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: G4ClassicalRK4.cc,v 1.14 2009/03/25 15:29:02 gcosmo Exp $ |
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28 | // GEANT4 tag $Name: geant4-09-04-beta-01 $ |
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29 | // |
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30 | // ------------------------------------------------------------------- |
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31 | |
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32 | #include "G4ClassicalRK4.hh" |
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33 | #include "G4ThreeVector.hh" |
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34 | |
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35 | ////////////////////////////////////////////////////////////////// |
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36 | // |
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37 | // Constructor sets the number of variables (default = 6) |
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38 | |
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39 | G4ClassicalRK4:: |
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40 | G4ClassicalRK4(G4EquationOfMotion* EqRhs, G4int numberOfVariables) |
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41 | : G4MagErrorStepper(EqRhs, numberOfVariables) |
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42 | { |
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43 | unsigned int noVariables= std::max(numberOfVariables,8); // For Time .. 7+1 |
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44 | |
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45 | dydxm = new G4double[noVariables]; |
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46 | dydxt = new G4double[noVariables]; |
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47 | yt = new G4double[noVariables]; |
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48 | } |
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49 | |
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50 | //////////////////////////////////////////////////////////////// |
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51 | // |
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52 | // Destructor |
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53 | |
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54 | G4ClassicalRK4::~G4ClassicalRK4() |
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55 | { |
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56 | delete[] dydxm; |
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57 | delete[] dydxt; |
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58 | delete[] yt; |
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59 | } |
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60 | |
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61 | ////////////////////////////////////////////////////////////////////// |
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62 | // |
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63 | // Given values for the variables y[0,..,n-1] and their derivatives |
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64 | // dydx[0,...,n-1] known at x, use the classical 4th Runge-Kutta |
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65 | // method to advance the solution over an interval h and return the |
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66 | // incremented variables as yout[0,...,n-1], which not be a distinct |
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67 | // array from y. The user supplies the routine RightHandSide(x,y,dydx), |
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68 | // which returns derivatives dydx at x. The source is routine rk4 from |
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69 | // NRC p. 712-713 . |
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70 | |
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71 | void |
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72 | G4ClassicalRK4::DumbStepper( const G4double yIn[], |
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73 | const G4double dydx[], |
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74 | G4double h, |
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75 | G4double yOut[]) |
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76 | { |
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77 | const G4int nvar = this->GetNumberOfVariables(); // fNumberOfVariables(); |
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78 | G4int i; |
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79 | G4double hh = h*0.5 , h6 = h/6.0 ; |
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80 | |
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81 | // Initialise time to t0, needed when it is not updated by the integration. |
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82 | // [ Note: Only for time dependent fields (usually electric) |
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83 | // is it neccessary to integrate the time.] |
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84 | yt[7] = yIn[7]; |
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85 | yOut[7] = yIn[7]; |
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86 | |
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87 | for(i=0;i<nvar;i++) |
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88 | { |
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89 | yt[i] = yIn[i] + hh*dydx[i] ; // 1st Step K1=h*dydx |
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90 | } |
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91 | RightHandSide(yt,dydxt) ; // 2nd Step K2=h*dydxt |
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92 | |
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93 | for(i=0;i<nvar;i++) |
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94 | { |
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95 | yt[i] = yIn[i] + hh*dydxt[i] ; |
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96 | } |
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97 | RightHandSide(yt,dydxm) ; // 3rd Step K3=h*dydxm |
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98 | |
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99 | for(i=0;i<nvar;i++) |
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100 | { |
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101 | yt[i] = yIn[i] + h*dydxm[i] ; |
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102 | dydxm[i] += dydxt[i] ; // now dydxm=(K2+K3)/h |
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103 | } |
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104 | RightHandSide(yt,dydxt) ; // 4th Step K4=h*dydxt |
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105 | |
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106 | for(i=0;i<nvar;i++) // Final RK4 output |
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107 | { |
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108 | yOut[i] = yIn[i]+h6*(dydx[i]+dydxt[i]+2.0*dydxm[i]); //+K1/6+K4/6+(K2+K3)/3 |
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109 | } |
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110 | if ( nvar == 12 ) { NormalisePolarizationVector ( yOut ); } |
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111 | |
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112 | } // end of DumbStepper .................................................... |
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113 | |
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114 | //////////////////////////////////////////////////////////////////// |
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115 | // |
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116 | // StepWithEst |
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117 | |
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118 | void |
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119 | G4ClassicalRK4::StepWithEst( const G4double*, |
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120 | const G4double*, |
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121 | G4double, |
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122 | G4double*, |
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123 | G4double&, |
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124 | G4double&, |
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125 | const G4double*, |
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126 | G4double* ) |
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127 | { |
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128 | G4Exception("G4ClassicalRK4::StepWithEst()", "ObsoleteMethod", |
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129 | FatalException, "Method no longer used."); |
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130 | |
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131 | } // end of StepWithEst ...................................................... |
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132 | |
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