| 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: $
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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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