gfield.cc

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// geant4
#include "G4Mag_UsualEqRhs.hh"
#include "G4DormandPrince745.hh"
#include "G4ClassicalRK4.hh"
#include "G4HelixSimpleRunge.hh"
#include "G4HelixExplicitEuler.hh"
#include "G4HelixImplicitEuler.hh"
#include "G4CashKarpRKF45.hh"
#include "G4RKG3_Stepper.hh"
#include "G4SimpleHeum.hh"
#include "G4NystromRK4.hh"
#include "G4ImplicitEuler.hh"
#include "G4ExplicitEuler.hh"
#include "G4ChordFinder.hh"
 
// gfield
#include "gfield.h"
#include "gfieldConventions.h"
#include "gfield_options.h"
 
 
// Create a Geant4 field manager and chord finder for this field (non-Doxygen summary).
// Notice: we are always using G4Mag_UsualEqRhs here.
G4FieldManager* GField::create_FieldManager() {
 
    std::string integration_stepper = gfield_definitions.integration_stepper;
    double minimum_step             = gfield_definitions.minimum_step;
 
    // Equation of motion for magnetic field integration.
    G4Mag_UsualEqRhs* iEquation = new G4Mag_UsualEqRhs(this);
 
    // Validate the requested stepper name and fall back to the default if unsupported.
    if (std::find(SUPPORTED_STEPPERS.begin(), SUPPORTED_STEPPERS.end(), integration_stepper) == SUPPORTED_STEPPERS.end()) {
        log->info(0, "Integration Stepper ", integration_stepper, " not supported. Using default: ", GFIELD_DEFAULT_INTEGRATION_STEPPER);
        integration_stepper = GFIELD_DEFAULT_INTEGRATION_STEPPER;
    }
 
    G4MagIntegratorStepper* mag_int_stepper = nullptr;
 
    // Select the stepper implementation by name.
    // (This is intentionally explicit rather than reflective/automatic.)
    if (integration_stepper == "G4DormandPrince745") {
        mag_int_stepper = new G4DormandPrince745(iEquation);
    } else if (integration_stepper == "G4ClassicalRK4") {
        mag_int_stepper = new G4ClassicalRK4(iEquation);
    } else if (integration_stepper == "G4SimpleRunge") {
        mag_int_stepper = new G4HelixSimpleRunge(iEquation);
    } else if (integration_stepper == "G4HelixExplicitEuler") {
        mag_int_stepper = new G4HelixExplicitEuler(iEquation);
    } else if (integration_stepper == "G4HelixImplicitEuler") {
        mag_int_stepper = new G4HelixImplicitEuler(iEquation);
    } else if (integration_stepper == "G4CashKarpRKF45") {
        mag_int_stepper = new G4CashKarpRKF45(iEquation);
    } else if (integration_stepper == "G4RKG3_Stepper") {
        mag_int_stepper = new G4RKG3_Stepper(iEquation);
    } else if (integration_stepper == "G4SimpleHeum") {
        mag_int_stepper = new G4SimpleHeum(iEquation);
    } else if (integration_stepper == "G4NystromRK4") {
        mag_int_stepper = new G4NystromRK4(iEquation);
    } else if (integration_stepper == "G4ImplicitEuler") {
        mag_int_stepper = new G4ImplicitEuler(iEquation);
    } else if (integration_stepper == "G4ExplicitEuler") {
        mag_int_stepper = new G4ExplicitEuler(iEquation);
    } else {
        // If we got here, the name was expected to be valid but no branch matched.
        log->error(ERR_STEPPER_NOT_FOUND, "Integration Stepper ", integration_stepper, " not found. Exiting.");
    }
 
    // Build the chord finder (controls step subdivision and interpolation along curved trajectories).
    G4ChordFinder* fChordFinder = new G4ChordFinder(this, minimum_step, mag_int_stepper);
 
    // Field manager owns the chord finder and ties the field into Geant4 transportation.
    return new G4FieldManager(this, fChordFinder);
}