Gabriele Cosmo
119 lines
4.4 KiB
C++
119 lines
4.4 KiB
C++
//
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// ********************************************************************
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// * DISCLAIMER *
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// * *
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// * The following disclaimer summarizes all the specific disclaimers *
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// * of contributors to this software. The specific disclaimers,which *
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// * govern, are listed with their locations in: *
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// * http://cern.ch/geant4/license *
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// * *
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// * Neither the authors of this software system, nor their employing *
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// * institutes,nor the agencies providing financial support for this *
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// * work make any representation or warranty, express or implied, *
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// * regarding this software system or assume any liability for its *
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// * use. *
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// * *
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// * This code implementation is the intellectual property of the *
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// * GEANT4 collaboration. *
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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 *
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// * statement, and all its terms. *
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// ********************************************************************
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//
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//
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// $Id: G4MagErrorStepper.cc,v 1.12 2003/10/31 14:35:54 gcosmo Exp $
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// GEANT4 tag $Name: geant4-08-00 $
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//
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// --------------------------------------------------------------------
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#include "G4MagErrorStepper.hh"
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#include "G4LineSection.hh"
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G4MagErrorStepper::~G4MagErrorStepper()
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{
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delete[] yMiddle;
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delete[] dydxMid;
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delete[] yInitial;
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delete[] yOneStep;
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}
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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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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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const G4int maxvar= GetNumberOfStateVariables();
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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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yInitial[7]= yInput[7]; // Copy the time in case ... even if not really needed
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yMiddle[7] = yInput[7]; // Copy the time from initial value
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yOneStep[7] = yInput[7]; // As it contributes to final value of yOutput ?
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// yOutput[7] = yInput[7]; // -> dumb stepper does it too for RK4
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for(i=nvar;i<maxvar;i++) yOutput[i]=yInput[i];
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// yError[7] = 0.0;
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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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// Estimate the maximum distance from the curve to the chord
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//
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// We estimate this using the distance of the midpoint to
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// chord (the line between
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//
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// Method below is good only for angle deviations < 2 pi,
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// This restriction should not a problem for the Runge cutta methods,
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// which generally cannot integrate accurately for large angle deviations.
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G4double distLine, distChord;
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if (fInitialPoint != fFinalPoint) {
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distLine= 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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distChord = distLine;
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}else{
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distChord = (fMidPoint-fInitialPoint).mag();
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}
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return distChord;
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}
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