LHEReader Class Reference

Class to read LHE files and store the content in a MCParticle graph. More...

#include <LHEReader.h>

Collaboration diagram for LHEReader:

Public Member Functions
	BELLE2_DEFINE_EXCEPTION (LHECouldNotOpenFileError, "Could not open file %1% !")
	Exception is thrown if the LHE file could not be opened.
	BELLE2_DEFINE_EXCEPTION (LHEInvalidDaughterIndicesError, "Line %1%: Invalid daughter indices d1=%2%, d2=%3%, N=%4% (0<=d1<=d2<=N required)")
	Exception is thrown if the given indices of the daughters are not valid.
	BELLE2_DEFINE_EXCEPTION (LHEHeaderNotValidError, "Line %1%: Event header not understood: %2%")
	Exception is thrown if the header specifying the event header could not be parsed.
	BELLE2_DEFINE_EXCEPTION (LHEConvertFieldError, "Line %1%: Could not convert field %2%: %3%")
	Exception is thrown if a field in the LHE file could not be converted to a number.
	BELLE2_DEFINE_EXCEPTION (LHEParticleFormatError, "Line %1%: Particle format not understood, got %2% fields !")
	Exception is thrown if the format of a line of the LHE file could not be parsed.
	BELLE2_DEFINE_EXCEPTION (LHEEmptyEventError, "Line %1%: Number of particles in event is %2% ! (This could mean EOF is reached.) ")
	Exception is thrown if the number of particles for this event is 0 or less.
	LHEReader ()
	Constructor.
	~LHEReader ()
	Destructor.
void	open (const std::string &filename)
	Opens an ascii file and prepares it for reading.
void	closeCurrentInputFile ()
	Closes the current input file to allow opening the next one.
int	getEvent (MCParticleGraph &graph, double &weight)
	Reads the next event and stores the result in the given MCParticle graph.
bool	skipEvents (int n)
	Skips a given number of events.
int	countEvents (const std::string &filename)
	Count events in the file by reading through it.
void	setInitialIndex (int index)
	Set the maximum index of particles in each event that must be set as c_Initial (1-based).
void	setVirtualIndex (int index)
	Set the maximum index of particles in each event that must be set as c_IsVirtual (1-based).

Public Attributes
bool	m_wrongSignPz
	Bool to indicate that HER and LER were swapped.

Protected Types
typedef boost::tokenizer< boost::char_separator< char > >	tokenizer
	Just a typedef for simple use of the boost::tokenizer to split the lines.

Protected Member Functions
std::string	getLine ()
	Returns the current line from the LHE ascii file.
int	readEventHeader (double &eventWeight)
	Reads the event header from the hepevt file.
int	readParticle (MCParticleGraph::GraphParticle &particle)
	Reads the information for a single particle from the LHE file.

Protected Attributes
int	m_lineNr
	The current line number within the ascii file.
std::ifstream	m_input
	The input stream of the ascii file.
int	m_indexInitial
	Maximum index of particles in each event that must be set as c_Initial (1-based).
int	m_indexVirtual
	Maximum index of particles in each event that must be set as c_IsVirtual (1-based).

Static Protected Attributes
static const boost::char_separator< char >	sep
	The characters at which to split, defaults to ",; \t".

Detailed Description

Class to read LHE files and store the content in a MCParticle graph.

The class is very similar to the HepEvt Reader

The events are read sequentially with the option of skipping a certain number of events. Random access of events is not possible.

Definition at line 31 of file LHEReader.h.

Member Typedef Documentation

tokenizer

typedef boost::tokenizer<boost::char_separator<char> > tokenizer

protected

Just a typedef for simple use of the boost::tokenizer to split the lines.

Definition at line 113 of file LHEReader.h.

Constructor & Destructor Documentation

LHEReader()

LHEReader ( )

inline

Constructor.

Definition at line 52 of file LHEReader.h.

               :
      m_wrongSignPz(false),
      m_lineNr(0),
      m_indexInitial(0),
      m_indexVirtual(0)
    {}

~LHEReader()

~LHEReader ( )

inline

Destructor.

Definition at line 62 of file LHEReader.h.

{ if (m_input) m_input.close(); }

Member Function Documentation

closeCurrentInputFile()

void closeCurrentInputFile ( )

inline

Closes the current input file to allow opening the next one.

Definition at line 73 of file LHEReader.h.

{m_input.close();}

countEvents()

int countEvents

(

const std::string &

filename

)

Count events in the file by reading through it.

Parameters

filename

The filename of the file to count events in.

Returns

The number of events in the file.

Definition at line 90 of file LHEReader.cc.

{
  std::ifstream input(filename.c_str());
  if (!input) throw(LHECouldNotOpenFileError() << filename);
 
  int count = 0;
  int lineNr = 0;
  std::string line;
 
  auto countEvent = [&]() {
    count++;
    while (std::getline(input, line)) {
      lineNr++;
      boost::trim(line);
      if (line == "</event>" || line.empty()) break;
    }
  };
 
  while (std::getline(input, line)) {
    lineNr++;
    boost::trim(line);
    if (line == "<event>") {
      countEvent();
    }
  }
 
  B2INFO("Counted " << count << " events in " << filename << ".");
  return count;
}

getEvent()

int getEvent	(	MCParticleGraph &	graph,
		double &	weight )

Reads the next event and stores the result in the given MCParticle graph.

Parameters

graph	Reference to the graph which should be filled with the information from the LHE file.
weight	Reference to the event weight which can be filled from the file.

Returns

event number if the event could be read and the number was provided in the file.

Definition at line 32 of file LHEReader.cc.

{
  int nparticles = readEventHeader(eventWeight);
  if (nparticles <= 0) {
    throw (LHEEmptyEventError() << m_lineNr << nparticles);
  }
 
  int first = graph.size();
  //Make list of particles
  for (int i = 0; i < nparticles; i++) {
    graph.addParticle();
  }
 
  //Read particles from file
  for (int i = 0; i < nparticles; ++i) {
    MCParticleGraph::GraphParticle& p = graph[first + i];
    int mother = readParticle(p);
 
    // add the mother
    if (mother > 0) {
      MCParticleGraph::GraphParticle* q = &graph[mother - 1];
      p.comesFrom(*q);
    }
 
    // if positron goes to positive z-direction, we have to rotate along y-axis by 180deg
    if (m_wrongSignPz) {
      ROOT::Math::PxPyPzEVector p4 = p.get4Vector();
      p4.SetPz(-1.0 * p4.Pz());
      p4.SetPx(-1.0 * p4.Px());
      p.set4Vector(p4);
    }
 
    // initial 2 (e+/e-), virtual 3 (Z/gamma*)
    // check if particle should be made virtual according to steering options:
    if (i < m_indexVirtual && i >= m_indexInitial)
      p.addStatus(MCParticle::c_IsVirtual);
 
    if (i < m_indexInitial)
      p.addStatus(MCParticle::c_Initial);
 
    if (m_indexVirtual < m_indexInitial) B2WARNING("IsVirtual particle requested but is overwritten by Initial");
 
  }
  return -1;
}

getLine()

std::string getLine ( )

protected

Returns the current line from the LHE ascii file.

Returns

The current line as a string.

Definition at line 124 of file LHEReader.cc.

{
  std::string line;
  do {
    getline(m_input, line);
    m_lineNr++;
    size_t commentPos = line.find_first_of('#');
    if (commentPos != string::npos) {
      line = line.substr(0, commentPos);
    }
    boost::trim(line);
 
  } while (line == "" && !m_input.eof());
 
  return line;
}

open()

void open

(

const std::string &

filename

)

Opens an ascii file and prepares it for reading.

Parameters

filename

The filename of the LHE ascii file which should be read.

Definition at line 25 of file LHEReader.cc.

{
  m_lineNr = 0;
  m_input.open(filename.c_str());
  if (!m_input) throw(LHECouldNotOpenFileError() << filename);
}

readEventHeader()

int readEventHeader ( double & eventWeight )

protected

Reads the event header from the hepevt file.

Returns

The number of particles for the current event.

Parameters

eventWeight

reference to the eventWeight which can both be read from the file.

Definition at line 141 of file LHEReader.cc.

{
 
  // Search for next <event>
  std::string line2;
  do {
    getline(m_input, line2);
    m_lineNr++;
    size_t commentPos = line2.find_first_of('#');
    if (commentPos != string::npos) {
      line2 = line2.substr(0, commentPos);
    }
    boost::trim(line2);
 
  } while (line2 != "<event>" && !m_input.eof());
 
  //Get number of particles from file
  int nparticles = -1;
  string line = getLine();
 
  if (line == "" || m_input.eof()) return -1;
 
  vector<double> fields;
  fields.reserve(15);
 
  tokenizer tokens(line, sep);
  int index(0);
 
  for (const string& tok : tokens) {
    ++index;
    try {
      fields.push_back(boost::lexical_cast<double>(tok));
    } catch (boost::bad_lexical_cast& e) {
      throw (LHEConvertFieldError() << m_lineNr << index << tok);
    }
  }
 
  if (fields.size() < 3) {
    nparticles = static_cast<int>(fields[0]);
    eventWeight = 1.0;
  } else {
    nparticles = static_cast<int>(fields[0]);
    eventWeight = static_cast<double>(fields[2]);
  }
  return nparticles;
}

readParticle()

int readParticle ( MCParticleGraph::GraphParticle & particle )

protected

Reads the information for a single particle from the LHE file.

Parameters

particle

Reference to the particle which will be filled with the information from the LHE file.

Definition at line 188 of file LHEReader.cc.

{
  int mother = -1;
 
  string line = getLine();
  vector<double> fields;
  fields.reserve(15);
 
  tokenizer tokens(line, sep);
  int index(0);
 
  for (const string& tok : tokens) {
    ++index;
    try {
      fields.push_back(boost::lexical_cast<double>(tok));
    } catch (boost::bad_lexical_cast& e) {
      throw (LHEConvertFieldError() << m_lineNr << index << tok);
    }
  }
 
  switch (fields.size()) {
    case 13:
      particle.addStatus(MCParticle::c_PrimaryParticle);
      particle.setPDG(static_cast<int>(fields[0]));
      mother = static_cast<int>(fields[2]);
      particle.setMomentum(ROOT::Math::XYZVector(fields[6], fields[7], fields[8]));
      particle.setEnergy(fields[9]);
      particle.setMass(fields[10]);
      break;
    default:
      throw (LHEParticleFormatError() << m_lineNr << fields.size());
  }
 
  return mother;
}

setInitialIndex()

void setInitialIndex ( int index )

inline

Set the maximum index of particles in each event that must be set as c_Initial (1-based).

Parameters

[in]

index

Maximum index for c_Initial.

Definition at line 101 of file LHEReader.h.

{ m_indexInitial = index; }

setVirtualIndex()

void setVirtualIndex ( int index )

inline

Set the maximum index of particles in each event that must be set as c_IsVirtual (1-based).

Parameters

[in]

index

Maximum index for c_IsVirtual.

Definition at line 107 of file LHEReader.h.

{ m_indexVirtual = index; }

skipEvents()

bool skipEvents

(

int

n

)

Skips a given number of events.

Parameters

n	The number of events which should be skipped.

Returns

True if the events could be skipped.

Definition at line 79 of file LHEReader.cc.

{
  double weight;
  for (int i = 0; i < n; i++) {
    int nparticles = readEventHeader(weight);
    if (nparticles < 0) return false;
    for (int j = 0; j < nparticles; j++) getLine();
  }
  return true;
}

Member Data Documentation

m_indexInitial

int m_indexInitial

protected

Maximum index of particles in each event that must be set as c_Initial (1-based).

Definition at line 139 of file LHEReader.h.

m_indexVirtual

int m_indexVirtual

protected

Maximum index of particles in each event that must be set as c_IsVirtual (1-based).

Definition at line 141 of file LHEReader.h.

m_input

std::ifstream m_input

protected

The input stream of the ascii file.

Definition at line 118 of file LHEReader.h.

m_lineNr

int m_lineNr

protected

The current line number within the ascii file.

Definition at line 117 of file LHEReader.h.

m_wrongSignPz

bool m_wrongSignPz

Bool to indicate that HER and LER were swapped.

Definition at line 109 of file LHEReader.h.

sep

const boost::char_separator< char > sep

staticprotected

The characters at which to split, defaults to ",; \t".

Definition at line 115 of file LHEReader.h.

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

• generators/lhe/include/LHEReader.h
• generators/lhe/src/LHEReader.cc