G4NystromRK4 Class Reference

#include <G4NystromRK4.hh>

Inheritance diagram for G4NystromRK4:

Collaboration diagram for G4NystromRK4:

Public Member Functions
	G4NystromRK4 (G4Mag_EqRhs *EquationMotion, G4double distanceConstField=0.0)
	~G4NystromRK4 ()
void	Stepper (const G4double P [], const G4double dPdS[], G4double step, G4double Po [], G4double Err [])
virtual void	ComputeRightHandSide (const double P[], double dPdS[])
void	SetDistanceForConstantField (G4double length)
G4double	GetDistanceForConstantField () const
G4int	IntegratorOrder () const
G4double	DistChord () const
Public Member Functions inherited from G4MagIntegratorStepper
	G4MagIntegratorStepper (G4EquationOfMotion *Equation, G4int numIntegrationVariables, G4int numStateVariables=12)
virtual	~G4MagIntegratorStepper ()
void	NormaliseTangentVector (G4double vec[6])
void	NormalisePolarizationVector (G4double vec[12])
void	RightHandSide (const double y[], double dydx[])
G4int	GetNumberOfVariables () const
G4int	GetNumberOfStateVariables () const
G4EquationOfMotion *	GetEquationOfMotion ()
void	SetEquationOfMotion (G4EquationOfMotion *newEquation)

Private Member Functions
void	getField (const G4double P[4])

Private Attributes
G4Mag_EqRhs *	m_fEq
G4double	m_lastField [3]
G4double	m_fldPosition [4]
G4double	m_magdistance
G4double	m_magdistance2
G4double	m_cof
G4double	m_mom
G4double	m_imom
G4bool	m_cachedMom
G4double	m_iPoint [3]
G4double	m_mPoint [3]
G4double	m_fPoint [3]

Detailed Description

Definition at line 51 of file G4NystromRK4.hh.

Constructor & Destructor Documentation

G4NystromRK4()

G4NystromRK4::G4NystromRK4	(	G4Mag_EqRhs *	EquationMotion,
		G4double	distanceConstField = 0.0
	)

Definition at line 41 of file G4NystromRK4.cc.

  : G4MagIntegratorStepper(magEqRhs, 6),            // number of variables
    m_fEq( magEqRhs ),
    m_magdistance( distanceConstField ),
    m_cof( 0.0 ),
    m_mom( 0.0 ),
    m_imom( 0.0 ),
    m_cachedMom( false )
{
  m_fldPosition[0]  = m_iPoint[0] = m_fPoint[0] = m_mPoint[0] = 9.9999999e+99 ;
  m_fldPosition[1]  = m_iPoint[1] = m_fPoint[1] = m_mPoint[1] = 9.9999999e+99 ;
  m_fldPosition[2]  = m_iPoint[2] = m_fPoint[2] = m_mPoint[2] = 9.9999999e+99 ;
  m_fldPosition[3]  = -9.9999999e+99;
  m_lastField[0] = m_lastField[1] = m_lastField[2] = 0.0;

  m_magdistance2 = distanceConstField*distanceConstField;
}

~G4NystromRK4()

G4NystromRK4::~G4NystromRK4

(

)

Definition at line 63 of file G4NystromRK4.cc.

{
}

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Member Function Documentation

ComputeRightHandSide()

void G4NystromRK4::ComputeRightHandSide ( const double  P[], double  dPdS[]  )

virtual

Reimplemented from G4MagIntegratorStepper.

Definition at line 196 of file G4NystromRK4.cc.

{
  G4double P4vec[4]= { P[0], P[1], P[2], P[7] }; // Time is P[7]
  getField(P4vec);
  m_mom   = std::sqrt(P[3]*P[3]+P[4]*P[4]+P[5]*P[5])     ; 
  m_imom  = 1./m_mom                                ;
  m_cof   = m_fEq->FCof()*m_imom                    ;
  m_cachedMom = true                                ; // Caching the value
  dPdS[0] = P[3]*m_imom                             ; // dx /ds
  dPdS[1] = P[4]*m_imom                             ; // dy /ds
  dPdS[2] = P[5]*m_imom                             ; // dz /ds
  dPdS[3] = m_cof*(P[4]*m_lastField[2]-P[5]*m_lastField[1]) ; // dPx/ds
  dPdS[4] = m_cof*(P[5]*m_lastField[0]-P[3]*m_lastField[2]) ; // dPy/ds
  dPdS[5] = m_cof*(P[3]*m_lastField[1]-P[4]*m_lastField[0]) ; // dPz/ds
}

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DistChord()

G4double G4NystromRK4::DistChord ( ) const

virtual

Implements G4MagIntegratorStepper.

Definition at line 172 of file G4NystromRK4.cc.

{
  G4double ax = m_fPoint[0]-m_iPoint[0];  
  G4double ay = m_fPoint[1]-m_iPoint[1];  
  G4double az = m_fPoint[2]-m_iPoint[2];
  G4double dx = m_mPoint[0]-m_iPoint[0]; 
  G4double dy = m_mPoint[1]-m_iPoint[1]; 
  G4double dz = m_mPoint[2]-m_iPoint[2];
  G4double d2 = (ax*ax+ay*ay+az*az)    ; 

  if(d2!=0.) {
    G4double ds = (ax*dx+ay*dy+az*dz)/d2;
    dx         -= (ds*ax)               ;
    dy         -= (ds*ay)               ;
    dz         -= (ds*az)               ;
  }
  return std::sqrt(dx*dx+dy*dy+dz*dz);
}

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GetDistanceForConstantField()

G4double G4NystromRK4::GetDistanceForConstantField ( ) const

inline

Definition at line 108 of file G4NystromRK4.hh.

{
  return m_magdistance; 
}

getField()

void G4NystromRK4::getField ( const G4double  P[4] )

inlineprivate

Definition at line 117 of file G4NystromRK4.hh.

{
  
  G4double dx = P[0]-m_fldPosition[0];
  G4double dy = P[1]-m_fldPosition[1];
  G4double dz = P[2]-m_fldPosition[2];

  if((dx*dx+dy*dy+dz*dz) > m_magdistance2)
  {
    m_fldPosition[0] = P[0];
    m_fldPosition[1] = P[1];
    m_fldPosition[2] = P[2];
    m_fldPosition[3] = P[3];   //  Generally it is P[7] - changed convention !!
    m_fEq->GetFieldValue(m_fldPosition, m_lastField);
  }
}

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IntegratorOrder()

G4int G4NystromRK4::IntegratorOrder ( ) const

inlinevirtual

Implements G4MagIntegratorStepper.

Definition at line 73 of file G4NystromRK4.hh.

{return 4;}

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SetDistanceForConstantField()

void G4NystromRK4::SetDistanceForConstantField ( G4double  length )

inline

Definition at line 102 of file G4NystromRK4.hh.

{
  m_magdistance=   length;
  m_magdistance2 = length*length;
}

Stepper()

void G4NystromRK4::Stepper ( const G4double  P[], const G4double  dPdS[], G4double  step, G4double  Po[], G4double  Err[]  )

virtual

Implements G4MagIntegratorStepper.

Definition at line 73 of file G4NystromRK4.cc.

{
  G4double R[3] = {   P[0],   P[1] ,    P[2]};
  G4double A[3] = {dPdS[0], dPdS[1], dPdS[2]};

  m_iPoint[0]=R[0]; m_iPoint[1]=R[1]; m_iPoint[2]=R[2];

  const G4double one_sixth= 1./6.;
  G4double S  =     Step   ;
  G4double S5 =  .5*Step   ;
  G4double S4 = .25*Step   ;
  G4double S6 =     Step * one_sixth;   // Step / 6.;


  // John A  added, in order to emulate effect of call to changed/derived RHS
  // m_mom   = sqrt(P[3]*P[3]+P[4]*P[4]+P[5]*P[5]); 
  // m_imom  = 1./m_mom;
  // m_cof   = m_fEq->FCof()*m_imom;

  // Point 1
  //
  G4double K1[3] = { m_imom*dPdS[3], m_imom*dPdS[4], m_imom*dPdS[5] };
  
  // Point2
  //
  G4double p[4] = {R[0]+S5*(A[0]+S4*K1[0]),
           R[1]+S5*(A[1]+S4*K1[1]),
           R[2]+S5*(A[2]+S4*K1[2]),
           P[7]                   }; 
  getField(p);

  G4double A2[3] = {A[0]+S5*K1[0],A[1]+S5*K1[1],A[2]+S5*K1[2]};
  G4double K2[3] = {(A2[1]*m_lastField[2]-A2[2]*m_lastField[1])*m_cof,
            (A2[2]*m_lastField[0]-A2[0]*m_lastField[2])*m_cof,
            (A2[0]*m_lastField[1]-A2[1]*m_lastField[0])*m_cof};
 
  m_mPoint[0]=p[0]; m_mPoint[1]=p[1]; m_mPoint[2]=p[2];

  // Point 3 with the same magnetic field
  //
  G4double A3[3] = {A[0]+S5*K2[0],A[1]+S5*K2[1],A[2]+S5*K2[2]};
  G4double K3[3] = {(A3[1]*m_lastField[2]-A3[2]*m_lastField[1])*m_cof,
            (A3[2]*m_lastField[0]-A3[0]*m_lastField[2])*m_cof,
            (A3[0]*m_lastField[1]-A3[1]*m_lastField[0])*m_cof};
  
  // Point 4
  //
  p[0] = R[0]+S*(A[0]+S5*K3[0]);
  p[1] = R[1]+S*(A[1]+S5*K3[1]);
  p[2] = R[2]+S*(A[2]+S5*K3[2]);             

  getField(p);
  
  G4double A4[3] = {A[0]+S*K3[0],A[1]+S*K3[1],A[2]+S*K3[2]};
  G4double K4[3] = {(A4[1]*m_lastField[2]-A4[2]*m_lastField[1])*m_cof,
            (A4[2]*m_lastField[0]-A4[0]*m_lastField[2])*m_cof,
            (A4[0]*m_lastField[1]-A4[1]*m_lastField[0])*m_cof};
  
  // New position
  //
  Po[0] = P[0]+S*(A[0]+S6*(K1[0]+K2[0]+K3[0]));
  Po[1] = P[1]+S*(A[1]+S6*(K1[1]+K2[1]+K3[1]));
  Po[2] = P[2]+S*(A[2]+S6*(K1[2]+K2[2]+K3[2]));

  m_fPoint[0]=Po[0]; m_fPoint[1]=Po[1]; m_fPoint[2]=Po[2];

  // New direction
  //
  Po[3] = A[0]+S6*(K1[0]+K4[0]+2.*(K2[0]+K3[0]));
  Po[4] = A[1]+S6*(K1[1]+K4[1]+2.*(K2[1]+K3[1]));
  Po[5] = A[2]+S6*(K1[2]+K4[2]+2.*(K2[2]+K3[2]));

  // Errors
  //
  Err[3] = S*std::fabs(K1[0]-K2[0]-K3[0]+K4[0]);
  Err[4] = S*std::fabs(K1[1]-K2[1]-K3[1]+K4[1]);
  Err[5] = S*std::fabs(K1[2]-K2[2]-K3[2]+K4[2]);
  Err[0] = S*Err[3]                       ;
  Err[1] = S*Err[4]                       ;
  Err[2] = S*Err[5]                       ;
  Err[3]*= m_mom                          ;
  Err[4]*= m_mom                          ;
  Err[5]*= m_mom                          ;

  // Normalize momentum
  //
  G4double normF = m_mom/std::sqrt(Po[3]*Po[3]+Po[4]*Po[4]+Po[5]*Po[5]);
  Po [3]*=normF; Po[4]*=normF; Po[5]*=normF; 

  // Pass Energy, time unchanged -- time is not integrated !!
  Po[6]=P[6]; Po[7]=P[7];
}

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Member Data Documentation

m_cachedMom

G4bool G4NystromRK4::m_cachedMom

private

Definition at line 92 of file G4NystromRK4.hh.

m_cof

G4double G4NystromRK4::m_cof

private

Definition at line 89 of file G4NystromRK4.hh.

m_fEq

G4Mag_EqRhs* G4NystromRK4::m_fEq

private

Definition at line 84 of file G4NystromRK4.hh.

m_fldPosition

G4double G4NystromRK4::m_fldPosition[4]

private

Definition at line 86 of file G4NystromRK4.hh.

m_fPoint

G4double G4NystromRK4::m_fPoint[3]

private

Definition at line 95 of file G4NystromRK4.hh.

m_imom

G4double G4NystromRK4::m_imom

private

Definition at line 91 of file G4NystromRK4.hh.

m_iPoint

G4double G4NystromRK4::m_iPoint[3]

private

Definition at line 93 of file G4NystromRK4.hh.

m_lastField

G4double G4NystromRK4::m_lastField[3]

private

Definition at line 85 of file G4NystromRK4.hh.

m_magdistance

G4double G4NystromRK4::m_magdistance

private

Definition at line 87 of file G4NystromRK4.hh.

m_magdistance2

G4double G4NystromRK4::m_magdistance2

private

Definition at line 88 of file G4NystromRK4.hh.

m_mom

G4double G4NystromRK4::m_mom

private

Definition at line 90 of file G4NystromRK4.hh.

m_mPoint

G4double G4NystromRK4::m_mPoint[3]

private

Definition at line 94 of file G4NystromRK4.hh.

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The documentation for this class was generated from the following files:

• G4NystromRK4.hh
• G4NystromRK4.cc