| 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: G4HelixExplicitEuler.cc,v 1.8 2007/12/10 16:29:49 gunter 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 | // Helix Explicit Euler: x_1 = x_0 + helix(h) |
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| 32 | // with helix(h) being a helix piece of length h |
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| 33 | // most simple approach for solving linear differential equations. |
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| 34 | // Take the current derivative and add it to the current position. |
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| 35 | // |
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| 36 | // W.Wander <wwc@mit.edu> 12/09/97 |
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| 37 | // ------------------------------------------------------------------- |
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| 38 | |
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| 39 | #include "G4HelixExplicitEuler.hh" |
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| 40 | #include "G4ThreeVector.hh" |
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| 41 | |
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| 42 | |
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| 43 | void G4HelixExplicitEuler::Stepper( const G4double yInput[7], |
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| 44 | const G4double*, |
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| 45 | G4double Step, |
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| 46 | G4double yOut[7], |
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| 47 | G4double yErr[]) |
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| 48 | |
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| 49 | { |
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| 50 | |
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| 51 | //Estimation of the Stepping Angle |
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| 52 | |
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| 53 | G4ThreeVector Bfld; |
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| 54 | MagFieldEvaluate(yInput, Bfld); |
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| 55 | |
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| 56 | const G4int nvar = 6 ; |
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| 57 | G4int i; |
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| 58 | G4double yTemp[7], yIn[7] ; |
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| 59 | G4ThreeVector Bfld_midpoint; |
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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 | |
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| 65 | // Do full step and two half steps |
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| 66 | G4double yTemp2[7]; |
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| 67 | AdvanceHelix(yIn, Bfld, h, yTemp2,yTemp); |
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| 68 | MagFieldEvaluate(yTemp2, Bfld_midpoint) ; |
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| 69 | AdvanceHelix(yTemp2, Bfld_midpoint, h, yOut); |
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| 70 | |
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| 71 | // Error estimation |
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| 72 | for(i=0;i<nvar;i++) { |
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| 73 | yErr[i] = yOut[i] - yTemp[i] ; |
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| 74 | } |
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| 75 | |
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| 76 | } |
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| 77 | |
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| 78 | G4double G4HelixExplicitEuler::DistChord() const |
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| 79 | { |
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| 80 | // Implementation : must check whether h/R > 2 pi !! |
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| 81 | // If( h/R < pi) use G4LineSection::DistLine |
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| 82 | // Else DistChord=R_helix |
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| 83 | // |
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| 84 | G4double distChord; |
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| 85 | G4double Ang_curve=GetAngCurve(); |
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| 86 | |
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| 87 | |
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| 88 | if(Ang_curve<=pi){ |
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| 89 | distChord=GetRadHelix()*(1-std::cos(0.5*Ang_curve)); |
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| 90 | } |
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| 91 | else |
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| 92 | if(Ang_curve<twopi){ |
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| 93 | distChord=GetRadHelix()*(1+std::cos(0.5*(twopi-Ang_curve))); |
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| 94 | } |
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| 95 | else{ |
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| 96 | distChord=2.*GetRadHelix(); |
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| 97 | } |
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| 98 | |
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| 99 | return distChord; |
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| 100 | |
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| 101 | } |
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| 102 | void |
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| 103 | G4HelixExplicitEuler::DumbStepper( const G4double yIn[], |
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| 104 | G4ThreeVector Bfld, |
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| 105 | G4double h, |
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| 106 | G4double yOut[]) |
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| 107 | { |
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| 108 | |
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| 109 | AdvanceHelix(yIn, Bfld, h, yOut); |
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| 110 | |
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| 111 | } |
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