| 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: G4NystromRK4.cc,v 1.9 2010/09/10 15:42:09 japost Exp $
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| 28 | // GEANT4 tag $Name: field-V09-03-03 $
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| 29 | //
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| 30 | // History:
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| 31 | // - Created: I.Gavrilenko 15.05.2009 (as G4AtlasRK4)
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| 32 | // - Adaptations: J. Apostolakis May-Nov 2009
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| 33 | // -------------------------------------------------------------------
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| 34 |
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| 35 | #include "G4NystromRK4.hh"
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| 36 | #include <iostream>
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| 37 |
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| 38 | //////////////////////////////////////////////////////////////////
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| 39 | // Constructor - with optional distance ( has default value)
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| 40 | //////////////////////////////////////////////////////////////////
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| 41 |
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| 42 | G4NystromRK4::G4NystromRK4(G4Mag_EqRhs* magEqRhs, G4double distanceConstField)
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| 43 | : G4MagIntegratorStepper(magEqRhs, 6), // number of variables
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| 44 | m_fEq( magEqRhs ),
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| 45 | m_magdistance( distanceConstField ),
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| 46 | m_cof( 0.0 ),
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| 47 | m_mom( 0.0 ),
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| 48 | m_imom( 0.0 ),
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| 49 | m_cachedMom( false )
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| 50 | {
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| 51 | m_fldPosition[0] = m_iPoint[0] = m_fPoint[0] = m_mPoint[0] = 9.9999999e+99 ;
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| 52 | m_fldPosition[1] = m_iPoint[1] = m_fPoint[1] = m_mPoint[1] = 9.9999999e+99 ;
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| 53 | m_fldPosition[2] = m_iPoint[2] = m_fPoint[2] = m_mPoint[2] = 9.9999999e+99 ;
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| 54 | m_fldPosition[3] = -9.9999999e+99;
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| 55 | m_lastField[0] = m_lastField[1] = m_lastField[2] = 0.0;
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| 56 |
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| 57 | m_magdistance2 = distanceConstField*distanceConstField;
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| 58 | }
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| 59 |
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| 60 | ////////////////////////////////////////////////////////////////
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| 61 | // Destructor
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| 62 | ////////////////////////////////////////////////////////////////
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| 63 |
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| 64 | G4NystromRK4::~G4NystromRK4()
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| 65 | {
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| 66 | }
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| 67 |
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| 68 | /////////////////////////////////////////////////////////////////////////////////
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| 69 | // Integration in one step
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| 70 | /////////////////////////////////////////////////////////////////////////////////
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| 71 |
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| 72 | void
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| 73 | G4NystromRK4::Stepper
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| 74 | (const G4double P[],const G4double dPdS[],G4double Step,G4double Po[],G4double Err[])
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| 75 | {
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| 76 | G4double R[3] = { P[0], P[1] , P[2]};
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| 77 | G4double A[3] = {dPdS[0], dPdS[1], dPdS[2]};
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| 78 |
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| 79 | m_iPoint[0]=R[0]; m_iPoint[1]=R[1]; m_iPoint[2]=R[2];
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| 80 |
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| 81 | const G4double one_sixth= 1./6.;
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| 82 | G4double S = Step ;
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| 83 | G4double S5 = .5*Step ;
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| 84 | G4double S4 = .25*Step ;
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| 85 | G4double S6 = Step * one_sixth; // Step / 6.;
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| 86 |
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| 87 |
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| 88 | // John A added, in order to emulate effect of call to changed/derived RHS
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| 89 | // m_mom = sqrt(P[3]*P[3]+P[4]*P[4]+P[5]*P[5]);
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| 90 | // m_imom = 1./m_mom;
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| 91 | // m_cof = m_fEq->FCof()*m_imom;
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| 92 |
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| 93 | // Point 1
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| 94 | //
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| 95 | G4double K1[3] = { m_imom*dPdS[3], m_imom*dPdS[4], m_imom*dPdS[5] };
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| 96 |
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| 97 | // Point2
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| 98 | //
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| 99 | G4double p[4] = {R[0]+S5*(A[0]+S4*K1[0]),
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| 100 | R[1]+S5*(A[1]+S4*K1[1]),
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| 101 | R[2]+S5*(A[2]+S4*K1[2]),
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| 102 | P[7] };
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| 103 | getField(p);
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| 104 |
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| 105 | G4double A2[3] = {A[0]+S5*K1[0],A[1]+S5*K1[1],A[2]+S5*K1[2]};
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| 106 | G4double K2[3] = {(A2[1]*m_lastField[2]-A2[2]*m_lastField[1])*m_cof,
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| 107 | (A2[2]*m_lastField[0]-A2[0]*m_lastField[2])*m_cof,
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| 108 | (A2[0]*m_lastField[1]-A2[1]*m_lastField[0])*m_cof};
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| 109 |
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| 110 | m_mPoint[0]=p[0]; m_mPoint[1]=p[1]; m_mPoint[2]=p[2];
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| 111 |
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| 112 | // Point 3 with the same magnetic field
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| 113 | //
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| 114 | G4double A3[3] = {A[0]+S5*K2[0],A[1]+S5*K2[1],A[2]+S5*K2[2]};
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| 115 | G4double K3[3] = {(A3[1]*m_lastField[2]-A3[2]*m_lastField[1])*m_cof,
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| 116 | (A3[2]*m_lastField[0]-A3[0]*m_lastField[2])*m_cof,
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| 117 | (A3[0]*m_lastField[1]-A3[1]*m_lastField[0])*m_cof};
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| 118 |
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| 119 | // Point 4
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| 120 | //
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| 121 | p[0] = R[0]+S*(A[0]+S5*K3[0]);
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| 122 | p[1] = R[1]+S*(A[1]+S5*K3[1]);
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| 123 | p[2] = R[2]+S*(A[2]+S5*K3[2]);
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| 124 |
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| 125 | getField(p);
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| 126 |
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| 127 | G4double A4[3] = {A[0]+S*K3[0],A[1]+S*K3[1],A[2]+S*K3[2]};
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| 128 | G4double K4[3] = {(A4[1]*m_lastField[2]-A4[2]*m_lastField[1])*m_cof,
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| 129 | (A4[2]*m_lastField[0]-A4[0]*m_lastField[2])*m_cof,
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| 130 | (A4[0]*m_lastField[1]-A4[1]*m_lastField[0])*m_cof};
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| 131 |
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| 132 | // New position
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| 133 | //
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| 134 | Po[0] = P[0]+S*(A[0]+S6*(K1[0]+K2[0]+K3[0]));
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| 135 | Po[1] = P[1]+S*(A[1]+S6*(K1[1]+K2[1]+K3[1]));
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| 136 | Po[2] = P[2]+S*(A[2]+S6*(K1[2]+K2[2]+K3[2]));
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| 137 |
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| 138 | m_fPoint[0]=Po[0]; m_fPoint[1]=Po[1]; m_fPoint[2]=Po[2];
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| 139 |
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| 140 | // New direction
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| 141 | //
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| 142 | Po[3] = A[0]+S6*(K1[0]+K4[0]+2.*(K2[0]+K3[0]));
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| 143 | Po[4] = A[1]+S6*(K1[1]+K4[1]+2.*(K2[1]+K3[1]));
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| 144 | Po[5] = A[2]+S6*(K1[2]+K4[2]+2.*(K2[2]+K3[2]));
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| 145 |
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| 146 | // Errors
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| 147 | //
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| 148 | Err[3] = S*std::fabs(K1[0]-K2[0]-K3[0]+K4[0]);
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| 149 | Err[4] = S*std::fabs(K1[1]-K2[1]-K3[1]+K4[1]);
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| 150 | Err[5] = S*std::fabs(K1[2]-K2[2]-K3[2]+K4[2]);
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| 151 | Err[0] = S*Err[3] ;
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| 152 | Err[1] = S*Err[4] ;
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| 153 | Err[2] = S*Err[5] ;
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| 154 | Err[3]*= m_mom ;
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| 155 | Err[4]*= m_mom ;
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| 156 | Err[5]*= m_mom ;
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| 157 |
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| 158 | // Normalize momentum
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| 159 | //
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| 160 | G4double normF = m_mom/std::sqrt(Po[3]*Po[3]+Po[4]*Po[4]+Po[5]*Po[5]);
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| 161 | Po [3]*=normF; Po[4]*=normF; Po[5]*=normF;
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| 162 |
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| 163 | // Pass Energy, time unchanged -- time is not integrated !!
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| 164 | Po[6]=P[6]; Po[7]=P[7];
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| 165 | }
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| 166 |
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| 167 |
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| 168 | /////////////////////////////////////////////////////////////////////////////////
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| 169 | // Estimate the maximum distance from the curve to the chord
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| 170 | /////////////////////////////////////////////////////////////////////////////////
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| 171 |
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| 172 | G4double
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| 173 | G4NystromRK4::DistChord() const
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| 174 | {
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| 175 | G4double ax = m_fPoint[0]-m_iPoint[0];
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| 176 | G4double ay = m_fPoint[1]-m_iPoint[1];
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| 177 | G4double az = m_fPoint[2]-m_iPoint[2];
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| 178 | G4double dx = m_mPoint[0]-m_iPoint[0];
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| 179 | G4double dy = m_mPoint[1]-m_iPoint[1];
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| 180 | G4double dz = m_mPoint[2]-m_iPoint[2];
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| 181 | G4double d2 = (ax*ax+ay*ay+az*az) ;
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| 182 |
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| 183 | if(d2!=0.) {
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| 184 | G4double s = (ax*dx+ay*dy+az*dz)/d2;
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| 185 | dx -= (s*ax) ;
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| 186 | dy -= (s*ay) ;
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| 187 | dz -= (s*az) ;
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| 188 | }
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| 189 | return std::sqrt(dx*dx+dy*dy+dz*dz);
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| 190 | }
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| 191 |
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| 192 | /////////////////////////////////////////////////////////////////////////////////
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| 193 | // Derivatives calculation - caching the momentum value
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| 194 | /////////////////////////////////////////////////////////////////////////////////
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| 195 |
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| 196 | void
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| 197 | G4NystromRK4::ComputeRightHandSide(const G4double P[],G4double dPdS[])
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| 198 | {
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| 199 | G4double P4vec[4]= { P[0], P[1], P[2], P[7] }; // Time is P[7]
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| 200 | getField(P4vec);
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| 201 | m_mom = std::sqrt(P[3]*P[3]+P[4]*P[4]+P[5]*P[5]) ;
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| 202 | m_imom = 1./m_mom ;
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| 203 | m_cof = m_fEq->FCof()*m_imom ;
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| 204 | m_cachedMom = true ; // Caching the value
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| 205 | dPdS[0] = P[3]*m_imom ; // dx /ds
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| 206 | dPdS[1] = P[4]*m_imom ; // dy /ds
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| 207 | dPdS[2] = P[5]*m_imom ; // dz /ds
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| 208 | dPdS[3] = m_cof*(P[4]*m_lastField[2]-P[5]*m_lastField[1]) ; // dPx/ds
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| 209 | dPdS[4] = m_cof*(P[5]*m_lastField[0]-P[3]*m_lastField[2]) ; // dPy/ds
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| 210 | dPdS[5] = m_cof*(P[3]*m_lastField[1]-P[4]*m_lastField[0]) ; // dPz/ds
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| 211 | }
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