Move FairRoot simulation infrastructure into O2

This is a step in the long-term refactoring towards a native Geant4
simulation. It decouples O2 from FairRoot by moving the simulation
infrastructure that o2-sim depends on into the O2 repository.

The imported classes retain their existing interfaces, so no changes are
required in the current simulation code. The runtime parameter database,
analysis framework, and other components that are unused by O2 are not
imported, as their functionality is already provided by CCDB and
ConfigurableParam.

Owning these classes locally will allow future refactoring and cleanup
without changing the current simulation behaviour.

The imported sources keep their upstream formatting and licence headers,
so they live under a 3rdparty directory and are excluded from
clang-format.

Requires the corresponding alidist update (fairroot.sh removal from o2.sh)
to avoid duplicate ROOT dictionaries.

Tested with o2-sim and o2-sim-serial; hits, MC tracks, and event headers
are unchanged.

Author: sawenzel

.clang-format-ignore

@@ -1 +1,3 @@
 *.json
+# vendored FairRoot sources: keep upstream formatting
+Detectors/3rdparty/FairRootBase/**

Common/Field/CMakeLists.txt

@@ -10,23 +10,17 @@
 # or submit itself to any jurisdiction.
 
 o2_add_library(Field
-               SOURCES src/MagFieldContFact.cxx
-                       src/MagFieldFact.cxx
-                       src/MagFieldFast.cxx
-                       src/MagFieldParam.cxx
+               SOURCES src/MagFieldFast.cxx
                        src/MagneticField.cxx
                        src/MagneticWrapperChebyshev.cxx
                        src/FieldOriginBiasParam.cxx
                        src/ALICE3MagneticField.cxx
-                       PUBLIC_LINK_LIBRARIES O2::MathUtils FairRoot::Base O2::CommonUtils)
+                       PUBLIC_LINK_LIBRARIES O2::MathUtils O2::FairRootBase O2::CommonUtils)
 
 o2_target_root_dictionary(Field
                           HEADERS include/Field/MagneticWrapperChebyshev.h
                                   include/Field/MagneticField.h
-                                  include/Field/MagFieldParam.h
-                                  include/Field/MagFieldContFact.h
                                   include/Field/MagFieldFast.h
-                                  include/Field/MagFieldFact.h
                                   include/Field/FieldOriginBiasParam.h
                                   include/Field/ALICE3MagneticField.h)
 

Common/Field/include/Field/MagFieldContFact.h

@@ -10,27 +10,24 @@
 // or submit itself to any jurisdiction.
 
 /// \file MagFieldParam.h
-/// \brief Definition of the MagFieldParam: container for ALICE mag. field parameters
+/// \brief Definition of the MagFieldParam: ALICE mag. field type enumerations
 /// \author ruben.shahoyan@cern.ch
 
 #ifndef ALICEO2_FIELD_MAGFIELDPARAM_H_
 #define ALICEO2_FIELD_MAGFIELDPARAM_H_
 
-#include "FairParGenericSet.h"
-#include <TString.h>
-
-class FairParamList;
-
 namespace o2
 {
 namespace field
 {
 
-class MagneticField;
-
-class MagFieldParam : public FairParGenericSet
-{
- public:
+/// Field map and beam type enumerations.
+///
+/// This used to be a FairParGenericSet container written into the FairRoot
+/// runtime database. That path was never populated nor read back in production
+/// (field settings come from CCDB/SimConfig via SimFieldUtils), so only the
+/// enumerations - which are used throughout O2 - are kept.
+struct MagFieldParam {
   enum BMap_t {
     k2kG,
     k5kG,
@@ -44,35 +41,8 @@ class MagFieldParam : public FairParGenericSet
     kBeamTypepA,
     kBeamTypeAp
   };
-
-  MagFieldParam(const char* name = "", const char* title = "", const char* context = "");
-
-  void SetParam(const MagneticField* field);
-
-  BMap_t GetMapType() const { return mMapType; }
-  BeamType_t GetBeamType() const { return mBeamType; }
-  Int_t GetDefInt() const { return mDefaultIntegration; }
-  Double_t GetFactorSol() const { return mFactorSol; }
-  Double_t GetFactorDip() const { return mFactorDip; }
-  Double_t GetBeamEnergy() const { return mBeamEnergy; }
-  Double_t GetMaxField() const { return mMaxField; }
-  const char* GetMapPath() const { return mMapPath.Data(); }
-
-  void putParams(FairParamList* list) override;
-  Bool_t getParams(FairParamList* list) override;
-
- private:
-  BMap_t mMapType;           ///< map type ID
-  BeamType_t mBeamType;      ///< beam type ID
-  Int_t mDefaultIntegration; ///< field integration type for MC
-  Double_t mFactorSol;       ///< solenoid current factor
-  Double_t mFactorDip;       ///< dipole current factor
-  Double_t mBeamEnergy;      ///< beam energy
-  Double_t mMaxField;        ///< max field for geant
-  TString mMapPath;          ///< path to map file
-
-  ClassDefOverride(MagFieldParam, 1);
 };
+
 } // namespace field
 } // namespace o2
 

Common/Field/include/Field/MagFieldFact.h

@@ -25,8 +25,6 @@
 #include "TNamed.h" // for TNamed
 #include <memory>   // for str::unique_ptr
 
-class FairParamList;
-
 namespace o2
 {
 namespace field
@@ -63,8 +61,6 @@ class MagneticField : public FairField
                 MagFieldParam::BeamType_t btype = MagFieldParam::kBeamTypepp, Double_t benergy = -1, Int_t integ = 2,
                 Double_t fmax = 15, const std::string path = "$(O2_ROOT)/share/Common/maps/mfchebKGI_sym.root");
 
-  MagneticField(const MagFieldParam& param);
-
   MagneticField& operator=(const MagneticField& src);
 
   /// Default destructor
@@ -147,9 +143,6 @@ class MagneticField : public FairField
   /// 3d field query alias for Alias Method to calculate the field at point xyz
   void GetBxyz(const Double_t p[3], Double_t* b) override { MagneticField::Field(p, b); }
 
-  /// Fill Paramater
-  void FillParContainer() override;
-
   /// Method to calculate the integral_0^z of br,bt,bz
   void getTPCIntegral(const Double_t* xyz, Double_t* b) const;
 

Common/Field/include/Field/MagFieldParam.h

@@ -16,9 +16,6 @@
 
 #pragma link C++ class o2::field::MagneticField + ;
 #pragma link C++ class o2::field::MagneticWrapperChebyshev + ;
-#pragma link C++ class o2::field::MagFieldParam + ;
-#pragma link C++ class o2::field::MagFieldContFact + ;
-#pragma link C++ class o2::field::MagFieldFact + ;
 #pragma link C++ class o2::field::MagFieldFast + ;
 #pragma link C++ class o2::field::ALICE3MagneticField + ;