1])); |
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136 | Po[2] = P[2]+S*(A[2]+S6*(K1[2]+K2[2]+K3[2])); |
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137 | |
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138 | m_fPoint[0]=Po[0]; m_fPoint[1]=Po[1]; m_fPoint[2]=Po[2]; |
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139 | |
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140 | // New direction |
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141 | // |
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142 | Po[3] = A[0]+S6*(K1[0]+K4[0]+2.*(K2[0]+K3[0])); |
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143 | Po[4] = A[1]+S6*(K1[1]+K4[1]+2.*(K2[1]+K3[1])); |
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144 | Po[5] = A[2]+S6*(K1[2]+K4[2]+2.*(K2[2]+K3[2])); |
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145 | |
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146 | // Errors |
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147 | // |
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148 | Err[3] = S*std::fabs(K1[0]-K2[0]-K3[0]+K4[0]); |
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149 | Err[4] = S*std::fabs(K1[1]-K2[1]-K3[1]+K4[1]); |
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150 | Err[5] = S*std::fabs(K1[2]-K2[2]-K3[2]+K4[2]); |
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151 | Err[0] = S*Err[3] ; |
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152 | Err[1] = S*Err[4] ; |
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153 | Err[2] = S*Err[5] ; |
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154 | Err[3]*= m_mom ; |
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155 | Err[4]*= m_mom ; |
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156 | Err[5]*= m_mom ; |
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157 | |
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158 | // Normalize momentum |
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159 | // |
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160 | G4double normF = m_mom/std::sqrt(Po[3]*Po[3]+Po[4]*Po[4]+Po[5]*Po[5]); |
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161 | Po [3]*=normF; Po[4]*=normF; Po[5]*=normF; |
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162 | |
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163 | // Pass Energy, time unchanged -- time is not integrated !! |
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164 | Po[6]=P[6]; Po[7]=P[7]; |
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165 | } |
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166 | |
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167 | |
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168 | ///////////////////////////////////////////////////////////////////////////////// |
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169 | // Estimate the maximum distance from the curve to the chord |
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170 | ///////////////////////////////////////////////////////////////////////////////// |
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171 | |
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172 | G4double |
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173 | G4NystromRK4::DistChord() const |
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174 | { |
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175 | G4double ax = m_fPoint[0]-m_iPoint[0]; |
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176 | G4double ay = m_fPoint[1]-m_iPoint[1]; |
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177 | G4double az = m_fPoint[2]-m_iPoint[2]; |
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178 | G4double dx = m_mPoint[0]-m_iPoint[0]; |
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179 | G4double dy = m_mPoint[1]-m_iPoint[1]; |
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180 | G4double dz = m_mPoint[2]-m_iPoint[2]; |
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181 | G4double d2 = (ax*ax+ay*ay+az*az) ; |
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182 | |
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183 | if(d2!=0.) { |
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184 | G4double s = (ax*dx+ay*dy+az*dz)/d2; |
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185 | dx -= (s*ax) ; |
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186 | dy -= (s*ay) ; |
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187 | dz -= (s*az) ; |
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188 | } |
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189 | return std::sqrt(dx*dx+dy*dy+dz*dz); |
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190 | } |
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191 | |
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192 | ///////////////////////////////////////////////////////////////////////////////// |
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193 | // Derivatives calculation - caching the momentum value |
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194 | ///////////////////////////////////////////////////////////////////////////////// |
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195 | |
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196 | void |
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197 | G4NystromRK4::ComputeRightHandSide(const G4double P[],G4double dPdS[]) |
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198 | { |
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199 | G4double P4vec[4]= { P[0], P[1], P[2], P[7] }; // Time is P[7] |
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200 | getField(P4vec); |
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201 | m_mom = std::sqrt(P[3]*P[3]+P[4]*P[4]+P[5]*P[5]) ; |
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202 | m_imom = 1./m_mom ; |
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203 | m_cof = m_fEq->FCof()*m_imom ; |
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204 | m_cachedMom = true ; // Caching the value |
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205 | dPdS[0] = P[3]*m_imom ; // dx /ds |
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206 | dPdS[1] = P[4]*m_imom ; // dy /ds |
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207 | dPdS[2] = P[5]*m_imom ; // dz /ds |
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208 | dPdS[3] = m_cof*(P[4]*m_lastField[2]-P[5]*m_lastField[1]) ; // dPx/ds |
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209 | dPdS[4] = m_cof*(P[5]*m_lastField[0]-P[3]*m_lastField[2]) ; // dPy/ds |
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210 | dPdS[5] = m_cof*(P[3]*m_lastField[1]-P[4]*m_lastField[0]) ; // dPz/ds |
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211 | } |
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