[831] | 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: G4RKG3_Stepper.cc,v 1.15 2007/08/21 10:17:41 tnikitin Exp $ |
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[1231] | 28 | // GEANT4 tag $Name: $ |
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[831] | 29 | // |
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| 30 | // ------------------------------------------------------------------- |
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| 31 | |
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| 32 | #include "G4RKG3_Stepper.hh" |
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| 33 | #include "G4LineSection.hh" |
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| 34 | #include "G4Mag_EqRhs.hh" |
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| 35 | |
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| 36 | G4RKG3_Stepper::G4RKG3_Stepper(G4Mag_EqRhs *EqRhs) |
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| 37 | : G4MagIntegratorStepper(EqRhs,6) |
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| 38 | { |
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| 39 | |
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| 40 | fPtrMagEqOfMot=EqRhs; |
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| 41 | |
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| 42 | } |
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| 43 | |
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| 44 | G4RKG3_Stepper::~G4RKG3_Stepper() |
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| 45 | { |
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| 46 | } |
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| 47 | |
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| 48 | void G4RKG3_Stepper::Stepper( const G4double yInput[7], |
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| 49 | const G4double dydx[7], |
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| 50 | G4double Step, |
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| 51 | G4double yOut[7], |
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| 52 | G4double yErr[]) |
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| 53 | { |
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| 54 | G4double B[3]; |
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| 55 | G4int nvar = 6 ; |
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| 56 | G4int i; |
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| 57 | G4double by15 = 1. / 15. ; // was 0.066666666 ; |
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| 58 | |
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| 59 | G4double yTemp[7], dydxTemp[6], yIn[7] ; |
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| 60 | // Saving yInput because yInput and yOut can be aliases for same array |
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| 61 | for(i=0;i<nvar;i++) yIn[i]=yInput[i]; |
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| 62 | |
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| 63 | G4double h = Step * 0.5; |
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| 64 | hStep=Step; |
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| 65 | // Do two half steps |
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| 66 | |
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| 67 | StepNoErr(yIn, dydx,h, yTemp,B) ; |
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| 68 | |
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| 69 | //Store Bfld for DistChord Calculation |
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| 70 | for(i=0;i<3;i++)BfldIn[i]=B[i]; |
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| 71 | |
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| 72 | // RightHandSide(yTemp,dydxTemp) ; |
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| 73 | |
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| 74 | GetEquationOfMotion()->EvaluateRhsGivenB(yTemp,B,dydxTemp) ; |
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| 75 | StepNoErr(yTemp,dydxTemp,h,yOut,B); |
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| 76 | |
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| 77 | // Store midpoint, chord calculation |
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| 78 | |
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| 79 | fyMidPoint = G4ThreeVector( yTemp[0], yTemp[1], yTemp[2]); |
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| 80 | |
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| 81 | // Do a full Step |
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| 82 | |
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| 83 | h *= 2 ; |
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| 84 | StepNoErr(yIn,dydx,h,yTemp,B); // ,beTemp2) ; |
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| 85 | for(i=0;i<nvar;i++) |
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| 86 | { |
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| 87 | yErr[i] = yOut[i] - yTemp[i] ; |
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| 88 | yOut[i] += yErr[i]*by15 ; // Provides 5th order of accuracy |
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| 89 | } |
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| 90 | |
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| 91 | //Store values for DistChord method |
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| 92 | |
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| 93 | fyInitial = G4ThreeVector( yIn[0], yIn[1], yIn[2]); |
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| 94 | fpInitial = G4ThreeVector( yIn[3], yIn[4], yIn[5]); |
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| 95 | fyFinal = G4ThreeVector( yOut[0], yOut[1], yOut[2]); |
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| 96 | |
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| 97 | // NormaliseTangentVector( yOut ); // Deleted |
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| 98 | } |
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| 99 | |
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| 100 | // --------------------------------------------------------------------------- |
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| 101 | |
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| 102 | // Integrator for RK from G3 with evaluation of error in solution and delta |
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| 103 | // geometry based on naive similarity with the case of uniform magnetic field. |
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| 104 | // B1[3] is input and is the first magnetic field values |
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| 105 | // B2[3] is output and is the final magnetic field values. |
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| 106 | |
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| 107 | void G4RKG3_Stepper::StepWithEst( const G4double*, |
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| 108 | const G4double*, |
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| 109 | G4double, |
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| 110 | G4double*, |
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| 111 | G4double&, |
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| 112 | G4double&, |
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| 113 | const G4double*, |
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| 114 | G4double* ) |
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| 115 | |
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| 116 | { |
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| 117 | G4Exception("G4RKG3_Stepper::StepWithEst()", "ObsoleteMethod", |
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| 118 | FatalException, "Method no longer used."); |
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| 119 | } |
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| 120 | |
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| 121 | // ----------------------------------------------------------------- |
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| 122 | |
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| 123 | |
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| 124 | // Integrator RK Stepper from G3 with only two field evaluation per Step. |
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| 125 | // It is used in propagation initial Step by small substeps after solution |
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| 126 | // error and delta geometry considerations. B[3] is magnetic field which |
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| 127 | // is passed from substep to substep. |
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| 128 | |
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| 129 | void G4RKG3_Stepper::StepNoErr(const G4double tIn[7], |
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| 130 | const G4double dydx[7], |
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| 131 | G4double Step, |
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| 132 | G4double tOut[7], |
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| 133 | G4double B[3] ) // const |
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| 134 | |
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| 135 | { |
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| 136 | |
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| 137 | // Copy and edit the routine above, to delete alpha2, beta2, ... |
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| 138 | G4double K1[7],K2[7],K3[7],K4[7] ; |
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| 139 | G4double tTemp[7], yderiv[6] ; |
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| 140 | |
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| 141 | // Need Momentum value to give correct values to the coefficients in equation |
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| 142 | // Integration on unit velocity, but tIn[3,4,5] is momentum |
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| 143 | G4double mom,inverse_mom; |
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| 144 | G4int i ; |
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| 145 | const G4double c1=0.5,c2=0.125,c3=1./6.; |
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| 146 | |
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| 147 | // GetEquationOfMotion()->EvaluateRhsReturnB(tIn,dydx,B1) ; |
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| 148 | // Correction for momentum not a velocity |
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| 149 | // Need the protection !!! must be not zero |
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| 150 | mom=std::sqrt(tIn[3]*tIn[3]+tIn[4]*tIn[4]+tIn[5]*tIn[5]); |
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| 151 | inverse_mom=1./mom; |
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| 152 | for(i=0;i<3;i++) |
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| 153 | { |
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| 154 | K1[i] = Step * dydx[i+3]*inverse_mom; |
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| 155 | tTemp[i] = tIn[i] + Step*(c1*tIn[i+3]*inverse_mom + c2*K1[i]) ; |
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| 156 | tTemp[i+3] = tIn[i+3] + c1*K1[i]*mom ; |
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| 157 | |
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| 158 | } |
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| 159 | |
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| 160 | GetEquationOfMotion()->EvaluateRhsReturnB(tTemp,yderiv,B) ; |
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| 161 | |
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| 162 | |
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| 163 | for(i=0;i<3;i++) |
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| 164 | { |
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| 165 | K2[i] = Step * yderiv[i+3]*inverse_mom; |
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| 166 | tTemp[i+3] = tIn[i+3] + c1*K2[i]*mom ; |
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| 167 | } |
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| 168 | |
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| 169 | // Given B, calculate yderiv ! |
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| 170 | GetEquationOfMotion()->EvaluateRhsGivenB(tTemp,B,yderiv) ; |
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| 171 | |
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| 172 | for(i=0;i<3;i++) |
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| 173 | { |
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| 174 | K3[i] = Step * yderiv[i+3]*inverse_mom; |
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| 175 | tTemp[i] = tIn[i] + Step*(tIn[i+3]*inverse_mom + c1*K3[i]) ; |
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| 176 | tTemp[i+3] = tIn[i+3] + K3[i]*mom ; |
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| 177 | } |
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| 178 | |
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| 179 | |
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| 180 | // Calculates y-deriv(atives) & returns B too! |
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| 181 | GetEquationOfMotion()->EvaluateRhsReturnB(tTemp,yderiv,B) ; |
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| 182 | |
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| 183 | |
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| 184 | for(i=0;i<3;i++) // Output trajectory vector |
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| 185 | { |
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| 186 | K4[i] = Step * yderiv[i+3]*inverse_mom; |
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| 187 | tOut[i] = tIn[i] + Step*(tIn[i+3]*inverse_mom+ (K1[i] + K2[i] + K3[i])*c3) ; |
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| 188 | tOut[i+3] = tIn[i+3] + mom*(K1[i] + 2*K2[i] + 2*K3[i] +K4[i])*c3 ; |
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| 189 | } |
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| 190 | |
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| 191 | // NormaliseTangentVector( tOut ); |
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| 192 | |
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| 193 | |
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| 194 | } |
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| 195 | |
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| 196 | |
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| 197 | // --------------------------------------------------------------------------- |
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| 198 | |
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| 199 | G4double G4RKG3_Stepper::DistChord() const |
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| 200 | { |
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| 201 | // Soon: must check whether h/R > 2 pi !! |
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| 202 | // Method below is good only for < 2 pi |
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| 203 | G4double distChord,distLine; |
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| 204 | |
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| 205 | if (fyInitial != fyFinal) { |
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| 206 | distLine= G4LineSection::Distline(fyMidPoint,fyInitial,fyFinal ); |
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| 207 | |
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| 208 | distChord = distLine; |
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| 209 | }else{ |
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| 210 | distChord = (fyMidPoint-fyInitial).mag(); |
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| 211 | } |
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| 212 | |
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| 213 | |
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| 214 | return distChord; |
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| 215 | |
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| 216 | } |
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| 217 | |
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