Gabriele Cosmo
183 lines
6.7 KiB
C++
183 lines
6.7 KiB
C++
//
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// ********************************************************************
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// * License and Disclaimer *
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// * *
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// * The Geant4 software is copyright of the Copyright Holders of *
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// * the Geant4 Collaboration. It is provided under the terms and *
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// * conditions of the Geant4 Software License, included in the file *
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// * LICENSE and available at http://cern.ch/geant4/license . These *
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// * include a list of copyright holders. *
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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. Please see the license in the file LICENSE and URL above *
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// * for the full disclaimer and the limitation of liability. *
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// * *
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// * This code implementation is the result of the scientific and *
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// * technical work of the GEANT4 collaboration. *
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// * By using, copying, modifying or distributing the software (or *
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// * any work based on the software) you agree to acknowledge its *
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// * use in resulting scientific publications, and indicate your *
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// * acceptance of all terms of the Geant4 Software license. *
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// ********************************************************************
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//
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// G4TMagErrorStepper
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//
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// Class description:
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//
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// Templated version of G4MagErrorStepper.
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// Adapted from G4G4TMagErrorStepper class.
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// Author: Josh Xie (CERN, Google Summer of Code 2014), June 2014
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// Supervisors: Sandro Wenzel, John Apostolakis (CERN)
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// --------------------------------------------------------------------
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#ifndef G4TMAG_ERROR_STEPPER_HH
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#define G4TMAG_ERROR_STEPPER_HH
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#include "G4Types.hh"
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#include "G4MagIntegratorStepper.hh"
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#include "G4ThreeVector.hh"
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#include "G4LineSection.hh"
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/**
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* @brief G4TMagErrorStepper is a templated version of G4MagErrorStepper.
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*/
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template <class T_Stepper, class T_Equation, unsigned int N>
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class G4TMagErrorStepper : public G4MagIntegratorStepper
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{
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public:
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G4TMagErrorStepper(T_Equation* EqRhs, G4int numberOfVariables,
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G4int numStateVariables = 12)
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: G4MagIntegratorStepper(EqRhs, numberOfVariables, numStateVariables)
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, fEquation_Rhs(EqRhs) { ; }
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virtual ~G4TMagErrorStepper() = default;
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G4TMagErrorStepper(const G4TMagErrorStepper&) = delete;
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G4TMagErrorStepper& operator=(const G4TMagErrorStepper&) = delete;
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inline void RightHandSide(G4double y[], G4double dydx[])
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{
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fEquation_Rhs->T_Equation::RightHandSide(y, dydx);
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}
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inline void Stepper(const G4double yInput[], const G4double dydx[],
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G4double hstep, G4double yOutput[], G4double yError[]) override final;
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inline G4double DistChord() const override final;
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G4StepperType StepperType() const override { return kTMagErrorStepper; }
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private:
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// STATE
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G4ThreeVector fInitialPoint, fMidPoint, fFinalPoint;
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// Data stored in order to find the chord
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// Dependent Objects, owned --- part of the STATE
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G4double yInitial[N < 8 ? 8 : N];
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G4double yMiddle[N < 8 ? 8 : N];
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G4double dydxMid[N < 8 ? 8 : N];
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G4double yOneStep[N < 8 ? 8 : N];
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// The following arrays are used only for temporary storage
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// they are allocated at the class level only for efficiency -
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// so that calls to new and delete are not made in Stepper().
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T_Equation* fEquation_Rhs;
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};
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// ------------ Implementation -----------------------
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template <class T_Stepper, class T_Equation, unsigned int N >
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void G4TMagErrorStepper<T_Stepper,T_Equation,N>::
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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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// The stepper for the Runge Kutta integration. The stepsize
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// is fixed, with the Step size given by hstep.
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// Integrates ODE starting values y[0 to N].
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// Outputs yout[] and its estimated error yerr[].
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{
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const unsigned int maxvar = GetNumberOfStateVariables();
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// Saving yInput because yInput and yOutput can be aliases for same array
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for(unsigned int i = 0; i < N; ++i)
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yInitial[i] = yInput[i];
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yInitial[7] =
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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(unsigned int i = N; i < maxvar; ++i)
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yOutput[i] = yInput[i];
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G4double halfStep = hstep * 0.5;
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// Do two half steps
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static_cast<T_Stepper*>(this)->DumbStepper(yInitial, dydx, halfStep,
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yMiddle);
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this->RightHandSide(yMiddle, dydxMid);
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static_cast<T_Stepper*>(this)->DumbStepper(yMiddle, dydxMid, halfStep,
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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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static_cast<T_Stepper*>(this)->DumbStepper(yInitial, dydx, hstep, yOneStep);
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for(unsigned int i = 0; i < N; ++i)
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{
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yError[i] = yOutput[i] - yOneStep[i];
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yOutput[i] +=
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yError[i] *
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T_Stepper::IntegratorCorrection; // 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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template <class T_Stepper, class T_Equation, unsigned int N >
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inline G4double
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G4TMagErrorStepper<T_Stepper,T_Equation,N>::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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{
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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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}
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else
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{
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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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#endif
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