source: trunk/source/geometry/magneticfield/src/G4HelixMixedStepper.cc @ 1202

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//
// class G4HelixMixedStepper
//
// Class description:
//
// G4HelixMixedStepper split the Method used for Integration in two:
//
// If Stepping Angle ( h / R_curve) < pi/3  
//        use Stepper for small step(ClassicalRK4 by default)
// Else use  HelixExplicitEuler Stepper
//
// History: 
// Derived from ExactHelicalStepper 18/05/07
//
// -------------------------------------------------------------------------

#include "G4HelixMixedStepper.hh"
#include "G4ClassicalRK4.hh"
#include "G4CashKarpRKF45.hh"
#include "G4SimpleRunge.hh"
#include "G4HelixImplicitEuler.hh"
#include "G4HelixExplicitEuler.hh"
#include "G4HelixSimpleRunge.hh"
#include "G4ExactHelixStepper.hh"
#include "G4ExplicitEuler.hh"
#include "G4ImplicitEuler.hh"
#include "G4SimpleHeum.hh"
#include "G4RKG3_Stepper.hh"

#include "G4ThreeVector.hh"
#include "G4LineSection.hh"
G4HelixMixedStepper::G4HelixMixedStepper(G4Mag_EqRhs *EqRhs,G4int fStepperNumber)
  : G4MagHelicalStepper(EqRhs)
    
{
   SetVerbose(1); fNumCallsRK4=0; fNumCallsHelix=0;
   if(!fStepperNumber) fStepperNumber=4;
   fRK4Stepper =  SetupStepper(EqRhs, fStepperNumber);
}


G4HelixMixedStepper::~G4HelixMixedStepper() {
     
     delete(fRK4Stepper);
     if (fVerbose>0){ PrintCalls();};
} 
void G4HelixMixedStepper::Stepper(  const G4double  yInput[7],
                               const G4double dydx[7],
                                     G4double Step,
                                     G4double yOut[7],
                                     G4double yErr[])

{

 //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<0.33*pi){
     fNumCallsRK4++;   
     fRK4Stepper->Stepper(yInput,dydx,Step,yOut,yErr);
    

   }
    else{
      fNumCallsHelix++;
      const G4int nvar = 6 ;
      G4int i;
      G4double      yTemp[7], yIn[7] ;
      G4double 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 h = Step * 0.5;
     // Do two half steps and full step
          AdvanceHelix(yIn,   Bfld,  h, yTemp,yTemp2);
          MagFieldEvaluate(yTemp, Bfld_midpoint) ;     
          AdvanceHelix(yTemp, Bfld_midpoint, h, yOut);
     // Error estimation
          for(i=0;i<nvar;i++) {
          yErr[i] = yOut[i] - yTemp2[i] ;
          
          }
    }




}

void
G4HelixMixedStepper::DumbStepper( const G4double  yIn[],
                                   G4ThreeVector   Bfld,
                                   G4double        h,
                                   G4double        yOut[])
{
 
    
       AdvanceHelix(yIn, Bfld, h, yOut);

    
               
}  

G4double G4HelixMixedStepper::DistChord()   const 
{
  // 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::PrintCalls()
{
  G4cout<<"In HelixMixedStepper::Number of calls to smallStepStepper = "<<fNumCallsRK4
        <<"  and Number of calls to Helix = "<<fNumCallsHelix<<G4endl;
}



G4MagIntegratorStepper* G4HelixMixedStepper:: SetupStepper(G4Mag_EqRhs* pE, G4int StepperNumber)
{
  G4MagIntegratorStepper* pStepper;
  if (fVerbose>0)G4cout<<"In G4HelixMixedStepper Stepper for small steps is "; 
  switch ( StepperNumber )
    {
     case 0: pStepper = new G4ExplicitEuler( pE ); if (fVerbose>0)G4cout<<"G4ExplicitEuler"<<G4endl; break;
     case 1: pStepper = new G4ImplicitEuler( pE ); if (fVerbose>0)G4cout<<"G4ImplicitEuler"<<G4endl; break;
     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;
     case 4: pStepper = new G4ClassicalRK4( pE ); if (fVerbose>0)G4cout<<"G4ClassicalRK4"<<G4endl; break;
     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;
     case 8: pStepper = new G4CashKarpRKF45( pE );    if (fVerbose>0)G4cout<<"G4CashKarpRKF45"<<G4endl; break;
     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;
      
      default: pStepper = new G4ClassicalRK4( pE );G4cout<<"Default G4ClassicalRK4"<<G4endl; break;
      
    }
  return pStepper;
}