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geant4/source/geometry/magneticfield/include/G4VIntegrationDriver.hh
2025-12-05 08:54:02 +01:00

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//
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//
// G4VIntegrationDriver
//
// Class description:
//
// Abstract base class for 'driver' classes which are responsible for
// undertaking integration of an state given an equation of motion and
// within acceptable error bound(s).
//
// Different integration methods are meant to be provided via this
// common interface, and can span the original type (explicit Runge Kutta
// methods), enhanced RK methods and alternatives such as the
// Bulirsch-Stoer and multi-step methods.
//
// The drivers' key mission is to insure that the error is below set values.
// Author: Dmitry Sorokin (CERN, Google Summer of Code 2017), 20.10.2017
// Supervision: John Apostolakis (CERN)
// --------------------------------------------------------------------
#ifndef G4VINTEGRATION_DRIVER_HH
#define G4VINTEGRATION_DRIVER_HH
#include "G4Types.hh"
#include "G4FieldTrack.hh"
#include "G4EquationOfMotion.hh"
class G4MagIntegratorStepper;
class G4VIntegrationDriver
{
public:
/**
* Default Destructor.
*/
virtual ~G4VIntegrationDriver() = default;
/**
* Computes the step to take, based on chord limits.
* @param[in,out] track The current track in field.
* @param[in] hstep Proposed step length.
* @param[in] eps Requested accuracy, y_err/hstep.
* @param[in] chordDistance Maximum sagitta distance.
* @returns The length of step taken.
*/
virtual G4double AdvanceChordLimited(G4FieldTrack& track,
G4double hstep,
G4double eps,
G4double chordDistance) = 0;
/**
* Advances integration accurately by relative accuracy better than 'eps'.
* On output the track is replaced by the value at the end of interval.
* @param[in,out] track The current track in field.
* @param[in] hstep Proposed step length.
* @param[in] eps Requested accuracy, y_err/hstep.
* @param[in] hinitial Initial minimum integration step.
* @returns true if integration succeeds.
*/
virtual G4bool AccurateAdvance(G4FieldTrack& track,
G4double hstep,
G4double eps, // Requested y_err/hstep
G4double hinitial = 0 ) = 0;
/**
* Setter and getter for the equation of motion.
*/
virtual void SetEquationOfMotion(G4EquationOfMotion* equation) = 0;
virtual G4EquationOfMotion* GetEquationOfMotion() = 0;
/**
* Method for compatibility -- relevant only for G4MagIntegratorDriver.
*/
virtual void RenewStepperAndAdjust(G4MagIntegratorStepper* pItsStepper);
/**
* Setter and getter for verbosity.
*/
virtual void SetVerboseLevel(G4int level) = 0;
virtual G4int GetVerboseLevel() const = 0;
/**
* Dispatch interface method for computing step.
*/
virtual void OnComputeStep(const G4FieldTrack* /*track*/ = nullptr) = 0;
/**
* Dispatch interface method for initialisation/reset of driver.
*/
virtual void OnStartTracking() = 0;
/**
* Whether the driver implements re-integration:
* Does this driver *Recalculate* when AccurateAdvance() is called ?
*/
virtual G4bool DoesReIntegrate() const = 0;
/**
* Writes out to stream the parameters/state of the driver.
*/
virtual void StreamInfo( std::ostream& os ) const = 0;
/**
* Streaming operator.
*/
friend std::ostream& operator<<( std::ostream& os, const G4VIntegrationDriver& id);
// ------------------------------------------------------------------------
//[[deprecated("will be removed")]]
virtual G4bool QuickAdvance(G4FieldTrack& /*track*/, // INOUT
const G4double /*dydx*/[],
G4double /*hstep*/,
G4double& /*dchord_step*/,
G4double& /*dyerr*/) { return false; }
//[[deprecated("will be removed")]]
virtual void GetDerivatives(const G4FieldTrack& track,
G4double dydx[]) const = 0;
//[[deprecated("will be removed")]]
virtual void GetDerivatives(const G4FieldTrack& track,
G4double dydx[],
G4double field[]) const = 0;
//[[deprecated("use GetEquationOfMotion() instead of GetStepper()->GetEquationOfMotion()")]]
virtual const G4MagIntegratorStepper* GetStepper() const = 0;
virtual G4MagIntegratorStepper* GetStepper() = 0;
//[[deprecated("will be removed")]]
virtual G4double ComputeNewStepSize(G4double errMaxNorm, // normalised error
G4double hstepCurrent) = 0;
// Taking the last step's normalised error, calculate
// a step size for the next step.
// - Can limit the next step's size within a factor of the current one.
protected:
static constexpr G4double max_stepping_increase = 5;
static constexpr G4double max_stepping_decrease = 0.1;
};
#endif