G4HelixExplicitEuler implements an Explicit Euler stepper for magnetic field: x_1 = x_0 + helix(h), with helix(h) being a helix piece of length h. A simple approach for solving linear differential equations. Takes the current derivative and adds it to the current position. More...

#include <G4HelixExplicitEuler.hh>

Inheritance diagram for G4HelixExplicitEuler:

Public Member Functions
	G4HelixExplicitEuler (G4Mag_EqRhs *EqRhs)
	~G4HelixExplicitEuler () override=default
void	Stepper (const G4double y[], const G4double *na, G4double h, G4double yout[], G4double yerr[]) override
void	DumbStepper (const G4double y[], G4ThreeVector Bfld, G4double h, G4double yout[]) override
G4double	DistChord () const override
G4int	IntegratorOrder () const override
G4StepperType	StepperType () const override
Public Member Functions inherited from G4MagHelicalStepper
	G4MagHelicalStepper (G4Mag_EqRhs *EqRhs)
	~G4MagHelicalStepper () override=default
	G4MagHelicalStepper (const G4MagHelicalStepper &)=delete
G4MagHelicalStepper &	operator= (const G4MagHelicalStepper &)=delete
void	Stepper (const G4double y[], const G4double dydx[], G4double h, G4double yout[], G4double yerr[]) override
G4double	DistChord () const override
Public Member Functions inherited from G4MagIntegratorStepper
	G4MagIntegratorStepper (G4EquationOfMotion *Equation, G4int numIntegrationVariables, G4int numStateVariables=12, G4bool isFSAL=false)
virtual	~G4MagIntegratorStepper ()=default
	G4MagIntegratorStepper (const G4MagIntegratorStepper &)=delete
G4MagIntegratorStepper &	operator= (const G4MagIntegratorStepper &)=delete
void	NormaliseTangentVector (G4double vec[6])
void	NormalisePolarizationVector (G4double vec[12])
void	RightHandSide (const G4double y[], G4double dydx[]) const
void	RightHandSide (const G4double y[], G4double dydx[], G4double field[]) const
G4int	GetNumberOfVariables () const
G4int	GetNumberOfStateVariables () const
G4int	IntegrationOrder ()
G4EquationOfMotion *	GetEquationOfMotion ()
const G4EquationOfMotion *	GetEquationOfMotion () const
void	SetEquationOfMotion (G4EquationOfMotion *newEquation)
unsigned long	GetfNoRHSCalls ()
void	ResetfNORHSCalls ()
G4bool	IsFSAL () const
G4bool	isQSS () const
void	SetIsQSS (G4bool val)

Additional Inherited Members
Protected Member Functions inherited from G4MagHelicalStepper
void	LinearStep (const G4double yIn[], G4double h, G4double yHelix[]) const
void	AdvanceHelix (const G4double yIn[], const G4ThreeVector &Bfld, G4double h, G4double yHelix[], G4double yHelix2[]=nullptr)
void	MagFieldEvaluate (const G4double y[], G4ThreeVector &Bfield)
G4double	GetInverseCurve (const G4double Momentum, const G4double Bmag)
void	SetAngCurve (const G4double Ang)
G4double	GetAngCurve () const
void	SetCurve (const G4double Curve)
G4double	GetCurve () const
void	SetRadHelix (const G4double Rad)
G4double	GetRadHelix () const
Protected Member Functions inherited from G4MagIntegratorStepper
void	SetIntegrationOrder (G4int order)
void	SetFSAL (G4bool flag=true)

Detailed Description

G4HelixExplicitEuler implements an Explicit Euler stepper for magnetic field: x_1 = x_0 + helix(h), with helix(h) being a helix piece of length h. A simple approach for solving linear differential equations. Takes the current derivative and adds it to the current position.

Definition at line 49 of file G4HelixExplicitEuler.hh.

Constructor & Destructor Documentation

◆ G4HelixExplicitEuler()

G4HelixExplicitEuler::G4HelixExplicitEuler ( G4Mag_EqRhs * EqRhs )

Constructor for G4HelixExplicitEuler.

Parameters

[in] EqRhs Pointer to the provided equation of motion.

Definition at line 40 of file G4HelixExplicitEuler.cc.

  : G4MagHelicalStepper(EqRhs)
{
}

◆ ~G4HelixExplicitEuler()

G4HelixExplicitEuler::~G4HelixExplicitEuler ( )

overridedefault

Default Destructor.

Member Function Documentation

◆ DistChord()

G4double G4HelixExplicitEuler::DistChord ( ) const

overridevirtual

Returns the distance from chord line.

Implements G4MagIntegratorStepper.

Definition at line 85 of file G4HelixExplicitEuler.cc.

{
  // Implementation : must check whether h/R > 2 pi  !!
  //   If( h/R <  pi) use G4LineSection::DistLine
  //   Else           DistChord=R_helix
  //
  G4double distChord;
  G4double Ang_curve=GetAngCurve();
 
  if(Ang_curve<=pi)
  {
    distChord=GetRadHelix()*(1-std::cos(0.5*Ang_curve));
  }
  else if(Ang_curve<twopi)
  {
    distChord=GetRadHelix()*(1+std::cos(0.5*(twopi-Ang_curve)));
  }
  else
  {
    distChord=2.*GetRadHelix();  
  }
 
  return distChord;
}

◆ DumbStepper()

void G4HelixExplicitEuler::DumbStepper	(	const G4double	y[],
		G4ThreeVector	Bfld,
		G4double	h,
		G4double	yout[] )

overridevirtual

The stepper function for the integration.

Parameters

[in]	y	Starting values array of integration variables.
[in]	Bfld	Derivatives array.
[in]	h	The given step size.
[out]	yout	Integration output.

Implements G4MagHelicalStepper.

Definition at line 110 of file G4HelixExplicitEuler.cc.

{
   AdvanceHelix(yIn, Bfld, h, yOut);
}  

◆ IntegratorOrder()

G4int G4HelixExplicitEuler::IntegratorOrder ( ) const

inlineoverridevirtual

Returns the order, 1, of integration.

Implements G4MagIntegratorStepper.

Definition at line 98 of file G4HelixExplicitEuler.hh.

98{ return 1; }

◆ Stepper()

void G4HelixExplicitEuler::Stepper	(	const G4double	y[],
		const G4double *	na,
		G4double	h,
		G4double	yout[],
		G4double	yerr[] )

override

The stepper function for the integration.

Parameters

[in]	y	Starting values array of integration variables.
[in]	na	Not used.
[in]	h	The given step size.
[out]	yout	Integration output.
[out]	yerr	Integration error.

Definition at line 45 of file G4HelixExplicitEuler.cc.

{
  // Estimation of the Stepping Angle
  //
  G4ThreeVector Bfld;
  MagFieldEvaluate(yInput, Bfld); 
  
  const G4int nvar = 6 ;
  G4double yTemp[8], yIn[8] ;
  G4ThreeVector  Bfld_midpoint;
 
  // Saving yInput because yInput and yOut can be aliases for same array
  //
  for(G4int i=0; i<nvar; ++i)
  {
    yIn[i] = yInput[i];
  }
     
  G4double h = Step * 0.5;
 
  // Do full step and two half steps
  //
  G4double yTemp2[7];
  AdvanceHelix(yIn, Bfld, h, yTemp2,yTemp);
  MagFieldEvaluate(yTemp2, Bfld_midpoint) ;     
  AdvanceHelix(yTemp2, Bfld_midpoint, h, yOut);
  SetAngCurve(GetAngCurve() * 2);
    
  // Error estimation
  //
  for(G4int i=0; i<nvar; ++i)
  {
    yErr[i] = yOut[i] - yTemp[i];
  }
}