gfield.h

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#pragma once
 
// G4 headers
#include "G4MagneticField.hh"
#include "G4FieldManager.hh"
#include "G4MagIntegratorStepper.hh"
 
// gemc
#include "gfactory.h"
#include "goptions.h"
#include "gfieldConventions.h"
 
struct GFieldDefinition {
    GFieldDefinition() {}
 
    std::string name; 
    std::string integration_stepper; 
    double minimum_step; 
    std::string type; 
 
    map <std::string, string> field_parameters; 
 
    void add_map_parameter(std::string key, std::string value) {
        field_parameters[key] = value;
    }
 
    string gfieldPluginName() {
        return "gfield" + type + "Factory";
    }
 
    // overload << to print the field definition
    friend std::ostream &operator<<(std::ostream &stream, GFieldDefinition gfd) {
        stream << "  > Field name:            " << gfd.name << std::endl;
        stream << "    - integration stepper  " << gfd.integration_stepper << std::endl;
        stream << "    - minimum step         " << gfd.minimum_step << " mm" << std::endl;
        stream << "    - type                 " << gfd.type << std::endl;
 
        // print the field parameters
        // align the keys to the left
        for (auto &field_parameter: gfd.field_parameters) {
            stream << "    - " << std::left << std::setw(21) << field_parameter.first  << field_parameter.second << std::endl;
        }
 
        return stream;
    }
};
 
class GField : public G4MagneticField {
 
public:
    GField() = default;
 
    virtual ~GField() = default;
 
    virtual void GetFieldValue(const double x[3], double *bfield) const = 0;
 
    G4FieldManager *create_FieldManager();
 
    virtual void load_field_definitions(GFieldDefinition gfd) {
        gfield_definitions = gfd;
    }
 
    void gFLogMessage(std::string message) {
        gLogMessage(GFIELDLOGHEADER + gfield_definitions.name + " " + message);
    }
 
    int get_field_parameter_int(std::string key) {
        return stoi(gfield_definitions.field_parameters[key]);
    }
    double get_field_parameter_double(std::string key) {
        return stod(gfield_definitions.field_parameters[key]);
    }
 
private:
 
 
    std::vector <std::string> SUPPORTED_STEPPERS = { 
            "G4DormandPrince745", "G4ClassicalRK4", "G4SimpleRunge", "G4HelixExplicitEuler",
            "G4HelixImplicitEuler", "G4CashKarpRKF45", "G4RKG3_Stepper", "G4SimpleHeum",
            "G4NystromRK4", "G4ImplicitEuler", "G4ExplicitEuler"
    };
 
 
protected:
    GFieldDefinition gfield_definitions;
 
public:
 
    static GField *instantiate(const dlhandle handle) {
 
        if (handle == nullptr) return nullptr;
 
        // must match the extern C declaration in the derived factories
        void *maker = dlsym(handle, "GFieldFactory");
 
        if (maker == nullptr) return nullptr;
 
        typedef GField *(*fptr)();
 
        // static_cast not allowed here
        // see http://stackoverflow.com/questions/573294/when-to-use-reinterpret-cast
        // need to run the DLL GMediaFactory function that returns the factory
        fptr func = reinterpret_cast<fptr>(reinterpret_cast<void *>(maker));
 
        return func();
    }
};