BTagEntry.cc

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#include <algorithm>
#include <sstream>

#include "CondFormats/BTauObjects/interface/BTagEntry.h"
#include "FWCore/Utilities/interface/Exception.h"

BTagEntry::Parameters::Parameters(
  OperatingPoint op,
  std::string measurement_type,
  std::string sys_type,
  JetFlavor jf,
  float eta_min,
  float eta_max,
  float pt_min,
  float pt_max,
  float discr_min,
  float discr_max
):
  operatingPoint(op),
  measurementType(measurement_type),
  sysType(sys_type),
  jetFlavor(jf),
  etaMin(eta_min),
  etaMax(eta_max),
  ptMin(pt_min),
  ptMax(pt_max),
  discrMin(discr_min),
  discrMax(discr_max)
{
  std::transform(measurementType.begin(), measurementType.end(),
                 measurementType.begin(), ::tolower);
  std::transform(sysType.begin(), sysType.end(),
                 sysType.begin(), ::tolower);
}

BTagEntry::BTagEntry(const std::string &csvLine)
{
  // make tokens
  std::stringstream buff(csvLine);
  std::vector<std::string> vec;
  std::string token;
  while (std::getline(buff, token, ","[0])) {
    token = BTagEntry::trimStr(token);
    if (token.empty()) {
      continue;
    }
    vec.push_back(token);
  }
  if (vec.size() != 11) {
    throw cms::Exception("BTagCalibration")
          << "Invalid csv line; num tokens != 11: "
          << csvLine;
  }

  // clean string values
  char chars[] = " \"\n";
  for (unsigned int i = 0; i < strlen(chars); ++i) {
    vec[1].erase(remove(vec[1].begin(),vec[1].end(),chars[i]),vec[1].end());
    vec[2].erase(remove(vec[2].begin(),vec[2].end(),chars[i]),vec[2].end());
    vec[10].erase(remove(vec[10].begin(),vec[10].end(),chars[i]),vec[10].end());
  }

  // make formula
  formula = vec[10];
  TF1 f1("", formula.c_str());  // compile formula to check validity
  if (f1.IsZombie()) {
    throw cms::Exception("BTagCalibration")
          << "Invalid csv line; formula does not compile: "
          << csvLine;
  }

  // make parameters
  unsigned op = stoi(vec[0]);
  if (op > 3) {
    throw cms::Exception("BTagCalibration")
          << "Invalid csv line; OperatingPoint > 3: "
          << csvLine;
  }
  unsigned jf = stoi(vec[3]);
  if (jf > 2) {
    throw cms::Exception("BTagCalibration")
          << "Invalid csv line; JetFlavor > 2: "
          << csvLine;
  }
  params = BTagEntry::Parameters(
    BTagEntry::OperatingPoint(op),
    vec[1],
    vec[2],
    BTagEntry::JetFlavor(jf),
    stof(vec[4]),
    stof(vec[5]),
    stof(vec[6]),
    stof(vec[7]),
    stof(vec[8]),
    stof(vec[9])
  );
}

BTagEntry::BTagEntry(const std::string &func, BTagEntry::Parameters p):
  formula(func),
  params(p)
{
  TF1 f1("", formula.c_str());  // compile formula to check validity
  if (f1.IsZombie()) {
    throw cms::Exception("BTagCalibration")
          << "Invalid func string; formula does not compile: "
          << func;
  }
}

BTagEntry::BTagEntry(const TF1* func, BTagEntry::Parameters p):
  formula(std::string(func->GetExpFormula("p").Data())),
  params(p)
{
  if (func->IsZombie()) {
    throw cms::Exception("BTagCalibration")
          << "Invalid TF1 function; function is zombie: "
          << func->GetName();
  }
}

// Creates chained step functions like this:
// "<prevous_bin> : x<bin_high_bound ? bin_value : <next_bin>"
// e.g. "x<0 ? 1 : x<1 ? 2 : x<2 ? 3 : 4"
std::string th1ToFormulaLin(const TH1* hist) {
  int nbins = hist->GetNbinsX();
  TAxis const* axis = hist->GetXaxis();
  std::stringstream buff;
  buff << "x<" << axis->GetBinLowEdge(1) << " ? 0. : ";  // default value
  for (int i=1; i<nbins+1; ++i) {
    char tmp_buff[50];
    sprintf(tmp_buff,
            "x<%g ? %g : ",  // %g is the smaller one of %e or %f
            axis->GetBinUpEdge(i),
            hist->GetBinContent(i));
    buff << tmp_buff;
  }
  buff << 0.;  // default value
  return buff.str();
}

// Creates step functions making a binary search tree:
// "x<mid_bin_bound ? (<left side tree>) : (<right side tree>)"
// e.g. "x<2 ? (x<1 ? (x<0 ? 0:0.1) : (1)) : (x<4 ? (x<3 ? 2:3) : (0))"
std::string th1ToFormulaBinTree(const TH1* hist, int start=0, int end=-1) {
  if (end == -1) {                      // initialize
    start = 0.;
    end = hist->GetNbinsX()+1;
    TH1* h2 = (TH1*) hist->Clone();
    h2->SetBinContent(start, 0);  // kill underflow
    h2->SetBinContent(end, 0);    // kill overflow
    std::string res = th1ToFormulaBinTree(h2, start, end);
    delete h2;
    return res;
  }
  if (start == end) {                   // leave is reached
    char tmp_buff[20];
    sprintf(tmp_buff, "%g", hist->GetBinContent(start));
    return std::string(tmp_buff);
  }
  if (start == end - 1) {               // no parenthesis for neighbors
    char tmp_buff[70];
    sprintf(tmp_buff,
            "x<%g ? %g:%g",
            hist->GetXaxis()->GetBinUpEdge(start),
            hist->GetBinContent(start),
            hist->GetBinContent(end));
    return std::string(tmp_buff);
  }

  // top-down recursion
  std::stringstream buff;
  int mid = (end-start)/2 + start;
  char tmp_buff[25];
  sprintf(tmp_buff,
          "x<%g ? (",
          hist->GetXaxis()->GetBinUpEdge(mid));
  buff << tmp_buff
       << th1ToFormulaBinTree(hist, start, mid)
       << ") : ("
       << th1ToFormulaBinTree(hist, mid+1, end)
       << ")";
  return buff.str();
}

BTagEntry::BTagEntry(const TH1* hist, BTagEntry::Parameters p):
  params(p)
{
  int nbins = hist->GetNbinsX();
  TAxis const* axis = hist->GetXaxis();

  // overwrite bounds with histo values
  if (params.operatingPoint == BTagEntry::OP_RESHAPING) {
    params.discrMin = axis->GetBinLowEdge(1);
    params.discrMax = axis->GetBinUpEdge(nbins);
  } else {
    params.ptMin = axis->GetBinLowEdge(1);
    params.ptMax = axis->GetBinUpEdge(nbins);
  }

  // balanced full binary tree height = ceil(log(2*n_leaves)/log(2))
  // breakes even around 10, but lower values are more propable in pt-spectrum
  if (nbins < 15) {
    formula = th1ToFormulaLin(hist);
  } else {
    formula = th1ToFormulaBinTree(hist);
  }

  // compile formula to check validity
  TF1 f1("", formula.c_str());
  if (f1.IsZombie()) {
    throw cms::Exception("BTagCalibration")
          << "Invalid histogram; formula does not compile (>150 bins?): "
          << hist->GetName();
  }
}

std::string BTagEntry::makeCSVHeader()
{
  return "OperatingPoint, "
         "measurementType, "
         "sysType, "
         "jetFlavor, "
         "etaMin, "
         "etaMax, "
         "ptMin, "
         "ptMax, "
         "discrMin, "
         "discrMax, "
         "formula \n";
}

std::string BTagEntry::makeCSVLine() const
{
  std::stringstream buff;
  buff << params.operatingPoint
       << ", " << params.measurementType
       << ", " << params.sysType
       << ", " << params.jetFlavor
       << ", " << params.etaMin
       << ", " << params.etaMax
       << ", " << params.ptMin
       << ", " << params.ptMax
       << ", " << params.discrMin
       << ", " << params.discrMax
       << ", \"" << formula
       << "\" \n";
  return buff.str();
}

std::string BTagEntry::trimStr(std::string str) {
  size_t s = str.find_first_not_of(" \n\r\t");
  size_t e = str.find_last_not_of (" \n\r\t");

  if((std::string::npos == s) || (std::string::npos == e))
    return "";
  else
    return str.substr(s, e-s+1);
}