VertexTrackMatcher.cxx

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// Copyright 2019-2020 CERN and copyright holders of ALICE O2.
// See https://alice-o2.web.cern.ch/copyright for details of the copyright holders.
// All rights not expressly granted are reserved.
//
// This software is distributed under the terms of the GNU General Public
// License v3 (GPL Version 3), copied verbatim in the file "COPYING".
//
// In applying this license CERN does not waive the privileges and immunities
// granted to it by virtue of its status as an Intergovernmental Organization
// or submit itself to any jurisdiction.
 
 
#include "DataFormatsGlobalTracking/RecoContainerCreateTracksVariadic.h"
#include "DetectorsVertexing/VertexTrackMatcher.h"
#include "ITSMFTBase/DPLAlpideParam.h"
#include <unordered_map>
#include <numeric>
 
using namespace o2::vertexing;
 
void VertexTrackMatcher::process(const o2::globaltracking::RecoContainer& recoData,
                                 std::vector<VTIndex>& trackIndex,
                                 std::vector<VRef>& vtxRefs)
{
  auto vertices = recoData.getPrimaryVertices();
  auto v2tfitIDs = recoData.getPrimaryVertexContributors();
  auto v2tfitRefs = recoData.getPrimaryVertexContributorsRefs();
  const auto& PVParams = o2::vertexing::PVertexerParams::Instance();
 
  int nv = vertices.size(), nv1 = nv + 1;
  TmpMap tmpMap(nv1);
  auto& orphans = tmpMap.back(); // in the last element we store unassigned track indices
 
  // register vertex contributors
  std::unordered_map<GIndex, bool> vcont;
  std::vector<VtxTBracket> vtxOrdBrack; // vertex indices and brackets sorted in tmin
  float maxVtxSpan = 0;
  for (int iv = 0; iv < nv; iv++) {
    int idMin = v2tfitRefs[iv].getFirstEntry(), idMax = idMin + v2tfitRefs[iv].getEntries();
    auto& vtxIds = tmpMap[iv]; // global IDs of contibuting tracks
    vtxIds.reserve(v2tfitRefs[iv].getEntries());
    for (int id = idMin; id < idMax; id++) {
      auto gid = v2tfitIDs[id];
      vtxIds.emplace_back(gid).setPVContributor();
      vcont[gid] = true;
    }
    const auto& vtx = vertices[iv];
    const auto& vto = vtxOrdBrack.emplace_back(VtxTBracket{
      {float((vtx.getIRMin().differenceInBC(recoData.startIR) - 0.5f) * o2::constants::lhc::LHCBunchSpacingMUS - PVParams.timeMarginVertexTime),
       float((vtx.getIRMax().differenceInBC(recoData.startIR) + 0.5f) * o2::constants::lhc::LHCBunchSpacingMUS + PVParams.timeMarginVertexTime)},
      iv});
    if (vto.tBracket.delta() > maxVtxSpan) {
      maxVtxSpan = vto.tBracket.delta();
    }
  }
  // sort vertices in tmin
  std::sort(vtxOrdBrack.begin(), vtxOrdBrack.end(), [](const VtxTBracket& a, const VtxTBracket& b) { return a.tBracket.getMin() < b.tBracket.getMin(); });
 
  extractTracks(recoData, vcont); // extract all track t-brackets, excluding those tracks which contribute to vertex (already attached)
 
  int ivStart = 0, nAssigned = 0, nAmbiguous = 0;
  std::vector<int> vtxList; // list of vertices which match to checked track
  for (const auto& tro : mTBrackets) {
    vtxList.clear();
    for (int iv = ivStart; iv < nv; iv++) {
      const auto& vto = vtxOrdBrack[iv];
      auto res = tro.tBracket.isOutside(vto.tBracket);
      if (res == TBracket::Below) {                                       // vertex preceeds the track
        if (tro.tBracket.getMin() > vto.tBracket.getMin() + maxVtxSpan) { // all following vertices will be preceeding all following tracks times
          ivStart = iv + 1;
        }
        continue; // following vertex with longer span might still match this track
      }
      if (res == TBracket::Above) { // track preceeds the vertex, so will preceed also all following vertices
        break;
      }
      // track matches to vertex, register
      vtxList.push_back(vto.origID); // flag matching vertex
    }
    if (vtxList.size()) {
      nAssigned++;
      bool ambig = vtxList.size() > 1;
      for (auto v : vtxList) {
        auto& ref = tmpMap[v].emplace_back(tro.origID);
        if (ambig) {
          ref.setAmbiguous();
        }
      }
      if (ambig) { // did track match to multiple vertices?
        nAmbiguous++;
      }
    } else {
      orphans.emplace_back(tro.origID); // register unassigned track
    }
  }
 
  // build final vector of global indices
  trackIndex.clear();
  vtxRefs.clear();
  static size_t logCounter = 0;
  bool logVertices = mPrescaleLogs > 0 ? (logCounter % mPrescaleLogs) == 0 : true;
  for (int iv = 0; iv < nv1; iv++) {
    auto& trvec = tmpMap[iv];
    // sort entries in each vertex track indices list according to the source
    std::sort(trvec.begin(), trvec.end(), [](VTIndex a, VTIndex b) { return a.getSource() < b.getSource(); });
 
    auto entry0 = trackIndex.size(); // start of entries for this vertex
    auto& vr = vtxRefs.emplace_back();
    vr.setVtxID(iv < nv ? iv : -1); // flag table for unassigned tracks by VtxID = -1
    int oldSrc = -1;
    for (const auto gid0 : trvec) {
      int src = gid0.getSource();
      while (oldSrc < src) {
        oldSrc++;
        vr.setFirstEntryOfSource(oldSrc, trackIndex.size()); // register start of new source
      }
      trackIndex.push_back(gid0);
    }
    while (++oldSrc < GIndex::NSources) {
      vr.setFirstEntryOfSource(oldSrc, trackIndex.size());
    }
    vr.setEnd(trackIndex.size());
    if (logVertices) {
      LOG(info) << vr;
    }
  }
  logCounter++;
  LOG(info) << "Assigned " << nAssigned << " (" << nAmbiguous << " ambiguously) out of " << mTBrackets.size() << " non-contributor tracks + " << vcont.size() << " contributors";
}
 
//________________________________________________________
void VertexTrackMatcher::extractTracks(const o2::globaltracking::RecoContainer& data, const std::unordered_map<GIndex, bool>& vcont)
{
  // Scan all inputs and create tracks
  mTBrackets.clear();
  float itsBias = 0.5 * mITSROFrameLengthMUS + o2::itsmft::DPLAlpideParam<o2::detectors::DetID::ITS>::Instance().roFrameBiasInBC * o2::constants::lhc::LHCBunchSpacingNS * 1e-3; // ITS time is supplied in \mus as beginning of ROF
  float mftBias = 0.5 * mMFTROFrameLengthMUS + o2::itsmft::DPLAlpideParam<o2::detectors::DetID::MFT>::Instance().roFrameBiasInBC * o2::constants::lhc::LHCBunchSpacingNS * 1e-3; // MFT time is supplied in \mus as beginning of ROF
  auto creator = [this, itsBias, mftBias, &vcont](auto& _tr, GIndex _origID, float t0, float terr) {
    if constexpr (!(isMFTTrack<decltype(_tr)>() || isMCHTrack<decltype(_tr)>() || isGlobalFwdTrack<decltype(_tr)>())) { // Skip test for forward tracks; do not contribute to vertex
      if (vcont.find(_origID) != vcont.end()) {                                                                         // track is contributor to vertex, already accounted
        return true;
      }
    }
    const auto& PVParams = o2::vertexing::PVertexerParams::Instance();
    if constexpr (isTPCTrack<decltype(_tr)>()) {
      // unconstrained TPC track, with t0 = TrackTPC.getTime0+0.5*(DeltaFwd-DeltaBwd) and terr = 0.5*(DeltaFwd+DeltaBwd) in TimeBins
      t0 *= this->mTPCBin2MUS;
      t0 -= this->mTPCTDriftOffset;
      terr *= this->mTPCBin2MUS;
    } else if constexpr (isITSTrack<decltype(_tr)>()) {
      t0 += itsBias;
      terr *= this->mITSROFrameLengthMUS;               // error is supplied as a half-ROF duration, convert to \mus
    } else if constexpr (isMFTTrack<decltype(_tr)>()) { // Same for MFT
      t0 += mftBias;
      terr *= this->mMFTROFrameLengthMUS;
    } else if constexpr (!(isMCHTrack<decltype(_tr)>() || isGlobalFwdTrack<decltype(_tr)>())) {
      // for all other tracks the time is in \mus with gaussian error
      terr *= PVParams.nSigmaTimeTrack; // gaussian errors must be scaled by requested n-sigma
    }
 
    terr += PVParams.timeMarginTrackTime;
    mTBrackets.emplace_back(TrackTBracket{{t0 - terr, t0 + terr}, _origID});
 
    if constexpr (isGlobalFwdTrack<decltype(_tr)>() || isMFTTrack<decltype(_tr)>()) {
      return false;
    }
    return true;
  };
 
  data.createTracksVariadic(creator);
 
  // add non-tracks
  unsigned int cntEMC = 0, cntPHS = 0, cntCPV = 0, cntFT0 = 0, cntFV0 = 0, cntFDD = 0;
  for (const auto& trig : data.getEMCALTriggers()) {
    auto t = trig.getBCData().differenceInBCMUS(data.startIR);
    mTBrackets.emplace_back(TrackTBracket{{t, t}, GIndex{cntEMC++, GIndex::EMC}});
  }
  for (const auto& trig : data.getPHOSTriggers()) {
    auto t = trig.getBCData().differenceInBCMUS(data.startIR);
    mTBrackets.emplace_back(TrackTBracket{{t, t}, GIndex{cntPHS++, GIndex::PHS}});
  }
  for (const auto& trig : data.getPHOSTriggers()) {
    auto t = trig.getBCData().differenceInBCMUS(data.startIR);
    mTBrackets.emplace_back(TrackTBracket{{t, t}, GIndex{cntCPV++, GIndex::CPV}});
  }
  for (const auto& rec : data.getFT0RecPoints()) {
    auto t = rec.getInteractionRecord().differenceInBCMUS(data.startIR);
    mTBrackets.emplace_back(TrackTBracket{{t, t}, GIndex{cntFT0++, GIndex::FT0}});
  }
  for (const auto& rec : data.getFV0RecPoints()) {
    auto t = rec.getInteractionRecord().differenceInBCMUS(data.startIR);
    mTBrackets.emplace_back(TrackTBracket{{t, t}, GIndex{cntFV0++, GIndex::FV0}});
  }
  for (const auto& rec : data.getFDDRecPoints()) {
    auto t = rec.getInteractionRecord().differenceInBCMUS(data.startIR);
    mTBrackets.emplace_back(TrackTBracket{{t, t}, GIndex{cntFDD++, GIndex::FDD}});
  }
 
  // sort in increasing min.time
  std::sort(mTBrackets.begin(), mTBrackets.end(), [](const TrackTBracket& a, const TrackTBracket& b) { return a.tBracket.getMin() < b.tBracket.getMin(); });
 
  LOG(info) << "collected " << mTBrackets.size() << " non-contributor and " << vcont.size() << " contributor seeds";
}