G4HelixSimpleRunge.cc

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// $Id$
//
//
//  Simple Runge:
//        x_1 = x_0 + h * ( dx( t_0+h/2, x_0 + h/2 * dx( t_0, x_0) ) )
//
//  Second order solver.
//  Take the derivative at a position to be assumed at the middle of the
//  Step and add it to the current position.
//
//  W.Wander <wwc@mit.edu> 12/09/97 
// -------------------------------------------------------------------------
 
#include "G4HelixSimpleRunge.hh"
#include "G4ThreeVector.hh"
 
void
G4HelixSimpleRunge::DumbStepper( const G4double  yIn[],
                 G4ThreeVector   Bfld,
                 G4double        h,
                 G4double        yOut[])
{
  const G4int nvar = 6 ;
  G4double yTemp[nvar];   // , yAdd[nvar];
  G4ThreeVector Bfld_midpoint;
 
  AdvanceHelix( yIn, Bfld, 0.5 * h, yTemp);
  
  // now obtain the new field value at the new point
  MagFieldEvaluate(yTemp, Bfld_midpoint);      
 
  AdvanceHelix( yIn, Bfld_midpoint, h, yOut);
  
  // NormaliseTangentVector( yOut );           
}