[EMCAL-1157] Update clusterizer algorithm to use relative time window always relative to seed cell

- Update clusterizer algorithm to use relative time window always relative to seed cell instead of the current cell during clusterization. So right now when looking for another cell to add to the cluster the relative time check is always done in respect to the time of the new cell and the cell from which this new cell would be added (so +-1 in eta or +-1 in phi direction). Most clusters arent that big and thus this change should only have minor consequences to the resulting clusters.

Author: mhemmer-cern

Detectors/EMCAL/reconstruction/include/EMCALReconstruction/Clusterizer.h

@@ -143,7 +143,8 @@ class Clusterizer
   /// \param[in,out] clusterInputs Cells/digits of prototype cluster
   /// \param row Row number from neighbor search in recursion step
   /// \param column Column number for neighbor search in recursion step
-  void getClusterFromNeighbours(std::vector<InputwithIndex>& clusterInputs, int row, int column);
+  /// \param seedTime Timestamp of the seed cell, used as fixed reference for the time cut
+  void getClusterFromNeighbours(std::vector<InputwithIndex>& clusterInputs, int row, int column, double seedTime);
 
   /// \brief Get row (phi) and column (eta) of a cell/digit, values corresponding to topology
   /// \param input Input object (cell/digit)

Detectors/EMCAL/reconstruction/src/Clusterizer.cxx

@@ -45,7 +45,7 @@ void Clusterizer<InputType>::initialize(double timeCut, double timeMin, double t
 
 //____________________________________________________________________________
 template <class InputType>
-void Clusterizer<InputType>::getClusterFromNeighbours(std::vector<InputwithIndex>& clusterInputs, int row, int column)
+void Clusterizer<InputType>::getClusterFromNeighbours(std::vector<InputwithIndex>& clusterInputs, int row, int column, double seedTime)
 {
   // Recursion 0, add seed cell/digit to cluster
   if (!clusterInputs.size()) {
@@ -71,8 +71,8 @@ void Clusterizer<InputType>::getClusterFromNeighbours(std::vector<InputwithIndex
         if (mDoEnergyGradientCut && (mInputMap[row + rowDiffs[dir]][column + colDiffs[dir]].mInput->getEnergy() > mInputMap[row][column].mInput->getEnergy() + mGradientCut)) {
           continue;
         }
-        if (not(TMath::Abs(mInputMap[row + rowDiffs[dir]][column + colDiffs[dir]].mInput->getTimeStamp() - mInputMap[row][column].mInput->getTimeStamp()) > mTimeCut)) {
-          getClusterFromNeighbours(clusterInputs, row + rowDiffs[dir], column + colDiffs[dir]);
+        if (not(TMath::Abs(mInputMap[row + rowDiffs[dir]][column + colDiffs[dir]].mInput->getTimeStamp() - seedTime) > mTimeCut)) {
+          getClusterFromNeighbours(clusterInputs, row + rowDiffs[dir], column + colDiffs[dir], seedTime);
           // Add the cell/digit to the current cluster -- if we end up here, the selected cluster fulfills the condition
           clusterInputs.emplace_back(mInputMap[row + rowDiffs[dir]][column + colDiffs[dir]]);
         }
@@ -182,7 +182,8 @@ void Clusterizer<InputType>::findClusters(const gsl::span<InputType const>& inpu
 
     // Seed is found, form cluster recursively
     std::vector<InputwithIndex> clusterInputs;
-    getClusterFromNeighbours(clusterInputs, row, column);
+    double seedTime = mInputMap[row][column].mInput->getTimeStamp();
+    getClusterFromNeighbours(clusterInputs, row, column, seedTime);
 
     // Add cells/digits for current cluster to cell/digit index vector
     int inputIndexStart = mInputIndices.size();