Gabriele Cosmo
141 lines
4.7 KiB
C++
141 lines
4.7 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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// G4TSimpleHeum
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//
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// Class description:
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//
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// Templated version of G4SimpleHeum.
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// Adapted from G4G4TSimpleHeum class.
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// Original desription:
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//
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// Simple Heum stepper for magnetic field:
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// x_1 = x_0 +
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// h * 1/4 * dx(t0,x0) +
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// 3/4 * dx(t0+2/3*h, x0+2/3*h*(dx(t0+h/3,x0+h/3*dx(t0,x0))))
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//
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// Third order solver.
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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 G4TSIMPLEHEUM_HH
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#define G4TSIMPLEHEUM_HH
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#include <cassert>
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#include "G4TMagErrorStepper.hh"
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#include "G4ThreeVector.hh"
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/**
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* @brief G4TSimpleHeum is a templated version of G4SimpleHeum.
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*/
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template <class T_Equation, unsigned int N>
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class G4TSimpleHeum
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: public G4TMagErrorStepper<G4TSimpleHeum<T_Equation, N>, T_Equation, N>
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{
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public:
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constexpr static unsigned int gIntegratorOrder = 3;
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static constexpr double IntegratorCorrection= 1.0 / ((1<<gIntegratorOrder) - 1);
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G4TSimpleHeum(T_Equation* EqRhs, unsigned int numberOfVariables = 6);
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~G4TSimpleHeum() = default;
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inline void RightHandSide(G4double y[],
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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 DumbStepper(const G4double yIn[],
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const G4double dydx[],
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G4double h, G4double yOut[]); // override final
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inline G4int IntegratorOrder() const { return gIntegratorOrder; }
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private:
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G4int fNumberOfVariables;
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G4double dydxTemp[N];
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G4double dydxTemp2[N];
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G4double yTemp[N];
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G4double yTemp2[N];
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// scratch space
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T_Equation* fEquation_Rhs;
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};
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template <class T_Equation, unsigned int N >
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G4TSimpleHeum<T_Equation,N>::G4TSimpleHeum(T_Equation* EqRhs,
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unsigned int numberOfVariables )
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: G4TMagErrorStepper<G4TSimpleHeum<T_Equation, N>, T_Equation, N>(
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EqRhs, numberOfVariables)
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, fNumberOfVariables(numberOfVariables)
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, fEquation_Rhs(EqRhs)
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{
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assert(fNumberOfVariables == N);
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if( dynamic_cast<G4EquationOfMotion*>(EqRhs) == nullptr )
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{
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G4Exception("G4TSimpleHeum: constructor", "GeomField0001",
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FatalException, "Equation is not an G4EquationOfMotion.");
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}
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}
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template <class T_Equation, unsigned int N >
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inline void
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G4TSimpleHeum<T_Equation,N>::DumbStepper(const G4double yIn[],
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const G4double dydx[],
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G4double h, G4double yOut[])
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{
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for(unsigned int i = 0; i < N; ++i)
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{
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yTemp[i] = yIn[i] + (1.0 / 3.0) * h * dydx[i];
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}
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this->RightHandSide(yTemp, dydxTemp);
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for(unsigned int i = 0; i < N; ++i)
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{
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yTemp2[i] = yIn[i] + (2.0 / 3.0) * h * dydxTemp[i];
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}
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this->RightHandSide(yTemp2, dydxTemp2);
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for(unsigned int i = 0; i < N; ++i)
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{
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yOut[i] = yIn[i] + h * (0.25 * dydx[i] + 0.75 * dydxTemp2[i]);
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}
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if(fNumberOfVariables == 12)
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{
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this->NormalisePolarizationVector(yOut);
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}
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}
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#endif
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