Gabriele Cosmo
211 lines
7.9 KiB
C++
211 lines
7.9 KiB
C++
//
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// ********************************************************************
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// * License and Disclaimer *
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// * *
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// * The Geant4 software is copyright of the Copyright Holders of *
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// * the Geant4 Collaboration. It is provided under the terms and *
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// * conditions of the Geant4 Software License, included in the file *
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// * LICENSE and available at http://cern.ch/geant4/license . These *
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// * include a list of copyright holders. *
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// * *
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// * Neither the authors of this software system, nor their employing *
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// * institutes,nor the agencies providing financial support for this *
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// * work make any representation or warranty, express or implied, *
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// * regarding this software system or assume any liability for its *
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// * use. Please see the license in the file LICENSE and URL above *
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// * for the full disclaimer and the limitation of liability. *
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// * *
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// * This code implementation is the result of the scientific and *
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// * technical work of the GEANT4 collaboration. *
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// * By using, copying, modifying or distributing the software (or *
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// * any work based on the software) you agree to acknowledge its *
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// * use in resulting scientific publications, and indicate your *
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// * acceptance of all terms of the Geant4 Software license. *
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// ********************************************************************
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//
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//
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// $Id: G4NystromRK4.cc 66356 2012-12-18 09:02:32Z gcosmo $
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//
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// History:
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// - Created: I.Gavrilenko 15.05.2009 (as G4AtlasRK4)
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// - Adaptations: J. Apostolakis May-Nov 2009
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// -------------------------------------------------------------------
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#include "G4NystromRK4.hh"
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#include <iostream>
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//////////////////////////////////////////////////////////////////
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// Constructor - with optional distance ( has default value)
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//////////////////////////////////////////////////////////////////
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G4NystromRK4::G4NystromRK4(G4Mag_EqRhs* magEqRhs, G4double distanceConstField)
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: G4MagIntegratorStepper(magEqRhs, 6), // number of variables
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m_fEq( magEqRhs ),
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m_magdistance( distanceConstField ),
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m_cof( 0.0 ),
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m_mom( 0.0 ),
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m_imom( 0.0 ),
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m_cachedMom( false )
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{
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m_fldPosition[0] = m_iPoint[0] = m_fPoint[0] = m_mPoint[0] = 9.9999999e+99 ;
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m_fldPosition[1] = m_iPoint[1] = m_fPoint[1] = m_mPoint[1] = 9.9999999e+99 ;
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m_fldPosition[2] = m_iPoint[2] = m_fPoint[2] = m_mPoint[2] = 9.9999999e+99 ;
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m_fldPosition[3] = -9.9999999e+99;
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m_lastField[0] = m_lastField[1] = m_lastField[2] = 0.0;
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m_magdistance2 = distanceConstField*distanceConstField;
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}
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////////////////////////////////////////////////////////////////
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// Destructor
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////////////////////////////////////////////////////////////////
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G4NystromRK4::~G4NystromRK4()
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{
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}
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/////////////////////////////////////////////////////////////////////////////////
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// Integration in one step
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/////////////////////////////////////////////////////////////////////////////////
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void
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G4NystromRK4::Stepper
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(const G4double P[],const G4double dPdS[],G4double Step,G4double Po[],G4double Err[])
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{
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G4double R[3] = { P[0], P[1] , P[2]};
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G4double A[3] = {dPdS[0], dPdS[1], dPdS[2]};
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m_iPoint[0]=R[0]; m_iPoint[1]=R[1]; m_iPoint[2]=R[2];
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const G4double one_sixth= 1./6.;
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G4double S = Step ;
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G4double S5 = .5*Step ;
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G4double S4 = .25*Step ;
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G4double S6 = Step * one_sixth; // Step / 6.;
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// John A added, in order to emulate effect of call to changed/derived RHS
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// m_mom = sqrt(P[3]*P[3]+P[4]*P[4]+P[5]*P[5]);
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// m_imom = 1./m_mom;
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// m_cof = m_fEq->FCof()*m_imom;
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// Point 1
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//
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G4double K1[3] = { m_imom*dPdS[3], m_imom*dPdS[4], m_imom*dPdS[5] };
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// Point2
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//
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G4double p[4] = {R[0]+S5*(A[0]+S4*K1[0]),
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R[1]+S5*(A[1]+S4*K1[1]),
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R[2]+S5*(A[2]+S4*K1[2]),
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P[7] };
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getField(p);
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G4double A2[3] = {A[0]+S5*K1[0],A[1]+S5*K1[1],A[2]+S5*K1[2]};
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G4double K2[3] = {(A2[1]*m_lastField[2]-A2[2]*m_lastField[1])*m_cof,
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(A2[2]*m_lastField[0]-A2[0]*m_lastField[2])*m_cof,
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(A2[0]*m_lastField[1]-A2[1]*m_lastField[0])*m_cof};
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m_mPoint[0]=p[0]; m_mPoint[1]=p[1]; m_mPoint[2]=p[2];
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// Point 3 with the same magnetic field
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//
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G4double A3[3] = {A[0]+S5*K2[0],A[1]+S5*K2[1],A[2]+S5*K2[2]};
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G4double K3[3] = {(A3[1]*m_lastField[2]-A3[2]*m_lastField[1])*m_cof,
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(A3[2]*m_lastField[0]-A3[0]*m_lastField[2])*m_cof,
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(A3[0]*m_lastField[1]-A3[1]*m_lastField[0])*m_cof};
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// Point 4
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//
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p[0] = R[0]+S*(A[0]+S5*K3[0]);
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p[1] = R[1]+S*(A[1]+S5*K3[1]);
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p[2] = R[2]+S*(A[2]+S5*K3[2]);
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getField(p);
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G4double A4[3] = {A[0]+S*K3[0],A[1]+S*K3[1],A[2]+S*K3[2]};
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G4double K4[3] = {(A4[1]*m_lastField[2]-A4[2]*m_lastField[1])*m_cof,
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(A4[2]*m_lastField[0]-A4[0]*m_lastField[2])*m_cof,
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(A4[0]*m_lastField[1]-A4[1]*m_lastField[0])*m_cof};
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// New position
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//
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Po[0] = P[0]+S*(A[0]+S6*(K1[0]+K2[0]+K3[0]));
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Po[1] = P[1]+S*(A[1]+S6*(K1[1]+K2[1]+K3[1]));
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Po[2] = P[2]+S*(A[2]+S6*(K1[2]+K2[2]+K3[2]));
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m_fPoint[0]=Po[0]; m_fPoint[1]=Po[1]; m_fPoint[2]=Po[2];
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// New direction
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//
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Po[3] = A[0]+S6*(K1[0]+K4[0]+2.*(K2[0]+K3[0]));
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Po[4] = A[1]+S6*(K1[1]+K4[1]+2.*(K2[1]+K3[1]));
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Po[5] = A[2]+S6*(K1[2]+K4[2]+2.*(K2[2]+K3[2]));
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// Errors
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//
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Err[3] = S*std::fabs(K1[0]-K2[0]-K3[0]+K4[0]);
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Err[4] = S*std::fabs(K1[1]-K2[1]-K3[1]+K4[1]);
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Err[5] = S*std::fabs(K1[2]-K2[2]-K3[2]+K4[2]);
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Err[0] = S*Err[3] ;
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Err[1] = S*Err[4] ;
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Err[2] = S*Err[5] ;
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Err[3]*= m_mom ;
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Err[4]*= m_mom ;
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Err[5]*= m_mom ;
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// Normalize momentum
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//
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G4double normF = m_mom/std::sqrt(Po[3]*Po[3]+Po[4]*Po[4]+Po[5]*Po[5]);
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Po [3]*=normF; Po[4]*=normF; Po[5]*=normF;
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// Pass Energy, time unchanged -- time is not integrated !!
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Po[6]=P[6]; Po[7]=P[7];
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}
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/////////////////////////////////////////////////////////////////////////////////
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// Estimate the maximum distance from the curve to the chord
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/////////////////////////////////////////////////////////////////////////////////
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G4double
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G4NystromRK4::DistChord() const
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{
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G4double ax = m_fPoint[0]-m_iPoint[0];
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G4double ay = m_fPoint[1]-m_iPoint[1];
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G4double az = m_fPoint[2]-m_iPoint[2];
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G4double dx = m_mPoint[0]-m_iPoint[0];
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G4double dy = m_mPoint[1]-m_iPoint[1];
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G4double dz = m_mPoint[2]-m_iPoint[2];
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G4double d2 = (ax*ax+ay*ay+az*az) ;
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if(d2!=0.) {
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G4double ds = (ax*dx+ay*dy+az*dz)/d2;
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dx -= (ds*ax) ;
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dy -= (ds*ay) ;
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dz -= (ds*az) ;
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}
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return std::sqrt(dx*dx+dy*dy+dz*dz);
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}
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/////////////////////////////////////////////////////////////////////////////////
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// Derivatives calculation - caching the momentum value
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/////////////////////////////////////////////////////////////////////////////////
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void
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G4NystromRK4::ComputeRightHandSide(const G4double P[],G4double dPdS[])
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{
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G4double P4vec[4]= { P[0], P[1], P[2], P[7] }; // Time is P[7]
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getField(P4vec);
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m_mom = std::sqrt(P[3]*P[3]+P[4]*P[4]+P[5]*P[5]) ;
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m_imom = 1./m_mom ;
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m_cof = m_fEq->FCof()*m_imom ;
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m_cachedMom = true ; // Caching the value
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dPdS[0] = P[3]*m_imom ; // dx /ds
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dPdS[1] = P[4]*m_imom ; // dy /ds
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dPdS[2] = P[5]*m_imom ; // dz /ds
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dPdS[3] = m_cof*(P[4]*m_lastField[2]-P[5]*m_lastField[1]) ; // dPx/ds
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dPdS[4] = m_cof*(P[5]*m_lastField[0]-P[3]*m_lastField[2]) ; // dPy/ds
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dPdS[5] = m_cof*(P[3]*m_lastField[1]-P[4]*m_lastField[0]) ; // dPz/ds
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}
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