G4NystromRK4 Class Reference

#include <G4NystromRK4.hh>

Inheritance diagram for G4NystromRK4:

G4MagIntegratorStepper

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

Detailed Description

Definition at line 51 of file G4NystromRK4.hh.

Constructor & Destructor Documentation

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

Definition at line 41 of file G4NystromRK4.cc.

00042   : G4MagIntegratorStepper(magEqRhs, 6),            // number of variables
00043     m_fEq( magEqRhs ),
00044     m_magdistance( distanceConstField ),
00045     m_cof( 0.0 ),
00046     m_mom( 0.0 ),
00047     m_imom( 0.0 ),
00048     m_cachedMom( false )
00049 {
00050   m_fldPosition[0]  = m_iPoint[0] = m_fPoint[0] = m_mPoint[0] = 9.9999999e+99 ;
00051   m_fldPosition[1]  = m_iPoint[1] = m_fPoint[1] = m_mPoint[1] = 9.9999999e+99 ;
00052   m_fldPosition[2]  = m_iPoint[2] = m_fPoint[2] = m_mPoint[2] = 9.9999999e+99 ;
00053   m_fldPosition[3]  = -9.9999999e+99;
00054   m_lastField[0] = m_lastField[1] = m_lastField[2] = 0.0;
00055 
00056   m_magdistance2 = distanceConstField*distanceConstField;
00057 }

G4NystromRK4::~G4NystromRK4 (  ) 

Definition at line 63 of file G4NystromRK4.cc.

00064 {
00065 }

Member Function Documentation

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

Reimplemented from G4MagIntegratorStepper.

Definition at line 196 of file G4NystromRK4.cc.

References G4Mag_EqRhs::FCof().

00197 {
00198   G4double P4vec[4]= { P[0], P[1], P[2], P[7] }; // Time is P[7]
00199   getField(P4vec);
00200   m_mom   = std::sqrt(P[3]*P[3]+P[4]*P[4]+P[5]*P[5])     ; 
00201   m_imom  = 1./m_mom                                ;
00202   m_cof   = m_fEq->FCof()*m_imom                    ;
00203   m_cachedMom = true                                ; // Caching the value
00204   dPdS[0] = P[3]*m_imom                             ; // dx /ds
00205   dPdS[1] = P[4]*m_imom                             ; // dy /ds
00206   dPdS[2] = P[5]*m_imom                             ; // dz /ds
00207   dPdS[3] = m_cof*(P[4]*m_lastField[2]-P[5]*m_lastField[1]) ; // dPx/ds
00208   dPdS[4] = m_cof*(P[5]*m_lastField[0]-P[3]*m_lastField[2]) ; // dPy/ds
00209   dPdS[5] = m_cof*(P[3]*m_lastField[1]-P[4]*m_lastField[0]) ; // dPz/ds
00210 }

G4double G4NystromRK4::DistChord (  )  const [virtual]

Implements G4MagIntegratorStepper.

Definition at line 172 of file G4NystromRK4.cc.

00173 {
00174   G4double ax = m_fPoint[0]-m_iPoint[0];  
00175   G4double ay = m_fPoint[1]-m_iPoint[1];  
00176   G4double az = m_fPoint[2]-m_iPoint[2];
00177   G4double dx = m_mPoint[0]-m_iPoint[0]; 
00178   G4double dy = m_mPoint[1]-m_iPoint[1]; 
00179   G4double dz = m_mPoint[2]-m_iPoint[2];
00180   G4double d2 = (ax*ax+ay*ay+az*az)    ; 
00181 
00182   if(d2!=0.) {
00183     G4double ds = (ax*dx+ay*dy+az*dz)/d2;
00184     dx         -= (ds*ax)               ;
00185     dy         -= (ds*ay)               ;
00186     dz         -= (ds*az)               ;
00187   }
00188   return std::sqrt(dx*dx+dy*dy+dz*dz);
00189 }

G4double G4NystromRK4::GetDistanceForConstantField (  )  const [inline]

Definition at line 108 of file G4NystromRK4.hh.

00109 {
00110   return m_magdistance; 
00111 }

G4int G4NystromRK4::IntegratorOrder (  )  const [inline, virtual]

Implements G4MagIntegratorStepper.

Definition at line 73 of file G4NystromRK4.hh.

00073 {return 4;}

void G4NystromRK4::SetDistanceForConstantField ( G4double  length  )  [inline]

Definition at line 102 of file G4NystromRK4.hh.

00103 {
00104   m_magdistance=   length;
00105   m_magdistance2 = length*length;
00106 }

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.

00074 {
00075   G4double R[3] = {   P[0],   P[1] ,    P[2]};
00076   G4double A[3] = {dPdS[0], dPdS[1], dPdS[2]};
00077 
00078   m_iPoint[0]=R[0]; m_iPoint[1]=R[1]; m_iPoint[2]=R[2];
00079 
00080   const G4double one_sixth= 1./6.;
00081   G4double S  =     Step   ;
00082   G4double S5 =  .5*Step   ;
00083   G4double S4 = .25*Step   ;
00084   G4double S6 =     Step * one_sixth;   // Step / 6.;
00085 
00086 
00087   // John A  added, in order to emulate effect of call to changed/derived RHS
00088   // m_mom   = sqrt(P[3]*P[3]+P[4]*P[4]+P[5]*P[5]); 
00089   // m_imom  = 1./m_mom;
00090   // m_cof   = m_fEq->FCof()*m_imom;
00091 
00092   // Point 1
00093   //
00094   G4double K1[3] = { m_imom*dPdS[3], m_imom*dPdS[4], m_imom*dPdS[5] };
00095   
00096   // Point2
00097   //
00098   G4double p[4] = {R[0]+S5*(A[0]+S4*K1[0]),
00099                    R[1]+S5*(A[1]+S4*K1[1]),
00100                    R[2]+S5*(A[2]+S4*K1[2]),
00101                    P[7]                   }; 
00102   getField(p);
00103 
00104   G4double A2[3] = {A[0]+S5*K1[0],A[1]+S5*K1[1],A[2]+S5*K1[2]};
00105   G4double K2[3] = {(A2[1]*m_lastField[2]-A2[2]*m_lastField[1])*m_cof,
00106                     (A2[2]*m_lastField[0]-A2[0]*m_lastField[2])*m_cof,
00107                     (A2[0]*m_lastField[1]-A2[1]*m_lastField[0])*m_cof};
00108  
00109   m_mPoint[0]=p[0]; m_mPoint[1]=p[1]; m_mPoint[2]=p[2];
00110 
00111   // Point 3 with the same magnetic field
00112   //
00113   G4double A3[3] = {A[0]+S5*K2[0],A[1]+S5*K2[1],A[2]+S5*K2[2]};
00114   G4double K3[3] = {(A3[1]*m_lastField[2]-A3[2]*m_lastField[1])*m_cof,
00115                     (A3[2]*m_lastField[0]-A3[0]*m_lastField[2])*m_cof,
00116                     (A3[0]*m_lastField[1]-A3[1]*m_lastField[0])*m_cof};
00117   
00118   // Point 4
00119   //
00120   p[0] = R[0]+S*(A[0]+S5*K3[0]);
00121   p[1] = R[1]+S*(A[1]+S5*K3[1]);
00122   p[2] = R[2]+S*(A[2]+S5*K3[2]);             
00123 
00124   getField(p);
00125   
00126   G4double A4[3] = {A[0]+S*K3[0],A[1]+S*K3[1],A[2]+S*K3[2]};
00127   G4double K4[3] = {(A4[1]*m_lastField[2]-A4[2]*m_lastField[1])*m_cof,
00128                     (A4[2]*m_lastField[0]-A4[0]*m_lastField[2])*m_cof,
00129                     (A4[0]*m_lastField[1]-A4[1]*m_lastField[0])*m_cof};
00130   
00131   // New position
00132   //
00133   Po[0] = P[0]+S*(A[0]+S6*(K1[0]+K2[0]+K3[0]));
00134   Po[1] = P[1]+S*(A[1]+S6*(K1[1]+K2[1]+K3[1]));
00135   Po[2] = P[2]+S*(A[2]+S6*(K1[2]+K2[2]+K3[2]));
00136 
00137   m_fPoint[0]=Po[0]; m_fPoint[1]=Po[1]; m_fPoint[2]=Po[2];
00138 
00139   // New direction
00140   //
00141   Po[3] = A[0]+S6*(K1[0]+K4[0]+2.*(K2[0]+K3[0]));
00142   Po[4] = A[1]+S6*(K1[1]+K4[1]+2.*(K2[1]+K3[1]));
00143   Po[5] = A[2]+S6*(K1[2]+K4[2]+2.*(K2[2]+K3[2]));
00144 
00145   // Errors
00146   //
00147   Err[3] = S*std::fabs(K1[0]-K2[0]-K3[0]+K4[0]);
00148   Err[4] = S*std::fabs(K1[1]-K2[1]-K3[1]+K4[1]);
00149   Err[5] = S*std::fabs(K1[2]-K2[2]-K3[2]+K4[2]);
00150   Err[0] = S*Err[3]                       ;
00151   Err[1] = S*Err[4]                       ;
00152   Err[2] = S*Err[5]                       ;
00153   Err[3]*= m_mom                          ;
00154   Err[4]*= m_mom                          ;
00155   Err[5]*= m_mom                          ;
00156 
00157   // Normalize momentum
00158   //
00159   G4double normF = m_mom/std::sqrt(Po[3]*Po[3]+Po[4]*Po[4]+Po[5]*Po[5]);
00160   Po [3]*=normF; Po[4]*=normF; Po[5]*=normF; 
00161 
00162   // Pass Energy, time unchanged -- time is not integrated !!
00163   Po[6]=P[6]; Po[7]=P[7];
00164 }

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