EffectiveAreas.cc

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#include "CommonTools/Egamma/interface/EffectiveAreas.h"
#include "FWCore/Utilities/interface/Exception.h"

#include <cmath>
#include <fstream>
#include <string>
#include <sstream>

EffectiveAreas::EffectiveAreas(const std::string& filename) : filename_(filename) {
  // Open the file with the effective area constants
  std::ifstream inputFile;
  inputFile.open(filename_.c_str());
  if (!inputFile.is_open())
    throw cms::Exception("EffectiveAreas config failure") << "failed to open the file " << filename_ << std::endl;

  // Read file line by line
  std::string line;
  const float undef = -999;
  while (getline(inputFile, line)) {
    if (line[0] == '#')
      continue;  // skip the comments lines
    float etaMin = undef, etaMax = undef, effArea = undef;
    std::stringstream ss(line);
    ss >> etaMin >> etaMax >> effArea;
    // In case if the format is messed up, there are letters
    // instead of numbers, or not exactly three numbers in the line,
    // it is likely that one or more of these vars never changed
    // the original "undef" value:
    if (etaMin == undef || etaMax == undef || effArea == undef)
      throw cms::Exception("EffectiveAreas config failure")
          << "wrong file format, file name " << filename_ << std::endl;

    absEtaMin_.push_back(etaMin);
    absEtaMax_.push_back(etaMax);
    effectiveAreaValues_.push_back(effArea);
  }

  // Extra consistency checks are in the function below.
  // If any of them fail, an exception is thrown.
  checkConsistency();
}

// Return effective area for given eta
const float EffectiveAreas::getEffectiveArea(float eta) const {
  float effArea = 0;
  uint nEtaBins = absEtaMin_.size();
  for (uint iEta = 0; iEta < nEtaBins; iEta++) {
    if (std::abs(eta) >= absEtaMin_[iEta] && std::abs(eta) < absEtaMax_[iEta]) {
      effArea = effectiveAreaValues_[iEta];
      break;
    }
  }

  return effArea;
}

void EffectiveAreas::printEffectiveAreas() const {
  printf("EffectiveAreas: source file %s\n", filename_.c_str());
  printf("  eta_min   eta_max    effective area\n");
  uint nEtaBins = absEtaMin_.size();
  for (uint iEta = 0; iEta < nEtaBins; iEta++) {
    printf("  %8.4f    %8.4f   %8.5f\n", absEtaMin_[iEta], absEtaMax_[iEta], effectiveAreaValues_[iEta]);
  }
}

// Basic common sense checks
void EffectiveAreas::checkConsistency() const {
  // There should be at least one eta range with one constant
  if (effectiveAreaValues_.empty())
    throw cms::Exception("EffectiveAreas config failure")
        << "found no effective area constans in the file " << filename_ << std::endl;

  uint nEtaBins = absEtaMin_.size();
  for (uint iEta = 0; iEta < nEtaBins; iEta++) {
    // The low limit should be lower than the upper limit
    if (!(absEtaMin_[iEta] < absEtaMax_[iEta]))
      throw cms::Exception("EffectiveAreas config failure")
          << "eta ranges improperly defined (min>max) in the file" << filename_ << std::endl;

    // The low limit of the next range should be (near) equal to the
    // upper limit of the previous range
    if (iEta != nEtaBins - 1)  // don't do the check for the last bin
      if (!(absEtaMin_[iEta + 1] - absEtaMax_[iEta] < 0.0001))
        throw cms::Exception("EffectiveAreas config failure")
            << "eta ranges improperly defined (disjointed) in the file " << filename_ << std::endl;

    // The effective area should be non-negative number,
    // and should be less than the whole calorimeter area
    // eta range -2.5 to 2.5, phi 0 to 2pi => Amax = 5*2*pi ~= 31.4
    if (!(effectiveAreaValues_[iEta] >= 0 && effectiveAreaValues_[iEta] < 31.4))
      throw cms::Exception("EffectiveAreas config failure")
          << "effective area values are too large or negative in the file" << filename_ << std::endl;
  }
}