[Backport v1.30] Add generator status filter to UndoAfterBurner for memory efficiency (#2176)

# Description
Backport of #2175 to `v1.30`.

Co-authored-by: Sakib Rahman <[email protected]>
Co-authored-by: Sakib Rahman <[email protected]>
Co-authored-by: pre-commit-ci[bot] <66853113+pre-commit-ci[bot]@users.noreply.github.com>
Co-authored-by: Copilot <[email protected]>

Author: 5 people

src/algorithms/reco/UndoAfterBurner.cc

@@ -116,11 +116,18 @@ void eicrecon::UndoAfterBurner::process(const UndoAfterBurner::Input& input,
                                       head_on_frame_boost.Pz() / head_on_frame_boost.E());
 
   // Now, loop through events and apply operations to the MCparticles
+  const int maxGenStatus = m_cfg.m_max_gen_status;
+
   for (const auto& p : *mcparts) {
     if (p.isCreatedInSimulation()) {
       continue;
     }
 
+    // Filter by generator status to exclude background particles and conserve memory
+    if (maxGenStatus >= 0 && p.getGeneratorStatus() > maxGenStatus) {
+      continue;
+    }
+
     ROOT::Math::PxPyPzEVector mc(p.getMomentum().x, p.getMomentum().y, p.getMomentum().z,
                                  p.getEnergy());
 

src/algorithms/reco/UndoAfterBurnerConfig.h

@@ -13,6 +13,7 @@ struct UndoAfterBurnerConfig {
   double m_pid_purity         = 0.51;
   bool m_correct_beam_FX      = true;
   bool m_pid_use_MC_truth     = true;
+  int m_max_gen_status        = 1000; // Upper limit on generator status to process (-1 = no limit)
 };
 
 } // namespace eicrecon

src/factories/reco/UndoAfterBurnerMCParticles_factory.h

@@ -34,6 +34,9 @@ class UndoAfterBurnerMCParticles_factory
   ParameterRef<double> m_pid_purity{this, "m_pid_purity", config().m_pid_purity};
   ParameterRef<bool> m_correct_beam_FX{this, "m_correct_beam_FX", config().m_correct_beam_FX};
   ParameterRef<bool> m_pid_use_MC_truth{this, "m_pid_use_MC_truth", config().m_pid_use_MC_truth};
+  ParameterRef<int> m_max_gen_status{this, "m_max_gen_status", config().m_max_gen_status,
+                                     "Upper limit on generator status to process (-1 = no limit). "
+                                     "Use to filter out background particles and conserve memory."};
 
 public:
   void Configure() {