G4HelixMixedStepper Class Reference

#include <G4HelixMixedStepper.hh>

Inheritance diagram for G4HelixMixedStepper:

Public Member Functions
	G4HelixMixedStepper (G4Mag_EqRhs *EqRhs, G4int fStepperNumber=-1, G4double Angle_threshold=-1.0)
	~G4HelixMixedStepper ()
void	Stepper (const G4double y[], const G4double dydx[], G4double h, G4double yout[], G4double yerr[])
void	DumbStepper (const G4double y[], G4ThreeVector Bfld, G4double h, G4double yout[])
G4double	DistChord () const
void	SetVerbose (G4int newvalue)
void	PrintCalls ()
G4MagIntegratorStepper *	SetupStepper (G4Mag_EqRhs *EqRhs, G4int StepperName)
void	SetAngleThreshold (G4double val)
G4double	GetAngleThreshold ()
G4int	IntegratorOrder () const
Public Member Functions inherited from G4MagHelicalStepper
	G4MagHelicalStepper (G4Mag_EqRhs *EqRhs)
virtual	~G4MagHelicalStepper ()
G4double	DistChord () const
Public Member Functions inherited from G4MagIntegratorStepper
	G4MagIntegratorStepper (G4EquationOfMotion *Equation, G4int numIntegrationVariables, G4int numStateVariables=12)
virtual	~G4MagIntegratorStepper ()
virtual void	ComputeRightHandSide (const G4double y[], G4double dydx[])
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)

Additional Inherited Members
Protected Member Functions inherited from G4MagHelicalStepper
void	LinearStep (const G4double yIn[], G4double h, G4double yHelix[]) const
void	AdvanceHelix (const G4double yIn[], G4ThreeVector Bfld, G4double h, G4double yHelix[], G4double yHelix2[]=0)
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

Detailed Description

Definition at line 58 of file G4HelixMixedStepper.hh.

Constructor & Destructor Documentation

G4HelixMixedStepper::G4HelixMixedStepper	(	G4Mag_EqRhs *	EqRhs,
		G4int	fStepperNumber = -1,
		G4double	Angle_threshold = -1.0
	)

Definition at line 59 of file G4HelixMixedStepper.cc.

References python.hepunit::pi, SetupStepper(), and SetVerbose().

  : G4MagHelicalStepper(EqRhs), fNumCallsRK4(0), fNumCallsHelix(0)
{
   SetVerbose(1);
   if( angleThr < 0.0 ){
     fAngle_threshold= 0.33*pi;
   }else{
     fAngle_threshold= angleThr;
   }

   if(fStepperNumber<0)
     fStepperNumber=4;  // Default is RK4
   fRK4Stepper =  SetupStepper(EqRhs, fStepperNumber);
}

G4HelixMixedStepper::~G4HelixMixedStepper

(

)

Definition at line 74 of file G4HelixMixedStepper.cc.

References PrintCalls().

{  
  delete(fRK4Stepper);
  if (fVerbose>0){ PrintCalls();};
}

Member Function Documentation

G4double G4HelixMixedStepper::DistChord ( ) const

virtual

Implements G4MagIntegratorStepper.

Definition at line 147 of file G4HelixMixedStepper.cc.

References G4MagHelicalStepper::GetAngCurve(), G4MagHelicalStepper::GetRadHelix(), python.hepunit::pi, and python.hepunit::twopi.

{
  // 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;
}

void G4HelixMixedStepper::DumbStepper ( const G4double  y[], G4ThreeVector  Bfld, G4double  h, G4double  yout[]  )

virtual

Implements G4MagHelicalStepper.

Definition at line 139 of file G4HelixMixedStepper.cc.

References G4MagHelicalStepper::AdvanceHelix().

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

G4double G4HelixMixedStepper::GetAngleThreshold ( )

inline

Definition at line 93 of file G4HelixMixedStepper.hh.

{ return fAngle_threshold; }

G4int G4HelixMixedStepper::IntegratorOrder ( ) const

inlinevirtual

Implements G4MagIntegratorStepper.

Definition at line 95 of file G4HelixMixedStepper.hh.

{ return 4; }

void G4HelixMixedStepper::PrintCalls

(

)

Definition at line 173 of file G4HelixMixedStepper.cc.

References G4cout, and G4endl.

Referenced by ~G4HelixMixedStepper().

{
  G4cout<<"In HelixMixedStepper::Number of calls to smallStepStepper = "<<fNumCallsRK4
        <<"  and Number of calls to Helix = "<<fNumCallsHelix<<G4endl;
}

void G4HelixMixedStepper::SetAngleThreshold ( G4double  val )

inline

Definition at line 92 of file G4HelixMixedStepper.hh.

{ fAngle_threshold= val;}

G4MagIntegratorStepper * G4HelixMixedStepper::SetupStepper	(	G4Mag_EqRhs *	EqRhs,
		G4int	StepperName
	)

Definition at line 180 of file G4HelixMixedStepper.cc.

References G4cout, and G4endl.

Referenced by G4HelixMixedStepper().

{
  G4MagIntegratorStepper* pStepper;
  if (fVerbose>0)
    G4cout<<"In G4HelixMixedStepper: Choosing Stepper for small steps. Choice is ";
  switch ( StepperNumber )
    {
     case 0:
     case 4: pStepper = new G4ClassicalRK4( pE ); if (fVerbose>0)G4cout<<"G4ClassicalRK4"<<G4endl; break;

     // Steppers with embedded estimation of error
     case 1: pStepper = new G4NystromRK4( pE ); if (fVerbose>0)G4cout<<"G4NystromRK4"<<G4endl; break;
     case 8: pStepper = new G4CashKarpRKF45( pE );    if (fVerbose>0)G4cout<<"G4CashKarpRKF45"<<G4endl; break;
        
     // Lower order RK Steppers - ok overall, good for uneven fields
     case 2: pStepper = new G4SimpleRunge( pE ); if (fVerbose>0)G4cout<<"G4SimpleRunge"<<G4endl; break;
     case 3: pStepper = new G4SimpleHeum( pE );  if (fVerbose>0)G4cout<<"G4SimpleHeum"<<G4endl;break;

     // Helical Steppers - 
     //   Since these are used for long steps, less useful
     case 5: pStepper = new G4HelixExplicitEuler( pE ); if (fVerbose>0)G4cout<<"G4HelixExplicitEuler"<<G4endl; break;
     case 6: pStepper = new G4HelixImplicitEuler( pE ); if (fVerbose>0)G4cout<<"G4HelixImplicitEuler"<<G4endl; break;
     case 7: pStepper = new G4HelixSimpleRunge( pE ); if (fVerbose>0)G4cout<<"G4HelixSimpleRunge"<<G4endl; break;

     // Exact Helix - only for cases of i)uniform field
     //  ii) segmented uniform field (maybe)
     case 9: pStepper = new G4ExactHelixStepper( pE );  if (fVerbose>0)G4cout<<"G4ExactHelixStepper"<<G4endl;   break;

     case 10: pStepper = new G4RKG3_Stepper( pE );  if (fVerbose>0)G4cout<<"G4RKG3_Stepper"<<G4endl;   break;

     // Low Order Steppers - not good except for very weak fields
     case 11: pStepper = new G4ExplicitEuler( pE ); if (fVerbose>0)G4cout<<"G4ExplicitEuler"<<G4endl; break;
     case 12: pStepper = new G4ImplicitEuler( pE ); if (fVerbose>0)G4cout<<"G4ImplicitEuler"<<G4endl; break;
        
     case -1:
     default: pStepper = new G4ClassicalRK4( pE );G4cout<<"G4ClassicalRK4 (Default)."<<G4endl; break;
      
    }
  return pStepper;
}

void G4HelixMixedStepper::SetVerbose ( G4int  newvalue )

inline

Definition at line 86 of file G4HelixMixedStepper.hh.

Referenced by G4HelixMixedStepper().

{fVerbose=newvalue;}

void G4HelixMixedStepper::Stepper ( const G4double  y[], const G4double  dydx[], G4double  h, G4double  yout[], G4double  yerr[]  )

virtual

Reimplemented from G4MagHelicalStepper.

Definition at line 80 of file G4HelixMixedStepper.cc.

References G4MagHelicalStepper::AdvanceHelix(), G4MagHelicalStepper::GetInverseCurve(), CLHEP::Hep3Vector::mag(), G4MagHelicalStepper::MagFieldEvaluate(), G4MagHelicalStepper::SetAngCurve(), G4MagHelicalStepper::SetCurve(), and G4MagIntegratorStepper::Stepper().

{
  //Estimation of the Stepping Angle
  
  G4ThreeVector Bfld;
  MagFieldEvaluate(yInput, Bfld);
  
  G4double Bmag = Bfld.mag();
  const G4double *pIn = yInput+3;
  G4ThreeVector initVelocity= G4ThreeVector( pIn[0], pIn[1], pIn[2]);
  G4double      velocityVal = initVelocity.mag();
  G4double R_1;
  G4double Ang_curve;
  
  R_1=std::abs(GetInverseCurve(velocityVal,Bmag));
  Ang_curve=R_1*Step;
  SetAngCurve(Ang_curve);
  SetCurve(std::abs(1/R_1));
  
  if(Ang_curve< fAngle_threshold){
    fNumCallsRK4++;
    fRK4Stepper->Stepper(yInput,dydx,Step,yOut,yErr);
  }
  else
  {
    fNumCallsHelix++;
    const G4int    nvar = 6 ;
    G4int          i;
    G4double       yTemp[7], yIn[7], yTemp2[7];
    G4ThreeVector  Bfld_midpoint;

    //  Saving yInput because yInput and yOut can be aliases for same array
    for(i=0;i<nvar;i++) yIn[i]=yInput[i];
    
    G4double halfS = Step * 0.5;
    // 1. Do first half step and full step
    AdvanceHelix(yIn,   Bfld,          halfS, yTemp, yTemp2); // yTemp2 for s=2*h (halfS)
    //**********

    MagFieldEvaluate(yTemp, Bfld_midpoint) ;

    // 2. Do second half step - with revised field
    // NOTE: Could avoid this call if  'Bfld_midpoint == Bfld' or diff 'almost' zero
    AdvanceHelix(yTemp, Bfld_midpoint, halfS, yOut); // Not requesting y at s=2*h (halfS)
    //**********
    
    // 3. Estimate the integration error - should be (nearly) zero if Bfield= constant
    for(i=0;i<nvar;i++) {
      yErr[i] = yOut[i] - yTemp2[i] ;
    }
  }
}

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

• G4HelixMixedStepper.hh
• G4HelixMixedStepper.cc