The interface to various event generators.

Is an base class, that defines the interface of ROOT to various
event generators. Every event generator should inherit from
TGenerator or its subclasses.

Derived class can overload the member function GenerateEvent
to do the actual event generation (e.g., call PYEVNT or similar).

The derived class should overload the member function
ImportParticles (both types) to read the internal storage of the
generated event into either the internal TObjArray or the passed
TClonesArray of TParticles.

If the generator code stores event data in the /HEPEVT/ common block Then the default implementation of ImportParticles should suffice.
The common block /HEPEVT/ is structed like

  // C                                                            
  typedef struct {                                                   
     Int_t    nevhep;           // Event number                      
     Int_t    nhep;             // # of particles                    
     Int_t    isthep[4000];     // Status flag of i'th particle      
     Int_t    idhep[4000];      // PDG # of particle                 
     Int_t    jmohep[4000][2];  // 1st & 2nd mother particle #       
     Int_t    jdahep[4000][2];  // 1st & 2nd daughter particle #     
     Double_t phep[4000][5];    // 4-momentum and 1 word             
     Double_t vhep[4000][4];    // 4-position of production          
  } HEPEVT_DEF;                                                      
                                                                     
                                                                     
  C Fortran                                                          
        COMMON/HEPEVT/NEVHEP,NHEP,ISTHEP(4000),IDHEP(4000),          
      +    JMOHEP(2,4000),JDAHEP(2,4000),PHEP(5,4000),VHEP(4,4000)   
        INTEGER NEVHEP,NHEP,ISTHEP,IDHEP,JMOHEP,JDAHEP               
        DOUBLE PRECISION PHEP,VHEP

The generic member functions SetParameter and GetParameter can be overloaded to set and get parameters of the event generator.

Note, if the derived class interfaces a (set of) Fortran common blocks (like TPythia, TVenus does), one better make the derived class a singleton. That is, something like

    class MyGenerator : public TGenerator                            
    {                                                                
    public:                                                          
      static MyGenerator* Instance()                                 
      {                                                              
        if (!fgInstance) fgInstance = new MyGenerator;               
        return fgInstance;                                           
      }                                                              
      void  GenerateEvent() { ... }                                  
      void  ImportParticles(TClonesArray* a, Option_t opt="") {...}  
      Int_t ImportParticles(Option_t opt="") { ... }                 
      Int_t    SetParameter(const char* name, Double_t val) { ... }  
      Double_t GetParameter(const char* name) { ... }                
      virtual ~MyGenerator() { ... }                                 
    protected:                                                       
      MyGenerator() { ... }                                          
      MyGenerator(const MyGenerator& o) { ... }                      
      MyGenerator& operator=(const MyGenerator& o) { ... }           
      static MyGenerator* fgInstance;                                
      ClassDefOverride(MyGenerator,0);                                       
    };

Having multiple objects accessing the same common blocks is not
safe.

Concrete TGenerator classes can be loaded in scripts and subseqent-
ly used in compiled code:

    // MyRun.h                                                       
    class MyRun : public TObject                                     
    {                                                                
    public:                                                          
      static MyRun* Instance() { ... }                               
      void SetGenerator(TGenerator* g) { fGenerator = g; }           
      void Run(Int_t n, Option_t* option="")                         
      {                                                              
        TFile*        file = TFile::Open("file.root","RECREATE");    
        TTree*        tree = new TTree("T","T");                     
        TClonesArray* p    = new TClonesArray("TParticles");         
        tree->Branch("particles", &p);                               
        for (Int_t event = 0; event < n; event++) {                  
          fGenerator->GenerateEvent();                               
          fGenerator->ImportParticles(p,option);                     
          tree->Fill();                                              
        }                                                            
        file->Write();                                               
        file->Close();                                               
      }                                                              
      ...                                                            
    protected:                                                       
      TGenerator* fGenerator;                                        
      ClassDefOverride(MyRun,0);                                             
    };                                                               
                                                                     
    // Config.C                                                      
    void Config()                                                    
    {                                                                
       MyRun* run = MyRun::Instance();                               
       run->SetGenerator(MyGenerator::Instance());                   
    }                                                                
                                                                     
    // main.cxx                                                      
    int                                                              
    main(int argc, char** argv)                                      
    {                                                                
      TApplication app("", 0, 0);                                    
      gSystem->ProcessLine(".x Config.C");                           
      MyRun::Instance()->Run(10);                                    
      return 0;                                                      
    }

This is especially useful for example with TVirtualMC or similar.

Definition at line 144 of file TGenerator.h.

Public Member Functions
	TGenerator ()

	TGenerator (const char name, const char title="Generator class")
	Event generator default constructor.

	~TGenerator () override
	Event generator default destructor.

void	Browse (TBrowser *b) override
	browse generator

Int_t	DistancetoPrimitive (Int_t px, Int_t py) override
	Compute distance from point px,py to objects in event.

void	Draw (Option_t *option="") override
	Insert one event in the pad list.

void	ExecuteEvent (Int_t event, Int_t px, Int_t py) override
	Execute action corresponding to one event.

virtual void	GenerateEvent ()
	must be implemented in concrete class (see eg TPythia6)

virtual TObjArray *	GetListOfParticles () const

Int_t	GetNumberOfParticles () const
	Return the number of particles in the stack.

virtual Double_t	GetParameter (const char *) const

virtual TParticle *	GetParticle (Int_t i) const
	Returns pointer to primary number i;.

virtual TObjArray *	GetPrimaries (Option_t *option="")

Float_t	GetPtCut () const

virtual TObjArray *	ImportParticles (Option_t *option="")
	It reads the /HEPEVT/ common block which has been filled by the GenerateEvent method.

virtual Int_t	ImportParticles (TClonesArray particles, Option_t option="")
	It reads the /HEPEVT/ common block which has been filled by the GenerateEvent method.

TClass *	IsA () const override

void	Paint (Option_t *option="") override
	Paint one event.

virtual void	SetParameter (const char *, Double_t)

virtual void	SetPtCut (Float_t ptcut=0)
	Set Pt threshold below which primaries are not drawn.

virtual void	SetViewRadius (Float_t rbox=1000)
	Set lower and upper values of the view range.

virtual void	SetViewRange (Float_t xmin=-10000, Float_t ymin=-10000, Float_t zmin=-10000, Float_t xmax=10000, Float_t ymax=10000, Float_t zmax=10000)
	Set lower and upper values of the view range.

virtual void	ShowNeutrons (Bool_t show=1)
	Set flag to display or not neutrons.

void	Streamer (TBuffer &) override
	Stream an object of class TObject.

void	StreamerNVirtual (TBuffer &ClassDef_StreamerNVirtual_b)

Public Member Functions inherited from TNamed
	TNamed ()

	TNamed (const char name, const char title)

	TNamed (const TNamed &named)
	TNamed copy ctor.

	TNamed (const TString &name, const TString &title)

virtual	~TNamed ()
	TNamed destructor.

void	Clear (Option_t *option="") override
	Set name and title to empty strings ("").

TObject *	Clone (const char *newname="") const override
	Make a clone of an object using the Streamer facility.

Int_t	Compare (const TObject *obj) const override
	Compare two TNamed objects.

void	Copy (TObject &named) const override
	Copy this to obj.

virtual void	FillBuffer (char *&buffer)
	Encode TNamed into output buffer.

const char *	GetName () const override
	Returns name of object.

const char *	GetTitle () const override
	Returns title of object.

ULong_t	Hash () const override
	Return hash value for this object.

TClass *	IsA () const override

Bool_t	IsSortable () const override

void	ls (Option_t *option="") const override
	List TNamed name and title.

TNamed &	operator= (const TNamed &rhs)
	TNamed assignment operator.

void	Print (Option_t *option="") const override
	Print TNamed name and title.

virtual void	SetName (const char *name)
	Set the name of the TNamed.

virtual void	SetNameTitle (const char name, const char title)
	Set all the TNamed parameters (name and title).

virtual void	SetTitle (const char *title="")
	Set the title of the TNamed.

virtual Int_t	Sizeof () const
	Return size of the TNamed part of the TObject.

void	Streamer (TBuffer &) override
	Stream an object of class TObject.

void	StreamerNVirtual (TBuffer &ClassDef_StreamerNVirtual_b)

Public Member Functions inherited from TObject
	TObject ()
	TObject constructor.

	TObject (const TObject &object)
	TObject copy ctor.

virtual	~TObject ()
	TObject destructor.

void	AbstractMethod (const char *method) const
	Use this method to implement an "abstract" method that you don't want to leave purely abstract.

virtual void	AppendPad (Option_t *option="")
	Append graphics object to current pad.

ULong_t	CheckedHash ()
	Check and record whether this class has a consistent Hash/RecursiveRemove setup (*) and then return the regular Hash value for this object.

virtual const char *	ClassName () const
	Returns name of class to which the object belongs.

virtual void	Delete (Option_t *option="")
	Delete this object.

virtual void	DrawClass () const
	Draw class inheritance tree of the class to which this object belongs.

virtual TObject *	DrawClone (Option_t *option="") const
	Draw a clone of this object in the current selected pad with: `gROOT->SetSelectedPad(c1)`.

virtual void	Dump () const
	Dump contents of object on stdout.

virtual void	Error (const char method, const char msgfmt,...) const
	Issue error message.

virtual void	Execute (const char method, const char params, Int_t *error=nullptr)
	Execute method on this object with the given parameter string, e.g.

virtual void	Execute (TMethod method, TObjArray params, Int_t *error=nullptr)
	Execute method on this object with parameters stored in the TObjArray.

virtual void	Fatal (const char method, const char msgfmt,...) const
	Issue fatal error message.

virtual TObject *	FindObject (const char *name) const
	Must be redefined in derived classes.

virtual TObject *	FindObject (const TObject *obj) const
	Must be redefined in derived classes.

virtual Option_t *	GetDrawOption () const
	Get option used by the graphics system to draw this object.

virtual const char *	GetIconName () const
	Returns mime type name of object.

virtual char *	GetObjectInfo (Int_t px, Int_t py) const
	Returns string containing info about the object at position (px,py).

virtual Option_t *	GetOption () const

virtual UInt_t	GetUniqueID () const
	Return the unique object id.

virtual Bool_t	HandleTimer (TTimer *timer)
	Execute action in response of a timer timing out.

Bool_t	HasInconsistentHash () const
	Return true is the type of this object is known to have an inconsistent setup for Hash and RecursiveRemove (i.e.

virtual void	Info (const char method, const char msgfmt,...) const
	Issue info message.

virtual Bool_t	InheritsFrom (const char *classname) const
	Returns kTRUE if object inherits from class "classname".

virtual Bool_t	InheritsFrom (const TClass *cl) const
	Returns kTRUE if object inherits from TClass cl.

virtual void	Inspect () const
	Dump contents of this object in a graphics canvas.

void	InvertBit (UInt_t f)

Bool_t	IsDestructed () const
	IsDestructed.

virtual Bool_t	IsEqual (const TObject *obj) const
	Default equal comparison (objects are equal if they have the same address in memory).

virtual Bool_t	IsFolder () const
	Returns kTRUE in case object contains browsable objects (like containers or lists of other objects).

R__ALWAYS_INLINE Bool_t	IsOnHeap () const

R__ALWAYS_INLINE Bool_t	IsZombie () const

void	MayNotUse (const char *method) const
	Use this method to signal that a method (defined in a base class) may not be called in a derived class (in principle against good design since a child class should not provide less functionality than its parent, however, sometimes it is necessary).

virtual Bool_t	Notify ()
	This method must be overridden to handle object notification (the base implementation is no-op).

void	Obsolete (const char method, const char asOfVers, const char *removedFromVers) const
	Use this method to declare a method obsolete.

void	operator delete (void *ptr)
	Operator delete.

void	operator delete (void ptr, void vp)
	Only called by placement new when throwing an exception.

void	operator delete[] (void *ptr)
	Operator delete [].

void	operator delete[] (void ptr, void vp)
	Only called by placement new[] when throwing an exception.

void *	operator new (size_t sz)

void *	operator new (size_t sz, void *vp)

void *	operator new[] (size_t sz)

void *	operator new[] (size_t sz, void *vp)

TObject &	operator= (const TObject &rhs)
	TObject assignment operator.

virtual void	Pop ()
	Pop on object drawn in a pad to the top of the display list.

virtual Int_t	Read (const char *name)
	Read contents of object with specified name from the current directory.

virtual void	RecursiveRemove (TObject *obj)
	Recursively remove this object from a list.

void	ResetBit (UInt_t f)

virtual void	SaveAs (const char filename="", Option_t option="") const
	Save this object in the file specified by filename.

virtual void	SavePrimitive (std::ostream &out, Option_t *option="")
	Save a primitive as a C++ statement(s) on output stream "out".

void	SetBit (UInt_t f)

void	SetBit (UInt_t f, Bool_t set)
	Set or unset the user status bits as specified in f.

virtual void	SetDrawOption (Option_t *option="")
	Set drawing option for object.

virtual void	SetUniqueID (UInt_t uid)
	Set the unique object id.

void	StreamerNVirtual (TBuffer &ClassDef_StreamerNVirtual_b)

virtual void	SysError (const char method, const char msgfmt,...) const
	Issue system error message.

R__ALWAYS_INLINE Bool_t	TestBit (UInt_t f) const

Int_t	TestBits (UInt_t f) const

virtual void	UseCurrentStyle ()
	Set current style settings in this object This function is called when either TCanvas::UseCurrentStyle or TROOT::ForceStyle have been invoked.

virtual void	Warning (const char method, const char msgfmt,...) const
	Issue warning message.

virtual Int_t	Write (const char *name=nullptr, Int_t option=0, Int_t bufsize=0)
	Write this object to the current directory.

virtual Int_t	Write (const char *name=nullptr, Int_t option=0, Int_t bufsize=0) const
	Write this object to the current directory.

Static Public Member Functions
static TClass *	Class ()

static const char *	Class_Name ()

static constexpr Version_t	Class_Version ()

static const char *	DeclFileName ()

Static Public Member Functions inherited from TNamed
static TClass *	Class ()

static const char *	Class_Name ()

static constexpr Version_t	Class_Version ()

static const char *	DeclFileName ()

Static Public Member Functions inherited from TObject
static TClass *	Class ()

static const char *	Class_Name ()

static constexpr Version_t	Class_Version ()

static const char *	DeclFileName ()

static Longptr_t	GetDtorOnly ()
	Return destructor only flag.

static Bool_t	GetObjectStat ()
	Get status of object stat flag.

static void	SetDtorOnly (void *obj)
	Set destructor only flag.

static void	SetObjectStat (Bool_t stat)
	Turn on/off tracking of objects in the TObjectTable.

Protected Member Functions
	TGenerator (const TGenerator &tg)

TGenerator &	operator= (const TGenerator &tg)

Protected Member Functions inherited from TObject
virtual void	DoError (int level, const char location, const char fmt, va_list va) const
	Interface to ErrorHandler (protected).

void	MakeZombie ()

Protected Attributes
TObjArray *	fParticles
	display neutrons if true

Float_t	fPtCut

Bool_t	fShowNeutrons
	Pt cut. Do not show primaries below.

Protected Attributes inherited from TNamed
TString	fName

TString	fTitle

Additional Inherited Members
Public Types inherited from TObject
enum	{ kIsOnHeap = 0x01000000 , kNotDeleted = 0x02000000 , kZombie = 0x04000000 , kInconsistent = 0x08000000 , kBitMask = 0x00ffffff }

enum	{ kSingleKey = (1ULL << ( 0 )) , kOverwrite = (1ULL << ( 1 )) , kWriteDelete = (1ULL << ( 2 )) }

enum	EDeprecatedStatusBits { kObjInCanvas = (1ULL << ( 3 )) }

enum	EStatusBits { kCanDelete = (1ULL << ( 0 )) , kMustCleanup = (1ULL << ( 3 )) , kIsReferenced = (1ULL << ( 4 )) , kHasUUID = (1ULL << ( 5 )) , kCannotPick = (1ULL << ( 6 )) , kNoContextMenu = (1ULL << ( 8 )) , kInvalidObject = (1ULL << ( 13 )) }

Protected Types inherited from TObject
enum	{ kOnlyPrepStep = (1ULL << ( 3 )) }

#include <TGenerator.h>

Inheritance diagram for TGenerator:

[legend]

Constructor & Destructor Documentation

◆ TGenerator() [1/3]

TGenerator::TGenerator ( const TGenerator & tg )

inlineprotected

Definition at line 151 of file TGenerator.h.

◆ TGenerator() [2/3]

TGenerator::TGenerator ( )

inline

Definition at line 163 of file TGenerator.h.

◆ TGenerator() [3/3]

TGenerator::TGenerator	(	const char *	name,
		const char *	title = `"Generator class"`
	)

Event generator default constructor.

Definition at line 163 of file TGenerator.cxx.

◆ ~TGenerator()

TGenerator::~TGenerator ( )

override

Event generator default destructor.

Definition at line 179 of file TGenerator.cxx.

Member Function Documentation

◆ Browse()

void TGenerator::Browse ( TBrowser * b )

overridevirtual

browse generator

Reimplemented from TObject.

Definition at line 327 of file TGenerator.cxx.

◆ Class()

static TClass * TGenerator::Class ( )

static

Returns: TClass describing this class

◆ Class_Name()

static const char * TGenerator::Class_Name ( )

static

Returns: Name of this class

◆ Class_Version()

static constexpr Version_t TGenerator::Class_Version ( )

inlinestaticconstexpr

Returns: Version of this class

Definition at line 187 of file TGenerator.h.

◆ DeclFileName()

static const char * TGenerator::DeclFileName ( )

inlinestatic

Returns: Name of the file containing the class declaration

Definition at line 187 of file TGenerator.h.

◆ DistancetoPrimitive()

Int_t TGenerator::DistancetoPrimitive	(	Int_t	px,
		Int_t	py
	)

overridevirtual

Compute distance from point px,py to objects in event.

Reimplemented from TObject.

Definition at line 337 of file TGenerator.cxx.

◆ Draw()

void TGenerator::Draw ( Option_t * option = "" )

overridevirtual

Insert one event in the pad list.

Reimplemented from TObject.

Definition at line 351 of file TGenerator.cxx.

◆ ExecuteEvent()

void TGenerator::ExecuteEvent	(	Int_t	event,
		Int_t	px,
		Int_t	py
	)

overridevirtual

Execute action corresponding to one event.

Reimplemented from TObject.

Definition at line 498 of file TGenerator.cxx.

◆ GenerateEvent()

void TGenerator::GenerateEvent ( )

virtual

must be implemented in concrete class (see eg TPythia6)

Reimplemented in TPythia8.

Definition at line 192 of file TGenerator.cxx.

◆ GetListOfParticles()

virtual TObjArray * TGenerator::GetListOfParticles ( ) const

inlinevirtual

Definition at line 176 of file TGenerator.h.

◆ GetNumberOfParticles()

Int_t TGenerator::GetNumberOfParticles ( ) const

Return the number of particles in the stack.

Definition at line 509 of file TGenerator.cxx.

◆ GetParameter()

virtual Double_t TGenerator::GetParameter ( const char * ) const

inlinevirtual

Definition at line 171 of file TGenerator.h.

◆ GetParticle()

TParticle * TGenerator::GetParticle ( Int_t i ) const

virtual

Returns pointer to primary number i;.

Definition at line 518 of file TGenerator.cxx.

◆ GetPrimaries()

virtual TObjArray * TGenerator::GetPrimaries ( Option_t * option = "" )

inlinevirtual

Definition at line 177 of file TGenerator.h.

◆ GetPtCut()

Float_t TGenerator::GetPtCut ( ) const

inline

Definition at line 178 of file TGenerator.h.

◆ ImportParticles() [1/2]

TObjArray * TGenerator::ImportParticles ( Option_t * option = "" )

virtual

It reads the /HEPEVT/ common block which has been filled by the GenerateEvent method.

If the event generator does not use the HEPEVT common block, This routine has to be overloaded by the subclasses.

The default action is to store only the stable particles (ISTHEP = 1) This can be demanded explicitly by setting the option = "Final" If the option = "All", all the particles are stored.

Reimplemented in TPythia8.

Definition at line 208 of file TGenerator.cxx.

◆ ImportParticles() [2/2]

Int_t TGenerator::ImportParticles	(	TClonesArray *	particles,
		Option_t *	option = `""`
	)

virtual

It reads the /HEPEVT/ common block which has been filled by the GenerateEvent method.

If the event generator does not use the HEPEVT common block, This routine has to be overloaded by the subclasses.

The function loops on the generated particles and store them in the TClonesArray pointed by the argument particles. The default action is to store only the stable particles (ISTHEP = 1) This can be demanded explicitly by setting the option = "Final" If the option = "All", all the particles are stored.

Reimplemented in TPythia8.

Definition at line 273 of file TGenerator.cxx.

◆ IsA()

TClass * TGenerator::IsA ( ) const

inlineoverridevirtual

Returns: TClass describing current object

Reimplemented from TObject.

Definition at line 187 of file TGenerator.h.

◆ operator=()

TGenerator & TGenerator::operator= ( const TGenerator & tg )

inlineprotected

Definition at line 153 of file TGenerator.h.

◆ Paint()

void TGenerator::Paint ( Option_t * option = "" )

overridevirtual

Paint one event.

Reimplemented from TObject.

Definition at line 531 of file TGenerator.cxx.

◆ SetParameter()

virtual void TGenerator::SetParameter	(	const char *	,
		Double_t
	)

inlinevirtual

Definition at line 180 of file TGenerator.h.

◆ SetPtCut()

void TGenerator::SetPtCut ( Float_t ptcut = 0 )

virtual

Set Pt threshold below which primaries are not drawn.

Definition at line 540 of file TGenerator.cxx.

◆ SetViewRadius()

void TGenerator::SetViewRadius ( Float_t rbox = 1000 )

virtual

Set lower and upper values of the view range.

Definition at line 552 of file TGenerator.cxx.

◆ SetViewRange()

void TGenerator::SetViewRange	(	Float_t	xmin = `-10000`,
		Float_t	ymin = `-10000`,
		Float_t	zmin = `-10000`,
		Float_t	xmax = `10000`,
		Float_t	ymax = `10000`,
		Float_t	zmax = `10000`
	)

virtual

Set lower and upper values of the view range.

Definition at line 562 of file TGenerator.cxx.

◆ ShowNeutrons()

void TGenerator::ShowNeutrons ( Bool_t show = 1 )

virtual

Set flag to display or not neutrons.

Definition at line 577 of file TGenerator.cxx.

◆ Streamer()

void TGenerator::Streamer ( TBuffer & R__b )

overridevirtual

Stream an object of class TObject.

Reimplemented from TObject.

◆ StreamerNVirtual()

void TGenerator::StreamerNVirtual ( TBuffer & ClassDef_StreamerNVirtual_b )

inline

Definition at line 187 of file TGenerator.h.

Member Data Documentation

◆ fParticles

TObjArray* TGenerator::fParticles

protected

display neutrons if true

Definition at line 149 of file TGenerator.h.

◆ fPtCut

Float_t TGenerator::fPtCut

protected

Definition at line 147 of file TGenerator.h.

◆ fShowNeutrons

Bool_t TGenerator::fShowNeutrons

protected

Pt cut. Do not show primaries below.

Definition at line 148 of file TGenerator.h.

Libraries for TGenerator:

[legend]

The documentation for this class was generated from the following files:

montecarlo/eg/inc/TGenerator.h
montecarlo/eg/src/TGenerator.cxx

Public Member Functions

Static Public Member Functions

Protected Member Functions

Protected Attributes

Additional Inherited Members

Constructor & Destructor Documentation

◆ TGenerator() [1/3]

◆ TGenerator() [2/3]

◆ TGenerator() [3/3]

◆ ~TGenerator()

Member Function Documentation

◆ Browse()

◆ Class()

◆ Class_Name()

◆ Class_Version()

◆ DeclFileName()

◆ DistancetoPrimitive()

◆ Draw()

◆ ExecuteEvent()

◆ GenerateEvent()

◆ GetListOfParticles()

◆ GetNumberOfParticles()

◆ GetParameter()

◆ GetParticle()

◆ GetPrimaries()

◆ GetPtCut()

◆ ImportParticles() [1/2]

◆ ImportParticles() [2/2]

◆ IsA()

◆ operator=()

◆ Paint()

◆ SetParameter()

◆ SetPtCut()

◆ SetViewRadius()

◆ SetViewRange()

◆ ShowNeutrons()

◆ Streamer()

◆ StreamerNVirtual()

Member Data Documentation

◆ fParticles

◆ fPtCut

◆ fShowNeutrons