[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: G4MagErrorStepper.cc,v 1.13 2006/06/29 18:24:18 gunter Exp $ |
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[850] | 28 | // GEANT4 tag $Name: HEAD $ |
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[831] | 29 | // |
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| 30 | // -------------------------------------------------------------------- |
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| 31 | |
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| 32 | #include "G4MagErrorStepper.hh" |
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| 33 | #include "G4LineSection.hh" |
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| 34 | |
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| 35 | G4MagErrorStepper::~G4MagErrorStepper() |
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| 36 | { |
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| 37 | delete[] yMiddle; |
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| 38 | delete[] dydxMid; |
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| 39 | delete[] yInitial; |
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| 40 | delete[] yOneStep; |
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| 41 | } |
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| 42 | |
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| 43 | void |
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| 44 | G4MagErrorStepper::Stepper( const G4double yInput[], |
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| 45 | const G4double dydx[], |
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| 46 | G4double hstep, |
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| 47 | G4double yOutput[], |
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| 48 | G4double yError [] ) |
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| 49 | { |
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| 50 | const G4int nvar = this->GetNumberOfVariables() ; |
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| 51 | const G4int maxvar= GetNumberOfStateVariables(); |
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| 52 | |
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| 53 | G4int i; |
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| 54 | // correction for Richardson Extrapolation. |
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| 55 | G4double correction = 1. / ( (1 << IntegratorOrder()) -1 ); |
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| 56 | |
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| 57 | // Saving yInput because yInput and yOutput can be aliases for same array |
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| 58 | |
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| 59 | for(i=0;i<nvar;i++) yInitial[i]=yInput[i]; |
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| 60 | yInitial[7]= yInput[7]; // Copy the time in case ... even if not really needed |
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| 61 | yMiddle[7] = yInput[7]; // Copy the time from initial value |
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| 62 | yOneStep[7] = yInput[7]; // As it contributes to final value of yOutput ? |
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| 63 | // yOutput[7] = yInput[7]; // -> dumb stepper does it too for RK4 |
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| 64 | for(i=nvar;i<maxvar;i++) yOutput[i]=yInput[i]; |
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| 65 | // yError[7] = 0.0; |
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| 66 | |
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| 67 | G4double halfStep = hstep * 0.5; |
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| 68 | |
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| 69 | // Do two half steps |
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| 70 | |
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| 71 | DumbStepper (yInitial, dydx, halfStep, yMiddle); |
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| 72 | RightHandSide(yMiddle, dydxMid); |
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| 73 | DumbStepper (yMiddle, dydxMid, halfStep, yOutput); |
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| 74 | |
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| 75 | // Store midpoint, chord calculation |
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| 76 | |
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| 77 | fMidPoint = G4ThreeVector( yMiddle[0], yMiddle[1], yMiddle[2]); |
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| 78 | |
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| 79 | // Do a full Step |
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| 80 | DumbStepper(yInitial, dydx, hstep, yOneStep); |
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| 81 | for(i=0;i<nvar;i++) { |
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| 82 | yError [i] = yOutput[i] - yOneStep[i] ; |
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| 83 | yOutput[i] += yError[i]*correction ; // Provides accuracy increased |
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| 84 | // by 1 order via the |
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| 85 | // Richardson Extrapolation |
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| 86 | } |
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| 87 | |
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| 88 | fInitialPoint = G4ThreeVector( yInitial[0], yInitial[1], yInitial[2]); |
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| 89 | fFinalPoint = G4ThreeVector( yOutput[0], yOutput[1], yOutput[2]); |
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| 90 | |
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| 91 | return ; |
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| 92 | } |
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| 93 | |
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| 94 | |
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| 95 | |
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| 96 | G4double |
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| 97 | G4MagErrorStepper::DistChord() const |
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| 98 | { |
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| 99 | // Estimate the maximum distance from the curve to the chord |
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| 100 | // |
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| 101 | // We estimate this using the distance of the midpoint to |
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| 102 | // chord (the line between |
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| 103 | // |
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| 104 | // Method below is good only for angle deviations < 2 pi, |
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| 105 | // This restriction should not a problem for the Runge cutta methods, |
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| 106 | // which generally cannot integrate accurately for large angle deviations. |
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| 107 | G4double distLine, distChord; |
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| 108 | |
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| 109 | if (fInitialPoint != fFinalPoint) { |
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| 110 | distLine= G4LineSection::Distline( fMidPoint, fInitialPoint, fFinalPoint ); |
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| 111 | // This is a class method that gives distance of Mid |
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| 112 | // from the Chord between the Initial and Final points. |
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| 113 | |
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| 114 | distChord = distLine; |
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| 115 | }else{ |
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| 116 | distChord = (fMidPoint-fInitialPoint).mag(); |
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| 117 | } |
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| 118 | |
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| 119 | return distChord; |
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| 120 | } |
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| 121 | |
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