G4CashKarpRKF45 Class Reference

#include <G4CashKarpRKF45.hh>

Inheritance diagram for G4CashKarpRKF45:

Collaboration diagram for G4CashKarpRKF45:

Public Member Functions
	G4CashKarpRKF45 (G4EquationOfMotion *EqRhs, G4int numberOfVariables=6, G4bool primary=true)
	~G4CashKarpRKF45 ()
void	Stepper (const G4double y[], const G4double dydx[], G4double h, G4double yout[], G4double yerr[])
G4double	DistChord () const
G4int	IntegratorOrder () const
Public Member Functions inherited from G4MagIntegratorStepper
	G4MagIntegratorStepper (G4EquationOfMotion *Equation, G4int numIntegrationVariables, G4int numStateVariables=12, bool isFSAL=false)
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
G4int	IntegrationOrder ()
G4EquationOfMotion *	GetEquationOfMotion ()
void	SetEquationOfMotion (G4EquationOfMotion *newEquation)
unsigned long	GetfNoRHSCalls ()
void	ResetfNORHSCalls ()
bool	IsFSAL ()

Additional Inherited Members
Protected Member Functions inherited from G4MagIntegratorStepper
void	SetIntegrationOrder (int order)
void	SetFSAL (bool flag=true)

Detailed Description

Definition at line 50 of file G4CashKarpRKF45.hh.

Constructor & Destructor Documentation

G4CashKarpRKF45::G4CashKarpRKF45	(	G4EquationOfMotion *	EqRhs,
		G4int	numberOfVariables = 6,
		G4bool	primary = true
	)

Definition at line 47 of file G4CashKarpRKF45.cc.

  : G4MagIntegratorStepper(EqRhs, noIntegrationVariables),
    fLastStepLength(0.), fAuxStepper(0)
{
  const G4int numberOfVariables =
      std::max( noIntegrationVariables,
               ( ( (noIntegrationVariables-1)/4 + 1 ) * 4 ) );
  // For better alignment with cache-line
  
  ak2 = new G4double[numberOfVariables] ;
  ak3 = new G4double[numberOfVariables] ;
  ak4 = new G4double[numberOfVariables] ;
  ak5 = new G4double[numberOfVariables] ;
  ak6 = new G4double[numberOfVariables] ;
  // ak7 = 0;

  // Must ensure space extra 'state' variables exists - i.e. yIn[7]
  const G4int numStateMax  = std::max(GetNumberOfStateVariables(), 8);  
  const G4int numStateVars = std::max(noIntegrationVariables,
                                      numStateMax );
                                   // GetNumberOfStateVariables() ); 
                                      
  yTemp = new G4double[numStateVars] ;
  yIn = new G4double[numStateVars] ;

  fLastInitialVector = new G4double[numStateVars] ;
  fLastFinalVector = new G4double[numStateVars] ;
  fLastDyDx = new G4double[numberOfVariables];

  fMidVector = new G4double[numStateVars];
  fMidError =  new G4double[numStateVars];
  if( primary )
  { 
    fAuxStepper = new G4CashKarpRKF45(EqRhs, numberOfVariables, !primary);
  }
}

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G4CashKarpRKF45::~G4CashKarpRKF45

(

)

Definition at line 90 of file G4CashKarpRKF45.cc.

{
  delete[] ak2;
  delete[] ak3;
  delete[] ak4;
  delete[] ak5;
  delete[] ak6;
  // delete[] ak7;
  delete[] yTemp;
  delete[] yIn;

  delete[] fLastInitialVector;
  delete[] fLastFinalVector;
  delete[] fLastDyDx;
  delete[] fMidVector;
  delete[] fMidError; 

  delete fAuxStepper;
}

Member Function Documentation

G4double G4CashKarpRKF45::DistChord ( ) const

virtual

Implements G4MagIntegratorStepper.

Definition at line 240 of file G4CashKarpRKF45.cc.

{
  G4double distLine, distChord; 
  G4ThreeVector initialPoint, finalPoint, midPoint;

  // Store last initial and final points (they will be overwritten in self-Stepper call!)
  initialPoint = G4ThreeVector( fLastInitialVector[0], 
                                fLastInitialVector[1], fLastInitialVector[2]); 
  finalPoint   = G4ThreeVector( fLastFinalVector[0],  
                                fLastFinalVector[1],  fLastFinalVector[2]); 

  // Do half a step using StepNoErr

  fAuxStepper->Stepper( fLastInitialVector, fLastDyDx, 0.5 * fLastStepLength, 
           fMidVector,   fMidError );

  midPoint = G4ThreeVector( fMidVector[0], fMidVector[1], fMidVector[2]);       

  // Use stored values of Initial and Endpoint + new Midpoint to evaluate
  //  distance of Chord


  if (initialPoint != finalPoint) 
  {
     distLine  = G4LineSection::Distline( midPoint, initialPoint, finalPoint );
     distChord = distLine;
  }
  else
  {
     distChord = (midPoint-initialPoint).mag();
  }
  return distChord;
}

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G4int G4CashKarpRKF45::IntegratorOrder ( ) const

inlinevirtual

Implements G4MagIntegratorStepper.

Definition at line 69 of file G4CashKarpRKF45.hh.

{ return 4; }

void G4CashKarpRKF45::Stepper ( const G4double  y[], const G4double  dydx[], G4double  h, G4double  yout[], G4double  yerr[]  )

virtual

Implements G4MagIntegratorStepper.

Definition at line 121 of file G4CashKarpRKF45.cc.

{
  // const G4int nvar = 6 ;
  // const G4double a2 = 0.2 , a3 = 0.3 , a4 = 0.6 , a5 = 1.0 , a6 = 0.875;
 G4int i;

 const G4double  b21 = 0.2 ,
                 b31 = 3.0/40.0 , b32 = 9.0/40.0 ,
                 b41 = 0.3 , b42 = -0.9 , b43 = 1.2 ,

                 b51 = -11.0/54.0 , b52 = 2.5 , b53 = -70.0/27.0 ,
                 b54 = 35.0/27.0 ,

                 b61 = 1631.0/55296.0 , b62 =   175.0/512.0 ,
                 b63 =  575.0/13824.0 , b64 = 44275.0/110592.0 ,
                 b65 =  253.0/4096.0 ,

                 c1 = 37.0/378.0 , c3 = 250.0/621.0 , c4 = 125.0/594.0 ,
                 c6 = 512.0/1771.0 ,
                                          dc5 = -277.0/14336.0 ;

 const G4double dc1 = c1 - 2825.0/27648.0 ,  dc3 = c3 - 18575.0/48384.0 ,
    dc4 = c4 - 13525.0/55296.0 , dc6 = c6 - 0.25 ;

 // Initialise time to t0, needed when it is not updated by the integration.
 //        [ Note: Only for time dependent fields (usually electric) 
 //                  is it neccessary to integrate the time.] 
 yOut[7] = yTemp[7]   = yIn[7]; 

 const G4int numberOfVariables= this->GetNumberOfVariables(); 
 // The number of variables to be integrated over

   //  Saving yInput because yInput and yOut can be aliases for same array

   for(i=0;i<numberOfVariables;i++) 
   {
     yIn[i]=yInput[i];
   }
 // RightHandSide(yIn, dydx) ;              // 1st Step

 for(i=0;i<numberOfVariables;i++) 
 {
   yTemp[i] = yIn[i] + b21*Step*dydx[i] ;
 }
 RightHandSide(yTemp, ak2) ;              // 2nd Step

 for(i=0;i<numberOfVariables;i++)
 {
    yTemp[i] = yIn[i] + Step*(b31*dydx[i] + b32*ak2[i]) ;
 }
 RightHandSide(yTemp, ak3) ;              // 3rd Step

 for(i=0;i<numberOfVariables;i++)
 {
    yTemp[i] = yIn[i] + Step*(b41*dydx[i] + b42*ak2[i] + b43*ak3[i]) ;
 }
 RightHandSide(yTemp, ak4) ;              // 4th Step

 for(i=0;i<numberOfVariables;i++)
 {
    yTemp[i] = yIn[i] + Step*(b51*dydx[i] + b52*ak2[i] + b53*ak3[i] +
                      b54*ak4[i]) ;
 }
 RightHandSide(yTemp, ak5) ;              // 5th Step

 for(i=0;i<numberOfVariables;i++)
 {
    yTemp[i] = yIn[i] + Step*(b61*dydx[i] + b62*ak2[i] + b63*ak3[i] +
                      b64*ak4[i] + b65*ak5[i]) ;
 }
 RightHandSide(yTemp, ak6) ;              // 6th Step

 for(i=0;i<numberOfVariables;i++)
 {
    // Accumulate increments with proper weights

    yOut[i] = yIn[i] + Step*(c1*dydx[i] + c3*ak3[i] + c4*ak4[i] + c6*ak6[i]) ;

    // Estimate error as difference between 4th and
    // 5th order methods

    yErr[i] = Step*(dc1*dydx[i] + dc3*ak3[i] + dc4*ak4[i] +
              dc5*ak5[i] + dc6*ak6[i]) ;

    // Store Input and Final values, for possible use in calculating chord
    fLastInitialVector[i] = yIn[i] ;
    fLastFinalVector[i]   = yOut[i];
    fLastDyDx[i]          = dydx[i];
 }
 // NormaliseTangentVector( yOut ); // Not wanted

 fLastStepLength =Step;

 return ;
} 

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---

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

• source/geant4.10.03.p02/source/geometry/magneticfield/include/G4CashKarpRKF45.hh
• source/geant4.10.03.p02/source/geometry/magneticfield/src/G4CashKarpRKF45.cc