Gabriele Cosmo
127 lines
4.7 KiB
C++
127 lines
4.7 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: G4ConstRK4.hh 66356 2012-12-18 09:02:32Z gcosmo $
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//
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//
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// Class G4ConstRK4
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//
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// class description:
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//
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// G4ConstRK4 performs the integration of one step with error calculation
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// in constant magnetic field. The integration method is the same as in
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// ClassicalRK4. The field value is assumed constant for the step.
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// This field evaluation is called only once per step.
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// G4ConstRK4 can be used only for magnetic fields.
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// History:
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// - 18.09.2008 - J.Apostolakis, T.Nikitina - Created
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// -------------------------------------------------------------------
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#ifndef G4CONSTRK4_HH
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#define G4CONSTRK4_HH
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#include "G4MagErrorStepper.hh"
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#include "G4EquationOfMotion.hh"
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#include "G4Mag_EqRhs.hh"
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class G4ConstRK4 : public G4MagErrorStepper
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{
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public: // with description
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G4ConstRK4(G4Mag_EqRhs *EquationMotion, G4int numberOfStateVariables=8);
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~G4ConstRK4();
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void Stepper( const G4double y[],
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const G4double dydx[],
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G4double h,
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G4double yout[],
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G4double yerr[] );
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void DumbStepper( const G4double yIn[],
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const G4double dydx[],
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G4double h,
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G4double yOut[] ) ;
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G4double DistChord() const;
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inline void RightHandSideConst(const G4double y[],
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G4double dydx[] ) const;
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inline void GetConstField(const G4double y[],G4double Field[]);
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public: // without description
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G4int IntegratorOrder() const { return 4; }
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private:
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G4ConstRK4(const G4ConstRK4&);
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G4ConstRK4& operator=(const G4ConstRK4&);
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// Private copy constructor and assignment operator.
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private:
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G4ThreeVector fInitialPoint, fMidPoint, fFinalPoint;
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// Data stored in order to find the chord
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G4double *dydxm, *dydxt, *yt; // scratch space - not state
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G4double *yInitial, *yMiddle, *dydxMid, *yOneStep;
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G4Mag_EqRhs *fEq;
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G4double Field[3];
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};
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// Inline methods
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inline void G4ConstRK4:: RightHandSideConst(const G4double y[],
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G4double dydx[] ) const
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{
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G4double momentum_mag_square = y[3]*y[3] + y[4]*y[4] + y[5]*y[5];
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G4double inv_momentum_magnitude = 1.0 / std::sqrt( momentum_mag_square );
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G4double cof =fEq->FCof()*inv_momentum_magnitude;
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dydx[0] = y[3]*inv_momentum_magnitude; // (d/ds)x = Vx/V
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dydx[1] = y[4]*inv_momentum_magnitude; // (d/ds)y = Vy/V
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dydx[2] = y[5]*inv_momentum_magnitude; // (d/ds)z = Vz/V
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dydx[3] = cof*(y[4]*Field[2] - y[5]*Field[1]) ; // Ax = a*(Vy*Bz - Vz*By)
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dydx[4] = cof*(y[5]*Field[0] - y[3]*Field[2]) ; // Ay = a*(Vz*Bx - Vx*Bz)
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dydx[5] = cof*(y[3]*Field[1] - y[4]*Field[0]) ; // Az = a*(Vx*By - Vy*Bx)
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}
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inline void G4ConstRK4::GetConstField(const G4double y[],G4double B[])
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{
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G4double PositionAndTime[4];
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PositionAndTime[0] = y[0];
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PositionAndTime[1] = y[1];
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PositionAndTime[2] = y[2];
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// Global Time
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PositionAndTime[3] = y[7];
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fEq -> GetFieldValue(PositionAndTime, B) ;
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}
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#endif // G4CONSTRK4_HH
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