SingleGen_module.cc

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// C++ includes.
#include <cctype> // std::tolower()
#include <cmath>
#include <initializer_list>
#include <iterator>
#include <map>
#include <memory>
#include <sstream>
#include <string>

// Framework includes
#include "art/Framework/Core/EDProducer.h"
#include "art/Framework/Core/ModuleMacros.h"
#include "art/Framework/Principal/Event.h"
#include "art/Framework/Principal/Run.h"
#include "art/Framework/Services/Registry/ServiceHandle.h"
#include "cetlib/filesystem.h"
#include "cetlib/search_path.h"
#include "cetlib_except/exception.h"
#include "fhiclcpp/types/Atom.h"
#include "fhiclcpp/types/Comment.h"
#include "fhiclcpp/types/Name.h"
#include "fhiclcpp/types/OptionalAtom.h"
#include "fhiclcpp/types/Sequence.h"
#include "messagefacility/MessageLogger/MessageLogger.h"

// nurandom includes
#include "nurandom/RandomUtils/NuRandomService.h"

//  nusimdata includes
#include "nusimdata/SimulationBase/MCParticle.h"
#include "nusimdata/SimulationBase/MCTruth.h"

// LArSoft libraries
#include "larcore/CoreUtils/ServiceUtil.h"
#include "larcore/Geometry/Geometry.h"
#include "larcorealg/Geometry/GeometryCore.h"
#include "larcoreobj/SummaryData/RunData.h"

#include "TDatabasePDG.h"
#include "TFile.h"
#include "TH1.h"
#include "TH2.h"
#include "TVector3.h"

#include "CLHEP/Random/RandFlat.h"
#include "CLHEP/Random/RandGaussQ.h"

namespace evgen {

  class SingleGen : public art::EDProducer {

  public:
    struct Config {
      using Name = fhicl::Name;
      using Comment = fhicl::Comment;

      fhicl::Atom<std::string> ParticleSelectionMode{
        Name("ParticleSelectionMode"),
        Comment("generate one particle, or one particle per PDG ID: " +
                presentOptions(ParticleSelectionModeNames))};

      fhicl::Atom<bool> PadOutVectors{
        Name("PadOutVectors"),
        Comment("if true, all per-PDG-ID quantities must contain only one value, which is then "
                "used for all PDG IDs")};

      fhicl::Sequence<int> PDG{Name("PDG"),
                               Comment("PDG ID of the particles to be generated; this is the key "
                                       "for the other options marked as \"per PDG ID\"")};

      fhicl::Atom<std::string> PDist{
        Name("PDist"),
        Comment("momentum distribution type: " + presentOptions(DistributionNames)),
        optionName(kHIST, DistributionNames)};

      fhicl::Sequence<double> P0{Name("P0"),
                                 Comment("central momentum (GeV/c) to generate"),
                                 [this]() { return !fromHistogram(PDist()); }};

      fhicl::Sequence<double> SigmaP{Name("SigmaP"),
                                     Comment("variation in momenta (GeV/c)"),
                                     [this]() { return !fromHistogram(PDist()); }};

      fhicl::Sequence<double> X0{
        Name("X0"),
        Comment("central x position (cm) in world coordinates [per PDG ID]")};

      fhicl::Sequence<double> Y0{
        Name("Y0"),
        Comment("central y position (cm) in world coordinates [per PDG ID]")};

      fhicl::Sequence<double> Z0{
        Name("Z0"),
        Comment("central z position (cm) in world coordinates [per PDG ID]")};

      fhicl::Sequence<double> T0{Name("T0"), Comment("central time (ns) [per PDG ID]")};

      fhicl::Sequence<double> SigmaX{
        Name("SigmaX"),
        Comment("variation (radius or RMS) in x position (cm) [per PDG ID]")};

      fhicl::Sequence<double> SigmaY{
        Name("SigmaY"),
        Comment("variation (radius or RMS) in y position (cm) [per PDG ID]")};

      fhicl::Sequence<double> SigmaZ{
        Name("SigmaZ"),
        Comment("variation (radius or RMS) in z position (cm) [per PDG ID]")};

      fhicl::Sequence<double> SigmaT{
        Name("SigmaT"),
        Comment("variation (semi-interval or RMS) in time (ns) [per PDG ID]")};

      fhicl::Atom<std::string> PosDist{Name("PosDist"),
                                       Comment("distribution of starting position: " +
                                               presentOptions(DistributionNames, true, {kHIST}))};

      fhicl::Atom<std::string> TDist{
        Name("TDist"),
        Comment("time distribution type: " + presentOptions(DistributionNames, true, {kHIST}))};

      fhicl::Atom<bool> SingleVertex{
        Name("SingleVertex"),
        Comment("if true, all particles are produced at the same location"),
        false};

      fhicl::Sequence<double> Theta0XZ{Name("Theta0XZ"),
                                       Comment("angle from Z axis on world X-Z plane (degrees)")};

      fhicl::Sequence<double> Theta0YZ{Name("Theta0YZ"),
                                       Comment("angle from Z axis on world Y-Z plane (degrees)")};

      fhicl::Sequence<double> SigmaThetaXZ{Name("SigmaThetaXZ"),
                                           Comment("variation in angle in X-Z plane (degrees)")};

      fhicl::Sequence<double> SigmaThetaYZ{Name("SigmaThetaYZ"),
                                           Comment("variation in angle in Y-Z plane (degrees)")};

      fhicl::Atom<std::string> AngleDist{
        Name("AngleDist"),
        Comment("angular distribution type: " + presentOptions(DistributionNames)),
        optionName(kHIST, DistributionNames)};

      fhicl::Atom<std::string> HistogramFile{
        Name("HistogramFile"),
        Comment("ROOT file containing the required distributions for the generation"),
        [this]() { return fromHistogram(AngleDist()) || fromHistogram(PDist()); }};

      fhicl::Sequence<std::string> PHist{
        Name("PHist"),
        Comment("name of the histograms of momentum distributions"),
        [this]() { return fromHistogram(PDist()); }};

      /*
      fhicl::Sequence<std::string> ThetaPhiHist{
        Name("ThetaPhiHist"),
        Comment("name of the histograms of angular (theta/phi) distribution"),
        [this](){ return fromHistogram(AngleDist()); }
      };
      */
      fhicl::Sequence<std::string> ThetaXzYzHist{
        Name("ThetaXzYzHist"),
        Comment("name of the histograms of angular (X-Z and Y-Z) distribution"),
        [this]() { return fromHistogram(AngleDist()); }};

      fhicl::Atom<rndm::NuRandomService::seed_t> Seed{
        Name("Seed"),
        Comment("override the random number generator seed"),
        rndm::NuRandomService::InvalidSeed};

    private:
      bool fromHistogram(std::string const& key) const;

    }; // struct Config

    using Parameters = art::EDProducer::Table<Config>;

    explicit SingleGen(Parameters const& config);

    // This is called for each event.
    void produce(art::Event& evt) override;

  private:
    static const std::map<int, std::string> ParticleSelectionModeNames;
    static const std::map<int, std::string> DistributionNames;

    void SampleOne(unsigned int i, simb::MCTruth& mct);
    void SampleMany(simb::MCTruth& mct);
    void Sample(simb::MCTruth& mct);
    void printVecs(std::vector<std::string> const& list);
    bool PadVector(std::vector<double>& vec);
    double SelectFromHist(const TH1& h);
    void SelectFromHist(const TH2& h, double& x, double& y);
    double particle_mass(int particle_id);
    simb::MCParticle mc_particle(int track_id, int particle_id, double mass);


    static constexpr int kSelectAllParts = 0; 
    static constexpr int kSelectOneRandPart =
      1; 


    static constexpr int kUNIF = 0; 
    static constexpr int kGAUS = 1; 
    static constexpr int kHIST = 2; 

    int fMode;           
    bool fPadOutVectors; 
    std::vector<int> fPDG;             
    std::vector<double> fP0;           
    std::vector<double> fSigmaP;       
    int fPDist;                        
    std::vector<double> fX0;           
    std::vector<double> fY0;           
    std::vector<double> fZ0;           
    std::vector<double> fT0;           
    std::vector<double> fSigmaX;       
    std::vector<double> fSigmaY;       
    std::vector<double> fSigmaZ;       
    std::vector<double> fSigmaT;       
    int fPosDist;                      
    int fTDist;                        
    bool fSingleVertex;                
    std::vector<double> fTheta0XZ;     
    std::vector<double> fTheta0YZ;     
    std::vector<double> fSigmaThetaXZ; 
    std::vector<double> fSigmaThetaYZ; 
    int fAngleDist;                    
    std::string fHistFileName;         
    std::vector<std::string> fPHist;   
    std::vector<std::string> fThetaXzYzHist; 

    std::vector<std::unique_ptr<TH1>> hPHist; 
    std::vector<std::unique_ptr<TH2>>
      hThetaXzYzHist; 
    // FYI - thetaxz and thetayz are related to standard polar angles as follows:
    // thetaxz = atan2(math.sin(theta) * cos(phi), cos(theta))
    // thetayz = asin(sin(theta) * sin(phi));

    CLHEP::HepRandomEngine& fEngine; 

    static std::map<int, std::string> makeParticleSelectionModeNames();

    static std::map<int, std::string> makeDistributionNames();

    void beginRun(art::Run& run) override;

    void setup();

    template <typename OptionList>
    static auto selectOption(std::string Option, OptionList const& allowedOptions)
      -> decltype(auto);

    template <typename OptionList>
    static std::string presentOptions(
      OptionList const& allowedOptions,
      bool printKey,
      std::initializer_list<typename OptionList::value_type::first_type> exclude);

    template <typename OptionList>
    static std::string presentOptions(OptionList const& allowedOptions, bool printKey = true)
    {
      return presentOptions(allowedOptions, printKey, {});
    }

    template <typename OptionList>
    static std::string optionName(typename OptionList::value_type::first_type optionKey,
                                  OptionList const& allowedOptions,
                                  std::string defName = "<unknown>");

  }; // class SingleGen
}

namespace evgen {

  std::map<int, std::string> SingleGen::makeParticleSelectionModeNames()
  {
    std::map<int, std::string> names;
    names[int(kSelectAllParts)] = "all";
    names[int(kSelectOneRandPart)] = "singleRandom";
    return names;
  } // SingleGen::makeParticleSelectionModeNames()

  std::map<int, std::string> SingleGen::makeDistributionNames()
  {
    std::map<int, std::string> names;
    names[int(kUNIF)] = "uniform";
    names[int(kGAUS)] = "Gaussian";
    names[int(kHIST)] = "histograms";
    return names;
  } // SingleGen::makeDistributionNames()

  const std::map<int, std::string> SingleGen::ParticleSelectionModeNames =
    SingleGen::makeParticleSelectionModeNames();
  const std::map<int, std::string> SingleGen::DistributionNames =
    SingleGen::makeDistributionNames();

  template <typename OptionList>
  auto SingleGen::selectOption(std::string Option, OptionList const& allowedOptions)
    -> decltype(auto)
  {
    using key_type = typename OptionList::value_type::first_type;
    using tolower_type = int (*)(int);
    auto toLower = [](auto const& S) {
      std::string s;
      s.reserve(S.size());
      std::transform(S.cbegin(), S.cend(), std::back_inserter(s), (tolower_type)&std::tolower);
      return s;
    };
    auto option = toLower(Option);
    for (auto const& candidate : allowedOptions) {
      if (toLower(candidate.second) == option) return candidate.first;
    }
    try {
      std::size_t end;
      key_type num = std::stoi(Option, &end);
      if (allowedOptions.count(num) && (end == Option.length())) return num;
    }
    catch (std::invalid_argument const&) {
    }
    throw std::runtime_error("Option '" + Option + "' not supported.");
  } // SingleGen::selectOption()

  template <typename OptionList>
  std::string SingleGen::presentOptions(
    OptionList const& allowedOptions,
    bool printKey /* = true */,
    std::initializer_list<typename OptionList::value_type::first_type> exclude /* = {} */
  )
  {
    std::string msg;

    unsigned int n = 0;
    for (auto const& option : allowedOptions) {
      auto const& key = option.first;
      if (std::find(exclude.begin(), exclude.end(), key) != exclude.end()) continue;
      if (n++ > 0) msg += ", ";
      msg += '\"' + std::string(option.second) + '\"';
      if (printKey) msg += " (" + std::to_string(key) + ")";
    } // for
    return msg;
  } // SingleGen::presentOptions()

  template <typename OptionList>
  std::string SingleGen::optionName(typename OptionList::value_type::first_type optionKey,
                                    OptionList const& allowedOptions,
                                    std::string defName /* = "<unknown>" */
  )
  {
    auto iOption = allowedOptions.find(optionKey);
    return (iOption != allowedOptions.end()) ? iOption->second : defName;
  } // SingleGen::optionName()

  //____________________________________________________________________________
  bool SingleGen::Config::fromHistogram(std::string const& key) const
  {
    return selectOption(PDist(), DistributionNames) == kHIST;
  } // SingleGen::Config::fromHistogram()

  double SingleGen::particle_mass(int particle_id)
  {
    constexpr double kAlphaMass = 3.727379240;
    if (particle_id == 1000020040) {
      return kAlphaMass; // alpha particles
    }

    static TDatabasePDG pdgt;
    TParticlePDG* pdgp = pdgt.GetParticle(particle_id);
    return pdgp ? pdgp->Mass() : 0.;
  }

  simb::MCParticle SingleGen::mc_particle(int track_id, int particle_id, double mass)
  {
    if (particle_id == 1000020040) {
      return simb::MCParticle{track_id, particle_id, "primary", -1, mass, 1};
    }
    return simb::MCParticle{track_id, particle_id, "primary"};
  }

  //____________________________________________________________________________
  SingleGen::SingleGen(Parameters const& config)
    : EDProducer{config}
    , fMode(selectOption(config().ParticleSelectionMode(), ParticleSelectionModeNames))
    , fPadOutVectors(config().PadOutVectors())
    , fPDG(config().PDG())
    , fP0(config().P0())
    , fSigmaP(config().SigmaP())
    , fPDist(selectOption(config().PDist(), DistributionNames))
    , fX0(config().X0())
    , fY0(config().Y0())
    , fZ0(config().Z0())
    , fT0(config().T0())
    , fSigmaX(config().SigmaX())
    , fSigmaY(config().SigmaY())
    , fSigmaZ(config().SigmaZ())
    , fSigmaT(config().SigmaT())
    , fPosDist(selectOption(config().PosDist(), DistributionNames))
    , fTDist(selectOption(config().TDist(), DistributionNames))
    , fSingleVertex(config().SingleVertex())
    , fTheta0XZ(config().Theta0XZ())
    , fTheta0YZ(config().Theta0YZ())
    , fSigmaThetaXZ(config().SigmaThetaXZ())
    , fSigmaThetaYZ(config().SigmaThetaYZ())
    , fAngleDist(selectOption(config().AngleDist(), DistributionNames))
    , fHistFileName(config().HistogramFile())
    , fPHist(config().PHist())
    , fThetaXzYzHist(config().ThetaXzYzHist())
    , fEngine(art::ServiceHandle<rndm::NuRandomService>()
                ->registerAndSeedEngine(createEngine(config().Seed()), "", "", config().Seed()))
  {
    setup();
    mf::LogInfo("SingleGen") << "Seed set to " << fEngine.getSeed();

    produces<std::vector<simb::MCTruth>>();
    produces<sumdata::RunData, art::InRun>();
  }

  //____________________________________________________________________________
  void SingleGen::beginRun(art::Run& run)
  {
    geo::GeometryCore const& geom = *(lar::providerFrom<geo::Geometry>());
    run.put(std::make_unique<sumdata::RunData>(geom.DetectorName()), art::fullRun());
  }

  //____________________________________________________________________________
  void SingleGen::setup()
  {
    // do not put seed in reconfigure because we don't want to reset
    // the seed midstream
    std::vector<std::string> vlist(15);
    vlist[0] = "PDG";
    vlist[1] = "P0";
    vlist[2] = "SigmaP";
    vlist[3] = "X0";
    vlist[4] = "Y0";
    vlist[5] = "Z0";
    vlist[6] = "SigmaX";
    vlist[7] = "SigmaY";
    vlist[8] = "SigmaZ";
    vlist[9] = "Theta0XZ";
    vlist[10] = "Theta0YZ";
    vlist[11] = "SigmaThetaXZ";
    vlist[12] = "SigmaThetaYZ";
    vlist[13] = "T0";
    vlist[14] = "SigmaT";

    //    vlist[15] = "PHist";
    //    vlist[16] = "ThetaHist";
    //    vlist[17] = "PhiHist";

    // begin tests for multiple particle error possibilities
    std::string list;
    if (fPDist != kHIST) {
      if (!this->PadVector(fP0)) { list.append(vlist[1].append(", \n")); }
      if (!this->PadVector(fSigmaP)) { list.append(vlist[2].append(", \n")); }
    }
    if (!this->PadVector(fX0)) { list.append(vlist[3].append(", \n")); }
    if (!this->PadVector(fY0)) { list.append(vlist[4].append(", \n")); }
    if (!this->PadVector(fZ0)) { list.append(vlist[5].append(", \n")); }
    if (!this->PadVector(fSigmaX)) { list.append(vlist[6].append(", \n")); }
    if (!this->PadVector(fSigmaY)) { list.append(vlist[7].append(", \n")); }
    if (!this->PadVector(fSigmaZ)) { list.append(vlist[8].append(", \n")); }
    if (!this->PadVector(fTheta0XZ)) { list.append(vlist[9].append(", \n")); }
    if (!this->PadVector(fTheta0YZ)) { list.append(vlist[10].append(", \n")); }
    if (!this->PadVector(fSigmaThetaXZ)) { list.append(vlist[11].append(", \n")); }
    if (!this->PadVector(fSigmaThetaYZ)) { list.append(vlist[12].append("  \n")); }
    if (!this->PadVector(fT0)) { list.append(vlist[13].append(", \n")); }
    if (!this->PadVector(fSigmaT)) { list.append(vlist[14].append(", \n")); }

    if (list.size() > 0)
      throw cet::exception("SingleGen")
        << "The " << list << "\n vector(s) defined in the fhicl files has/have "
        << "a different size than the PDG vector "
        << "\n and it has (they have) more than one value, "
        << "\n disallowing sensible padding "
        << " and/or you have set fPadOutVectors to false. \n";

    if (fPDG.size() > 1 && fPadOutVectors) this->printVecs(vlist);

    // If needed, get histograms for momentum and angle distributions
    TFile* histFile = nullptr;
    if (!fHistFileName.empty()) {
      if (fHistFileName[0] == '/') {
        // We have an absolute path, use given name exactly.
        if (cet::file_exists(fHistFileName)) {
          histFile = new TFile(fHistFileName.c_str());
          if (!histFile || histFile->IsZombie() || !histFile->IsOpen()) {
            delete histFile;
            histFile = nullptr;
            throw art::Exception(art::errors::NotFound)
              << "Cannot open ROOT file specified in parameter HistogramFile: \"" << fHistFileName
              << "\"";
          }
        }
        else {
          throw art::Exception(art::errors::NotFound)
            << "ROOT file specified in parameter HistogramFile: \"" << fHistFileName
            << "\" does not exist!";
        }
      }
      else {
        // We have a relative path, search starting from current directory.
        std::string relative_filename{"./"};
        relative_filename += fHistFileName;
        if (cet::file_exists(relative_filename)) {
          histFile = new TFile(relative_filename.c_str());
          if (!histFile || histFile->IsZombie() || !histFile->IsOpen()) {
            delete histFile;
            histFile = nullptr;
            throw art::Exception(art::errors::NotFound)
              << "Cannot open ROOT file found using relative path and originally specified in "
                 "parameter HistogramFile: \""
              << relative_filename << '"';
          }
        }
        else {
          cet::search_path sp{"FW_SEARCH_PATH"};
          std::string found_filename;
          auto found = sp.find_file(fHistFileName, found_filename);
          if (!found) {
            throw art::Exception(art::errors::NotFound)
              << "Cannot find ROOT file in current directory nor on FW_SEARCH_PATH specified in "
                 "parameter HistogramFile: \""
              << fHistFileName << '"';
          }
          histFile = new TFile(found_filename.c_str());
          if (!histFile || histFile->IsZombie() || !histFile->IsOpen()) {
            delete histFile;
            histFile = nullptr;
            throw art::Exception(art::errors::NotFound)
              << "Cannot open ROOT file found on FW_SEARCH_PATH and originally specified in "
                 "parameter HistogramFile: \""
              << found_filename << '"';
          }
        }
      }
    }

    //
    // deal with position distribution
    //
    switch (fPosDist) {
    case kGAUS:
    case kUNIF: break; // supported, no further action needed
    default:
      throw art::Exception(art::errors::Configuration)
        << "Position distribution of type '" << optionName(fPosDist, DistributionNames) << "' ("
        << std::to_string(fPosDist) << ") is not supported.";
    } // switch(fPosDist)

    //
    // deal with time distribution
    //
    switch (fTDist) {
    case kGAUS:
    case kUNIF: break; // supported, no further action needed
    default:
      throw art::Exception(art::errors::Configuration)
        << "Time distribution of type '" << optionName(fTDist, DistributionNames) << "' ("
        << std::to_string(fTDist) << ") is not supported.";
    } // switch(fTDist)

    //
    // deal with momentum distribution
    //
    switch (fPDist) {
    case kHIST:
      if (fPHist.size() != fPDG.size()) {
        throw art::Exception(art::errors::Configuration)
          << fPHist.size() << " momentum histograms to describe " << fPDG.size()
          << " particle types...";
      }
      hPHist.reserve(fPHist.size());
      for (auto const& histName : fPHist) {
        TH1* pHist = dynamic_cast<TH1*>(histFile->Get(histName.c_str()));
        if (!pHist) {
          throw art::Exception(art::errors::NotFound)
            << "Failed to read momentum histogram '" << histName << "' from '"
            << histFile->GetPath() << "\'";
        }
        pHist->SetDirectory(nullptr); // make it independent of the input file
        hPHist.emplace_back(pHist);
      } // for
      break;
    default: // supported, no further action needed
      break;
    } // switch(fPDist)

    switch (fAngleDist) {
    case kHIST:
      if (fThetaXzYzHist.size() != fPDG.size()) {
        throw art::Exception(art::errors::Configuration)
          << fThetaXzYzHist.size() << " direction histograms to describe " << fPDG.size()
          << " particle types...";
      }
      hThetaXzYzHist.reserve(fThetaXzYzHist.size());
      for (auto const& histName : fThetaXzYzHist) {
        TH2* pHist = dynamic_cast<TH2*>(histFile->Get(histName.c_str()));
        if (!pHist) {
          throw art::Exception(art::errors::NotFound)
            << "Failed to read direction histogram '" << histName << "' from '"
            << histFile->GetPath() << "\'";
        }
        pHist->SetDirectory(nullptr); // make it independent of the input file
        hThetaXzYzHist.emplace_back(pHist);
      }      // for
    default: // supported, no further action needed
      break;
    } // switch(fAngleDist)

    delete histFile;
  }

  //____________________________________________________________________________
  bool SingleGen::PadVector(std::vector<double>& vec)
  {
    // check if the vec has the same size as fPDG
    if (vec.size() != fPDG.size()) {
      // if not padding out the vectors always cause an
      // exception to be thrown if the vector in question
      // is not the same size as the fPDG vector
      // the exception is thrown in the reconfigure method
      // that calls this one
      if (!fPadOutVectors)
        return false;
      else if (fPadOutVectors) {
        // if padding of vectors is desired but the vector in
        // question has more than one entry it isn't clear
        // what the padded values should be so cause
        // an exception
        if (vec.size() != 1) return false;

        // pad it out
        vec.resize(fPDG.size(), vec[0]);

      } // end if padding out vectors
    }   // end if the vector size is not the same as fPDG

    return true;
  }

  //____________________________________________________________________________
  void SingleGen::produce(art::Event& evt)
  {

    std::unique_ptr<std::vector<simb::MCTruth>> truthcol(new std::vector<simb::MCTruth>);

    simb::MCTruth truth;
    truth.SetOrigin(simb::kSingleParticle);
    Sample(truth);

    MF_LOG_DEBUG("SingleGen") << truth;

    truthcol->push_back(truth);

    evt.put(std::move(truthcol));

    return;
  }

  //____________________________________________________________________________
  // Draw the type, momentum and position of a single particle from the
  // FCIHL description
  void SingleGen::SampleOne(unsigned int i, simb::MCTruth& mct)
  {

    CLHEP::RandFlat flat(fEngine);
    CLHEP::RandGaussQ gauss(fEngine);

    // Choose momentum
    double p = 0.0;
    double m = 0.0;
    if (fPDist == kGAUS) { p = gauss.fire(fP0[i], fSigmaP[i]); }
    else if (fPDist == kHIST) {
      p = SelectFromHist(*(hPHist[i]));
    }
    else { // if (fPDist == kUNIF) {
      p = fP0[i] + fSigmaP[i] * (2.0 * flat.fire() - 1.0);
    }
    //    else {std::cout << "do not understand the value of PDist!";}
    m = particle_mass(fPDG[i]);

    // Choose position
    TVector3 x;
    if (fPosDist == kGAUS) {
      x[0] = gauss.fire(fX0[i], fSigmaX[i]);
      ;
      x[1] = gauss.fire(fY0[i], fSigmaY[i]);
      x[2] = gauss.fire(fZ0[i], fSigmaZ[i]);
    }
    else {
      x[0] = fX0[i] + fSigmaX[i] * (2.0 * flat.fire() - 1.0);
      x[1] = fY0[i] + fSigmaY[i] * (2.0 * flat.fire() - 1.0);
      x[2] = fZ0[i] + fSigmaZ[i] * (2.0 * flat.fire() - 1.0);
    }

    double t = 0.;
    if (fTDist == kGAUS) { t = gauss.fire(fT0[i], fSigmaT[i]); }
    else {
      t = fT0[i] + fSigmaT[i] * (2.0 * flat.fire() - 1.0);
    }

    TLorentzVector pos(x[0], x[1], x[2], t);

    // Choose angles
    double thxz = 0;
    double thyz = 0;

    double thyzrads = 0;
    double thyzradsplussigma = 0;
    double thyzradsminussigma = 0;

    if (fAngleDist == kGAUS) {
      thxz = gauss.fire(fTheta0XZ[i], fSigmaThetaXZ[i]);
      thyz = gauss.fire(fTheta0YZ[i], fSigmaThetaYZ[i]);
    }
    else if (fAngleDist == kHIST) { // Select thetaxz and thetayz from histogram
      double thetaxz = 0;
      double thetayz = 0;
      SelectFromHist(*(hThetaXzYzHist[i]), thetaxz, thetayz);
      thxz = (180. / M_PI) * thetaxz;
      thyz = (180. / M_PI) * thetayz;
    }
    else {

      // Choose angles flat in phase space, which is flat in theta_xz
      // and flat in sin(theta_yz).

      thxz = fTheta0XZ[i] + fSigmaThetaXZ[i] * (2.0 * flat.fire() - 1.0);

      thyzrads = std::asin(std::sin(
        (M_PI / 180.) *
        (fTheta0YZ
           [i]))); //Taking asin of sin gives value between -Pi/2 and Pi/2 regardless of user input
      thyzradsplussigma =
        TMath::Min((thyzrads + ((M_PI / 180.) * fabs(fSigmaThetaYZ[i]))), M_PI / 2.);
      thyzradsminussigma =
        TMath::Max((thyzrads - ((M_PI / 180.) * fabs(fSigmaThetaYZ[i]))), -M_PI / 2.);

      //uncomment line to print angular variation info
      //std::cout << "Central angle: " << (180./M_PI)*thyzrads << " Max angle: " << (180./M_PI)*thyzradsplussigma << " Min angle: " << (180./M_PI)*thyzradsminussigma << std::endl;

      double sinthyzmin = std::sin(thyzradsminussigma);
      double sinthyzmax = std::sin(thyzradsplussigma);
      double sinthyz = sinthyzmin + flat.fire() * (sinthyzmax - sinthyzmin);
      thyz = (180. / M_PI) * std::asin(sinthyz);
    }

    double thxzrad = thxz * M_PI / 180.0;
    double thyzrad = thyz * M_PI / 180.0;

    TLorentzVector pvec(p * std::cos(thyzrad) * std::sin(thxzrad),
                        p * std::sin(thyzrad),
                        p * std::cos(thxzrad) * std::cos(thyzrad),
                        std::sqrt(p * p + m * m));

    // set track id to -i as these are all primary particles and have id <= 0
    int trackid = -1 * (i + 1);
    std::string primary("primary");

    auto part = mc_particle(trackid, fPDG[i], m);
    part.AddTrajectoryPoint(pos, pvec);
    mct.Add(part);

    //std::cout << "Px: " <<  pvec.Px() << " Py: " << pvec.Py() << " Pz: " << pvec.Pz() << std::endl;
    //std::cout << "x: " <<  pos.X() << " y: " << pos.Y() << " z: " << pos.Z() << " time: " << pos.T() << std::endl;
    //std::cout << "YZ Angle: " << (thyzrad * (180./M_PI)) << " XZ Angle: " << (thxzrad * (180./M_PI)) << std::endl;
  }

  //____________________________________________________________________________
  // Draw the type, momentum and position for all particles from the
  // FCIHL description.  Start positions will all match but momenta and angles drawn from
  // distributions defined in the fhicls
  void SingleGen::SampleMany(simb::MCTruth& mct)
  {

    CLHEP::RandFlat flat(fEngine);
    CLHEP::RandGaussQ gauss(fEngine);

    // Choose position
    TVector3 x;
    if (fPosDist == kGAUS) {
      x[0] = gauss.fire(fX0[0], fSigmaX[0]);
      ;
      x[1] = gauss.fire(fY0[0], fSigmaY[0]);
      x[2] = gauss.fire(fZ0[0], fSigmaZ[0]);
    }
    else {
      x[0] = fX0[0] + fSigmaX[0] * (2.0 * flat.fire() - 1.0);
      x[1] = fY0[0] + fSigmaY[0] * (2.0 * flat.fire() - 1.0);
      x[2] = fZ0[0] + fSigmaZ[0] * (2.0 * flat.fire() - 1.0);
    }

    double t = 0.;
    if (fTDist == kGAUS) { t = gauss.fire(fT0[0], fSigmaT[0]); }
    else {
      t = fT0[0] + fSigmaT[0] * (2.0 * flat.fire() - 1.0);
    }

    TLorentzVector pos(x[0], x[1], x[2], t);

    // loop through particles and select momenta and angles
    for (unsigned int i(0); i < fPDG.size(); ++i) {
      // Choose momentum
      double p = 0.0;
      double m = 0.0;
      if (fPDist == kGAUS) { p = gauss.fire(fP0[i], fSigmaP[i]); }
      else if (fPDist == kHIST) {
        p = SelectFromHist(*(hPHist[i]));
      }
      else {
        p = fP0[i] + fSigmaP[i] * (2.0 * flat.fire() - 1.0);
      }

      m = particle_mass(fPDG[i]);

      // Choose angles
      double thxz = 0;
      double thyz = 0;

      double thyzrads = 0;
      double thyzradsplussigma = 0;
      double thyzradsminussigma = 0;

      if (fAngleDist == kGAUS) {
        thxz = gauss.fire(fTheta0XZ[i], fSigmaThetaXZ[i]);
        thyz = gauss.fire(fTheta0YZ[i], fSigmaThetaYZ[i]);
      }
      else if (fAngleDist == kHIST) {
        double thetaxz = 0;
        double thetayz = 0;
        SelectFromHist(*(hThetaXzYzHist[i]), thetaxz, thetayz);
        thxz = (180. / M_PI) * thetaxz;
        thyz = (180. / M_PI) * thetayz;
      }
      else {

        // Choose angles flat in phase space, which is flat in theta_xz
        // and flat in sin(theta_yz).

        thxz = fTheta0XZ[i] + fSigmaThetaXZ[i] * (2.0 * flat.fire() - 1.0);

        thyzrads = std::asin(std::sin(
          (M_PI / 180.) *
          (fTheta0YZ
             [i]))); //Taking asin of sin gives value between -Pi/2 and Pi/2 regardless of user input
        thyzradsplussigma =
          TMath::Min((thyzrads + ((M_PI / 180.) * fabs(fSigmaThetaYZ[i]))), M_PI / 2.);
        thyzradsminussigma =
          TMath::Max((thyzrads - ((M_PI / 180.) * fabs(fSigmaThetaYZ[i]))), -M_PI / 2.);

        //uncomment line to print angular variation info
        //std::cout << "Central angle: " << (180./M_PI)*thyzrads << " Max angle: " << (180./M_PI)*thyzradsplussigma << " Min angle: " << (180./M_PI)*thyzradsminussigma << std::endl;

        double sinthyzmin = std::sin(thyzradsminussigma);
        double sinthyzmax = std::sin(thyzradsplussigma);
        double sinthyz = sinthyzmin + flat.fire() * (sinthyzmax - sinthyzmin);
        thyz = (180. / M_PI) * std::asin(sinthyz);
      }

      double thxzrad = thxz * M_PI / 180.0;
      double thyzrad = thyz * M_PI / 180.0;

      TLorentzVector pvec(p * std::cos(thyzrad) * std::sin(thxzrad),
                          p * std::sin(thyzrad),
                          p * std::cos(thxzrad) * std::cos(thyzrad),
                          std::sqrt(p * p + m * m));

      // set track id to -i as these are all primary particles and have id <= 0
      int trackid = -1 * (i + 1);
      std::string primary("primary");

      auto part = mc_particle(trackid, fPDG[i], m);
      part.AddTrajectoryPoint(pos, pvec);
      mct.Add(part);

      //std::cout << "Px: " <<  pvec.Px() << " Py: " << pvec.Py() << " Pz: " << pvec.Pz() << std::endl;
      //std::cout << "x: " <<  pos.X() << " y: " << pos.Y() << " z: " << pos.Z() << " time: " << pos.T() << std::endl;
      //std::cout << "YZ Angle: " << (thyzrad * (180./M_PI)) << " XZ Angle: " << (thxzrad * (180./M_PI)) << std::endl;
    }
  }

  //____________________________________________________________________________
  void SingleGen::Sample(simb::MCTruth& mct)
  {

    switch (fMode) {
    case 0: // List generation mode: every event will have one of each
            // particle species in the fPDG array
      if (fSingleVertex) { SampleMany(mct); }
      else {
        for (unsigned int i = 0; i < fPDG.size(); ++i) {
          SampleOne(i, mct);
        } //end loop over particles
      }
      break;
    case 1: // Random selection mode: every event will exactly one particle
            // selected randomly from the fPDG array
    {
      CLHEP::RandFlat flat(fEngine);

      unsigned int i = flat.fireInt(fPDG.size());
      SampleOne(i, mct);
    } break;
    default:
      mf::LogWarning("UnrecognizeOption")
        << "SingleGen does not recognize ParticleSelectionMode " << fMode;
      break;
    } // switch on fMode

    return;
  }

  //____________________________________________________________________________
  void SingleGen::printVecs(std::vector<std::string> const& list)
  {

    mf::LogInfo("SingleGen") << " You are using vector values for SingleGen configuration.\n   "
                             << " Some of the configuration vectors may have been padded out ,"
                             << " because they (weren't) as long as the pdg vector"
                             << " in your configuration. \n"
                             << " The new input particle configuration is:\n";

    std::string values;
    for (size_t i = 0; i <= 1; ++i) { // list.size(); ++i){

      values.append(list[i]);
      values.append(": [ ");

      for (size_t e = 0; e < fPDG.size(); ++e) {
        std::stringstream buf;
        buf.width(10);
        if (i == 0) buf << fPDG[e] << ", ";
        buf.precision(5);
        if (i == 1) buf << fP0[e] << ", ";
        if (i == 2) buf << fSigmaP[e] << ", ";
        if (i == 3) buf << fX0[e] << ", ";
        if (i == 4) buf << fY0[e] << ", ";
        if (i == 5) buf << fZ0[e] << ", ";
        if (i == 6) buf << fSigmaX[e] << ", ";
        if (i == 7) buf << fSigmaY[e] << ", ";
        if (i == 8) buf << fSigmaZ[e] << ", ";
        if (i == 9) buf << fTheta0XZ[e] << ", ";
        if (i == 10) buf << fTheta0YZ[e] << ", ";
        if (i == 11) buf << fSigmaThetaXZ[e] << ", ";
        if (i == 12) buf << fSigmaThetaYZ[e] << ", ";
        if (i == 13) buf << fT0[e] << ", ";
        if (i == 14) buf << fSigmaT[e] << ", ";
        values.append(buf.str());
      }

      values.erase(values.find_last_of(","));
      values.append(" ] \n");

    } // end loop over vector names in list

    mf::LogInfo("SingleGen") << values;

    return;
  }

  //____________________________________________________________________________
  double SingleGen::SelectFromHist(const TH1& h) // select from a 1D histogram
  {
    CLHEP::RandFlat flat(fEngine);

    double throw_value = h.Integral() * flat.fire();
    double cum_value(0);
    for (int i(0); i < h.GetNbinsX() + 1; ++i) {
      cum_value += h.GetBinContent(i);
      if (throw_value < cum_value) { return flat.fire() * h.GetBinWidth(i) + h.GetBinLowEdge(i); }
    }
    return throw_value; // for some reason we've gone through all bins and failed?
  }
  //____________________________________________________________________________
  void SingleGen::SelectFromHist(const TH2& h, double& x, double& y) // select from a 2D histogram
  {
    CLHEP::RandFlat flat(fEngine);

    double throw_value = h.Integral() * flat.fire();
    double cum_value(0);
    for (int i(0); i < h.GetNbinsX() + 1; ++i) {
      for (int j(0); j < h.GetNbinsY() + 1; ++j) {
        cum_value += h.GetBinContent(i, j);
        if (throw_value < cum_value) {
          x = flat.fire() * h.GetXaxis()->GetBinWidth(i) + h.GetXaxis()->GetBinLowEdge(i);
          y = flat.fire() * h.GetYaxis()->GetBinWidth(j) + h.GetYaxis()->GetBinLowEdge(j);
          return;
        }
      }
    }
    return; // for some reason we've gone through all bins and failed?
  }
  //____________________________________________________________________________

} //end namespace evgen

namespace evgen {

  DEFINE_ART_MODULE(SingleGen)

} //end namespace evgen