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geant4/source/geometry/magneticfield/include/G4QSStepper.hh
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Gabriele Cosmo b4a16de652 Import Geant4 11.4.0 source tree
2025-12-05 08:54:02 +01:00

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//
// ********************************************************************
// * License and Disclaimer *
// * *
// * The Geant4 software is copyright of the Copyright Holders of *
// * the Geant4 Collaboration. It is provided under the terms and *
// * conditions of the Geant4 Software License, included in the file *
// * LICENSE and available at http://cern.ch/geant4/license . These *
// * include a list of copyright holders. *
// * *
// * Neither the authors of this software system, nor their employing *
// * institutes,nor the agencies providing financial support for this *
// * work make any representation or warranty, express or implied, *
// * regarding this software system or assume any liability for its *
// * use. Please see the license in the file LICENSE and URL above *
// * for the full disclaimer and the limitation of liability. *
// * *
// * This code implementation is the result of the scientific and *
// * technical work of the GEANT4 collaboration. *
// * By using, copying, modifying or distributing the software (or *
// * any work based on the software) you agree to acknowledge its *
// * use in resulting scientific publications, and indicate your *
// * acceptance of all terms of the Geant4 Software license. *
// ********************************************************************
//
// G4QSStepper
//
// QSS Integrator Stepper
//
// Authors: version 1 - Lucio Santi, Rodrigo Castro (Univ. Buenos Aires), 2018-2021
// version 2 - Mattias Portnoy (Univ. Buenos Aires), 2024
// --------------------------------------------------------------------
#ifndef G4QSS_STEPPER_HH
#define G4QSS_STEPPER_HH
#include "G4FieldTrack.hh"
#include "G4MagIntegratorStepper.hh"
#include "G4QSSubstepStruct.hh"
#include <cmath>
#include <CLHEP/Units/PhysicalConstants.h>
/**
* @brief G4QSStepper is an integrator of particle's equation of
* motion based on the QSS implementation.
*/
class G4QSStepper : public G4MagIntegratorStepper
{
public:
/**
* Constructor for G4QSStepper.
* @param[in] equation Pointer to the provided equation of motion.
* @param[in] num_integration_vars The number of integration variables.
* @param[in] qssOrder The QSS order (2 or 3 expected; if <= 0 , use value
* from Messenger.
*/
G4QSStepper( G4EquationOfMotion* equation,
G4int num_integration_vars = 6, // always 6 -- ignore
G4int qssOrder= -1 );
/**
* Default Destructor. Freeing of memory is done in susbsteps destructor.
*/
~G4QSStepper() override = default;
/**
* Utility methods.
*/
inline constexpr G4double Cubic_Function(const QSStateVector* states,
G4int index, G4double delta_t);
inline constexpr G4double Parabolic_Function(const QSStateVector* states,
G4int index, G4double delta_t);
inline constexpr G4double Linear_Function(const QSStateVector* states,
G4int index, G4double delta_t);
/**
* 0 means position type, 1 means velocity type.
*/
inline constexpr int INDEX_TYPE(G4int i);
/**
* Auxiliary methods.
*/
inline void momentum_to_velocity(const G4double* momentum, G4double* out);
void set_relativistic_coeff(const G4double* momentum);
inline void velocity_to_momentum(G4double *y);
/**
* Key methods.
*/
void initialize(const G4double y[]);
inline void compare_time_and_update(G4int& index, G4int i);
inline G4int get_next_sync_index();
inline void update_field();
inline G4double extrapolate_polynomial(QSStateVector* states,
G4int index, G4double delta_t, G4int order);
inline void extrapolate_all_states_to_t(Substep* substep,
G4double t, G4double* yOut);
/**
* Moves all the x states of variable index to the current time t.
*/
inline void update_x(G4int index, G4double t);
/**
* Moves all the q states of variable index to the current t.
*/
inline void update_q(G4int index, G4double t);
/**
* Update methods.
*/
inline void update_x_position_derivates_using_q(G4int index);
inline void update_x_velocity_derivates_using_q(G4int index);
inline void update_x_derivates_using_q(G4int index);
inline void update_sync_time_one_coefficient(G4int index);
/*
* Updates when does the x,q distance goes beyond the quantum.
* Uses polynomial roots-finding formulas.
*/
void update_sync_time(G4int index);
/**
* The stepper for the integration.
* The stepsize is fixed, with the step size given by 'h'.
* Integrates ODE starting values y[0 to 6]. Outputs yout[].
* @param[in] y Starting values array of integration variables.
* @param[in] dydx Derivatives array - Not used.
* @param[in] h The given step size.
* @param[out] yout Integration output.
* @param[out] yError The estimated error - Not used.
*/
void Stepper( const G4double y[],
const G4double /*dydx*/ [],
G4double h,
G4double yout[],
G4double /* yerr */ [] ) override;
/**
* Returns the QSS order of integration.
*/
inline G4int IntegratorOrder() const override;
/**
* Returns the stepper type-ID, "kQSStepper".
*/
inline G4StepperType StepperType() const override { return kQSStepper; }
/**
* Returns a pointer to the equation of motion.
*/
inline G4EquationOfMotion* GetSpecificEquation();
/**
* Returns current track state.
*/
inline const field_utils::State& GetYOut() const;
/**
* Track interpolation.
* @param[in] tau Step start, x.
* @param[in,out] yOut The current track state, y.
*/
void Interpolate(G4double tau, G4double yOut[]);
/**
* Returns the distance from chord line.
*/
inline G4double DistChord() const override;
/**
* Wrapper for the Stepper() function above.
*/
inline void Stepper(const G4double yInput[],
const G4double dydx[],
G4double hstep,
G4double yOutput[],
G4double yError[],
G4double /*dydxOutput*/ []);
/**
* Sets up interpolation. Does nothing.
*/
inline void SetupInterpolation();
/*
* Obligatory qss driver methods.
*/
inline void reset(const G4FieldTrack* track);
inline void SetPrecision(G4double dq_rel, G4double dq_min);
inline G4double GetLastStepLength();
/*
* Sets the mass at rest. Checking/ensuring that it is positive.
*/
inline void setRestMass(G4double restMass);
private:
// Constants
static constexpr int DERIVATIVE_0{0};
static constexpr int DERIVATIVE_1{1};
static constexpr int DERIVATIVE_2{2};
static constexpr int DERIVATIVE_3{3};
static constexpr int VX{3};
static constexpr int VY{4};
static constexpr int VZ{5};
static constexpr int POSITION_IDX{0};
static constexpr int VELOCITY_IDX{3};
static constexpr G4double INFTY{1e+20};
/** Used to check if field changed from last update field during substeps. */
G4bool fField_changed{true};
G4bool fTrack_changed{true};
const G4int qss_order{2};
Substeps substeps;
Substep current_substep;
const G4FieldTrack* fCurrent_track{nullptr};
QSStateVector dq_vector;
/** Invariants for this track -- during propagation. */
G4double fCharge{-1.0};
G4double fCharge_c2;
G4double fRestMass{CLHEP::electron_mass_c2};
G4double fGamma{1.0};
G4double fCoeff; // coeff;
/** Cached values -- for tiny speed up. */
G4double fMassOverC ; // was mass_times_gamma_over_speed_of_light;
G4double fInv_mass_over_c;
/** Used by interpolation driver, need to copy state here when stepper finished. */
G4double fYout[12];
/** QSS parameters separated into velocity and position. */
G4double dqrel[2] = {0.0,0.0};
G4double dqmin[2] = {0.001,0.001};
G4double fVelocity{0.0};
G4double fFinal_t{0.0};
};
// ----------------------------------------------------------------------------
// Inline methods
// ----------------------------------------------------------------------------
#include "G4QSStepper.icc"
#endif
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