[PWGJE] Add an extra table and vertexClustering function for GNN b-jet tagging (#8597)

Co-authored-by: chchoi <changhwan.choi@cern.ch>

Author: choich08365

PWGJE/Core/JetTaggingUtilities.h

@@ -26,6 +26,8 @@
 #include <algorithm>
 #include <functional>
 #include <memory>
+#include <string>
+#include <unordered_map>
 
 #include "TF1.h"
 #include "Framework/Logger.h"
@@ -629,6 +631,177 @@ bool isTaggedJetSV(T const jet, U const& /*prongs*/, float const& prongChi2PCAMi
   return true;
 }
 
+/**
+ * Clusters jet constituent tracks into groups of tracks originating from same mcParticle position (trkVtxIndex), and finds each track origin (trkOrigin). (for GNN b-jet tagging)
+ * @param trkLabels Track labels for GNN vertex and track origin predictions. trkVtxIndex: The index value of each vertex (cluster) which is determined by the function. trkOrigin: The category of the track origin (0: not physical primary, 1: charm, 2: beauty, 3: primary vertex, 4: other secondary vertex).
+ * @param vtxResParam Vertex resolution parameter which determines the cluster size. (cm)
+ * @param trackPtMin Minimum value of track pT.
+ * @return The number of vertices (clusters) in the jet.
+ */
+template <typename AnyCollision, typename AnalysisJet, typename AnyTracks, typename AnyParticles, typename AnyOriginalParticles>
+int vertexClustering(AnyCollision const& collision, AnalysisJet const& jet, AnyTracks const&, AnyParticles const& particles, AnyOriginalParticles const&, std::unordered_map<std::string, std::vector<int>>& trkLabels, bool searchUpToQuark, float vtxResParam = 0.01 /* 0.01cm = 100um */, float trackPtMin = 0.5)
+{
+  const auto& tracks = jet.template tracks_as<AnyTracks>();
+  const int n_trks = tracks.size();
+
+  // trkVtxIndex
+
+  std::vector<int> tempTrkVtxIndex;
+
+  int i = 0;
+  for (const auto& constituent : tracks) {
+    if (!constituent.has_mcParticle() || !constituent.template mcParticle_as<AnyParticles>().isPhysicalPrimary() || constituent.pt() < trackPtMin)
+      tempTrkVtxIndex.push_back(-1);
+    else
+      tempTrkVtxIndex.push_back(i++);
+  }
+  tempTrkVtxIndex.push_back(i); // temporary index for PV
+  if (n_trks < 1) {             // the process should be done for n_trks == 1 as well
+    trkLabels["trkVtxIndex"] = tempTrkVtxIndex;
+    return n_trks;
+  }
+
+  int n_pos = n_trks + 1;
+  std::vector<float> dists(n_pos * (n_pos - 1) / 2);
+  auto trk_pair_idx = [n_pos](int ti, int tj) {
+    if (ti == tj || ti >= n_pos || tj >= n_pos || ti < 0 || tj < 0) {
+      LOGF(info, "Track pair index out of range");
+      return -1;
+    } else {
+      return (ti < tj) ? (ti * n_pos - (ti * (ti + 1)) / 2 + tj - ti - 1) : (tj * n_pos - (tj * (tj + 1)) / 2 + ti - tj - 1);
+    }
+  }; // index n_trks is for PV
+
+  for (int ti = 0; ti < n_pos - 1; ti++)
+    for (int tj = ti + 1; tj < n_pos; tj++) {
+      std::array<float, 3> posi, posj;
+
+      if (tj < n_trks) {
+        if (tracks[tj].has_mcParticle()) {
+          const auto& pj = tracks[tj].template mcParticle_as<AnyParticles>().template mcParticle_as<AnyOriginalParticles>();
+          posj = std::array<float, 3>{pj.vx(), pj.vy(), pj.vz()};
+        } else {
+          dists[trk_pair_idx(ti, tj)] = std::numeric_limits<float>::max();
+          continue;
+        }
+      } else {
+        posj = std::array<float, 3>{collision.posX(), collision.posY(), collision.posZ()};
+      }
+
+      if (tracks[ti].has_mcParticle()) {
+        const auto& pi = tracks[ti].template mcParticle_as<AnyParticles>().template mcParticle_as<AnyOriginalParticles>();
+        posi = std::array<float, 3>{pi.vx(), pi.vy(), pi.vz()};
+      } else {
+        dists[trk_pair_idx(ti, tj)] = std::numeric_limits<float>::max();
+        continue;
+      }
+
+      dists[trk_pair_idx(ti, tj)] = RecoDecay::distance(posi, posj);
+    }
+
+  int clusteri = -1, clusterj = -1;
+  float min_min_dist = -1.f; // If there is an not-merge-able min_dist pair, check the 2nd-min_dist pair.
+  while (true) {
+
+    float min_dist = -1.f; // Get min_dist pair
+    for (int ti = 0; ti < n_pos - 1; ti++)
+      for (int tj = ti + 1; tj < n_pos; tj++)
+        if (tempTrkVtxIndex[ti] != tempTrkVtxIndex[tj] && tempTrkVtxIndex[ti] >= 0 && tempTrkVtxIndex[tj] >= 0) {
+          float dist = dists[trk_pair_idx(ti, tj)];
+          if ((dist < min_dist || min_dist < 0.f) && dist > min_min_dist) {
+            min_dist = dist;
+            clusteri = ti;
+            clusterj = tj;
+          }
+        }
+    if (clusteri < 0 || clusterj < 0)
+      break;
+
+    bool mrg = true; // Merge-ability check
+    for (int ti = 0; ti < n_pos && mrg; ti++)
+      if (tempTrkVtxIndex[ti] == tempTrkVtxIndex[clusteri] && tempTrkVtxIndex[ti] >= 0) {
+        for (int tj = 0; tj < n_pos && mrg; tj++)
+          if (tj != ti && tempTrkVtxIndex[tj] == tempTrkVtxIndex[clusterj] && tempTrkVtxIndex[tj] >= 0) {
+            if (dists[trk_pair_idx(ti, tj)] > vtxResParam) { // If there is more distant pair compared to vtx_res between two clusters, they cannot be merged.
+              mrg = false;
+              min_min_dist = min_dist;
+            }
+          }
+      }
+    if (min_dist > vtxResParam || min_dist < 0.f)
+      break;
+
+    if (mrg) { // Merge two clusters
+      int old_index = tempTrkVtxIndex[clusterj];
+      for (int t = 0; t < n_pos; t++)
+        if (tempTrkVtxIndex[t] == old_index)
+          tempTrkVtxIndex[t] = tempTrkVtxIndex[clusteri];
+    }
+  }
+
+  int n_vertices = 0;
+
+  // Sort the indices from PV (as 0) to the most distant SV (as 1~).
+  int idxPV = tempTrkVtxIndex[n_trks];
+  for (int t = 0; t < n_trks; t++)
+    if (tempTrkVtxIndex[t] == idxPV) {
+      tempTrkVtxIndex[t] = -2;
+      n_vertices = 1; // There is a track originating from PV
+    }
+
+  std::unordered_map<int, float> avgDistances;
+  std::unordered_map<int, int> count;
+  for (int t = 0; t < n_trks; t++) {
+    if (tempTrkVtxIndex[t] >= 0) {
+      avgDistances[tempTrkVtxIndex[t]] += dists[trk_pair_idx(t, n_trks)];
+      count[tempTrkVtxIndex[t]]++;
+    }
+  }
+
+  trkLabels["trkVtxIndex"] = std::vector<int>(n_trks, -1);
+  if (count.size() != 0) { // If there is any SV cluster not only PV cluster
+    for (auto& [idx, avgDistance] : avgDistances)
+      avgDistance /= count[idx];
+
+    n_vertices += avgDistances.size();
+
+    std::vector<std::pair<int, float>> sortedIndices(avgDistances.begin(), avgDistances.end());
+    std::sort(sortedIndices.begin(), sortedIndices.end(), [](const auto& a, const auto& b) { return a.second < b.second; });
+    int rank = 1;
+    for (const auto& [idx, avgDistance] : sortedIndices) {
+      bool found = false;
+      for (int t = 0; t < n_trks; t++)
+        if (tempTrkVtxIndex[t] == idx) {
+          trkLabels["trkVtxIndex"][t] = rank;
+          found = true;
+        }
+      rank += found;
+    }
+  }
+
+  for (int t = 0; t < n_trks; t++)
+    if (tempTrkVtxIndex[t] == -2)
+      trkLabels["trkVtxIndex"][t] = 0;
+
+  // trkOrigin
+
+  int trkIdx = 0;
+  for (auto& constituent : jet.template tracks_as<AnyTracks>()) {
+    if (!constituent.has_mcParticle() || !constituent.template mcParticle_as<AnyParticles>().isPhysicalPrimary() || constituent.pt() < trackPtMin) {
+      trkLabels["trkOrigin"].push_back(0);
+    } else {
+      const auto& particle = constituent.template mcParticle_as<AnyParticles>();
+      int orig = RecoDecay::getParticleOrigin(particles, particle, searchUpToQuark);
+      trkLabels["trkOrigin"].push_back((orig > 0) ? orig : (trkLabels["trkVtxIndex"][trkIdx] == 0) ? 3
+                                                                                                   : 4);
+    }
+
+    trkIdx++;
+  }
+
+  return n_vertices;
+}
+
 }; // namespace jettaggingutilities
 
 #endif // PWGJE_CORE_JETTAGGINGUTILITIES_H_