LesHouchesFileReader is an base class to be used for objects which reads event files from matrix element generators. More...

#include <LesHouchesFileReader.h>

Inheritance diagram for ThePEG::LesHouchesFileReader:

[legend]

Public Member Functions
string	filename () const
	Return the name of the file from where to read events.

virtual vector< string >	optWeightsNamesFunc ()
	Return the optional weights information string ("Names")

void	erase_substr (std::string &subject, const std::string &search)
	Erases all occurences of a substring from a string.

Standard constructors and destructors.
	LesHouchesFileReader ()
	Default constructor.

	LesHouchesFileReader (const LesHouchesFileReader &)
	Copy-constructor. More...

virtual	~LesHouchesFileReader ()
	Destructor.

Virtual functions specified by the LesHouchesReader base class.
virtual void	initialize (LesHouchesEventHandler &eh)
	Initialize. More...

virtual void	open ()
	Open a file with events. More...

virtual void	close ()
	Close the file from which events have been read.

virtual bool	doReadEvent ()
	Read the next event from the file or stream into the corresponding protected variables. More...

Functions used by the persistent I/O system.
void	persistentOutput (PersistentOStream &os) const
	Function used to write out object persistently. More...

void	persistentInput (PersistentIStream &is, int version)
	Function used to read in object persistently. More...

Public Member Functions inherited from ThePEG::LesHouchesReader
	LesHouchesReader (bool active=false)
	Default constructor. More...

	LesHouchesReader (const LesHouchesReader &)
	Copy-constructor.

virtual	~LesHouchesReader ()
	Destructor.

virtual double	getEvent ()
	Calls readEvent() or uncacheEvent() to read information into the LesHouches common block variables. More...

virtual bool	readEvent ()
	Calls doReadEvent() and performs pre-defined reweightings. More...

virtual void	skip (long n)
	Skip n events. More...

tXCombPtr	getXComb ()
	Get an XComb object. More...

tSubProPtr	getSubProcess ()
	Get a SubProcess object corresponding to the information in the Les Houches common block variables.

virtual long	scan ()
	Scan the file or stream to obtain information about cross section weights and particles etc. More...

virtual void	initStat ()
	Take the information corresponding to the HEPRUP common block and initialize the statistics for this reader.

double	reweight ()
	Reweights the current event using the reweights and preweights vectors. More...

virtual void	fillEvent ()
	Converts the information in the Les Houches common block variables into a Particle objects.

void	reset ()
	Removes the particles created in the last generated event, preparing to produce a new one.

virtual void	setWeightScale (long neve)
	Possibility for subclasses to recover from non-conformant settings of XMAXUP when an event file has been scanned with neve events. More...

long	NEvents () const
	The number of events found in this reader. More...

long	currentPosition () const
	The number of events produced so far. More...

long	maxScan () const
	The maximum number of events to scan to collect information about processes and cross sections. More...

bool	active () const
	Return true if this reader is active.

bool	negativeWeights () const
	True if negative weights may be produced.

const XSecStat &	xSecStats () const
	The collected cross section statistics for this reader.

const StatMap &	processStats () const
	Collected statistics about the individual processes.

void	select (double weight)
	Select the current event. More...

void	accept ()
	Accept the current event assuming it was previously selcted.

void	reject (double w)
	Reject the current event assuming it was previously accepted.

virtual void	increaseMaxXSec (CrossSection maxxsec)
	Increase the overestimated cross section for this reader.

tPExtrPtr	partonExtractor () const
	The PartonExtractor object used to construct remnants.

tCascHdlPtr	CKKWHandler () const
	Return a possibly null pointer to a CascadeHandler to be used for CKKW-reweighting.

const PartonPairVec &	partonBins () const
	The pairs of PartonBin objects describing the partons which can be extracted by the PartonExtractor object.

const XCombMap &	xCombs () const
	The map of XComb objects indexed by the corresponding PartonBin pair.

const Cuts &	cuts () const
	The Cuts object to be used for this reader.

void	persistentOutput (PersistentOStream &os) const
	Function used to write out object persistently. More...

void	persistentInput (PersistentIStream &is, int version)
	Function used to read in object persistently. More...

double	eventWeight () const
	The current event weight given by XWGTUP times possible reweighting. More...

const map< string, double > &	optionalEventWeights () const
	Return the optional named weights associated to the current event.

const int &	optionalEventnpLO () const
	Return the optional npLO and npNLO.

const int &	optionalEventnpNLO () const

const PBIPair &	partonBinInstances () const
	The pair of PartonBinInstance objects describing the current incoming partons in the event.

const PPair &	beams () const
	Return the instances of the beam particles for the current event.

const PPair &	incoming () const
	Return the instances of the incoming particles to the sub process for the current event.

const PVector &	outgoing () const
	Return the instances of the outgoing particles from the sub process for the current event.

const PVector &	intermediates () const
	Return the instances of the intermediate particles in the sub process for the current event.

int	maxMultCKKW () const
	If this reader is to be used (possibly together with others) for CKKW reweighting and veto, this should give the multiplicity of outgoing particles in the highest multiplicity matrix element in the group.

int	minMultCKKW () const
	If this reader is to be used (possibly together with others) for CKKW reweighting and veto, this should give the multiplicity of outgoing particles in the lowest multiplicity matrix element in the group.

Public Member Functions inherited from ThePEG::HandlerBaseT< UseRandom >
double	rnd () const
	Return a simple flat random number in the range ]0,1[.

double	rnd (double xu) const
	Return a simple flat random number in the range ]0,xu[.

double	rnd (double xl, double xu) const
	Return a simple flat random number in the range ]xl,xu[.

bool	rndbool () const
	Return true with 50% probability.

bool	rndbool (double p) const
	Return a true with probability p.

bool	rndbool (double p1, double p2) const
	Return a true with probability p1/(p1+p2).

int	rndsign (double p1, double p2, double p3) const
	Return -1, 0, or 1 with relative probabilities p1, p2, p3.

int	rnd2 (double p0, double p1) const
	Return an integer with probability p /(p0+p1).

int	rnd3 (double p0, double p1, double p2) const
	Return an integer with probability p /(p0+p1+p2).

int	rnd4 (double p0, double p1, double p2, double p3) const
	Return an integer/ with probability p (p0+p1+p2+p3).

long	irnd (long xu=2) const
	Return a simple flat random integrer number in the range [0,xu[.

long	irnd (long xl, long xu) const
	Return a simple flat random integrer number in the range [xl,xu[.

const StandardModelBase &	SM () const
	Return a reference to the object containing the standard model parameters for this run.

tSMPtr	standardModel () const
	Return a pointer to the object containing the standard model parameters for this run.

virtual	~HandlerBaseT ()
	Destructor.

Public Member Functions inherited from ThePEG::Interfaced
virtual	~Interfaced ()
	Empty virtual destructor.

virtual bool	defaultInit ()
	Functions which are to be used during the actual event generation, after the setup is complete. More...

PPtr	getParticle (PID) const
	Create a new Particle instance given a id number.

PDPtr	getParticleData (PID) const
	Return a pointer to the ParticleData object corresponding to the given id number.

bool	used () const
	Returns true if this object has actally been used.

void	useMe () const
	Should be called to indicate that this object has actually been used.

tEGPtr	generator () const
	Return a pointer to the EventGenerator controlling the run. More...

void	persistentOutput (PersistentOStream &os) const
	Function used to write out object persistently. More...

void	persistentInput (PersistentIStream &is, int version)
	Function used to read in object persistently. More...

Public Member Functions inherited from ThePEG::InterfacedBase
virtual	~InterfacedBase ()
	The virtual (empty) destructor;.

string	fullName () const
	Returns the full name of this object including its path, e.g. More...

string	name () const
	Returns the name of this object, without the path.

string	path () const
	Returns the path to this object including the trailing '/'. More...

string	comment () const
	Returns a comment assigned to this object.

void	setup (istream &is)
	Read setup info from a standard istream is. More...

virtual void	debugme () const
	Print out debugging information for this object on std::cerr. More...

void	update ()
	Calls the doupdate() function with recursion prevention.

void	init ()
	Calls the doinit() function with recursion prevention.

void	initrun ()
	Calls the doinitrun() function with recursion prevention.

void	finish ()
	Calls the dofinish() function with recursion prevention.

void	touch ()
	This function should be called every time something in this object has changed in a way that a sanity check with update() is needed.

void	reset ()
	Set the state of this object to uninitialized.

void	clear ()
	Calls reset() and unTouch().

InitState	state () const
	Return the state of initialization of this object.

bool	locked () const
	Return true if the BaseRepository is not allowed to change the state of this object.

bool	touched () const
	Return true if the state of this object has been changed since the last call to update().

void	persistentOutput (PersistentOStream &os) const
	Function used to write out object persistently. More...

void	persistentInput (PersistentIStream &is, int version)
	Function used to read in object persistently. More...

Public Member Functions inherited from ThePEG::Base
virtual	~Base ()
	The virtual destructor.

void	debug () const
	Print out debugging information for this object on std::cerr. More...

Public Member Functions inherited from ThePEG::Pointer::ReferenceCounted
CounterType	referenceCount () const
	Return the reference count.

Public Member Functions inherited from ThePEG::Named
	Named (const string &newName=string())
	Constructor with name.

	Named (const Named &)=default
	Explicit default copy-constructor (too avoid compiler warnings)

const string &	name () const
	Return name.

bool	operator== (const Named &other) const
	Test for equality.

bool	operator< (const Named &other) const
	Lexicographical comparison.

Public Member Functions inherited from ThePEG::LastXCombInfo<>
const XComb &	lastXComb () const
	Return a reference to the last selected XComb.

tXCPtr	lastXCombPtr () const
	Return a pointer to the last selected XComb.

const XComb &	lastHeadXComb () const
	If the last selected XComb object belongs to a group of XComb's return a reference to the head XComb object for this group.

tXCPtr	lastHeadXCombPtr () const
	If the last selected XComb object belongs to a group of XComb's return a pointer to the head XComb object for this group.

const EventHandler &	lastEventHandler () const
	Return a reference to the currently used EventHandler.

tPExtrPtr	lastExtractor () const
	A pointer to the currently used parton extractor.

PDFT	pdf (tcPPtr parton) const
	Return the parton density used to extract the given parton. More...

const Cuts &	lastCuts () const
	A reference to the currently used kinematical cuts.

tCutsPtr	lastCutsPtr () const
	A pointer to the currently used kinematical cuts.

const PPair &	lastParticles () const
	Return the pair of incoming parton instances.

Energy2	lastS () const
	The last generated total energy squared of the incoming particles.

const PPair &	lastPartons () const
	Return the pair of incoming parton instances.

Energy2	lastSHat () const
	The last used interval in total parton-parton energy squared.

double	lastTau () const
	Return lastSHat()/lastS().

double	lastY () const
	The generated rapidity of the hard scattering sub-system.

double	lastP1 () const
	Log of one over the momentum fraction of the first incoming particle w.r.t. More...

double	lastP2 () const
	Log of one over the momentum fraction of the second incoming particle w.r.t. More...

double	lastL1 () const
	Log of one over the first incoming parton momentum fraction w.r.t. More...

double	lastL2 () const
	Log of one over the second incoming parton momentum fraction w.r.t. More...

double	lastX1 () const
	The first incoming parton momentum fraction w.r.t. More...

double	lastX2 () const
	The second incoming parton momentum fraction w.r.t. More...

double	lastE1 () const
	Return 1-lastX1() to highest possible precision for x $\rightarrow$ 1.

double	lastE2 () const
	Return 1-lastX2() to highest possible precision for x $\rightarrow$ 1.

double	lastFL1L2 () const
	The product of the parton density functions at the last generated phase-space point.

Energy2	lastScale () const
	The chosen scale of the hard scattering.

double	lastAlphaS () const
	Get the $\alpha_S$ used in the hard scattering. More...

double	lastAlphaEM () const
	Get the $\alpha_{EM}$ used in the hard scattering. More...

const vector< Lorentz5Momentum > &	meMomenta () const
	Return the momenta of the incoming and outgoing partons to be used by the matrix element object, in the order specified by the TreeDiagram objects given by the matrix element.

double	lastME2 () const
	Return the matrix element squared as calculated for the last phase space point. More...

double	lastPreweight () const
	Return the last preweight factor.

double	jacobian () const
	Get the last jacobian obtained when generating the kinematics for the call to dSigHatDR.

CrossSection	lastMECrossSection () const
	Return the partonic cross section as calculated for the last phase space point. More...

double	lastMEPDFWeight () const
	Return the PDF weight as calculated for the last phase space point, if the matrix element does supply PDF weights. More...

double	lastMECouplings () const
	Return the coupling weight as calculated for the last phase space point.

tSubProPtr	subProcess () const
	Return the SubProcess object corresponding to the last generated sub-process.

const cPDVector &	mePartonData () const
	Return the incoming and outgoing parton types to be used by the matrix element object, in the order specified by the TreeDiagram objects given by the matrix element.

Static Public Member Functions
static void	Init ()
	Standard Init function used to initialize the interfaces.

Static Public Member Functions inherited from ThePEG::LesHouchesReader
static void	Init ()
	Standard Init function used to initialize the interfaces.

static size_t	eventSize (int N)
	Return the size of this event in bytes. More...

Static Public Member Functions inherited from ThePEG::HandlerBase
static void	Init ()
	Standard Init function used to initialize the interface.

Static Public Member Functions inherited from ThePEG::Interfaced
static void	Init ()
	Standard Init function.

Static Public Member Functions inherited from ThePEG::InterfacedBase
static void	Init ()
	Standard Init function.

Static Public Member Functions inherited from ThePEG::Base
static void	Init ()
	The standard Init function used to initialize the interfaces. More...

Protected Member Functions
Clone Methods.
virtual IBPtr	clone () const
	Make a simple clone of this object. More...

virtual IBPtr	fullclone () const
	Make a clone of this object, possibly modifying the cloned object to make it sane. More...

Protected Member Functions inherited from ThePEG::LesHouchesReader
virtual bool	checkPartonBin ()
	Check the existence of a pair of PartonBin objects corresponding to the current event. More...

virtual void	createParticles ()
	Create instances of all particles in the event and store them in particleIndex.

virtual tcPBPair	createPartonBinInstances ()
	Using the already created particles create a pair of PartonBinInstance objects corresponding to the incoming partons. More...

virtual void	createBeams ()
	Create instances of the incoming beams in the event and store them in particleIndex. More...

virtual void	connectMothers ()
	Go through the mother indices and connect up the Particles.

void	NEvents (long x)
	The number of events in this reader. More...

XCombMap &	xCombs ()
	The map of XComb objects indexed by the corresponding PartonBin pair.

virtual void	doinitrun ()
	Initialize this object. More...

virtual void	dofinish ()
	Finalize this object. More...

virtual void	initPDFs ()
	Called from doinit() to extract PDFs from the event file and add the corresponding objects to the current EventGenerator.

string	cacheFileName () const
	Name of file used to cache the events form the reader in a fast-readable form. More...

bool	cutEarly () const
	Determines whether to apply cuts to events converting them to ThePEG format.

CFile	cacheFile () const
	File stream for the cache.

void	openReadCacheFile ()
	Open the cache file for reading.

void	openWriteCacheFile ()
	Open the cache file for writing.

void	closeCacheFile ()
	Close the cache file;.

void	cacheEvent () const
	Write the current event to the cache file.

bool	uncacheEvent ()
	Read an event from the cache file. More...

void	reopen ()
	Reopen a reader. More...

Protected Member Functions inherited from ThePEG::Interfaced
void	reporeg (IBPtr object, string name) const
	Register the given object in the Repository with the given name in a subdirectory with the same name as this object. More...

template<typename PtrT >
bool	setDefaultReference (PtrT &ptr, string classname, string objectname)
	If the pointer, ptr, to an object is not set, create an object of class classname and register it with the Repository with the given objectname in a sib-directory with the same name as this object.

	Interfaced ()
	Protected default constructor.

	Interfaced (const string &newName)
	Protected constructor taking a name as argument.

	Interfaced (const Interfaced &i)
	Protected copy-constructor.

void	setGenerator (tEGPtr generator)
	Protected function to reset the generator pointer, required for automatic decayer generation in Herwig++ BSM models.

Protected Member Functions inherited from ThePEG::InterfacedBase
	InterfacedBase ()
	Protected default constructor.

	InterfacedBase (string newName)
	Protected constructor with the name given as argument.

	InterfacedBase (const InterfacedBase &i)
	Protected copy-constructor.

virtual void	readSetup (istream &is)
	Read setup info from a standard istream is. More...

virtual void	doupdate ()
	Check sanity of the object during the setup phase. More...

virtual IVector	getReferences ()
	Return a vector of all pointers to Interfaced objects used in this object. More...

virtual void	rebind (const TranslationMap &)
	Rebind pointer to other Interfaced objects. More...

Protected Member Functions inherited from ThePEG::Pointer::ReferenceCounted
	ReferenceCounted ()
	Default constructor.

	ReferenceCounted (const ReferenceCounted &)
	Copy-constructor.

ReferenceCounted &	operator= (const ReferenceCounted &)
	Assignment.

Protected Member Functions inherited from ThePEG::Named
const Named &	operator= (const Named &other)
	Assignment.

const string &	name (const string &newName)
	Set new name.

Standard (and non-standard) Interfaced functions.
CFileLineReader	cfile
	The wrapper around the C FILE stream from which to read.

long	neve
	The number of events in this file.

long	ieve
	The current event number.

string	LHFVersion
	If the file is a standard Les Houches formatted file (LHF) this is its version number. More...

string	outsideBlock
	If LHF. More...

string	headerBlock
	If LHF. More...

string	initComments
	If LHF. More...

map< string, string >	initAttributes
	If LHF. More...

string	eventComments
	If LHF. More...

map< string, string >	eventAttributes
	If LHF. More...

string	theFileName
	The name of the file from where to read events.

bool	theQNumbers
	Whether or not to search for QNUMBERS stuff.

bool	theIncludeFxFxTags
	Include/Read FxFx tags.

bool	theIncludeCentral
	Include central weight (for backup use)

DecayerPtr	theDecayer
	Decayer for any decay modes read from the file.

map< string, string >	scalemap
	Further information on the weights.

map< string, double >	optionalWeightsTemp
	Temporary holder for optional weights.

static ClassDescription< LesHouchesFileReader >	initLesHouchesFileReader
	Describe an abstract base class with persistent data.

virtual void	doinit ()
	Initialize this object after the setup phase before saving an EventGenerator to disk. More...

virtual bool	preInitialize () const
	Return true if this object needs to be initialized before all other objects because it needs to extract PDFs from the event file.

LesHouchesFileReader &	operator= (const LesHouchesFileReader &)=delete
	Private and non-existent assignment operator.

Additional Inherited Members
Public Types inherited from ThePEG::InterfacedBase
enum	InitState { initializing = -1, uninitialized = 0, initialized = 1, runready = 2 }
	Enumeration reflecting the state of an InterfacedBase object. More...

Public Types inherited from ThePEG::Pointer::ReferenceCounted
typedef unsigned int	CounterType
	The integer type used for counting.

Public Types inherited from ThePEG::LastXCombInfo<>
typedef ThePEG::Ptr< XComb >::pointer	XCPtr
	Alias for a reference counted pointer to XC . More...

typedef ThePEG::Ptr< XComb >::const_pointer	cXCPtr
	Alias for a reference counted pointer to a const XC . More...

typedef ThePEG::Ptr< XComb >::transient_pointer	tXCPtr
	Alias for a transient pointer to XC . More...

typedef ThePEG::Ptr< XComb >::transient_const_pointer	tcXCPtr
	Alias for a transient pointer to a const XC . More...

Public Attributes inherited from ThePEG::LesHouchesReader
vector< string >	optionalWeightsNames
	vector with the optional weights names

Public Attributes inherited from ThePEG::Pointer::ReferenceCounted
const unsigned long	uniqueId
	The unique ID. More...

Static Protected Member Functions inherited from ThePEG::LesHouchesReader
template<typename T >
static char *	mwrite (char *pos, const T &t, size_t n=1)
	Helper function to write a variable to a memory location.

template<typename T >
static const char *	mread (const char *pos, T &t, size_t n=1)
	Helper function to read a variable from a memory location.

Static Protected Member Functions inherited from ThePEG::Interfaced
static void	registerRepository (IBPtr)
	Register an Interfaced object with the Repository.

static void	registerRepository (IBPtr, string newName)
	Register an Interfaced object with the Repository, giving it a name.

Protected Attributes inherited from ThePEG::LesHouchesReader
HEPRUP	heprup
	The HEPRUP common block.

HEPEUP	hepeup
	The HEPEUP common block.

tcPDPair	inData
	The ParticleData objects corresponding to the incoming particles.

pair< PDFPtr, PDFPtr >	inPDF
	The PDFBase objects which has been used for the beam particle when generating the events being read. More...

pair< cPDFPtr, cPDFPtr >	outPDF
	The PDFBase object to be used in the subsequent generation.

PExtrPtr	thePartonExtractor
	The PartonExtractor object used to construct remnants.

tCascHdlPtr	theCKKW
	A pointer to a CascadeHandler to be used for CKKW-reweighting.

PartonPairVec	thePartonBins
	The pairs of PartonBin objects describing the partons which can be extracted by the PartonExtractor object.

XCombMap	theXCombs
	The map of XComb objects indexed by the corresponding PartonBin pair.

CutsPtr	theCuts
	The Cuts object to be used for this reader.

long	theNEvents
	The number of events in this reader. More...

long	position
	The number of events produced by this reader so far. More...

int	reopened
	The number of times this reader has been reopened.

long	theMaxScan
	The maximum number of events to scan to collect information about processes and cross sections. More...

bool	scanning
	Flag to tell whether we are in the process of scanning.

bool	isActive
	True if this is an active reader.

string	theCacheFileName
	Name of file used to cache the events form the reader in a fast-readable form. More...

bool	doCutEarly
	Determines whether to apply cuts to events before converting them to ThePEG format.

XSecStat	stats
	Collect statistics for this reader.

StatMap	statmap
	Collect statistics for each individual process.

PBIPair	thePartonBinInstances
	The pair of PartonBinInstance objects describing the current incoming partons in the event.

ObjectIndexer< long, ColourLine >	colourIndex
	Association between ColourLines and colour indices in the current translation.

ObjectIndexer< long, Particle >	particleIndex
	Association between Particles and indices in the current translation.

PPair	theBeams
	The instances of the beam particles for the current event.

PPair	theIncoming
	The instances of the incoming particles to the sub process for the current event.

PVector	theOutgoing
	The instances of the outgoing particles from the sub process for the current event.

PVector	theIntermediates
	The instances of the intermediate particles in the sub process for the current event.

CFile	theCacheFile
	File stream for the cache.

ReweightVector	reweights
	The reweight objects modifying the weights of this reader.

ReweightVector	preweights
	The preweight objects modifying the weights of this reader.

double	preweight
	The factor with which this reader was last pre-weighted.

bool	reweightPDF
	Should the event be reweighted by PDFs used by the PartonExtractor?

bool	doInitPDFs
	Should PDFBase objects be constructed from the information in the event file in the initialization?

int	theMaxMultCKKW
	If this reader is to be used (possibly together with others) for CKKW reweighting and veto, this should give the multiplicity of outgoing particles in the highest multiplicity matrix element in the group.

int	theMinMultCKKW
	If this reader is to be used (possibly together with others) for CKKW reweighting and veto, this should give the multiplicity of outgoing particles in the lowest multiplicity matrix element in the group.

double	lastweight
	The weight multiplying the last read event due to PDF reweighting, CKKW reweighting or assigned reweight and preweight objects.

map< string, double >	optionalWeights
	The optional weights associated to the last read events.

double	maxFactor
	If the maximum cross section of this reader has been increased with increaseMaxXSec(), this is the total factor with which it has been increased.

int	optionalnpLO
	npLO for LesHouches merging

int	optionalnpNLO
	npNLO for LesHouches merging

CrossSection	weightScale
	The (reweighted) XWGTUP value should be scaled with this cross section when compared to the overestimated cross section.

vector< double >	xSecWeights
	Individual scales for different sub-processes if reweighted.

map< int, double >	maxWeights
	Individual maximum weights for individual (possibly reweighted) processes.

bool	skipping
	Is set to true when getEvent() is called from skip(int).

unsigned int	theMomentumTreatment
	Option for the treatment of the momenta supplied.

bool	useWeightWarnings
	Set to true if warnings about possible weight incompatibilities should be issued.

bool	theReOpenAllowed
	Option to allow reopening of the file.

bool	theIncludeSpin
	Use the spin information.

Protected Attributes inherited from ThePEG::LastXCombInfo<>
XCPtr	theLastXComb
	The pointer to the last selected XComb.

Detailed Description

LesHouchesFileReader is an base class to be used for objects which reads event files from matrix element generators.

It inherits from LesHouchesReader and extends it by defining a file handle to be read from, which is opened and closed by the open() and close() functions. Note that the file handle is a standard C filehandle and not a C++ stream. This is because there is no standard way in C++ to connect a pipe to a stream for reading eg. gzipped files. This class is able to read plain event files conforming to the Les Houches Event File accord.