Gabriele Cosmo
144 lines
5.5 KiB
C++
144 lines
5.5 KiB
C++
// ********************************************************************
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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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// G4BorisScheme
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//
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// Class description:
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//
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// Implementation of the Boris algorithm for advancing
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// charged particles in an electromagnetic field.
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// Author: Divyansh Tiwari (CERN, Google Summer of Code 2022), 05.11.2022
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// Supervision: John Apostolakis (CERN), Renee Fatemi, Soon Yung Jun (FNAL)
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// --------------------------------------------------------------------
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#ifndef G4BORIS_SCHEME_HH
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#define G4BORIS_SCHEME_HH
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#include "G4Types.hh"
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#include <CLHEP/Units/PhysicalConstants.h>
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class G4EquationOfMotion;
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/**
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* @brief The G4BorisScheme class implements of the Boris algorithm for
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* advancing charged particles in an electromagnetic field.
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*/
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class G4BorisScheme
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{
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public:
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/**
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* Default Constructor.
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*/
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G4BorisScheme() = default;
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/**
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* Constructor for the equation of motion.
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* @param[in] equation Pointer to the equation of motion algorithm.
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* @param[in] nvar The number of integration variables.
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*/
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G4BorisScheme( G4EquationOfMotion* equation, G4int nvar = 6 );
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/**
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* Default Destructor.
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*/
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~G4BorisScheme() = default;
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/**
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* Does one step, updating velocity and position.
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* @param[in] restMass Particle mass.
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* @param[in] charge Particle charge.
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* @param[in] yIn Initial position.
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* @param[out] yOut Updated position.
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* @param[in] hstep Proposed step.
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*/
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void DoStep(G4double restMass, G4double charge, const G4double yIn[],
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G4double yOut[], G4double hstep) const;
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/**
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* Adopts the Boris Scheme Stepping to estimate the integration error.
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* Uses two half-steps (comparing to a full step) to obtain output and
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* error estimate.
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* @param[in] yIn Initial position.
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* @param[in] restMass Particle mass.
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* @param[in] charge Particle charge.
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* @param[in] hstep Proposed step.
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* @param[out] yOut Updated position.
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* @param[out] yErr The estimated error.
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*/
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void StepWithErrorEstimate(const G4double yIn[], G4double restMass,
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G4double charge, G4double hstep,
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G4double yOut[], G4double yErr[]) const;
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/**
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* Adopts the Boris Scheme Stepping to estimate the integration error.
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* Uses two half-steps (comparing to a full step) to obtain output and
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* error estimate. Same as above, but also returns the mid-point evaluation.
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* @param[in] yIn Initial position.
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* @param[in] restMass Particle mass.
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* @param[in] charge Particle charge.
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* @param[in] hstep Proposed step.
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* @param[out] yMid tThe mid-point evaluation.
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* @param[out] yOut Updated position.
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* @param[out] yErr The estimated error.
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*/
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void StepWithMidAndErrorEstimate(const G4double yIn[], G4double restMass,
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G4double charge, G4double hstep,
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G4double yMid[], G4double yOut[], G4double yErr[]) const;
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/**
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* Auxiliary methods returning a pointer to the equation of motion
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* and the number of integration variables.
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*/
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inline G4EquationOfMotion* GetEquationOfMotion() const;
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inline G4int GetNumberOfVariables() const;
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private:
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/**
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* Internal methods for updating position and velocity, used in DoStep().
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*/
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void UpdatePosition(const G4double restMass, const G4double charge,
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const G4double yIn[], G4double yOut[], G4double hstep) const;
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void UpdateVelocity(const G4double restMass, const G4double charge,
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const G4double yIn[], G4double yOut[], G4double hstep) const;
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/**
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* Utility to mem-copy 'src' array data to 'dst'.
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*/
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void copy(G4double dst[], const G4double src[]) const;
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private:
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G4EquationOfMotion* fEquation = nullptr;
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G4int fnvar = 8;
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static constexpr G4double c_l = CLHEP::c_light/CLHEP::m*CLHEP::second;
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};
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#include "G4BorisScheme.icc"
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#endif
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