Gabriele Cosmo
72 lines
2.1 KiB
C++
72 lines
2.1 KiB
C++
// This code implementation is the intellectual property of
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// the GEANT4 collaboration.
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//
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// By copying, distributing or modifying the Program (or any work
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// based on the Program) you indicate your acceptance of this statement,
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// and all its terms.
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//
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// $Id: G4MagErrorStepper.cc,v 1.6 1999/12/15 14:49:49 gunter Exp $
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// GEANT4 tag $Name: geant4-01-01 $
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//
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#include "G4MagErrorStepper.hh"
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#include "G4ThreeVector.hh"
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#include "G4LineSection.hh"
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void
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G4MagErrorStepper::Stepper( const G4double yInput[],
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const G4double dydx[],
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const G4double hstep,
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G4double yOutput[],
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G4double yError [] )
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{
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const G4int nvar = this->GetNumberOfVariables() ;
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G4int i;
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// correction for Richardson Extrapolation.
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G4double correction = 1. / ( (1 << IntegratorOrder()) -1 );
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// Saving yInput because yInput and yOutput can be aliases for same array
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for(i=0;i<nvar;i++) yInitial[i]=yInput[i];
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G4double halfStep = hstep * 0.5;
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// Do two half steps
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DumbStepper (yInitial, dydx, halfStep, yMiddle);
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RightHandSide(yMiddle, dydxMid);
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DumbStepper (yMiddle, dydxMid, halfStep, yOutput);
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// Store midpoint, chord calculation
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fMidPoint = G4ThreeVector( yMiddle[0], yMiddle[1], yMiddle[2]);
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// Do a full Step
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DumbStepper(yInitial, dydx, hstep, yOneStep);
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for(i=0;i<nvar;i++) {
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yError [i] = yOutput[i] - yOneStep[i] ;
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yOutput[i] += yError[i]*correction ; // Provides accuracy increased
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// by 1 order via the
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// Richardson Extrapolation
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}
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fInitialPoint = G4ThreeVector( yInitial[0], yInitial[1], yInitial[2]);
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fFinalPoint = G4ThreeVector( yOutput[0], yOutput[1], yOutput[2]);
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return ;
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}
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G4double
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G4MagErrorStepper::DistChord() const
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{
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// Soon: must check whether h/R > 2 pi !!
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// Method below is good only for < 2 pi
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return G4LineSection::Distline( fMidPoint, fInitialPoint, fFinalPoint );
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// This is a class method that gives distance of Mid
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// from the Chord between the Initial and Final points.
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}
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