Gabriele Cosmo
138 lines
5.1 KiB
C++
138 lines
5.1 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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// $Id: G4NystromRK4.hh 106564 2017-10-13 09:06:13Z gcosmo $
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//
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// class G4NystromRK4
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//
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// Class description:
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//
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// Integrate the equations of the motion of a particle in a magnetic field
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// using 4th Runge-Kutta-Nystrom method with errors estimation
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// (ATL-SOFT-PUB-2009-01)
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// Current form can be used only for 'pure' magnetic field.
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// Notes: 1) field must be time-independent.
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// 2) time is not integrated
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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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#ifndef G4NYSTROMRK4_HH
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#define G4NYSTROMRK4_HH
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#include "globals.hh"
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#include "G4MagIntegratorStepper.hh"
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#include "G4Mag_EqRhs.hh"
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class G4NystromRK4 : public G4MagIntegratorStepper
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{
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public:
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G4NystromRK4(G4Mag_EqRhs *EquationMotion, G4double distanceConstField=0.0);
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// Can be used only for Magnetic Fields - and for 6 variables (x,p)
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~G4NystromRK4() ;
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void Stepper(const G4double P [],
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const G4double dPdS[],
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G4double step ,
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G4double Po [],
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G4double Err []);
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// Single call for integration result and error
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// - Provides Error via analytical method
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virtual void ComputeRightHandSide(const G4double P[],G4double dPdS[]);
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// Must compute RHS - and does caches result
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void SetDistanceForConstantField( G4double length );
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G4double GetDistanceForConstantField() const;
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G4int IntegratorOrder() const {return 4;}
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G4double DistChord() const;
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private:
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inline void getField (const G4double P[4]);
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G4bool CheckCachedMomemtum( const G4double PosMom[6], G4double savedMom );
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G4bool CheckFieldPosition( const G4double Position[3],
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const G4double lastPosition[3] );
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////////////////////////////////////////////////////////////////
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// Private data
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////////////////////////////////////////////////////////////////
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G4Mag_EqRhs* m_fEq;
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G4double m_lastField[3];
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G4double m_fldPosition[4];
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G4double m_magdistance ;
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G4double m_magdistance2;
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G4double m_cof ;
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G4double m_mom ;
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G4double m_imom ;
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G4bool m_cachedMom ;
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G4double m_iPoint [3];
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G4double m_mPoint [3];
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G4double m_fPoint [3];
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};
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/////////////////////////////////////////////////////////////////////////////////
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// Inline methods
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/////////////////////////////////////////////////////////////////////////////////
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inline void G4NystromRK4::SetDistanceForConstantField( G4double length )
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{
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m_magdistance= length;
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m_magdistance2 = length*length;
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}
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inline G4double G4NystromRK4::GetDistanceForConstantField() const
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{
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return m_magdistance;
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}
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/////////////////////////////////////////////////////////////////////////////////
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// Get value of magnetic field while checking distance from last stored call
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/////////////////////////////////////////////////////////////////////////////////
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inline void G4NystromRK4::getField (const G4double P[4])
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{
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G4double dx = P[0]-m_fldPosition[0];
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G4double dy = P[1]-m_fldPosition[1];
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G4double dz = P[2]-m_fldPosition[2];
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if((dx*dx+dy*dy+dz*dz) > m_magdistance2)
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{
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m_fldPosition[0] = P[0];
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m_fldPosition[1] = P[1];
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m_fldPosition[2] = P[2];
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m_fldPosition[3] = P[3]; // Generally it is P[7] - changed convention !!
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m_fEq->GetFieldValue(m_fldPosition, m_lastField);
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}
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}
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#endif // G4NYSTROMRK4
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