Make EMCAL clusterizer to process empty input data

Author: shahor02

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

@@ -67,6 +67,11 @@ class Clusterizer
   Clusterizer();
   ~Clusterizer() = default;
 
+  void clear()
+  {
+    mFoundClusters.clear();
+    mInputIndices.clear();
+  }
   void initialize(double timeCut, double timeMin, double timeMax, double gradientCut, bool doEnergyGradientCut, double thresholdSeedE, double thresholdCellE);
   void findClusters(const gsl::span<InputType const>& inputArray);
   const std::vector<Cluster>* getFoundClusters() const { return &mFoundClusters; }

Detectors/EMCAL/reconstruction/src/Clusterizer.cxx

@@ -124,8 +124,7 @@ void Clusterizer<InputType>::getTopologicalRowColumn(const InputType& input, int
 template <class InputType>
 void Clusterizer<InputType>::findClusters(const gsl::span<InputType const>& inputArray)
 {
-  mFoundClusters.clear();
-  mInputIndices.clear();
+  clear();
 
   // Algorithm
   // - Fill cells/digits in 2D topological map

Detectors/EMCAL/workflow/src/ClusterizerSpec.cxx

@@ -78,9 +78,11 @@ void ClusterizerSpec<InputType>::run(framework::ProcessingContext& ctx)
   int currentStartClusters = mOutputClusters->size();
   int currentStartIndices = mOutputCellDigitIndices->size();
   for (auto iTrgRcrd : InputTriggerRecord) {
-
-    mClusterizer.findClusters(gsl::span<const InputType>(&Inputs[iTrgRcrd.getFirstEntry()], iTrgRcrd.getNumberOfObjects())); // Find clusters on cells/digits (pass by ref)
-
+    if (Inputs.size() && iTrgRcrd.getNumberOfObjects()) {
+      mClusterizer.findClusters(gsl::span<const InputType>(&Inputs[iTrgRcrd.getFirstEntry()], iTrgRcrd.getNumberOfObjects())); // Find clusters on cells/digits (pass by ref)
+    } else {
+      mClusterizer.clear();
+    }
     // Get found clusters + cell/digit indices for output
     // * A cluster contains a range that correspond to the vector of cell/digit indices
     // * The cell/digit index vector contains the indices of the clusterized cells/digits wrt to the original cell/digit array