FastSimulation/TrackingRecHitProducer/src/PixelTemplateSmearerBase.cc - master - githubmirror/cmssw

FastSimulation/TrackingRecHitProducer/src/PixelTemplateSmearerBase.cc
941 строка37 KB
Shahzad Malik Muzaffar
[FASTSIM] Drop Geometry/CommonDetUnit package
28 май 2026, 12:58
28 май 2026, 12:58c911cd1

/** PixelTemplateSmearerBase.cc
 * ---------------------------------------------------------------------
 * Base class for FastSim plugins to simulate all simHits on one DetUnit.
 * 
 * Petar Maksimovic (JHU), based the code by 
 * Guofan Hu (JHU) from SiPixelGaussianSmearingRecHitConverterAlgorithm.cc
 * Alice Sady (JHU): new pixel resolutions (2015) and hit merging code.
 * ---------------------------------------------------------------------
 */

// SiPixel Gaussian Smearing
#include "FastSimulation/TrackingRecHitProducer/interface/PixelTemplateSmearerBase.h"
#include "FastSimulation/TrackingRecHitProducer/interface/TrackingRecHitAlgorithmFactory.h"
#include "FastSimulation/TrackingRecHitProducer/interface/TrackingRecHitProduct.h"
#include "FastSimulation/TrackingRecHitProducer/interface/PixelResolutionHistograms.h"

// Pixel related stuff
#include "CondFormats/SiPixelObjects/interface/SiPixelTemplateDBObject.h"

// Geometry
/// #include "Geometry/CommonTopologies/interface/GeomDetUnit.h"  // Keep... needed if we backport to CMSSW_9
#include "Geometry/CommonTopologies/interface/PixelGeomDetUnit.h"
#include "Geometry/TrackerGeometryBuilder/interface/RectangularPixelTopology.h"
#include "DataFormats/GeometryVector/interface/LocalPoint.h"
#include "DataFormats/GeometryCommonDetAlgo/interface/MeasurementPoint.h"

// Famos
#include "FastSimulation/Utilities/interface/RandomEngineAndDistribution.h"
#include "FastSimulation/Utilities/interface/SimpleHistogramGenerator.h"

// Framework (includes ESHandle<>)
#include "FWCore/Framework/interface/EventSetup.h"
#include "FWCore/MessageLogger/interface/MessageLogger.h"
#include "CalibTracker/Records/interface/SiPixelTemplateDBObjectESProducerRcd.h"

// ROOT
#include <TFile.h>
#include <TH1F.h>
#include <TH2F.h>

using namespace std;

const double microntocm = 0.0001;

PixelTemplateSmearerBase::PixelTemplateSmearerBase(const std::string& name,
                                                   const edm::ParameterSet& config,
                                                   edm::ConsumesCollector& consumesCollector)
    : TrackingRecHitAlgorithm(name, config, consumesCollector) {
  //--- Basic stuff
  mergeHitsOn = config.getParameter<bool>("MergeHitsOn");
  isBarrel = config.getParameter<bool>("isBarrel");
  int detType = (isBarrel) ? 1 : 0;  // 1 for barrel, 0 for forward  (or could we just promote bool into int...?)

  //--- Resolution file names.
  theBigPixelResolutionFileName = config.getParameter<string>("BigPixelResolutionFile");
  theBigPixelResolutionFileName = edm::FileInPath(theBigPixelResolutionFileName).fullPath();

  theEdgePixelResolutionFileName = config.getParameter<string>("EdgePixelResolutionFile");
  theEdgePixelResolutionFileName = edm::FileInPath(theEdgePixelResolutionFileName).fullPath();

  theRegularPixelResolutionFileName = config.getParameter<string>("RegularPixelResolutionFile");
  theRegularPixelResolutionFileName = edm::FileInPath(theRegularPixelResolutionFileName).fullPath();

  //--- Create the resolution histogram objects, which will load the histograms
  //    and initialize random number generators.
  //
  int status = 0;
  theRegularPixelResolutions = std::make_shared<PixelResolutionHistograms>(theRegularPixelResolutionFileName, "");
  if ((status = theRegularPixelResolutions->status()) != 0) {
    throw cms::Exception("PixelTemplateSmearerBase:")
        << " constructing Regular PixelResolutionHistograms file " << theRegularPixelResolutionFileName
        << " failed with status = " << status << std::endl;
  }

  theBigPixelResolutions = std::make_shared<PixelResolutionHistograms>(
      theBigPixelResolutionFileName, "", detType, (!isBarrel), false, true);  // can miss qBin
  if ((status = theBigPixelResolutions->status()) != 0) {
    throw cms::Exception("PixelTemplateSmearerBase:")
        << " constructing Big PixelResolutionHistograms file " << theBigPixelResolutionFileName
        << " failed with status = " << status << std::endl;
  }

  theEdgePixelResolutions = std::make_shared<PixelResolutionHistograms>(
      theEdgePixelResolutionFileName, "", detType, false, true, true);  // can miss both single & qBin
  if ((status = theEdgePixelResolutions->status()) != 0) {
    throw cms::Exception("PixelTemplateSmearerBase:")
        << " constructing Edge PixelResolutionHistograms file " << theEdgePixelResolutionFileName
        << " failed with status = " << status << std::endl;
  }

  //--- Merging info.
  theMergingProbabilityFileName = config.getParameter<string>("MergingProbabilityFile");
  theMergingProbabilityFileName = edm::FileInPath(theMergingProbabilityFileName).fullPath();
  theMergingProbabilityFile = std::make_unique<TFile>(theMergingProbabilityFileName.c_str(), "READ");

  theMergedPixelResolutionXFileName = config.getParameter<string>("MergedPixelResolutionXFile");
  theMergedPixelResolutionXFileName = edm::FileInPath(theMergedPixelResolutionXFileName).fullPath();
  theMergedPixelResolutionXFile = std::make_unique<TFile>(theMergedPixelResolutionXFileName.c_str(), "READ");

  theMergedPixelResolutionYFileName = config.getParameter<string>("MergedPixelResolutionYFile");
  theMergedPixelResolutionYFileName = edm::FileInPath(theMergedPixelResolutionYFileName).fullPath();
  theMergedPixelResolutionYFile = std::make_unique<TFile>(theMergedPixelResolutionYFileName.c_str(), "READ");

  // const SiPixelTemplateDBObject & dbobject;
  // const SiPixelTemplateDBObject dbobject;        // dummy, just to make it compile &&&

  //--- Load the templates.
  if (config.exists("templateId")) {
    //--- Load template with ID=templateId from a local ascii file.
    templateId = config.getParameter<int>("templateId");
    if (templateId > 0) {
      if (!SiPixelTemplate::pushfile(templateId, thePixelTemp_)) {
        throw cms::Exception("PixelTemplateSmearerBase:")
            << "SiPixel Template " << templateId << " Not Loaded Correctly!" << std::endl;
      }
    }
  }

  //--- Else... The templates will be loaded from the DB...
  //    (They are needed for data and full sim MC, so in a production FastSim
  //    run, everything should already be in the DB.)
  //
  //    But note that we can do it only at the beginning of the
  //    event.  So nothing happens now.
}

PixelTemplateSmearerBase::~PixelTemplateSmearerBase() {}

//-------------------------------------------------------------------------------
//   beginRun(); the templates are loaded in TrackingRecHitProducer, and unpacked
//   into the template store.  We get their references here, and use them.  However,
//   if we are loading a dedicated template ID from an ascii file just for this
//   rechit smearing algorithm, then we use our own template store.
//-------------------------------------------------------------------------------
void PixelTemplateSmearerBase::beginRun(edm::Run const& run,
                                        const edm::EventSetup& eventSetup,
                                        const SiPixelTemplateDBObject* pixelTemplateDBObjectPtr,
                                        const std::vector<SiPixelTemplateStore>& tempStoreRef) {
  //--- Check if we need to use the template from the DB (namely if
  //    id == -1).  Otherwise the template has already been loaded from
  //    the ascii file in constructor, and thePixelTempRef wakes up
  //    pointing to thePixelTemp_, so then we use our own store.
  //
  if (templateId == -1) {
    thePixelTempRef = &tempStoreRef;                    // we use the store from TrackingRecHitProducer
    pixelTemplateDBObject_ = pixelTemplateDBObjectPtr;  // needed for template<-->DetId map.
  }

  //--- Commented code below (the DB interface) should say here, in case we need it:
  // edm::ESHandle<SiPixelTemplateDBObject> templateDBobject;
  // eventSetup.get<SiPixelTemplateDBObjectESProducerRcd>().get(templateDBobject);
  // pixelTemplateDBObject_ = templateDBobject.product();

  // //--- Now that we have the DB object, load the correct templates from the DB.
  // //    (They are needed for data and full sim MC, so in a production FastSim
  // //    run, everything should already be in the DB.)
  // if ( !SiPixelTemplate::pushfile( *pixelTemplateDBObject_ , thePixelTemp_) ) {
  //   throw cms::Exception("PixelTemplateSmearerPlugin:")
  // 	<<"SiPixel Template " << templateId << " Not Loaded Correctly!"<<endl;
  // }
}

//-------------------------------------------------------------------------------
//   Simulate one DetUnit:
//   1. figure out where the hits are
//   2. figure out which hits merge; merge them into "merge groups"
//   3. smear all individual (unmerged hits)
//   4. smear all merge groups.
//-------------------------------------------------------------------------------
TrackingRecHitProductPtr PixelTemplateSmearerBase::process(TrackingRecHitProductPtr product) const {
  std::vector<std::pair<unsigned int, const PSimHit*>>& simHitIdPairs = product->getSimHitIdPairs();
  std::vector<const PSimHit*> simHits(simHitIdPairs.size());
  for (unsigned int ihit = 0; ihit < simHitIdPairs.size(); ++ihit) {
    simHits[ihit] = simHitIdPairs[ihit].second;
  }

  RandomEngineAndDistribution const& randomEngine = getRandomEngine();

  const GeomDet* geomDet = getTrackerGeometry().idToDetUnit(product->getDetId());
  const PixelGeomDetUnit* pixelGeomDet = dynamic_cast<const PixelGeomDetUnit*>(geomDet);
  if (pixelGeomDet == nullptr) {
    throw cms::Exception("FastSimulation/TrackingRecHitProducer")
        << "The GeomDetUnit is not a PixelGeomDetUnit.  This should never happen!";
  }
  const BoundPlane& theDetPlane = pixelGeomDet->surface();
  const Bounds& theBounds = theDetPlane.bounds();
  const double boundX = theBounds.width() / 2.;
  const double boundY = theBounds.length() / 2.;

  std::vector<TrackingRecHitProduct::SimHitIdPair> listOfUnmergedHits;
  std::vector<MergeGroup*> listOfMergeGroups;
  int nHits = simHits.size();

  // fixed size array, 0 if hit is unmerged
  MergeGroup* mergeGroupByHit[nHits];

  if (nHits == 0) {
    return product;
  } else if (nHits == 1) {
    listOfUnmergedHits.push_back(simHitIdPairs[0]);
  } else {
    if (mergeHitsOn) {
      for (int i = 0; i < nHits; ++i) {
        //initialize this cell to a NULL pointer here
        mergeGroupByHit[i] = nullptr;
      }
      for (int i = 0; i < nHits - 1; ++i) {
        for (int j = i + 1; j < nHits; ++j) {
          //--- Calculate the distance between hits i and j:
          bool merged = hitsMerge(*simHitIdPairs[i].second, *simHitIdPairs[j].second);

          if (merged) {
            // First, check if the other guy (j) is in some merge group already
            if (mergeGroupByHit[j] != nullptr) {
              if (mergeGroupByHit[i] == nullptr) {
                mergeGroupByHit[i] = mergeGroupByHit[j];
                mergeGroupByHit[i]->group.push_back(simHitIdPairs[i]);
                mergeGroupByHit[i]->smearIt = true;
              } else {
                if (mergeGroupByHit[i] != mergeGroupByHit[j]) {
                  for (auto hit_it = mergeGroupByHit[j]->group.begin(); hit_it != mergeGroupByHit[j]->group.end();
                       ++hit_it) {
                    mergeGroupByHit[i]->group.push_back(*hit_it);
                    mergeGroupByHit[i]->smearIt = true;
                  }

                  // Step 2: iterate over all hits, replace mgbh[j] by mgbh[i] (so that nobody points to i)
                  MergeGroup* mgbhj = mergeGroupByHit[j];
                  for (int k = 0; k < nHits; ++k) {
                    if (mgbhj == mergeGroupByHit[k]) {
                      // Hit k also uses the same merge group, tell them to switch to mgbh[i]
                      mergeGroupByHit[k] = mergeGroupByHit[i];
                    }
                  }
                  mgbhj->smearIt = false;
                  mergeGroupByHit[i]->smearIt = true;

                  //  Step 3 would have been to delete mgbh[j]... however, we'll do that at the end anyway.
                  //  The key was to prevent mgbh[j] from being accessed further, and we have done that,
                  //  since now no mergeGroupByHit[] points to mgbhj any more.  Note that the above loop
                  //  also set mergeGroupByHit[i] = mergeGroupByHit[j], too.
                }
              }
            } else {
              // j is not merged.  Check if i is merged with another hit yet.
              //
              if (mergeGroupByHit[i] == nullptr) {
                // This is the first time we realized i is merged with any
                // other hit.  Create a new merge group for i and j
                mergeGroupByHit[i] = new MergeGroup();
                listOfMergeGroups.push_back(mergeGroupByHit[i]);  // keep track of it
                //
                // Add hit i as the first to its own merge group
                // (simHits[i] is a const pointer to PSimHit).
                mergeGroupByHit[i]->group.push_back(simHitIdPairs[i]);
                mergeGroupByHit[i]->smearIt = true;
              }
              //--- Add hit j as well
              mergeGroupByHit[i]->group.push_back(simHitIdPairs[j]);
              mergeGroupByHit[i]->smearIt = true;

              mergeGroupByHit[j] = mergeGroupByHit[i];

            }  // --- end of else if ( j has merge group )

          }  //--- end of if (merged)

        }  //--- end of loop over j

        //--- At this point, there are two possibilities.  Either hit i
        //    was already chosen to be merged with some hit prior to it,
        //    or the loop over j found another merged hit.  In either
        //    case, if mergeGroupByHit[i] is empty, then the hit is
        //    unmerged.
        //
        if (mergeGroupByHit[i] == nullptr) {
          //--- Keep track of it.
          listOfUnmergedHits.push_back(simHitIdPairs[i]);
        }
      }  //--- end of loop over i
    }  // --- end of if (mergeHitsOn)
    else {
      // Now we've turned off hit merging, so all hits should be pushed
      // back to listOfUnmergedHits
      for (int i = 0; i < nHits; ++i) {
        listOfUnmergedHits.push_back(simHitIdPairs[i]);
      }
    }
  }  // --- end of if (nHits == 1) else {...}

  //--- We now have two lists: a list of hits that are unmerged, and
  //    the list of merge groups.  Process each separately.
  //
  product = processUnmergedHits(listOfUnmergedHits, product, pixelGeomDet, boundX, boundY, &randomEngine);

  product = processMergeGroups(listOfMergeGroups, product, pixelGeomDet, boundX, boundY, &randomEngine);

  //--- We're done with this det unit, and ought to clean up used
  //    memory.  We don't own the PSimHits, and the vector of
  //    listOfUnmergedHits simply goes out of scope.  However, we
  //    created the MergeGroups and thus we need to get rid of them.
  //
  for (auto mg_it = listOfMergeGroups.begin(); mg_it != listOfMergeGroups.end(); ++mg_it) {
    delete *mg_it;  // each MergeGroup is deleted; its ptrs to PSimHits we do not own...
  }

  return product;
}

//------------------------------------------------------------------------------
//   Smear one hit.  The main action is in here.
//------------------------------------------------------------------------------
FastSingleTrackerRecHit PixelTemplateSmearerBase::smearHit(const PSimHit& simHit,
                                                           const PixelGeomDetUnit* detUnit,
                                                           const double boundX,
                                                           const double boundY,
                                                           RandomEngineAndDistribution const* random) const {
  //--- At the beginning the position is the Local Point in the local pixel module reference frame
  //    same code as in PixelCPEBase
  //
  LocalVector localDir = simHit.momentumAtEntry();  // don't need .unit(), we will take the ratio
  float locx = localDir.x();
  float locy = localDir.y();
  float locz = localDir.z();

  //--- cotangent of local angles \alpha and \beta.
  //    alpha: angle with respect to local x axis in local (x,z) plane
  //    beta: angle with respect to local y axis in local (y,z) plane
  //
  float cotalpha = locx / locz;
  float cotbeta = locy / locz;

  //--- Save the original signs of cot\alpha and cot\beta
  int signOfCotalpha = (cotalpha < 0) ? -1 : 1;  // sign(cotalpha);
  int signOfCotbeta = (cotbeta < 0) ? -1 : 1;    // sign(cotbeta);
  //
  //--- Use absolute values to find the templates from the list
  cotalpha *= signOfCotalpha;  // = abs(cotalpha)
  cotbeta *= signOfCotbeta;    // = abs(cotbeta)

  LogDebug("SmearHit") << "LocalVector=" << locx << "," << locy << "," << locz << "   momentum=" << localDir.mag()
                       << "   cotalpha=" << cotalpha << ",  cotbeta=" << cotbeta;

  const PixelTopology* theSpecificTopology = &(detUnit->specificType().specificTopology());

  const int nrows = theSpecificTopology->nrows();
  const int ncolumns = theSpecificTopology->ncolumns();

  const Local3DPoint lp = simHit.localPosition();
  //Transform local position to measurement position
  const MeasurementPoint mp = theSpecificTopology->measurementPosition(lp);
  float mpy = mp.y();
  float mpx = mp.x();
  //Get the center of the struck pixel in measurement position
  float pixelCenterY = 0.5 + (int)mpy;
  float pixelCenterX = 0.5 + (int)mpx;

  const MeasurementPoint mpCenter(pixelCenterX, pixelCenterY);
  //Transform the center of the struck pixel back into local position
  const Local3DPoint lpCenter = theSpecificTopology->localPosition(mpCenter);

  //Get the relative position of struck point to the center of the struck pixel
  float xtrk = lp.x() - lpCenter.x();
  float ytrk = lp.y() - lpCenter.y();
  //Pixel Y, X pitch
  const float ysize = {0.015}, xsize = {0.01};
  //Variables for SiPixelTemplate input, see SiPixelTemplate reco
  float yhit = 20. + 8. * (ytrk / ysize);
  float xhit = 20. + 8. * (xtrk / xsize);
  int ybin = (int)yhit;
  int xbin = (int)xhit;
  float yfrac = yhit - (float)ybin;
  float xfrac = xhit - (float)xbin;
  //Protect againt ybin, xbin being outside of range [0-39]  // &&& Why limit of 39?
  if (ybin < 0)
    ybin = 0;
  if (ybin > 39)
    ybin = 39;
  if (xbin < 0)
    xbin = 0;
  if (xbin > 39)
    xbin = 39;

  int ID = templateId;
  if (templateId == -1) {
    // We have loaded the whole template set from the DB,
    // so ask the DB object to find us the right one.
    ID = pixelTemplateDBObject_->getTemplateID(detUnit->geographicalId());  // need uint32_t detid
    //				    theDetParam.theDet->geographicalId());
  }

  //--- Make the template object
  SiPixelTemplate templ(*thePixelTempRef);

  //--- Produce the template that corresponds to our local angles.
  templ.interpolate(ID, cotalpha, cotbeta);

  //Variables for SiPixelTemplate output
  //qBin -- normalized pixel charge deposition
  float qbin_frac[4];
  //Single pixel cluster projection possibility
  float ny1_frac, ny2_frac, nx1_frac, nx2_frac;
  bool singlex = false, singley = false;
  templ.qbin_dist(ID, cotalpha, cotbeta, qbin_frac, ny1_frac, ny2_frac, nx1_frac, nx2_frac);
  int nqbin;

  double xsizeProbability = random->flatShoot();
  double ysizeProbability = random->flatShoot();
  bool hitbigx = theSpecificTopology->isItBigPixelInX((int)mpx);  // pixel we hit in x
  bool hitbigy = theSpecificTopology->isItBigPixelInY((int)mpy);  // pixel we hit in y

  if (hitbigx)
    if (xsizeProbability < nx2_frac)
      singlex = true;
    else
      singlex = false;
  else if (xsizeProbability < nx1_frac)
    singlex = true;
  else
    singlex = false;

  if (hitbigy)
    if (ysizeProbability < ny2_frac)
      singley = true;
    else
      singley = false;
  else if (ysizeProbability < ny1_frac)
    singley = true;
  else
    singley = false;

  // random multiplicity for alpha and beta
  double qbinProbability = random->flatShoot();
  for (int i = 0; i < 4; ++i) {
    nqbin = i;
    if (qbinProbability < qbin_frac[i]) {
      break;
    }
  }

  //Store interpolated pixel cluster profile
  //BYSIZE, BXSIZE, const definition from SiPixelTemplate
  float ytempl[41][BYSIZE] = {{0}}, xtempl[41][BXSIZE] = {{0}};
  templ.ytemp(0, 40, ytempl);
  templ.xtemp(0, 40, xtempl);

  std::vector<double> ytemp(BYSIZE);
  for (int i = 0; i < BYSIZE; ++i) {
    ytemp[i] = (1. - yfrac) * ytempl[ybin][i] + yfrac * ytempl[ybin + 1][i];
  }

  std::vector<double> xtemp(BXSIZE);
  for (int i = 0; i < BXSIZE; ++i) {
    xtemp[i] = (1. - xfrac) * xtempl[xbin][i] + xfrac * xtempl[xbin + 1][i];
  }

  //Pixel readout threshold
  const float qThreshold = templ.s50() * 2.0;

  //Cut away pixels below readout threshold
  //For cluster lengths calculation
  int offsetX1 = 0, offsetX2 = 0, offsetY1 = 0, offsetY2 = 0;
  int firstY, lastY, firstX, lastX;
  for (firstY = 0; firstY < BYSIZE; ++firstY) {
    bool yCluster = ytemp[firstY] > qThreshold;
    if (yCluster) {
      offsetY1 = BHY - firstY;
      break;
    }
  }
  for (lastY = firstY; lastY < BYSIZE; ++lastY) {
    bool yCluster = ytemp[lastY] > qThreshold;
    if (!yCluster) {
      lastY = lastY - 1;
      offsetY2 = lastY - BHY;
      break;
    }
  }

  for (firstX = 0; firstX < BXSIZE; ++firstX) {
    bool xCluster = xtemp[firstX] > qThreshold;
    if (xCluster) {
      offsetX1 = BHX - firstX;
      break;
    }
  }
  for (lastX = firstX; lastX < BXSIZE; ++lastX) {
    bool xCluster = xtemp[lastX] > qThreshold;
    if (!xCluster) {
      lastX = lastX - 1;
      offsetX2 = lastX - BHX;
      break;
    }
  }

  //--- Prepare to return results
  Local3DPoint thePosition;
  double theShiftInX;
  double theShiftInY;
  double theShiftInZ;
  LocalError theError;
  double theErrorX;
  double theErrorY;

  //------------------------------
  //  Check if the cluster is near an edge.  If it protrudes
  //  outside the edge of the sensor, the truncate it and it will
  //  get significantly messed up.
  //------------------------------
  bool edge, edgex, edgey;
  //  bool bigx, bigy;

  int firstPixelInX = (int)mpx - offsetX1;
  int firstPixelInY = (int)mpy - offsetY1;
  int lastPixelInX = (int)mpx + offsetX2;
  int lastPixelInY = (int)mpy + offsetY2;
  firstPixelInX = (firstPixelInX >= 0) ? firstPixelInX : 0;
  firstPixelInY = (firstPixelInY >= 0) ? firstPixelInY : 0;
  lastPixelInX = (lastPixelInX < nrows) ? lastPixelInX : nrows - 1;
  lastPixelInY = (lastPixelInY < ncolumns) ? lastPixelInY : ncolumns - 1;

  edgex = theSpecificTopology->isItEdgePixelInX(firstPixelInX) || theSpecificTopology->isItEdgePixelInX(lastPixelInX);
  edgey = theSpecificTopology->isItEdgePixelInY(firstPixelInY) || theSpecificTopology->isItEdgePixelInY(lastPixelInY);
  edge = edgex || edgey;

  //  bigx = theSpecificTopology->isItBigPixelInX( firstPixelInX ) || theSpecificTopology->isItBigPixelInX( lastPixelInX );
  //  bigy = theSpecificTopology->isItBigPixelInY( firstPixelInY ) || theSpecificTopology->isItBigPixelInY( lastPixelInY );
  bool hasBigPixelInX = theSpecificTopology->containsBigPixelInX(firstPixelInX, lastPixelInX);
  bool hasBigPixelInY = theSpecificTopology->containsBigPixelInY(firstPixelInY, lastPixelInY);

  //Variables for SiPixelTemplate pixel hit error output
  float sigmay, sigmax, sy1, sy2, sx1, sx2;
  templ.temperrors(ID,
                   cotalpha,
                   cotbeta,
                   nqbin,  // inputs
                   sigmay,
                   sigmax,
                   sy1,
                   sy2,
                   sx1,
                   sx2  // outputs
  );

  if (edge) {
    if (edgex && !edgey) {
      theErrorX = 23.0 * microntocm;
      theErrorY = 39.0 * microntocm;
    } else if (!edgex && edgey) {
      theErrorX = 24.0 * microntocm;
      theErrorY = 96.0 * microntocm;
    } else {
      theErrorX = 31.0 * microntocm;
      theErrorY = 90.0 * microntocm;
    }
  } else {
    if (singlex) {
      if (hitbigx) {
        theErrorX = sx2 * microntocm;
      } else {
        theErrorX = sx1 * microntocm;
      }
    } else {
      theErrorX = sigmax * microntocm;
    }
    if (singley) {
      if (hitbigy) {
        theErrorY = sy2 * microntocm;
      } else {
        theErrorY = sy1 * microntocm;
      }
    } else {
      theErrorY = sigmay * microntocm;
    }
  }

  //add misalignment error
  const TrackerGeomDet* misalignmentDetUnit = getMisalignedGeometry().idToDet(detUnit->geographicalId());
  const LocalError& alignmentError = misalignmentDetUnit->localAlignmentError();
  if (alignmentError.valid()) {
    theError = LocalError(
        theErrorX * theErrorX + alignmentError.xx(), alignmentError.xy(), theErrorY * theErrorY + alignmentError.yy());
  } else {
    theError = LocalError(theErrorX * theErrorX, 0.0, theErrorY * theErrorY);
  }

  // Local Error is 2D: (xx,xy,yy), square of sigma in first an third position
  // as for resolution matrix

  //--- Next, we need to generate the smeared position.  First we need to figure
  //    out which kind of histograms we are supposed to use for this particular hit.
  //    These are pointers to the set of histograms used to generate the rec hit
  //    positions.  (We need to handle X and Y separately.)
  shared_ptr<PixelResolutionHistograms> resHistsX = nullptr;
  shared_ptr<PixelResolutionHistograms> resHistsY = nullptr;

  if (edge) {
    resHistsX = resHistsY = theEdgePixelResolutions;
    singlex = singley = false;  // no single resolutions for Edge
  } else {
    //--- Decide resolution histogram set for X
    if ((singlex && hitbigx) || (isBarrel && hasBigPixelInX)) {
      resHistsX = theBigPixelResolutions;
    } else {
      resHistsX = theRegularPixelResolutions;
    }
    //--- Decide resolution histogram set for Y
    if ((singley && hitbigy) || (isBarrel && hasBigPixelInY)) {
      resHistsY = theBigPixelResolutions;
    } else {
      resHistsY = theRegularPixelResolutions;
    }
  }

  //--- Get generators, separately for X and for Y.
  const SimpleHistogramGenerator* xgen = resHistsX->getGeneratorX(cotalpha, cotbeta, nqbin, singlex);
  const SimpleHistogramGenerator* ygen = resHistsY->getGeneratorY(cotalpha, cotbeta, nqbin, singley);

  //--- Check if we found a histogram.  If nullptr, then throw up.
  if (!xgen || !ygen) {
    throw cms::Exception("FastSimulation/TrackingRecHitProducer")
        << "Histogram (cot\alpha=" << cotalpha << ", cot\beta=" << cotbeta << ", nQbin=" << nqbin
        << ") was not found for PixelTemplateSmearer. Check if the smearing resolution histogram exists.";
  }

  //--- Smear the hit Position.  We do it in the do-while loop in order to
  //--- allow multiple tries, in case we generate a rec hit which is outside
  //--- of the boundaries of the sensor.
  unsigned int retry = 0;

  do {
    // Generate the position (x,y of the rec hit).
    theShiftInX = xgen->generate(random);
    theShiftInY = ygen->generate(random);

    // Now multiply by the sign of the cotangent of appropriate angle
    theShiftInX *= signOfCotalpha;
    theShiftInY *= signOfCotbeta;

    theShiftInZ = 0.0;  // set to the mid-plane of the sensor.

    thePosition = Local3DPoint(simHit.localPosition().x() + theShiftInX,
                               simHit.localPosition().y() + theShiftInY,
                               simHit.localPosition().z() + theShiftInZ);
    retry++;
    if (retry > 10) {
      // If we tried to generate thePosition, and it's out of the bounds
      // for 10 times, then take and return the simHit's location.
      thePosition = Local3DPoint(simHit.localPosition().x(), simHit.localPosition().y(), simHit.localPosition().z());
      break;
    }
  } while (fabs(thePosition.x()) > boundX || fabs(thePosition.y()) > boundY);

  FastSingleTrackerRecHit recHit(thePosition, theError, *detUnit, fastTrackerRecHitType::siPixel);
  return recHit;
}

//------------------------------------------------------------------------------
//   Smear all umerged hits on this DetUnit
//------------------------------------------------------------------------------
TrackingRecHitProductPtr PixelTemplateSmearerBase::processUnmergedHits(
    std::vector<TrackingRecHitProduct::SimHitIdPair>& unmergedHits,
    TrackingRecHitProductPtr product,
    const PixelGeomDetUnit* detUnit,
    const double boundX,
    const double boundY,
    RandomEngineAndDistribution const* random) const {
  for (auto simHitIdPair : unmergedHits) {
    FastSingleTrackerRecHit recHit = smearHit(*simHitIdPair.second, detUnit, boundX, boundY, random);
    product->addRecHit(recHit, {simHitIdPair});
  }
  return product;
}

//------------------------------------------------------------------------------
//   Smear all MERGED hits on this DetUnit
//------------------------------------------------------------------------------
TrackingRecHitProductPtr PixelTemplateSmearerBase::processMergeGroups(std::vector<MergeGroup*>& mergeGroups,
                                                                      TrackingRecHitProductPtr product,
                                                                      const PixelGeomDetUnit* detUnit,
                                                                      const double boundX,
                                                                      const double boundY,
                                                                      RandomEngineAndDistribution const* random) const {
  for (auto mg_it = mergeGroups.begin(); mg_it != mergeGroups.end(); ++mg_it) {
    if ((*mg_it)->smearIt) {
      FastSingleTrackerRecHit recHit = smearMergeGroup(*mg_it, detUnit, boundX, boundY, random);
      product->addRecHit(recHit, (*mg_it)->group);
    }
  }
  return product;
}

//------------------------------------------------------------------------------
//   Smear all hits MERGED together.  This is called a MergeGroup.
//------------------------------------------------------------------------------
FastSingleTrackerRecHit PixelTemplateSmearerBase::smearMergeGroup(MergeGroup* mg,
                                                                  const PixelGeomDetUnit* detUnit,
                                                                  const double boundX,
                                                                  const double boundY,
                                                                  RandomEngineAndDistribution const* random) const {
  float loccx = 0;
  float loccy = 0;
  float loccz = 0;
  float nHit = 0;
  float locpx = 0;
  float locpy = 0;
  float locpz = 0;

  for (auto hit_it = mg->group.begin(); hit_it != mg->group.end(); ++hit_it) {
    const PSimHit simHit = *hit_it->second;
    //getting local momentum and adding all of the hits' momentums up
    LocalVector localDir = simHit.momentumAtEntry().unit();
    loccx += localDir.x();
    loccy += localDir.y();
    loccz += localDir.z();
    //getting local position and adding all of the hits' positions up
    const Local3DPoint lpos = simHit.localPosition();
    locpx += lpos.x();
    locpy += lpos.y();
    locpz += lpos.z();
    //counting how many sim hits are in the merge group
    nHit += 1;
  }
  //averaging the momentums by diving momentums added up/number of hits
  float locx = loccx / nHit;
  float locy = loccy / nHit;
  float locz = loccz / nHit;

  //--- cotangent of local angles \alpha and \beta.
  //    alpha: angle with respect to local x axis in local (x,z) plane
  //    beta: angle with respect to local y axis in local (y,z) plane
  //
  float cotalpha = locx / locz;
  float cotbeta = locy / locz;

  //--- Save the original signs of cot\alpha and cot\beta
  int signOfCotalpha = (cotalpha < 0) ? -1 : 1;  // sign(cotalpha);
  int signOfCotbeta = (cotbeta < 0) ? -1 : 1;    // sign(cotbeta);
  //
  //--- Use absolute values to find the templates from the list
  cotalpha *= signOfCotalpha;  // = abs(cotalpha)
  cotbeta *= signOfCotbeta;    // = abs(cotbeta)

  float lpx = locpx / nHit;
  float lpy = locpy / nHit;
  float lpz = locpz / nHit;

  //Get the relative position of struck point to the center of the struck pixel
  float xtrk = lpx;
  float ytrk = lpy;
  //Pixel Y, X pitch
  const float ysize = {0.015}, xsize = {0.01};
  //Variables for SiPixelTemplate input, see SiPixelTemplate reco
  float yhit = 20. + 8. * (ytrk / ysize);
  float xhit = 20. + 8. * (xtrk / xsize);
  int ybin = (int)yhit;
  int xbin = (int)xhit;
  float yfrac = yhit - (float)ybin;
  float xfrac = xhit - (float)xbin;
  // Protect againt ybin, xbin being outside of range [0-39]
  if (ybin < 0)
    ybin = 0;
  if (ybin > 39)
    ybin = 39;
  if (xbin < 0)
    xbin = 0;
  if (xbin > 39)
    xbin = 39;

  int ID = templateId;
  if (templateId == -1) {
    // We have loaded the whole template set from the DB,
    // so ask the DB object to find us the right one.
    ID = pixelTemplateDBObject_->getTemplateID(detUnit->geographicalId());  // need uint32_t detid
    //				    theDetParam.theDet->geographicalId());
  }

  //--- Make the template object
  SiPixelTemplate templ(*thePixelTempRef);

  //--- Produce the template that corresponds to our local angles.
  templ.interpolate(ID, cotalpha, cotbeta);

  // Variables for SiPixelTemplate output
  // qBin -- normalized pixel charge deposition
  float qbin_frac[4];
  // Single pixel cluster projection possibility
  float ny1_frac, ny2_frac, nx1_frac, nx2_frac;
  bool singlex = false, singley = false;
  templ.qbin_dist(ID, cotalpha, cotbeta, qbin_frac, ny1_frac, ny2_frac, nx1_frac, nx2_frac);
  int nqbin;

  //  double xsizeProbability = random->flatShoot();
  //double ysizeProbability = random->flatShoot();
  bool hitbigx = false;
  bool hitbigy = false;

  // random multiplicity for alpha and beta

  double qbinProbability = random->flatShoot();
  for (int i = 0; i < 4; ++i) {
    nqbin = i;
    if (qbinProbability < qbin_frac[i])
      break;
  }

  //Store interpolated pixel cluster profile
  //BYSIZE, BXSIZE, const definition from SiPixelTemplate
  float ytempl[41][BYSIZE] = {{0}}, xtempl[41][BXSIZE] = {{0}};
  templ.ytemp(0, 40, ytempl);
  templ.xtemp(0, 40, xtempl);

  std::vector<double> ytemp(BYSIZE);
  for (int i = 0; i < BYSIZE; ++i) {
    ytemp[i] = (1. - yfrac) * ytempl[ybin][i] + yfrac * ytempl[ybin + 1][i];
  }

  std::vector<double> xtemp(BXSIZE);
  for (int i = 0; i < BXSIZE; ++i) {
    xtemp[i] = (1. - xfrac) * xtempl[xbin][i] + xfrac * xtempl[xbin + 1][i];
  }

  //--- Prepare to return results
  Local3DPoint thePosition;
  double theShiftInX;
  double theShiftInY;
  double theShiftInZ;
  LocalError theError;
  double theErrorX;
  double theErrorY;

  //------------------------------
  //  Check if the cluster is near an edge.  If it protrudes
  //  outside the edge of the sensor, the truncate it and it will
  //  get significantly messed up.
  //------------------------------
  bool edge = false;
  bool edgex = false;
  bool edgey = false;

  //Variables for SiPixelTemplate pixel hit error output
  float sigmay, sigmax, sy1, sy2, sx1, sx2;
  templ.temperrors(ID,
                   cotalpha,
                   cotbeta,
                   nqbin,  // inputs
                   sigmay,
                   sigmax,
                   sy1,
                   sy2,
                   sx1,
                   sx2);  // outputs

  // define private mebers --> Errors
  if (edge) {
    if (edgex && !edgey) {
      theErrorX = 23.0 * microntocm;
      theErrorY = 39.0 * microntocm;
    } else if (!edgex && edgey) {
      theErrorX = 24.0 * microntocm;
      theErrorY = 96.0 * microntocm;
    } else {
      theErrorX = 31.0 * microntocm;
      theErrorY = 90.0 * microntocm;
    }

  } else {
    if (singlex) {
      if (hitbigx) {
        theErrorX = sx2 * microntocm;
      } else {
        theErrorX = sx1 * microntocm;
      }
    } else {
      theErrorX = sigmax * microntocm;
    }

    if (singley) {
      if (hitbigy) {
        theErrorY = sy2 * microntocm;
      } else {
        theErrorY = sy1 * microntocm;
      }
    } else {
      theErrorY = sigmay * microntocm;
    }
  }

  theError = LocalError(theErrorX * theErrorX, 0., theErrorY * theErrorY);

  unsigned int retry = 0;
  do {
    const SimpleHistogramGenerator* xgen =
        new SimpleHistogramGenerator((TH1F*)theMergedPixelResolutionXFile->Get("th1x"));
    const SimpleHistogramGenerator* ygen =
        new SimpleHistogramGenerator((TH1F*)theMergedPixelResolutionYFile->Get("th1y"));

    // Generate the position (x,y of the rec hit).
    theShiftInX = xgen->generate(random);
    theShiftInY = ygen->generate(random);

    // Now multiply by the sign of the cotangent of appropriate angle
    theShiftInX *= signOfCotalpha;
    theShiftInY *= signOfCotbeta;

    theShiftInZ = 0.0;  // set at the centre of the active area

    thePosition = Local3DPoint(lpx + theShiftInX, lpy + theShiftInY, lpz + theShiftInZ);

    retry++;
    if (retry > 10) {
      // If we tried to generate thePosition, and it's out of the bounds
      // for 10 times, then take and return the simHit's location.
      thePosition = Local3DPoint(lpx, lpy, lpz);
      break;
    }
  } while (fabs(thePosition.x()) > boundX || fabs(thePosition.y()) > boundY);

  FastSingleTrackerRecHit recHit(thePosition, theError, *detUnit, fastTrackerRecHitType::siPixel);
  return recHit;
}

bool PixelTemplateSmearerBase::hitsMerge(const PSimHit& simHit1, const PSimHit& simHit2) const {
  LocalVector localDir = simHit1.momentumAtEntry().unit();
  float locy1 = localDir.y();
  float locz1 = localDir.z();
  float cotbeta = locy1 / locz1;
  float loceta = fabs(-log((double)(-cotbeta + sqrt((double)(1. + cotbeta * cotbeta)))));

  const Local3DPoint lp1 = simHit1.localPosition();
  const Local3DPoint lp2 = simHit2.localPosition();
  float lpy1 = lp1.y();
  float lpx1 = lp1.x();
  float lpy2 = lp2.y();
  float lpx2 = lp2.x();
  float locdis = 10000. * sqrt(pow(lpx1 - lpx2, 2) + pow(lpy1 - lpy2, 2));
  TH2F* probhisto = (TH2F*)theMergingProbabilityFile->Get("h2bc");
  float prob =
      probhisto->GetBinContent(probhisto->GetXaxis()->FindFixBin(locdis), probhisto->GetYaxis()->FindFixBin(loceta));
  return prob > 0;
}