G4RKG3_Stepper Class Reference

G4RKG3_Stepper implements a Runga-Kutta integrator stepper used in Geant-3. More...

#include <G4RKG3_Stepper.hh>

Inheritance diagram for G4RKG3_Stepper:

Public Member Functions
	G4RKG3_Stepper (G4Mag_EqRhs *EqRhs)
	~G4RKG3_Stepper () override=default
	G4RKG3_Stepper (const G4RKG3_Stepper &)=delete
G4RKG3_Stepper &	operator= (const G4RKG3_Stepper &)=delete
void	Stepper (const G4double yIn[], const G4double dydx[], G4double h, G4double yOut[], G4double yErr[]) override
G4double	DistChord () const override
void	StepNoErr (const G4double tIn[8], const G4double dydx[6], G4double Step, G4double tOut[8], G4double B[3])
void	StepWithEst (const G4double tIn[8], const G4double dydx[6], G4double Step, G4double tOut[8], G4double &alpha2, G4double &beta2, const G4double B1[3], G4double B2[3])
G4int	IntegratorOrder () const override
G4StepperType	StepperType () 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 G4MagIntegratorStepper
void	SetIntegrationOrder (G4int order)
void	SetFSAL (G4bool flag=true)

Detailed Description

G4RKG3_Stepper implements a Runga-Kutta integrator stepper used in Geant-3.

Definition at line 48 of file G4RKG3_Stepper.hh.

Constructor & Destructor Documentation

G4RKG3_Stepper() [1/2]

G4RKG3_Stepper::G4RKG3_Stepper

(

G4Mag_EqRhs *

EqRhs

)

Constructor for G4RKG3_Stepper.

Parameters

[in]

EqRhs

Pointer to the provided equation of motion.

Definition at line 35 of file G4RKG3_Stepper.cc.

  : G4MagIntegratorStepper(EqRhs,6)
{
}

Referenced by G4RKG3_Stepper(), and operator=().

~G4RKG3_Stepper()

G4RKG3_Stepper::~G4RKG3_Stepper ( )

overridedefault

Default Destructor.

G4RKG3_Stepper() [2/2]

G4RKG3_Stepper::G4RKG3_Stepper ( const G4RKG3_Stepper & )

delete

Copy constructor and assignment operator not allowed.

Member Function Documentation

DistChord()

G4double G4RKG3_Stepper::DistChord ( ) const

overridevirtual

Returns the distance from chord line.

Implements G4MagIntegratorStepper.

Definition at line 192 of file G4RKG3_Stepper.cc.

{
   // Soon: must check whether h/R > 2 pi  !!
   // Method below is good only for < 2 pi
 
   G4double distChord,distLine;
   
   if (fyInitial != fyFinal)
   {
      distLine = G4LineSection::Distline(fyMidPoint,fyInitial,fyFinal);
      distChord = distLine;
   }
   else
   {
      distChord = (fyMidPoint-fyInitial).mag();
   }
 
   return distChord;
}

IntegratorOrder()

G4int G4RKG3_Stepper::IntegratorOrder ( ) const

inlineoverridevirtual

Returns the order, 4, of integration.

Implements G4MagIntegratorStepper.

Definition at line 123 of file G4RKG3_Stepper.hh.

{ return 4; }

operator=()

G4RKG3_Stepper & G4RKG3_Stepper::operator= ( const G4RKG3_Stepper & )

delete

StepNoErr()

void G4RKG3_Stepper::StepNoErr	(	const G4double	tIn[8],
		const G4double	dydx[6],
		G4double	Step,
		G4double	tOut[8],
		G4double	B[3] )

Integrator of Runge-Kutta Stepper from Geant-3 with only two field evaluation per Step. It is used in propagating the initial Step by small substeps after solution error and delta geometry considerations. B[3] is magnetic field which is passed from substep to substep.

Definition at line 126 of file G4RKG3_Stepper.cc.

{ 
  
   // Copy and edit the routine above, to delete alpha2, beta2, ...
   //
   G4double K1[7], K2[7], K3[7], K4[7];
   G4double tTemp[8]={0.0}, yderiv[6]={0.0};
 
   // Need Momentum value to give correct values to the coefficients in
   // equation. Integration on unit velocity, but tIn[3,4,5] is momentum
 
   G4double mom, inverse_mom;
   const G4double c1=0.5, c2=0.125, c3=1./6.;
  
   // Correction for momentum not a velocity
   // Need the protection !!! must be not zero
   //
   mom = std::sqrt(tIn[3]*tIn[3]+tIn[4]*tIn[4]+tIn[5]*tIn[5]); 
   inverse_mom = 1./mom;    
   for(auto i=0; i<3; ++i)
   {
      K1[i] = Step * dydx[i+3]*inverse_mom;
      tTemp[i] = tIn[i] + Step*(c1*tIn[i+3]*inverse_mom + c2*K1[i]) ;
      tTemp[i+3] = tIn[i+3] + c1*K1[i]*mom ;
   }
    
   GetEquationOfMotion()->EvaluateRhsReturnB(tTemp,yderiv,B) ;
      
   for(auto i=0; i<3; ++i)
   {
      K2[i] = Step * yderiv[i+3]*inverse_mom;
      tTemp[i+3] = tIn[i+3] + c1*K2[i]*mom ;
   }
   
   // Given B, calculate yderiv !
   //
   GetEquationOfMotion()->EvaluateRhsGivenB(tTemp,B,yderiv) ;  
 
   for(auto i=0; i<3; ++i)
   {
      K3[i] = Step * yderiv[i+3]*inverse_mom;
      tTemp[i] = tIn[i] + Step*(tIn[i+3]*inverse_mom + c1*K3[i]) ;
      tTemp[i+3] = tIn[i+3] + K3[i]*mom ;
   }
 
   // Calculates y-deriv(atives) & returns B too!
   //
   GetEquationOfMotion()->EvaluateRhsReturnB(tTemp,yderiv,B) ;  
 
   for(auto i=0; i<3; ++i)        // Output trajectory vector
   {
      K4[i] = Step * yderiv[i+3]*inverse_mom;
      tOut[i] = tIn[i] + Step*(tIn[i+3]*inverse_mom+ (K1[i]+K2[i]+K3[i])*c3) ;
      tOut[i+3] = tIn[i+3] + mom*(K1[i] + 2*K2[i] + 2*K3[i] +K4[i])*c3 ;
   }
   tOut[6] = tIn[6];
   tOut[7] = tIn[7];
}

Referenced by Stepper().

Stepper()

void G4RKG3_Stepper::Stepper ( const G4double yIn[], const G4double dydx[], G4double h, G4double yOut[], G4double yErr[] )

overridevirtual

The stepper for the Runge Kutta integration. Method provided, even if less efficient. The stepsize is fixed, with the step size given by 'h'. Integrates ODE starting values yInput[0 to 6]. Outputs yOut[] and its estimated error yErr[].

Parameters

[in]	yIn	Starting values array of integration variables.
[in]	dydx	Derivatives array.
[in]	h	The given step size.
[out]	yOut	Integration output.
[out]	yErr	The estimated error.

Implements G4MagIntegratorStepper.

Definition at line 40 of file G4RKG3_Stepper.cc.

{
   G4double  B[3];
   G4int nvar = 6 ;
   G4double  by15 = 1. / 15. ; // was  0.066666666 ;
 
   G4double yTemp[8], dydxTemp[6], yIn[8];
 
   // Saving yInput because yInput and yOut can be aliases for same array
   //
   for(G4int i=0; i<nvar; ++i)
   {
     yIn[i]=yInput[i];
   }
   yIn[6] = yInput[6];
   yIn[7] = yInput[7];
   G4double h = Step * 0.5; 
   hStep = Step;
     // Do two half steps
 
   StepNoErr(yIn, dydx,h, yTemp,B) ;
   
   // Store Bfld for DistChord Calculation
   //
   for(auto i=0; i<3; ++i)
   {
     BfldIn[i] = B[i];
   }
   // RightHandSide(yTemp,dydxTemp) ;
 
   GetEquationOfMotion()->EvaluateRhsGivenB(yTemp,B,dydxTemp) ;  
   StepNoErr(yTemp,dydxTemp,h,yOut,B);      
        
   // Store midpoint, chord calculation
                                 
   fyMidPoint = G4ThreeVector(yTemp[0],  yTemp[1],  yTemp[2]); 
 
   // Do a full Step
  //
   h *= 2 ;
   StepNoErr(yIn,dydx,h,yTemp,B); 
   for(G4int i=0; i<nvar; ++i)
   {
      yErr[i] = yOut[i] - yTemp[i] ;
      yOut[i] += yErr[i]*by15 ;          // Provides 5th order of accuracy
   }
 
   // Store values for DistChord method
   //
   fyInitial = G4ThreeVector( yIn[0],   yIn[1],   yIn[2]);
   fpInitial = G4ThreeVector( yIn[3],   yIn[4],   yIn[5]);
   fyFinal   = G4ThreeVector( yOut[0],  yOut[1],  yOut[2]); 
}

StepperType()

G4StepperType G4RKG3_Stepper::StepperType ( ) const

inlineoverridevirtual

Returns the stepper type-ID, "kRKG3Stepper".

Reimplemented from G4MagIntegratorStepper.

Definition at line 128 of file G4RKG3_Stepper.hh.

{ return kRKG3Stepper; }

StepWithEst()

void G4RKG3_Stepper::StepWithEst	(	const G4double	tIn[8],
		const G4double	dydx[6],
		G4double	Step,
		G4double	tOut[8],
		G4double &	alpha2,
		G4double &	beta2,
		const G4double	B1[3],
		G4double	B2[3] )

Integrator for Runge-Kutta from Geant-3 with evaluation of error in solution and delta geometry based on naive similarity with the case of uniform magnetic field. B1[3] is in input and is the first magnetic field values B2[3] is the output and is the final magnetic field values.

Definition at line 105 of file G4RKG3_Stepper.cc.

{
  G4Exception("G4RKG3_Stepper::StepWithEst()", "GeomField0001",
              FatalException, "Method no longer used.");
}

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

• G4RKG3_Stepper.hh
• G4RKG3_Stepper.cc