TForwardElectronLikelihoodTool.cxx

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/*
  Copyright (C) 2002-2026 CERN for the benefit of the ATLAS collaboration
*/
 
#include "TForwardElectronLikelihoodTool.h"
#include "TROOT.h"
#include "TSystem.h"
#include <cmath>
#include <format>
 
const double Root::TForwardElectronLikelihoodTool::fIpBounds[IP_FBINS + 1] = {
  0.,
  500.
};
// These are the variables availalble in the likelihood.
const std::string
  Root::TForwardElectronLikelihoodTool::fVariables[s_fnVariables] = {
    "el_secondLambda", "el_lateral", "el_longitudinal", "el_centerLambda",
    "el_fracMax",      "el_secondR", "el_significance", "el_secondDensity"
  };
 
Root::TForwardElectronLikelihoodTool::TForwardElectronLikelihoodTool(
  const char* name)
  : asg::AsgMessaging(std::string(name))
  , m_doPileupCorrection(false)
  , m_variableNames("")
  , m_pdfFileName("")
  , m_variableBitMask(0x0)
  , m_cutPosition_kinematicEta(-9)
  , m_cutPosition_kinematicEt(-9)
  , m_cutPosition_LH(-9)
{
}
 
StatusCode
Root::TForwardElectronLikelihoodTool::initialize()
{
  ATH_MSG_DEBUG("TForwardElectronLikelihoodTool initialize.");
  // use an int as a StatusCode
  StatusCode sc(StatusCode::SUCCESS);
 
  // Check that all needed variables are setup
  if (m_pdfFileName.empty()) {
    ATH_MSG_WARNING(
      "You need to specify the input PDF file name before you call "
      "initialize() with setPDFFileName('your/file/name.root') ");
    sc = StatusCode::FAILURE;
  }
 
  unsigned int number_of_expected_bin = s_fnDiscEtBins * s_fnEtaBins;
  if (m_cutLikelihood.size() != number_of_expected_bin) {
    ATH_MSG_ERROR("Configuration issue :  CutLikelihood expected size "
                  << number_of_expected_bin << " input size "
                  << m_cutLikelihood.size());
    ATH_MSG_ERROR(
      "Could NOT initialize! Please fix the errors mentioned above...");
    sc = StatusCode::FAILURE;
    return sc;
  }
 
  // --------------------------------------------------------------------------
  // Register the cuts and check that the registration worked:
 
  // Cut position for the kineatic pre-selection, separately for eta/Et
  m_cutPosition_kinematicEta =
    m_acceptInfo.addCut("kinematicEta", "pass kinematic eta");
  if (m_cutPosition_kinematicEta < 0)
    sc = StatusCode::FAILURE;
  m_cutPosition_kinematicEt =
    m_acceptInfo.addCut("kinematicEt", "pass kinematic Et ");
  if (m_cutPosition_kinematicEt < 0)
    sc = StatusCode::FAILURE;
 
  // Cut position for the likelihood selection - DO NOT CHANGE ORDER!
  m_cutPosition_LH = m_acceptInfo.addCut("passLH", "pass Likelihood");
  if (m_cutPosition_LH < 0) {
    sc = StatusCode::FAILURE;
  }
 
  // Check that we got everything OK
  if (sc == StatusCode::FAILURE) {
    ATH_MSG_ERROR(
      "! Something went wrong with the setup of the return objects...");
    return sc;
  }
 
  // Get the correct bit mask for the current likelihood operating point
  m_variableBitMask = getLikelihoodBitmask(m_variableNames);
 
  //----------File/Histo operation------------------------------------
  // Load the ROOT file containing the PDFs
  TString tmpString(m_pdfFileName);
  gSystem->ExpandPathName(tmpString);
  std::string fname(tmpString.Data());
  m_pdfFile = TFile::Open(fname.c_str(), "READ");
  // Check that we could load the ROOT file
  if (!m_pdfFile) {
    ATH_MSG_ERROR(" No ROOT file found here: " << m_pdfFileName);
    return StatusCode::FAILURE;
  }
 
  // Load the histograms
  for (unsigned int varIndex = 0; varIndex < s_fnVariables; varIndex++) {
    const std::string& vstr = fVariables[varIndex];
    // Skip the loading of PDFs for variables we don't care about for this
    // operating point. If the string is empty (which is true in the default
    // 2012 case), load all of them.
    if (m_variableNames.find(vstr) == std::string::npos &&
        !m_variableNames.empty()) {
      continue;
    }
    loadVarHistograms(vstr, varIndex);
  }
 
  // TFile close does not free the memory
  m_pdfFile->Close();
  // We need the destructor to be called
  delete m_pdfFile;
  //----------End File/Histo operation------------------------------------
 
  ATH_MSG_DEBUG("Initialization complete for a LH tool with these specs:"
                << "\n - PdfFileName                                  : "
                << m_pdfFileName
                << "\n - Variable bitmask                             : "
                << m_variableBitMask
                << "\n - VariableNames                                : "
                << m_variableNames);
  return sc;
}
 
int
Root::TForwardElectronLikelihoodTool::loadVarHistograms(const std::string& vstr,
                                                        unsigned int varIndex)
{
  for (unsigned int s_or_b = 0; s_or_b < 2; ++s_or_b) {
    for (unsigned int ip = 0; ip < IP_FBINS; ++ip) {
      for (unsigned int et = 0; et < s_fnEtBinsHist; ++et) {
        for (unsigned int eta = 0; eta < s_fnEtaBins; ++eta) {
 
          std::string sig_bkg = (s_or_b == 0) ? "sig" : "bkg";
          // For the fwd LH PDFs and optimisation have matching eta bin
          // boundaries unsigned int eta_tmp = (eta > 0) ? eta-1 : eta ;
          unsigned int eta_tmp = eta;
          unsigned int et_tmp = et;
          std::string binname = getBinName(et_tmp, eta_tmp, ip, m_ipBinning);
 
          const std::string pdfdir = std::format("{}/{}", vstr, sig_bkg);
          std::string pdf = std::format("{}_{}_smoothed_hist_from_KDE_{}",
                                        vstr, sig_bkg, binname);
 
          if (!m_pdfFile->GetListOfKeys()->Contains(vstr.c_str())) {
            ATH_MSG_INFO("Warning: skipping variable "
                         << vstr << " because the folder does not exist.");
            return 1;
          }
          if (!((TDirectory*)m_pdfFile->Get(vstr.c_str()))
                 ->GetListOfKeys()
                 ->Contains(sig_bkg.c_str())) {
            ATH_MSG_INFO("Warning: skipping variable "
                         << vstr << " because the folder does not exist.");
            return 1;
          }
          // Use the first Et bin given in the root file for all Et ranges below
          if (et == 0 && !((TDirectory*)m_pdfFile->Get(pdfdir.c_str()))
                            ->GetListOfKeys()
                            ->Contains(pdf.c_str())) {
            ATH_MSG_INFO("using lowest GeV bin in place of all below.");
            binname = getBinName(et_tmp + 1, eta_tmp, ip, m_ipBinning);
            pdf = std::format("{}_{}_smoothed_hist_from_KDE_{}",
                              vstr, sig_bkg, binname);
          }
          if (((TDirectory*)m_pdfFile->Get(pdfdir.c_str()))
                ->GetListOfKeys()
                ->Contains(pdf.c_str())) {
            TH1F* hist =
              (TH1F*)(((TDirectory*)m_pdfFile->Get(pdfdir.c_str()))->Get(pdf.c_str()));
            m_fPDFbins[s_or_b][ip][et][eta][varIndex] =
              std::make_unique<EGSelectors::SafeTH1>(hist);
          } else {
            ATH_MSG_INFO("Warning: Object " << pdf << " does not exist.");
            ATH_MSG_INFO("Skipping all other histograms with this variable.");
            return 1;
          }
        }
      }
    }
  }
  return 1;
}
 
asg::AcceptData
Root::TForwardElectronLikelihoodTool::accept(double likelihood,
                                             double eta,
                                             double eT,
                                             double ip) const
{
  LikeEnumForward::LHAcceptVars_t vars{};
 
  vars.likelihood = likelihood;
  vars.eta = eta;
  vars.eT = eT;
  vars.ip = ip;
 
  return accept(vars);
}
 
// This method calculates if the current electron passes the requested
// likelihood cut
asg::AcceptData
Root::TForwardElectronLikelihoodTool::accept(
  LikeEnumForward::LHAcceptVars_t& vars_struct) const
{
  // Setup return accept with AcceptInfo
  asg::AcceptData acceptData(&m_acceptInfo);
 
  // Set up the individual cuts
  bool passKineEta(true);
  bool passKineEt(true);
  bool passLH(true);
 
  if (std::fabs(vars_struct.eta) < 2.5) {
    ATH_MSG_DEBUG("This forward electron has"
                  << vars_struct.eta
                  << ", which is fabs(eta)<2.5 Returning False.");
    passKineEta = false;
  }
  // Return if the kinematic requirements are not fulfilled
  acceptData.setCutResult(m_cutPosition_kinematicEta, passKineEta);
  if (!passKineEta) {
    return acceptData;
  }
 
  unsigned int etbin = getLikelihoodEtHistBin(vars_struct.eT);
  unsigned int etabin = getLikelihoodEtaBin(vars_struct.eta);
 
  if (etbin >= s_fnDiscEtBins) {
    ATH_MSG_WARNING("Cannot evaluate likelihood for Et "
                    << vars_struct.eT << ". Returning false..");
    passKineEt = false;
  }
 
  // Return if the kinematic requirements are not fulfilled
  acceptData.setCutResult(m_cutPosition_kinematicEt, passKineEt);
  if (!passKineEt) {
    return acceptData;
  }
 
  double cutDiscriminant = -999.;
  unsigned int ibin_combined = etbin * s_fnEtaBins + etabin;
 
  if (!m_cutLikelihood.empty()) {
 
    cutDiscriminant = m_cutLikelihood[ibin_combined];
    // If doPileupCorrection, then correct the discriminant itself instead of
    // the cut value
    if (m_doPileupCorrection) {
      cutDiscriminant +=
        vars_struct.ip * m_cutLikelihoodPileupCorrectionA[ibin_combined] +
        m_cutLikelihoodPileupCorrectionB[ibin_combined];
    }
  }
 
  // Determine if the calculated likelihood value passes the cut
  ATH_MSG_DEBUG("Likelihood macro: Discriminant: ");
  if (vars_struct.likelihood < cutDiscriminant) {
    ATH_MSG_DEBUG("Likelihood macro: Disciminant Cut Failed.");
    passLH = false;
  }
  acceptData.setCutResult(m_cutPosition_LH, passLH);
  return acceptData;
}
 
double
Root::TForwardElectronLikelihoodTool::calculate(double eta,
                                                double eT,
                                                double secondLambda,
                                                double lateral,
                                                double longitudinal,
                                                double centerLambda,
                                                double fracMax,
                                                double secondR,
                                                double significance,
                                                double secondDensity,
                                                double ip) const
{
  LikeEnumForward::LHCalcVars_t vars{};
  vars.eta = eta;
  vars.eT = eT;
  vars.secondLambda = secondLambda;
  vars.lateral = lateral;
  vars.longitudinal = longitudinal;
  vars.centerLambda = centerLambda;
  vars.fracMax = fracMax;
  vars.secondR = secondR;
  vars.significance = significance;
  vars.secondDensity = secondDensity;
  vars.ip = ip;
  return calculate(vars);
}
 
// The main public method to actually calculate the likelihood value
double
Root::TForwardElectronLikelihoodTool::calculate(
  LikeEnumForward::LHCalcVars_t& vars_struct) const
{
  // Reset the results to defaul values
  double result = -999;
  double arr[] = { vars_struct.secondLambda, vars_struct.lateral,
                   vars_struct.longitudinal, vars_struct.centerLambda,
                   vars_struct.fracMax,      vars_struct.secondR,
                   vars_struct.significance, vars_struct.secondDensity };
  std::vector<double> vec(arr, arr + sizeof(arr) / sizeof(double));
 
  // Calculate the actual likelihood value and fill the return object
  result = this->evaluateLikelihood(
    vec, vars_struct.eT, vars_struct.eta, vars_struct.ip);
  return result;
}
 
double
Root::TForwardElectronLikelihoodTool::evaluateLikelihood(
  const std::vector<float>& varVector,
  double et,
  double eta,
  double ip) const
{
  std::vector<double> vec;
  vec.reserve(s_fnVariables);
  for (unsigned int var = 0; var < s_fnVariables; var++) {
    vec.push_back(varVector[var]);
  }
  return evaluateLikelihood(vec, et, eta, ip);
}
 
double
Root::TForwardElectronLikelihoodTool::evaluateLikelihood(
  const std::vector<double>& varVector,
  double et,
  double eta,
  double ip) const
{
  // const double GeV = 1000;
  unsigned int etbin = getLikelihoodEtHistBin(et);
  unsigned int etabin = getLikelihoodEtaBin(eta);
  unsigned int ipbin = getIpBin(ip);
 
  if (etbin >= s_fnEtBinsHist) {
    ATH_MSG_WARNING("skipping etbin  " << etbin << ", et  " << et);
    return -999.;
  }
  if (etabin >= s_fnEtaBins) {
    ATH_MSG_WARNING("skipping etabin " << etabin << ", eta " << eta);
    return -999.;
  }
 
  if (varVector.size() != s_fnVariables) {
    ATH_MSG_WARNING("Error! Variable vector size mismatch! Check your vector!");
    return -999.;
  }
 
  double SigmaS = 1.;
  double SigmaB = 1.;
 
  for (unsigned int var = 0; var < s_fnVariables; var++) {
 
    std::string varstr = fVariables[var];
 
    // Skip variables that are masked off (not used) in the likelihood
    if (!(m_variableBitMask & (0x1 << var))) {
      continue;
    }
 
    for (unsigned int s_or_b = 0; s_or_b < 2; s_or_b++) {
 
      int bin =
        m_fPDFbins[s_or_b][ipbin][etbin][etabin][var]->FindBin(varVector[var]);
      double prob = 0;
 
      double integral =
        double(m_fPDFbins[s_or_b][ipbin][etbin][etabin][var]->Integral());
      if (integral == 0) { // currently, the crack always has integral == 0
        ATH_MSG_DEBUG(
          "Error! PDF integral == 0!"); // changed it to debug message since we
                                        // intend to run the tool in the
                                        // derivations
        return -1.35;
      }
 
      prob = double(m_fPDFbins[s_or_b][ipbin][etbin][etabin][var]->GetBinContent(
               bin)) /
             integral;
 
      if (s_or_b == 0)
        SigmaS *= prob;
      else if (s_or_b == 1)
        SigmaB *= prob;
    }
  }
 
  return TransformLikelihoodOutput(SigmaS, SigmaB);
}
 
// --------------------------------------------
double
Root::TForwardElectronLikelihoodTool::TransformLikelihoodOutput(double ps,
                                                                double pb) const
{
  // returns transformed or non-transformed output
  // (Taken mostly from TMVA likelihood code)
  double fEpsilon = 1e-99;
  // If both signal and bkg are 0, we want it to fail.
  if (ps < fEpsilon)
    ps = 0;
  if (pb < fEpsilon)
    pb = fEpsilon;
  double disc = ps / double(ps + pb);
 
  if (disc >= 1.0)
    disc = 1. - 1.e-15;
  else if (disc <= 0.0)
    disc = fEpsilon;
 
  double tau = 15.0;
  disc = -std::log(1.0 / disc - 1.0) * (1. / double(tau));
 
  ATH_MSG_DEBUG("disc is " << disc);
  return disc;
}
 
// Gets the IP bin
unsigned int
Root::TForwardElectronLikelihoodTool::getIpBin(double ip)
{
  for (unsigned int ipBin = 0; ipBin < IP_FBINS; ++ipBin) {
    if (ip < fIpBounds[ipBin + 1])
      return ipBin;
  }
  return 0;
}
 
// Gets the Eta bin  given the eta . Binning uses uper bound
unsigned int
Root::TForwardElectronLikelihoodTool::getLikelihoodEtaBin(double eta)
{
  const unsigned int nEtaBins = s_fnEtaBins;
  const double etaBins[nEtaBins] = { 2.6, 2.7,  2.8,  2.9, 3.0,
                                     3.1, 3.16, 3.35, 3.6, 4.9 };
  for (unsigned int etaBin = 0; etaBin < nEtaBins; ++etaBin) {
    if (std::fabs(eta) < etaBins[etaBin])
      return etaBin;
  }
  return (nEtaBins - 1);
}
// Gets the histogram Et bin given the et (MeV). Binning uses upper bound
unsigned int
Root::TForwardElectronLikelihoodTool::getLikelihoodEtHistBin(double eT)
{
  const double GeV = 1000;
  const unsigned int nEtBins = s_fnDiscEtBins;
  const double eTBins[nEtBins] = {
    30 * GeV, 40 * GeV, 50 * GeV, 7000 * GeV
  }; // removed 20 GeV bin since we're upper bound oriented
  for (unsigned int eTBin = 0; eTBin < nEtBins; ++eTBin) {
    if (eT < eTBins[eTBin]) {
      return eTBin;
    }
  }
  return (nEtBins - 1); // Return the last bin if > the last bin.
}
 
// Gets the bin name. Given the HISTOGRAM bin  naming used in the input file
// which seems to be lower bound oriented ...
std::string
Root::TForwardElectronLikelihoodTool::getBinName(
  int etbin,
  int etabin,
  int ipbin,
  const std::string& iptype)
{
  double eta_bounds[s_fnEtaBins] = { 2.5, 2.6, 2.7,  2.8,  2.9,
                                     3.0, 3.1, 3.16, 3.35, 3.6 };
  int et_bounds[s_fnEtBinsHist] = { 20, 30, 40, 50 };
  if (!iptype.empty()) {
    return std::format("{}{}et{:02}eta{:.2f}",
                       iptype, int(fIpBounds[ipbin]),
                       et_bounds[etbin], eta_bounds[etabin]);
  } else {
    return std::format("et{}eta{:.2f}",
                       et_bounds[etbin], eta_bounds[etabin]);
  }
}
 
unsigned int
Root::TForwardElectronLikelihoodTool::getLikelihoodBitmask(
  const std::string& vars) const
{
  unsigned int mask = 0x0;
  ATH_MSG_DEBUG("Variables to be used: ");
  for (unsigned int var = 0; var < s_fnVariables; var++) {
    if (vars.find(fVariables[var]) != std::string::npos) {
      ATH_MSG_DEBUG(fVariables[var]);
      mask = mask | 0x1 << var;
    }
  }
  ATH_MSG_DEBUG("mask: " << mask);
  return mask;
}