Gabriele Cosmo
193 lines
7.9 KiB
C++
193 lines
7.9 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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// G4BorisDriver
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//
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// Class description:
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//
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// G4BorisDriver is a driver class using the second order Boris
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// method to integrate the equation of motion.
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//
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//
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// Author: Divyansh Tiwari, Google Summer of Code 2022
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// Supervision: John Apostolakis,Renee Fatemi, Soon Yung Jun
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// --------------------------------------------------------------------
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#ifndef G4BORIS_DRIVER_HH
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#define G4BORIS_DRIVER_HH
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#include "G4VIntegrationDriver.hh"
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#include "G4BorisScheme.hh"
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#include "G4ChordFinderDelegate.hh"
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class G4BorisDriver : public G4VIntegrationDriver,
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public G4ChordFinderDelegate<G4BorisDriver>
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{
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public:
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G4BorisDriver( G4double hminimum,
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G4BorisScheme* Boris,
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G4int numberOfComponents = 6,
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G4bool verbosity = false);
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inline ~G4BorisDriver() override = default;
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inline G4BorisDriver(const G4BorisDriver&) = delete;
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inline G4BorisDriver& operator=(const G4BorisDriver&) = delete;
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// 1. Core methods that advance the integration
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G4bool AccurateAdvance( G4FieldTrack& track,
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G4double stepLen,
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G4double epsilon,
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G4double beginStep = 0) override;
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// Advance integration accurately
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// - by relative accuracy better than 'epsilon'
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G4bool QuickAdvance( G4FieldTrack& y_val, // In/Out
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const G4double dydx[],
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G4double hstep,
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G4double& missDist, // Out: estimated sagitta
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G4double& dyerr ) override;
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// Attempt one integration step, and return estimated error 'dyerr'
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void OneGoodStep(G4double yCurrentState[], // In/Out: state ('y')
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G4double& curveLength, // In/Out: 'x'
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G4double htry, // step to attempt
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G4double epsilon_rel, // relative accuracy
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G4double restMass,
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G4double charge,
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G4double& hdid, // Out: step achieved
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G4double& hnext); // Out: proposed next step
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// Method to implement Accurate Advance
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// 2. Methods needed to co-work with G4ChordFinder
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G4double AdvanceChordLimited(G4FieldTrack& track,
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G4double hstep,
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G4double eps,
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G4double chordDistance) override
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{
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return ChordFinderDelegate::
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AdvanceChordLimitedImpl(track, hstep, eps, chordDistance);
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}
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void OnStartTracking() override
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{
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ChordFinderDelegate::ResetStepEstimate();
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}
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void OnComputeStep(const G4FieldTrack*) override {}
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// 3. Does the method redo integrations when called to obtain values for
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// internal, smaller intervals? (when needed to identify an intersection)
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G4bool DoesReIntegrate() const override { return true; }
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// It would be no if it just used interpolation to provide a result.
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// 4. Relevant for calculating a new step size to achieve required accuracy
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inline G4double ComputeNewStepSize(G4double errMaxNorm, // normalised error
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G4double hstepCurrent) override; // current step size
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G4double ShrinkStepSize2(G4double h, G4double error2) const;
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G4double GrowStepSize2(G4double h, G4double error2) const;
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// Calculate the next step size given the square of the relative error
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// 5. Auxiliary Methods ...
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void GetDerivatives( const G4FieldTrack& track,
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G4double dydx[] ) const override;
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void GetDerivatives( const G4FieldTrack& track,
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G4double dydx[],
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G4double field[] ) const override;
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inline void SetVerboseLevel(G4int level) override;
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inline G4int GetVerboseLevel() const override;
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inline G4EquationOfMotion* GetEquationOfMotion() override;
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inline const G4EquationOfMotion* GetEquationOfMotion() const;
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void SetEquationOfMotion(G4EquationOfMotion* equation) override;
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void StreamInfo( std::ostream& os ) const override;
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// Write out the parameters / state of the driver
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// 6. Not relevant for Boris and other non-RK methods
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inline const G4MagIntegratorStepper* GetStepper() const override;
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inline G4MagIntegratorStepper* GetStepper() override;
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private:
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inline G4int GetNumberOfVariables() const;
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inline void CheckStep(const G4ThreeVector& posIn,
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const G4ThreeVector& posOut,
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G4double hdid) const;
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private:
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// INVARIANTS -- remain unchanged during tracking / integration
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// Parameters
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G4double fMinimumStep;
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G4bool fVerbosity;
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// State -- The core stepping algorithm
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G4BorisScheme* boris;
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// STATE -- intermediate state (to avoid creation / churn )
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G4double yIn[G4FieldTrack::ncompSVEC],
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yMid[G4FieldTrack::ncompSVEC],
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yOut[G4FieldTrack::ncompSVEC],
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yError[G4FieldTrack::ncompSVEC];
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G4double yCurrent[G4FieldTrack::ncompSVEC];
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// - Unused 2022.11.03:
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// G4double derivs[2][6][G4FieldTrack::ncompSVEC];
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// const G4int interval_sequence[2];
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// INVARIANTS -- Parameters for ensuring that one call has finite number of integration steps
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static constexpr G4int fMaxNoSteps = 300;
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static constexpr G4double fSmallestFraction= 1e-12; // To avoid FP underflow ! ( 1.e-6 for single prec)
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static constexpr G4int fIntegratorOrder= 2; // 2nd order method -- needed for error control
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static constexpr G4double fSafetyFactor = 0.9; //
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static constexpr G4double fMaxSteppingIncrease= 10.0; // Increase no more than 10x
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static constexpr G4double fMaxSteppingDecrease= 0.1; // Reduce no more than 10x
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static constexpr G4double fPowerShrink = -1.0 / fIntegratorOrder;
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static constexpr G4double fPowerGrow = -1.0 / (1.0 + fIntegratorOrder);
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static const G4double fErrorConstraintShrink;
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static const G4double fErrorConstraintGrow;
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using ChordFinderDelegate = G4ChordFinderDelegate<G4BorisDriver>;
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};
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#include "G4BorisDriver.icc"
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#endif
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