TripletFinder.cxx

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#include "larreco/SpacePointSolver/TripletFinder.h"

#include "art/Framework/Services/Registry/ServiceHandle.h"

namespace reco3d
{
  // -------------------------------------------------------------------------
  TripletFinder::TripletFinder(const std::vector<art::Ptr<recob::Hit>>& xhits,
                               const std::vector<art::Ptr<recob::Hit>>& uhits,
                               const std::vector<art::Ptr<recob::Hit>>& vhits,
                               const std::vector<raw::ChannelID_t>& xbad,
                               const std::vector<raw::ChannelID_t>& ubad,
                               const std::vector<raw::ChannelID_t>& vbad,
                               double distThresh, double distThreshDrift,
                               double xhitOffset)
    : geom(art::ServiceHandle<geo::Geometry>()->provider()),
      detprop(art::ServiceHandle<detinfo::DetectorPropertiesService>()->provider()),
      fDistThresh(distThresh),
      fDistThreshDrift(distThreshDrift),
      fXHitOffset(xhitOffset)
  {
    FillHitMap(xhits, fX_by_tpc);
    FillHitMap(uhits, fU_by_tpc);
    FillHitMap(vhits, fV_by_tpc);

    FillBadMap(xbad, fXbad_by_tpc);
    FillBadMap(ubad, fUbad_by_tpc);
    FillBadMap(vbad, fVbad_by_tpc);
  }

  // -------------------------------------------------------------------------
  void TripletFinder::
  FillHitMap(const std::vector<art::Ptr<recob::Hit>>& hits,
             std::map<geo::TPCID, std::vector<HitOrChan>>& out)
  {
    for(const art::Ptr<recob::Hit>& hit: hits){
      for(geo::TPCID tpc: geom->ROPtoTPCs(geom->ChannelToROP(hit->Channel()))){
        double xpos = 0;
        for(geo::WireID wire: geom->ChannelToWire(hit->Channel())){
          if(geo::TPCID(wire) == tpc){
            xpos = detprop->ConvertTicksToX(hit->PeakTime(), wire);
            if (geom->SignalType(wire) == geo::kCollection) xpos += fXHitOffset;
          }
        }

        out[tpc].emplace_back(hit.get(), xpos);
      }
    }
    for(auto& it: out)
      std::sort(it.second.begin(), it.second.end(),
                [](auto a, auto b){return a.xpos < b.xpos;});
  }

  // -------------------------------------------------------------------------
  void TripletFinder::
  FillBadMap(const std::vector<raw::ChannelID_t>& bads,
             std::map<geo::TPCID, std::vector<raw::ChannelID_t>>& out)
  {
    for(raw::ChannelID_t chan: bads){
      for(geo::TPCID tpc: geom->ROPtoTPCs(geom->ChannelToROP(chan))){
        out[tpc].push_back(chan);
      }
    }
  }

  // -------------------------------------------------------------------------
  class IntersectionCache
  {
  public:
    IntersectionCache(geo::TPCID tpc)
      : geom(art::ServiceHandle<geo::Geometry>()->provider()),
        fTPC(tpc)
    {
    }

    bool operator()(raw::ChannelID_t a, raw::ChannelID_t b,
                    geo::WireIDIntersection& pt)
    {
      const auto key = std::make_pair(a, b);

      auto it = fMap.find(key);
      if(it != fMap.end()){
        pt = fPtMap[key];
        return it->second;
      }

      const bool res = ISect(a, b, pt);
      fMap.insert({key, res});
      fPtMap.insert({key, pt});
      return res;
    }

  protected:
    bool ISect(raw::ChannelID_t chanA, raw::ChannelID_t chanB,
               geo::WireIDIntersection& pt) const
    {
      for(geo::WireID awire: geom->ChannelToWire(chanA)){
        if(geo::TPCID(awire) != fTPC) continue;
        for(geo::WireID bwire: geom->ChannelToWire(chanB)){
          if(geo::TPCID(bwire) != fTPC) continue;

          if(geom->WireIDsIntersect(awire, bwire, pt)) return true;
        }
      }

      return false;
    }

    const geo::GeometryCore* geom;

    std::map<std::pair<raw::ChannelID_t, raw::ChannelID_t>, bool> fMap;
    std::map<std::pair<raw::ChannelID_t, raw::ChannelID_t>, geo::WireIDIntersection> fPtMap;

    geo::TPCID fTPC;
  };

  // -------------------------------------------------------------------------
  bool TripletFinder::CloseDrift(double xa, double xb) const
  {
    return fabs(xa-xb) < fDistThreshDrift;
  }

  // -------------------------------------------------------------------------
  bool TripletFinder::CloseSpace(geo::WireIDIntersection ra,
                                 geo::WireIDIntersection rb) const
  {
    const TVector3 pa(ra.y, ra.z, 0);
    const TVector3 pb(rb.y, rb.z, 0);

    return (pa-pb).Mag() < fDistThresh;
  }

  bool LessThanXHit(const ChannelDoublet& a, const ChannelDoublet& b)
  {
    // Make sure the bad hits get sorted too
    if(a.a.hit == 0 && b.a.hit == 0) return a.a.chan < b.a.chan;
    // But mostly just order the real hits (in some arbitrary order)
    return a.a.hit < b.a.hit;
  }

  bool SameXHit(const ChannelDoublet& a, const ChannelDoublet& b)
  {
    if(a.a.hit == 0 && b.a.hit == 0) return a.a.chan == b.a.chan;
    return a.a.hit == b.a.hit;
  }

  // -------------------------------------------------------------------------
  std::vector<HitTriplet> TripletFinder::Triplets()
  {
    std::vector<HitTriplet> ret;

    for(const auto& it: fX_by_tpc){
      const geo::TPCID& tpc = it.first;

      std::vector<ChannelDoublet> xus = DoubletsXU(tpc);
      std::vector<ChannelDoublet> xvs = DoubletsXV(tpc);

      // Cache to prevent repeating the same questions
      IntersectionCache isectUV(tpc);

      // For the efficient looping below to work we need to sort the doublet
      // lists so the X hits occur in the same order.
      std::sort(xus.begin(), xus.end(), LessThanXHit);
      std::sort(xvs.begin(), xvs.end(), LessThanXHit);

      auto xvit_begin = xvs.begin();

      int nxuv = 0;
      for(const ChannelDoublet& xu: xus){
        const HitOrChan& x = xu.a;
        const HitOrChan& u = xu.b;

        // Catch up until we're looking at the same X hit in XV
        while(xvit_begin != xvs.end() && LessThanXHit(*xvit_begin, xu)) ++xvit_begin;

        // Loop through all those matching hits
        for(auto xvit = xvit_begin; xvit != xvs.end() && SameXHit(*xvit, xu); ++xvit){
          const HitOrChan& v = xvit->b;

          // Only allow one bad channel per triplet
          if(!x.hit && !u.hit) continue;
          if(!x.hit && !v.hit) continue;
          if(!u.hit && !v.hit) continue;

          if(u.hit && v.hit && !CloseDrift(u.xpos, v.xpos)) continue;

          geo::WireIDIntersection ptUV;
          if(!isectUV(u.chan, v.chan, ptUV)) continue;

          if(!CloseSpace(xu.pt, xvit->pt) ||
             !CloseSpace(xu.pt, ptUV) ||
             !CloseSpace(xvit->pt, ptUV)) continue;

          double xavg = 0;
          int nx = 0;
          if(x.hit){xavg += x.xpos; ++nx;}
          if(u.hit){xavg += u.xpos; ++nx;}
          if(v.hit){xavg += v.xpos; ++nx;}
          xavg /= nx;

          const XYZ pt{xavg,
              (xu.pt.y + xvit->pt.y + ptUV.y)/3,
              (xu.pt.z + xvit->pt.z + ptUV.z)/3};

          ret.emplace_back(HitTriplet{x.hit, u.hit, v.hit, pt});
          ++nxuv;
        } // end for xv
      } // end for xu

      std::cout << tpc << " " << xus.size() << " XUs and " << xvs.size() << " XVs -> " << nxuv << " XUVs" << std::endl;

    } // end for tpc

    std::cout << ret.size() << " XUVs total" << std::endl;

    return ret;
  }

  // -------------------------------------------------------------------------
  std::vector<HitTriplet> TripletFinder::TripletsTwoView()
  {
    std::vector<HitTriplet> ret;

    for(const auto& it: fX_by_tpc){
      const geo::TPCID& tpc = it.first;

      std::vector<ChannelDoublet> xus = DoubletsXU(tpc);

      for(const ChannelDoublet& xu: xus){
        const HitOrChan& x = xu.a;
        const HitOrChan& u = xu.b;

        double xavg = x.xpos;
        int nx = 1;
        if(u.hit){xavg += u.xpos; ++nx;}
        xavg /= nx;

        const XYZ pt{xavg, xu.pt.y, xu.pt.z};

        ret.emplace_back(HitTriplet{x.hit, u.hit, 0, pt});
      } // end for xu
    } // end for tpc

    std::cout << ret.size() << " XUs total" << std::endl;

    return ret;
  }

  // -------------------------------------------------------------------------
  std::vector<ChannelDoublet> TripletFinder::DoubletsXU(geo::TPCID tpc)
  {
    std::vector<ChannelDoublet> ret = DoubletHelper(tpc, fX_by_tpc[tpc], fU_by_tpc[tpc], fUbad_by_tpc[tpc]);

    // Find X(bad)+U(good) doublets, have to flip them for the final result
    for(auto it: DoubletHelper(tpc, fU_by_tpc[tpc], {}, fXbad_by_tpc[tpc])){
      ret.push_back({it.b, it.a, it.pt});
    }

    return ret;
  }

  // -------------------------------------------------------------------------
  std::vector<ChannelDoublet> TripletFinder::DoubletsXV(geo::TPCID tpc)
  {
    std::vector<ChannelDoublet> ret = DoubletHelper(tpc, fX_by_tpc[tpc], fV_by_tpc[tpc], fVbad_by_tpc[tpc]);

    // Find X(bad)+V(good) doublets, have to flip them for the final result
    for(auto it: DoubletHelper(tpc, fV_by_tpc[tpc], {}, fXbad_by_tpc[tpc])){
      ret.push_back({it.b, it.a, it.pt});
    }

    return ret;
  }

  // -------------------------------------------------------------------------
  std::vector<ChannelDoublet> TripletFinder::
  DoubletHelper(geo::TPCID tpc,
                const std::vector<HitOrChan>& ahits,
                const std::vector<HitOrChan>& bhits,
                const std::vector<raw::ChannelID_t>& bbads) const
  {
    std::vector<ChannelDoublet> ret;

    IntersectionCache isect(tpc);

    auto b_begin = bhits.begin();

    for(const HitOrChan& a: ahits){
      // Bad channels are easy because there's no timing constraint
      for(raw::ChannelID_t b: bbads){
        geo::WireIDIntersection pt;
        if(isect(a.chan, b, pt)){
          ret.emplace_back(a, b, pt);
        }
      }

      while(b_begin != bhits.end() &&
            b_begin->xpos < a.xpos &&
            !CloseDrift(b_begin->xpos, a.xpos)) ++b_begin;

      for(auto bit = b_begin; bit != bhits.end(); ++bit){
        const HitOrChan& b = *bit;

        if(b.xpos > a.xpos && !CloseDrift(b.xpos, a.xpos)) break;

        geo::WireIDIntersection pt;
        if(!isect(a.chan, b.chan, pt)) continue;

        ret.emplace_back(a, b, pt);
      } // end for b
    } // end for a

    return ret;
  }
}