PDFWeightsHelper.cc

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#include "PhysicsTools/HepMCCandAlgos/interface/PDFWeightsHelper.h"
#include "FWCore/MessageLogger/interface/MessageLogger.h"
#include <fstream>

PDFWeightsHelper::PDFWeightsHelper() {}

void PDFWeightsHelper::Init(unsigned int nreplicas, unsigned int neigenvectors, const edm::FileInPath &incsv) {
  transformation_.resize(nreplicas, neigenvectors);

  std::ifstream instream(incsv.fullPath());
  if (!instream.is_open()) {
    throw cms::Exception("PDFWeightsHelper") << "Could not open csv file" << incsv.relativePath();
  }

  for (unsigned int ireplica = 0; ireplica < nreplicas; ++ireplica) {
    std::string linestr;
    getline(instream, linestr);
    std::istringstream line(linestr);
    for (unsigned int ieigen = 0; ieigen < neigenvectors; ++ieigen) {
      std::string valstr;
      getline(line, valstr, ',');
      std::istringstream val(valstr);
      val >> transformation_(ireplica, ieigen);
    }
  }
}

void PDFWeightsHelper::DoMC2Hessian(double nomweight, const double *inweights, double *outweights) const {
  const unsigned int nreplicas = transformation_.rows();
  const unsigned int neigenvectors = transformation_.cols();

  Eigen::VectorXd inweightv(nreplicas);
  for (unsigned int irep = 0; irep < nreplicas; ++irep) {
    inweightv[irep] = inweights[irep] - nomweight;
  }

  Eigen::VectorXd outweightv = transformation_.transpose() * inweightv;

  for (unsigned int ieig = 0; ieig < neigenvectors; ++ieig) {
    outweights[ieig] = outweightv[ieig] + nomweight;
  }
}