CORSIKAGen_module.cc

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////////////////////////////////////////////////////////////////////////
/// \file  CORSIKAGen_module.cc
/// \brief Generator for cosmic-ray secondaries based on pre-generated CORSIKA shower databases.
///
/// \author  Matthew.Bass@physics.ox.ac.uk
////////////////////////////////////////////////////////////////////////

// ROOT includes
#include "TDatabasePDG.h"
#include "TString.h"
#include "TSystem.h" //need BaseName and DirName

// Framework includes
#include "art/Framework/Core/EDProducer.h"
#include "art/Framework/Core/ModuleMacros.h"
#include "art/Framework/Principal/Event.h"
#include "fhiclcpp/ParameterSet.h"
#include "art/Framework/Services/Registry/ServiceHandle.h"
#include "messagefacility/MessageLogger/MessageLogger.h"

// art extensions
#include "nurandom/RandomUtils/NuRandomService.h"

// larsoft includes
#include "nusimdata/SimulationBase/MCTruth.h"
#include "nusimdata/SimulationBase/MCParticle.h"
#include "larcore/Geometry/Geometry.h"
#include "larcoreobj/SummaryData/RunData.h"

#include <sqlite3.h>
#include "CLHEP/Random/RandFlat.h"
#include "CLHEP/Random/RandPoissonQ.h"
#include "ifdh.h"  //to handle flux files

namespace evgen {

  /**
   * @brief LArSoft interface to CORSIKA event generator.
   *
   * @note A presentation on this module by the original author is archived at:
   *       https://indico.fnal.gov/event/10893/contribution/3/material/slides
   *
   * In CORSIKA jargon, a "shower" is the cascade of particles resulting from
   * a primary cosmic ray interaction.
   * This module creates a single `simb::MCTruth` object (stored as data product
   * into a `std::vector<simb::MCTruth>` with a single entry) containing all
   * the particles from cosmic ray showers crossing a _surface_ above the
   * detector.
   *
   * The generation procedure consists of selecting showers from a database of
   * *pregenerated* events, and then to adapt them to the parameters requested
   * in the module configuration. Pregenerated showers are "observed" at a
   * altitude set in CORSIKA configuration.
   *
   * Databases need to be stored as files in SQLite3 format. Multiple file
   * sources can be specified (`ShowerInputFiles` configuration parameter).
   * From each source, one database file is selected and copied locally via
   * IFDH.
   * From each source, showers are extracted proportionally to the relative flux
   * specified in the configuration (specified in `ShowerFluxConstants`,
   * see @ref CORSIKAGen_Normalization "normalization" below).
   * The actual number of showers per event and per source is extracted
   * according to a Poisson distribution around the predicted average number of
   * primary cosmic rays for that source.
   *
   *
   * Flux normalization
   * -------------------
   *
   * @anchor CORSIKAGen_Normalization
   *
   * CORSIKA generates showers from each specific cosmic ray type @f$ A @f$
   * (e.g. iron, proton, etc.) according to a power law distribution
   * @f$ \Phi_{A}(E) \propto E^{-\gamma_{A}} @f$ of the primary
   * particle energy @f$ E @f$ [GeV]. When sampling pregenerated events, we
   * bypass the normalization imposed by CORSIKA and gain complete
   * control on it.
   *
   * Within CORSIKAGen, for each source (usually each on a different primary
   * cosmic ray type, e.g. iron, proton, etc.), the average number of generated
   * showers is
   * @f$ n_{A} = \pi S T k_{A} \int E^{-\gamma_{A}} dE @f$ with @f$ S @f$ the
   * area of the surface the flux passes across, @f$ T @f$ the exposure time,
   * the integral defined over the full energy range of the pregenerated showers
   * in the source, and @f$ k_{A} @f$ a factor specified in the configuration
   * (`ShowerFluxConstants` parameters).
   * This is the flux of primary cosmic rays, not of the observed particles
   * from their showers. Note that it depends on an area and a time interval,
   * but it is uniform with respect to translations and constant in time.
   *
   * As explained @ref CORSIKAGen_Coverage "below", we consider only the
   * secondary particles that cross an "observation" surface.
   * After cosmic ray primary particles cross the flux surface (@f$ S_{\Phi} @f$
   * above), they develop into showers of particles that spread across large
   * areas. Limiting ourself to the observation of particles on a small surface
   * @f$ S_{o} @f$ has two effects. We lose the part of the showers that misses
   * that surface @f$ S_{o} @f$. Also, considering a span of time with
   * multiple showers, we miss particles from other hypothetical showers
   * whose primaries crossed outside the generation surface @f$ S_{\Phi} @f$
   * whose shower development would leak into @f$ S_{o} @f$: we did not simulate
   * those showers at all!
   * In terms of total flux of observed particles, under the assumption that the
   * flux is uniform in space, choosing @f$ S_{\Phi} @f$ the same size as
   * @f$ S_{o} @f$ makes the two effects get the same size: just as many
   * particles from primaries from @f$ S_{\Phi} @f$ leak out of @f$ S_{o} @f$,
   * as many particles from primaries from outside @f$ S_{\Phi} @f$ sneak in
   * @f$ S_{o} @f$.
   * In that case, counting _all_ the particles from the primaries crossing a
   * surface @f$ S_{\Phi} @f$ of area _S_ regardless of where they land
   * yields the right amount of cosmic ray secondary particles across an
   * observation surface @f$ S_{o} @f$ also of area _S_. Practically,
   * the particles landing outside @f$ S_{o} @f$ need to be recovered to
   * preserve the correct normalization, which is described in the
   * @ref CORSIKAGen_Coverage "next section".
   *
   *
   * Surface coverage, position and timing
   * --------------------------------------
   *
   * @anchor CORSIKAGen_Coverage
   *
   * The surface we detect the particles through (let's call it @f$ S_{d} @f$)
   * is defined by the smallest _rectangle_ including all cryostats in the
   * detector, and located at the height of the ceiling of the tallest cryostat.
   * This surface can be increased by specifying a positive value for
   * `ShowerAreaExtension` configuration parameter, in which case each side of
   * the rectangle will be extended by that amount.
   *
   * Showers are extracted one by one from the pregenerated samples and treated
   * independently.
   * Ideally, the detection surface @f$ S_{d} @f$ would be at the same exact
   * altitude as the observation surface set in CORSIKA (called @f$ S_{o} @f$
   * above). In practice, we go the other way around, with the assumption that
   * the shower observed at @f$ S_{d} @f$ would be very close to the one we
   * actually generated at @f$ S_{o} @f$, and teleport the generated particles
   * on @f$ S_{d} @f$. Since the cryostats may be just meters from the earth
   * surface @f$ S_{o} @f$ lies on, this is an acceptable approximation.
   *
   * All the particles of one shower are compelled within surface @f$ S_{d} @f$
   * as a first step. As explained when describing the
   * @anchor CORSIKAGen_Normalization "normalization", we need to keep all the
   * shower particles, one way or the other.
   * So, particles of the shower that fell out of @f$ S_{d} @f$ are repackaged
   * into other showers and translated back in. This is equivalent to assume the
   * primary cosmic rays originating such shower would happen outside
   * our generation volume (@f$ S_{\Phi} @f$), and their shower would then spill
   * into @f$ S_{d} @f$. Since these repackaged showers are in principle
   * independent and uncorrelated, they are assigned a random time different
   * than the main shower, leveraging the assumption of constantness of the
   * flux.
   *
   * As for the azimuth, this module uses an approximation by setting north
   * direction to match the _z_ axis of LArSoft geometry (typically assumed
   * to be the direction of the beam particle).
   *
   * The particles so manipulated are then back-propagated from the observation
   * surface to an absolute height defined by `ProjectToHeight` (although for
   * particular combination of position and direction, the particles might be
   * propagated back to the edge of the world, or even outside it).
   *
   * As a final filter, only the particles whose straight projections cross any
   * of the cryostats (with some buffer volume around, defined by `BufferBox`)
   * are stored, while the other ones are discarded. Note that the actual
   * interactions that particles from the generation surface undergo may deviate
   * them enough to miss the cryostats anyway, and conversely particles that
   * have been filtered out because shooting off the cryostats might have been
   * subsequently deviated to actually cross them. This effect is not corrected
   * for at this time.
   *
   * The time of the showers is uniformly distributed within the configured
   * time interval, defined by `SampleTime` starting from `TimeOffset`.
   *
   *
   * Configuration parameters
   * =========================
   *
   * * `ShowerInputFiles` (list of paths; mandatory): a list of file paths to
   *     pregenerated CORSIKA shower files. Each entry can be a single file or
   *     use wildcards (`*`) to specify a set of files to choose among.
   *     Paths and wildcards are processed by IFDH.
   * * `ShowerFluxConstants` (list of real numbers; mandatory): for each entry
   *     @f$ A @f$ in `ShowerInputFiles`, specify the normalization factor
   *     @f$ K_{A} @f$ of their distribution [@f$ m^{-2}s^{-1} @f$]
   * * `ProjectToHeight` (real, default: `0`): the generated particles will
   *     appear to come from this height [cm]
   * * `TimeOffset` (real; default: `0`): start time of the exposure window [s],
   *     relative to the
   *     @ref DetectorClocksSimulationTime "simulation time start"
   * * `SampleTime` (real; mandatory): duration of the simulated exposure to
   *     cosmic rays [s]
   * * `ShowerAreaExtension` (real; default: `0`):
   *     extend the size of the observation surface of shower particles (_S_)
   *     by this much [cm]; e.g. 1000 will extend 10 m on each side
   * * `RandomXZShift` (real; default: `0`): the original position of each
   *     shower is randomly shifted within a square with this length as side
   *     [cm]
   * * `BufferBox` (list of six lengths, all `0` by default):
   *     extension to the volume of each cryostat for the purpose of filtering
   *     out the particles which do not cross the detector; each cryostat volume
   *     is independently extended by the same amount, specified here as
   *     *shifts* to lower _x_, higher _x_, lower _y_, higher _y_, lower _z_
   *     and higher _z_, in that order [cm] (note that to extend e.g. the
   *     negative _x_ side by 5 meters the parameter value should be -500)
   * * `SeedGenerator` (integer): force random number generator for event
   *     generation to the specified value
   * * `SeedPoisson` (integer): force random number generator for number of
   *     showers to the specified value
   * * `Seed`: alias for `SeedGenerator`
   *
   *
   * Random engines
   * ---------------
   *
   * Currently two random engines are used:
   * * a generator engine (driven by `SeedGenerator`), of general use
   * * a "Poisson" engine (driven by `SeedPoisson`), only used to determine the
   *     number of showers to be selected on each event
   *
   */
  class CORSIKAGen : public art::EDProducer {
  public:
    explicit CORSIKAGen(fhicl::ParameterSet const& pset);
    virtual ~CORSIKAGen();

    void produce(art::Event& evt);
    void beginRun(art::Run& run);


  private:
    void openDBs(std::string const& module_label);
    void populateNShowers();
    void populateTOffset();
    void GetSample(simb::MCTruth&);
    double wrapvar( const double var, const double low, const double high);
    double wrapvarBoxNo( const double var, const double low, const double high, int& boxno);
    /**
     * @brief Propagates a point back to the surface of a box.
     * @param xyz coordinates of the point to be propagated (`{ x, y, z }`)
     * @param dxyz direction of the point (`{ dx, dy, dz }`)
     * @param xlo lower _x_ coordinate of the target box
     * @param xhi upper _x_ coordinate of the target box
     * @param ylo lower _y_ coordinate of the target box
     * @param yhi upper _y_ coordinate of the target box
     * @param zlo lower _z_ coordinate of the target box
     * @param zhi upper _z_ coordinate of the target box
     * @param xyzout _(output, room for at least 3 numbers)_ propagated point
     *
     * The point `xyz`, assumed to be inside the box, is propagated at the level
     * of _the closest among the sides of the box_. Note that this means the
     * propagated point might still be not on the surface of the box, even if it
     * would later reach it.
     * It is anyway guaranteed that `xyzout` is not inside the target box, and
     * that at least one of its three coordinates is on the box surface.
     */
    void ProjectToBoxEdge(const double  xyz[],
                                        const double    dxyz[],
                                        const double xlo,
                                        const double xhi,
                                        const double ylo,
                                        const double yhi,
                                        const double zlo,
                                        const double zhi,
                                        double xyzout[]);

    int fShowerInputs=0; ///< Number of shower inputs to process from
    std::vector<double> fNShowersPerEvent; ///< Number of showers to put in each event of duration fSampleTime; one per showerinput
    std::vector<int> fMaxShowers; //< Max number of showers to query, one per showerinput
    double fShowerBounds[6]={0.,0.,0.,0.,0.,0.}; ///< Boundaries of area over which showers are to be distributed (x(min), x(max), _unused_, y, z(min), z(max) )
    double fToffset_corsika=0.; ///< Timing offset to account for propagation time through atmosphere, populated from db
    ifdh_ns::ifdh* fIFDH=0; ///< (optional) flux file handling

    //fcl parameters
    double fProjectToHeight=0.; ///< Height to which particles will be projected [cm]
    std::vector< std::string > fShowerInputFiles; ///< Set of CORSIKA shower data files to use
    std::string fShowerCopyType; // ifdh file selection and copying (default) or direct file path
    std::vector< double > fShowerFluxConstants; ///< Set of flux constants to be associated with each shower data file
    double fSampleTime=0.; ///< Duration of sample [s]
    double fToffset=0.; ///< Time offset of sample, defaults to zero (no offset) [s]
    std::vector<double> fBuffBox; ///< Buffer box extensions to cryostat in each direction (6 of them: x_lo,x_hi,y_lo,y_hi,z_lo,z_hi) [cm]
    double fShowerAreaExtension=0.; ///< Extend distribution of corsika particles in x,z by this much (e.g. 1000 will extend 10 m in -x, +x, -z, and +z) [cm]
    sqlite3* fdb[5]; ///< Pointers to sqlite3 database object, max of 5
    double fRandomXZShift=0.; ///< Each shower will be shifted by a random amount in xz so that showers won't repeatedly sample the same space [cm]
    CLHEP::HepRandomEngine& fGenEngine;
    CLHEP::HepRandomEngine& fPoisEngine;
  };
}

namespace evgen{

  CORSIKAGen::CORSIKAGen(fhicl::ParameterSet const& p)
    : EDProducer{p},
      fProjectToHeight(p.get< double >("ProjectToHeight",0.)),
      fShowerInputFiles(p.get< std::vector< std::string > >("ShowerInputFiles")),
      fShowerCopyType(p.get< std::string >("ShowerCopyType", "IFDH")),
      fShowerFluxConstants(p.get< std::vector< double > >("ShowerFluxConstants")),
      fSampleTime(p.get< double >("SampleTime",0.)),
      fToffset(p.get< double >("TimeOffset",0.)),
      fBuffBox(p.get< std::vector< double > >("BufferBox",{0.0, 0.0, 0.0, 0.0, 0.0, 0.0})),
      fShowerAreaExtension(p.get< double >("ShowerAreaExtension",0.)),
      fRandomXZShift(p.get< double >("RandomXZShift",0.)),
      fGenEngine(art::ServiceHandle<rndm::NuRandomService>{}->createEngine(*this, "HepJamesRandom", "gen", p, { "Seed", "SeedGenerator"})),
      fPoisEngine(art::ServiceHandle<rndm::NuRandomService>{}->createEngine(*this, "HepJamesRandom", "pois", p, "SeedPoisson"))
  {
    if(fShowerInputFiles.size() != fShowerFluxConstants.size() || fShowerInputFiles.size()==0 || fShowerFluxConstants.size()==0)
      throw cet::exception("CORSIKAGen") << "ShowerInputFiles and ShowerFluxConstants have different or invalid sizes!"<<"\n";
    fShowerInputs=fShowerInputFiles.size();

    if(fSampleTime==0.) throw cet::exception("CORSIKAGen") << "SampleTime not set!";

    if(fProjectToHeight==0.) mf::LogInfo("CORSIKAGen")<<"Using 0. for fProjectToHeight!"
    ;
    // create a default random engine; obtain the random seed from NuRandomService,
    // unless overridden in configuration with key "Seed"

    this->openDBs(p.get<std::string>("module_label"));
    this->populateNShowers();
    this->populateTOffset();

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

  }

  CORSIKAGen::~CORSIKAGen(){
    for(int i=0; i<fShowerInputs; i++){
      sqlite3_close(fdb[i]);
    }
    //cleanup temp files
    fIFDH->cleanup();
  }

  void CORSIKAGen::ProjectToBoxEdge(    const double    xyz[],
                                        const double    indxyz[],
                                        const double    xlo,
                                        const double    xhi,
                                        const double    ylo,
                                        const double    yhi,
                                        const double    zlo,
                                        const double    zhi,
                                        double xyzout[]  ){


    //we want to project backwards, so take mirror of momentum
    const double dxyz[3]={-indxyz[0],-indxyz[1],-indxyz[2]};

    // Compute the distances to the x/y/z walls
    double dx = 99.E99;
    double dy = 99.E99;
    double dz = 99.E99;
    if      (dxyz[0] > 0.0) { dx = (xhi-xyz[0])/dxyz[0]; }
    else if (dxyz[0] < 0.0) { dx = (xlo-xyz[0])/dxyz[0]; }
    if      (dxyz[1] > 0.0) { dy = (yhi-xyz[1])/dxyz[1]; }
    else if (dxyz[1] < 0.0) { dy = (ylo-xyz[1])/dxyz[1]; }
    if      (dxyz[2] > 0.0) { dz = (zhi-xyz[2])/dxyz[2]; }
    else if (dxyz[2] < 0.0) { dz = (zlo-xyz[2])/dxyz[2]; }


    // Choose the shortest distance
    double d = 0.0;
    if      (dx < dy && dx < dz) d = dx;
    else if (dy < dz && dy < dx) d = dy;
    else if (dz < dx && dz < dy) d = dz;

    // Make the step
    for (int i = 0; i < 3; ++i) {
      xyzout[i] = xyz[i] + dxyz[i]*d;
    }

  }

  void CORSIKAGen::openDBs(std::string const& module_label){
    //choose files based on fShowerInputFiles, copy them with ifdh, open them
    // for c2: statement is unused
    //sqlite3_stmt *statement;
    CLHEP::RandFlat flat(fGenEngine);

    //setup ifdh object
    if ( ! fIFDH ) fIFDH = new ifdh_ns::ifdh;
    const char* ifdh_debug_env = std::getenv("IFDH_DEBUG_LEVEL");
    if ( ifdh_debug_env ) {
      mf::LogInfo("CORSIKAGen") << "IFDH_DEBUG_LEVEL: " << ifdh_debug_env<<"\n";
      fIFDH->set_debug(ifdh_debug_env);
    }

    //get ifdh path for each file in fShowerInputFiles, put into selectedflist
    //if 1 file returned, use that file
    //if >1 file returned, randomly select one file
    //if 0 returned, make exeption for missing files
    std::vector<std::pair<std::string,long>> selectedflist;
    for(int i=0; i<fShowerInputs; i++){
      if(fShowerInputFiles[i].find("*")==std::string::npos){
        //if there are no wildcards, don't call findMatchingFiles
        selectedflist.push_back(std::make_pair(fShowerInputFiles[i],0));
        mf::LogInfo("CorsikaGen") << "Selected"<<selectedflist.back().first<<"\n";
          }else{
        //use findMatchingFiles
        //default to IFDH approach when wildcards in path
        std::vector<std::pair<std::string,long>> flist;
                std::string path(gSystem->DirName(fShowerInputFiles[i].c_str()));
                std::string pattern(gSystem->BaseName(fShowerInputFiles[i].c_str()));
                flist = fIFDH->findMatchingFiles(path,pattern);
                unsigned int selIndex=-1;
                if(flist.size()==1){ //0th element is the search path:pattern
                        selIndex=0;
                }else if(flist.size()>1){
                        selIndex= (unsigned int) (flat()*(flist.size()-1)+0.5); //rnd with rounding, dont allow picking the 0th element
                }else{
                        throw cet::exception("CORSIKAGen") << "No files returned for path:pattern: "<<path<<":"<<pattern<<std::endl;
                }
                selectedflist.push_back(flist[selIndex]);
                mf::LogInfo("CorsikaGen") << "For "<<fShowerInputFiles[i]<<":"<<pattern
        <<"\nFound "<< flist.size() << " candidate files"
        <<"\nChoosing file number "<< selIndex << "\n"
        <<"\nSelected "<<selectedflist.back().first<<"\n";
     }

    }

    //do the fetching, store local filepaths in locallist
    std::vector<std::string> locallist;
    for(unsigned int i=0; i<selectedflist.size(); i++){
      mf::LogInfo("CorsikaGen")
        << "Fetching: "<<selectedflist[i].first<<" "<<selectedflist[i].second<<"\n";
      if (fShowerCopyType == "IFDH") {
        std::string fetchedfile(fIFDH->fetchInput(selectedflist[i].first));
        MF_LOG_DEBUG("CorsikaGen") << "Fetched; local path: "<<fetchedfile << "; copy type: IFDH";
        locallist.push_back(fetchedfile);
      }
      else if (fShowerCopyType == "DIRECT") {
        std::string fetchedfile(selectedflist[i].first);
        MF_LOG_DEBUG("CorsikaGen") << "Fetched; local path: "<<fetchedfile << "; copy type: DIRECT";
        locallist.push_back(fetchedfile);
      }
      else throw cet::exception("CORSIKAGen") << "Error copying shower db: ShowerCopyType must be \"IFDH\" or \"DIRECT\"\n";
    }

    //open the files in fShowerInputFilesLocalPaths with sqlite3
    for(unsigned int i=0; i<locallist.size(); i++){
      //prepare and execute statement to attach db file
      int res=sqlite3_open(locallist[i].c_str(),&fdb[i]);
      if (res!= SQLITE_OK)
        throw cet::exception("CORSIKAGen") << "Error opening db: (" <<locallist[i].c_str()<<") ("<<res<<"): " << sqlite3_errmsg(fdb[i]) << "; memory used:<<"<<sqlite3_memory_used()<<"/"<<sqlite3_memory_highwater(0)<<"\n";
      else
        mf::LogInfo("CORSIKAGen")<<"Attached db "<< locallist[i]<<"\n";
    }
  }

  double CORSIKAGen::wrapvar( const double var, const double low, const double high){
    //wrap variable so that it's always between low and high
    return (var - (high - low) * floor(var/(high-low))) + low;
  }

  double CORSIKAGen::wrapvarBoxNo( const double var, const double low, const double high, int& boxno){
    //wrap variable so that it's always between low and high
    boxno=int(floor(var/(high-low)));
    return (var - (high - low) * floor(var/(high-low))) + low;
  }

  void CORSIKAGen::populateTOffset(){
    //populate TOffset_corsika by finding minimum ParticleTime from db file

    sqlite3_stmt *statement;
    const std::string kStatement("select min(t) from particles");
    double t=0.;

    for(int i=0; i<fShowerInputs; i++){
        //build and do query to get run min(t) from each db
        if ( sqlite3_prepare(fdb[i], kStatement.c_str(), -1, &statement, 0 ) == SQLITE_OK ){
          int res=0;
          res = sqlite3_step(statement);
          if ( res == SQLITE_ROW ){
            t=sqlite3_column_double(statement,0);
            mf::LogInfo("CORSIKAGen")<<"For showers input "<< i<<" found particles.min(t)="<<t<<"\n";
            if (i==0 || t<fToffset_corsika) fToffset_corsika=t;
          }else{
            throw cet::exception("CORSIKAGen") << "Unexpected sqlite3_step return value: (" <<res<<"); "<<"ERROR:"<<sqlite3_errmsg(fdb[i])<<"\n";
          }
        }else{
          throw cet::exception("CORSIKAGen") << "Error preparing statement: (" <<kStatement<<"); "<<"ERROR:"<<sqlite3_errmsg(fdb[i])<<"\n";
        }
    }

    mf::LogInfo("CORSIKAGen")<<"Found corsika timeoffset [ns]: "<< fToffset_corsika<<"\n";
  }

  void CORSIKAGen::populateNShowers(){
    //populate vector of the number of showers per event based on:
      //AREA the showers are being distributed over
      //TIME of the event (fSampleTime)
      //flux constants that determine the overall normalizations (fShowerFluxConstants)
      //Energy range over which the sample was generated (ERANGE_*)
      //power spectrum over which the sample was generated (ESLOPE)


    //compute shower area based on the maximal x,z dimensions of cryostat boundaries + fShowerAreaExtension
    art::ServiceHandle<geo::Geometry const> geom;
    for(unsigned int c = 0; c < geom->Ncryostats(); ++c){
      double bounds[6] = {0.};
      geom->CryostatBoundaries(bounds, c);
      for (unsigned int bnd = 0; bnd<6; bnd++){
        mf::LogVerbatim("CORSIKAGen")<<"Cryo Boundary: "<<bnd<<"="<<bounds[bnd]<<" ( + Buffer="<<fBuffBox[bnd]<<")\n";
        if(fabs(bounds[bnd])>fabs(fShowerBounds[bnd])){
          fShowerBounds[bnd]=bounds[bnd];
        }
      }
    }
    //add on fShowerAreaExtension without being clever
    fShowerBounds[0] = fShowerBounds[0] - fShowerAreaExtension;
    fShowerBounds[1] = fShowerBounds[1] + fShowerAreaExtension;
    fShowerBounds[4] = fShowerBounds[4] - fShowerAreaExtension;
    fShowerBounds[5] = fShowerBounds[5] + fShowerAreaExtension;

    double showersArea=(fShowerBounds[1]/100-fShowerBounds[0]/100)*(fShowerBounds[5]/100-fShowerBounds[4]/100);

    mf::LogInfo("CORSIKAGen")
      <<  "Area extended by : "<<fShowerAreaExtension
      <<"\nShowers to be distributed betweeen: x="<<fShowerBounds[0]<<","<<fShowerBounds[1]
                             <<" & z="<<fShowerBounds[4]<<","<<fShowerBounds[5]
      <<"\nShowers to be distributed with random XZ shift: "<<fRandomXZShift<<" cm"
      <<"\nShowers to be distributed over area: "<<showersArea<<" m^2"
      <<"\nShowers to be distributed over time: "<<fSampleTime<<" s"
      <<"\nShowers to be distributed with time offset: "<<fToffset<<" s"
      <<"\nShowers to be distributed at y: "<<fShowerBounds[3]<<" cm"
      ;

    //db variables
    sqlite3_stmt *statement;
    const std::string kStatement("select erange_high,erange_low,eslope,nshow from input");
    double upperLimitOfEnergyRange=0.,lowerLimitOfEnergyRange=0.,energySlope=0.,oneMinusGamma=0.,EiToOneMinusGamma=0.,EfToOneMinusGamma=0.;

    for(int i=0; i<fShowerInputs; i++){
        //build and do query to get run info from databases
      //  double thisrnd=flat();//need a new random number for each query
        if ( sqlite3_prepare(fdb[i], kStatement.c_str(), -1, &statement, 0 ) == SQLITE_OK ){
          int res=0;
          res = sqlite3_step(statement);
          if ( res == SQLITE_ROW ){
            upperLimitOfEnergyRange=sqlite3_column_double(statement,0);
            lowerLimitOfEnergyRange=sqlite3_column_double(statement,1);
            energySlope = sqlite3_column_double(statement,2);
            fMaxShowers.push_back(sqlite3_column_int(statement,3));
            oneMinusGamma = 1 + energySlope;
            EiToOneMinusGamma = pow(lowerLimitOfEnergyRange, oneMinusGamma);
            EfToOneMinusGamma = pow(upperLimitOfEnergyRange, oneMinusGamma);
            mf::LogVerbatim("CORSIKAGen")<<"For showers input "<< i<<" found e_hi="<<upperLimitOfEnergyRange<<", e_lo="<<lowerLimitOfEnergyRange<<", slope="<<energySlope<<", k="<<fShowerFluxConstants[i]<<"\n";
          }else{
            throw cet::exception("CORSIKAGen") << "Unexpected sqlite3_step return value: (" <<res<<"); "<<"ERROR:"<<sqlite3_errmsg(fdb[i])<<"\n";
          }
        }else{
          throw cet::exception("CORSIKAGen") << "Error preparing statement: (" <<kStatement<<"); "<<"ERROR:"<<sqlite3_errmsg(fdb[i])<<"\n";
        }

      //this is computed, how?
      double NShowers=( M_PI * showersArea * fShowerFluxConstants[i] * (EfToOneMinusGamma - EiToOneMinusGamma) / oneMinusGamma )*fSampleTime;
      fNShowersPerEvent.push_back(NShowers);
      mf::LogVerbatim("CORSIKAGen")<<"For showers input "<< i
                               <<" the number of showers per event is "<<(int)NShowers<<"\n";
    }
  }

  void CORSIKAGen::GetSample(simb::MCTruth& mctruth){
    //for each input, randomly pull fNShowersPerEvent[i] showers from the Particles table
    //and randomly place them in time (between -fSampleTime/2 and fSampleTime/2)
    //wrap their positions based on the size of the area under consideration
    //based on http://nusoft.fnal.gov/larsoft/doxsvn/html/CRYHelper_8cxx_source.html (Sample)

    //query from sqlite db with select * from particles where shower in (select id from showers ORDER BY substr(id*0.51123124141,length(id)+2) limit 100000) ORDER BY substr(shower*0.51123124141,length(shower)+2);
    //where 0.51123124141 is a random seed to allow randomly selecting rows and should be randomly generated for each query
    //the inner order by is to select randomly from the possible shower id's
    //the outer order by is to make sure the shower numbers are ordered randomly (without this, the showers always come out ordered by shower number
    //and 100000 is the number of showers to be selected at random and needs to be less than the number of showers in the showers table

    //TDatabasePDG is for looking up particle masses
    static TDatabasePDG* pdgt = TDatabasePDG::Instance();

    //db variables
    sqlite3_stmt *statement;
    const TString kStatement("select shower,pdg,px,py,pz,x,z,t,e from particles where shower in (select id from showers ORDER BY substr(id*%f,length(id)+2) limit %d) ORDER BY substr(shower*%f,length(shower)+2)");

    CLHEP::RandFlat flat(fGenEngine);
    CLHEP::RandPoissonQ randpois(fPoisEngine);

    // get geometry and figure where to project particles to, based on CRYHelper
    art::ServiceHandle<geo::Geometry const> geom;
    double x1, x2;
    double y1, y2;
    double z1, z2;
    geom->WorldBox(&x1, &x2, &y1, &y2, &z1, &z2);

    // make the world box slightly smaller so that the projection to
    // the edge avoids possible rounding errors later on with Geant4
    double fBoxDelta=1.e-5;
    x1 += fBoxDelta;
    x2 -= fBoxDelta;
    y1 += fBoxDelta;
    y2 = fProjectToHeight;
    z1 += fBoxDelta;
    z2 -= fBoxDelta;

    //populate mctruth
    int ntotalCtr=0; //count number of particles added to mctruth
    int lastShower=0; //keep track of last shower id so that t can be randomized on every new shower
    int nShowerCntr=0; //keep track of how many showers are left to be added to mctruth
    int nShowerQry=0; //number of showers to query from db
    int shower,pdg;
    double px,py,pz,x,z,tParticleTime,etot,showerTime=0.,showerTimex=0.,showerTimez=0.,showerXOffset=0.,showerZOffset=0.,t;
    for(int i=0; i<fShowerInputs; i++){
      nShowerCntr=randpois.fire(fNShowersPerEvent[i]);
      mf::LogInfo("CORSIKAGEN") << " Shower input " << i << " with mean " << fNShowersPerEvent[i] << " generating " << nShowerCntr;

      while(nShowerCntr>0){
        //how many showers should we query?
        if(nShowerCntr>fMaxShowers[i]){
          nShowerQry=fMaxShowers[i]; //take the group size
        }else{
          nShowerQry=nShowerCntr; //take the rest that are needed
        }
        //build and do query to get nshowers
        double thisrnd=flat(); //need a new random number for each query
        TString kthisStatement=TString::Format(kStatement.Data(),thisrnd,nShowerQry,thisrnd);
        MF_LOG_DEBUG("CORSIKAGen")<<"Executing: "<<kthisStatement;
        if ( sqlite3_prepare(fdb[i], kthisStatement.Data(), -1, &statement, 0 ) == SQLITE_OK ){
          int res=0;
          //loop over database rows, pushing particles into mctruth object
          while(1){
            res = sqlite3_step(statement);
            if ( res == SQLITE_ROW ){
              /*
               * Memo columns:
               * [0] shower
               * [1] particle ID (PDG)
               * [2] momentum: x component [GeV/c]
               * [3] momentum: y component [GeV/c]
               * [4] momentum: z component [GeV/c]
               * [5] position: x component [cm]
               * [6] position: z component [cm]
               * [7] time [ns]
               * [8] energy [GeV]
               */
              shower=sqlite3_column_int(statement,0);
              if(shower!=lastShower){
                //each new shower gets its own random time and position offsets
                showerTime=1e9*(flat()*fSampleTime); //converting from s to ns
                showerTimex=1e9*(flat()*fSampleTime); //converting from s to ns
                showerTimez=1e9*(flat()*fSampleTime); //converting from s to ns
                //and a random offset in both z and x controlled by the fRandomXZShift parameter
                showerXOffset=flat()*fRandomXZShift - (fRandomXZShift/2);
                showerZOffset=flat()*fRandomXZShift - (fRandomXZShift/2);
              }
              pdg=sqlite3_column_int(statement,1);
              //get mass for this particle
              double m = 0.; // in GeV
              TParticlePDG* pdgp = pdgt->GetParticle(pdg);
              if (pdgp) m = pdgp->Mass();

              //Note: position/momentum in db have north=-x and west=+z, rotate so that +z is north and +x is west
              //get momentum components
              px=sqlite3_column_double(statement,4);//uboone x=Particlez
              py=sqlite3_column_double(statement,3);
              pz=-sqlite3_column_double(statement,2);//uboone z=-Particlex
              etot=sqlite3_column_double(statement,8);

              //get/calculate position components
              int boxnoX=0,boxnoZ=0;
              x=wrapvarBoxNo(sqlite3_column_double(statement,6)+showerXOffset,fShowerBounds[0],fShowerBounds[1],boxnoX);
              z=wrapvarBoxNo(-sqlite3_column_double(statement,5)+showerZOffset,fShowerBounds[4],fShowerBounds[5],boxnoZ);
              tParticleTime=sqlite3_column_double(statement,7); //time offset, includes propagation time from top of atmosphere
              //actual particle time is particle surface arrival time
              //+ shower start time
              //+ global offset (fcl parameter, in s)
              //- propagation time through atmosphere
              //+ boxNo{X,Z} time offset to make grid boxes have different shower times
              t=tParticleTime+showerTime+(1e9*fToffset)-fToffset_corsika + showerTimex*boxnoX + showerTimez*boxnoZ;
              //wrap surface arrival so that it's in the desired time window
              t=wrapvar(t,(1e9*fToffset),1e9*(fToffset+fSampleTime));

              simb::MCParticle p(ntotalCtr,pdg,"primary",-200,m,1);

              //project back to wordvol/fProjectToHeight
              /*
               * This back propagation goes from a point on the upper surface of
               * the cryostat back to the edge of the world, except that that
               * world is cut short by `fProjectToHeight` (`y2`) ceiling.
               * The projection will most often lie on that ceiling, but it may
               * end up instead on one of the side edges of the world, or even
               * outside it.
               */
              double xyzo[3];
              double x0[3]={x,fShowerBounds[3],z};
              double dx[3]={px,py,pz};
              this->ProjectToBoxEdge(x0, dx, x1, x2, y1, y2, z1, z2, xyzo);

              TLorentzVector pos(xyzo[0],xyzo[1],xyzo[2],t);// time needs to be in ns to match GENIE, etc
              TLorentzVector mom(px,py,pz,etot);
              p.AddTrajectoryPoint(pos,mom);
              mctruth.Add(p);
              ntotalCtr++;
              lastShower=shower;
            }else if ( res == SQLITE_DONE ){
              break;
            }else{
              throw cet::exception("CORSIKAGen") << "Unexpected sqlite3_step return value: (" <<res<<"); "<<"ERROR:"<<sqlite3_errmsg(fdb[i])<<"\n";
            }
          }
        }else{
          throw cet::exception("CORSIKAGen") << "Error preparing statement: (" <<kthisStatement<<"); "<<"ERROR:"<<sqlite3_errmsg(fdb[i])<<"\n";
        }
        nShowerCntr=nShowerCntr-nShowerQry;
      }
    }
  }

  void CORSIKAGen::beginRun(art::Run& run)
  {
    art::ServiceHandle<geo::Geometry const> geo;
    run.put(std::make_unique<sumdata::RunData>(geo->DetectorName()));
  }

  void CORSIKAGen::produce(art::Event& evt){
    std::unique_ptr< std::vector<simb::MCTruth> > truthcol(new std::vector<simb::MCTruth>);

    art::ServiceHandle<geo::Geometry const> geom;

    simb::MCTruth truth;
    truth.SetOrigin(simb::kCosmicRay);

    simb::MCTruth pretruth;
    GetSample(pretruth);
    mf::LogInfo("CORSIKAGen")<<"GetSample number of particles returned: "<<pretruth.NParticles()<<"\n";
    // loop over particles in the truth object
    for(int i = 0; i < pretruth.NParticles(); ++i){
      simb::MCParticle particle = pretruth.GetParticle(i);
      const TLorentzVector& v4 = particle.Position();
      const TLorentzVector& p4 = particle.Momentum();
      double x0[3] = {v4.X(),  v4.Y(),  v4.Z() };
      double dx[3] = {p4.Px(), p4.Py(), p4.Pz()};

      // now check if the particle goes through any cryostat in the detector
      // if so, add it to the truth object.
      for(unsigned int c = 0; c < geom->Ncryostats(); ++c){
        double bounds[6] = {0.};
        geom->CryostatBoundaries(bounds, c);

        //add a buffer box around the cryostat bounds to increase the acceptance and account for scattering
        //By default, the buffer box has zero size
        for (unsigned int cb=0; cb<6; cb++)
           bounds[cb] = bounds[cb]+fBuffBox[cb];

        //calculate the intersection point with each cryostat surface
        bool intersects_cryo = false;
        for (int bnd=0; bnd!=6; ++bnd) {
          if (bnd<2) {
            double p2[3] = {bounds[bnd],  x0[1] + (dx[1]/dx[0])*(bounds[bnd] - x0[0]), x0[2] + (dx[2]/dx[0])*(bounds[bnd] - x0[0])};
            if ( p2[1] >= bounds[2] && p2[1] <= bounds[3] &&
                 p2[2] >= bounds[4] && p2[2] <= bounds[5] ) {
              intersects_cryo = true;
              break;
            }
          }
          else if (bnd>=2 && bnd<4) {
            double p2[3] = {x0[0] + (dx[0]/dx[1])*(bounds[bnd] - x0[1]), bounds[bnd], x0[2] + (dx[2]/dx[1])*(bounds[bnd] - x0[1])};
            if ( p2[0] >= bounds[0] && p2[0] <= bounds[1] &&
                 p2[2] >= bounds[4] && p2[2] <= bounds[5] ) {
              intersects_cryo = true;
        break;
            }
          }
          else if (bnd>=4) {
            double p2[3] = {x0[0] + (dx[0]/dx[2])*(bounds[bnd] - x0[2]), x0[1] + (dx[1]/dx[2])*(bounds[bnd] - x0[2]), bounds[bnd]};
            if ( p2[0] >= bounds[0] && p2[0] <= bounds[1] &&
                 p2[1] >= bounds[2] && p2[1] <= bounds[3] ) {
              intersects_cryo = true;
        break;
            }
          }
        }

        if (intersects_cryo){
          truth.Add(particle);
          break; //leave loop over cryostats to avoid adding particle multiple times
        }// end if particle goes into a cryostat
      }// end loop over cryostats in the detector

    }// loop on particles

    mf::LogInfo("CORSIKAGen")<<"Number of particles from getsample crossing cryostat + bounding box: "<<truth.NParticles()<<"\n";

    truthcol->push_back(truth);
    evt.put(std::move(truthcol));

    return;
  }// end produce

}// end namespace


namespace evgen{

  DEFINE_ART_MODULE(CORSIKAGen)

}