From 4e4c8014f4935c7b52a230a50ddc5705646ee5d1 Mon Sep 17 00:00:00 2001
From: Marco Giacalone <mgiacalo@gmail.com>
Date: Tue, 14 Oct 2025 17:25:41 +0200
Subject: [PATCH 1/2] Make Generators list static

---
 Generators/include/Generators/GeneratorHybrid.h | 3 ++-
 Generators/src/GeneratorHybrid.cxx              | 2 ++
 2 files changed, 4 insertions(+), 1 deletion(-)

diff --git a/Generators/include/Generators/GeneratorHybrid.h b/Generators/include/Generators/GeneratorHybrid.h
index b92437b02d874..06018e4adafdc 100644
--- a/Generators/include/Generators/GeneratorHybrid.h
+++ b/Generators/include/Generators/GeneratorHybrid.h
@@ -66,10 +66,11 @@ class GeneratorHybrid : public Generator
   Bool_t confSetter(const auto& gen);
   template <typename T>
   std::string jsonValueToString(const T& value);
+  static std::vector<std::shared_ptr<o2::eventgen::Generator>> const& getGenerators() { return gens; }
 
  private:
   o2::eventgen::Generator* currentgen = nullptr;
-  std::vector<std::shared_ptr<o2::eventgen::Generator>> gens;
+  static std::vector<std::shared_ptr<o2::eventgen::Generator>> gens;
   const std::vector<std::string> generatorNames = {"extkinO2", "evtpool", "boxgen", "external", "hepmc", "pythia8", "pythia8pp", "pythia8hi", "pythia8hf", "pythia8powheg"};
   std::vector<std::string> mInputGens;
   std::vector<std::string> mGens;
diff --git a/Generators/src/GeneratorHybrid.cxx b/Generators/src/GeneratorHybrid.cxx
index 83a694703c259..cfd1d7ba4e166 100644
--- a/Generators/src/GeneratorHybrid.cxx
+++ b/Generators/src/GeneratorHybrid.cxx
@@ -23,6 +23,8 @@ namespace o2
 namespace eventgen
 {
 
+std::vector<std::shared_ptr<o2::eventgen::Generator>> GeneratorHybrid::gens;
+
 GeneratorHybrid::GeneratorHybrid(const std::string& inputgens)
 {
   // This generator has trivial unit conversions

From 1002ed826c751da43fd003fb2bc7b09817abf704 Mon Sep 17 00:00:00 2001
From: Marco Giacalone <mgiacalo@gmail.com>
Date: Fri, 24 Oct 2025 22:52:28 +0200
Subject: [PATCH 2/2] Made GeneratorHybrid a singleton

---
 Generators/include/Generators/GeneratorHybrid.h | 13 +++++++++----
 Generators/src/GeneratorFactory.cxx             |  4 ++--
 Generators/src/GeneratorHybrid.cxx              |  6 +++++-
 3 files changed, 16 insertions(+), 7 deletions(-)

diff --git a/Generators/include/Generators/GeneratorHybrid.h b/Generators/include/Generators/GeneratorHybrid.h
index 06018e4adafdc..97422df1c8e2d 100644
--- a/Generators/include/Generators/GeneratorHybrid.h
+++ b/Generators/include/Generators/GeneratorHybrid.h
@@ -54,8 +54,11 @@ class GeneratorHybrid : public Generator
 {
 
  public:
-  GeneratorHybrid(const std::string& inputgens);
-  ~GeneratorHybrid();
+  GeneratorHybrid& operator=(const GeneratorHybrid&) = delete;
+  GeneratorHybrid(const GeneratorHybrid&) = delete;
+
+  // Singleton access method
+  static GeneratorHybrid& Instance(const std::string& inputgens = "");
 
   Bool_t Init() override;
   Bool_t generateEvent() override;
@@ -66,11 +69,13 @@ class GeneratorHybrid : public Generator
   Bool_t confSetter(const auto& gen);
   template <typename T>
   std::string jsonValueToString(const T& value);
-  static std::vector<std::shared_ptr<o2::eventgen::Generator>> const& getGenerators() { return gens; }
+  std::vector<std::shared_ptr<o2::eventgen::Generator>> const& getGenerators() { return gens; }
 
  private:
+  GeneratorHybrid(const std::string& inputgens);
+  ~GeneratorHybrid();
   o2::eventgen::Generator* currentgen = nullptr;
-  static std::vector<std::shared_ptr<o2::eventgen::Generator>> gens;
+  std::vector<std::shared_ptr<o2::eventgen::Generator>> gens;
   const std::vector<std::string> generatorNames = {"extkinO2", "evtpool", "boxgen", "external", "hepmc", "pythia8", "pythia8pp", "pythia8hi", "pythia8hf", "pythia8powheg"};
   std::vector<std::string> mInputGens;
   std::vector<std::string> mGens;
diff --git a/Generators/src/GeneratorFactory.cxx b/Generators/src/GeneratorFactory.cxx
index 8a6001b2cd5e6..4102bd8ffd9b2 100644
--- a/Generators/src/GeneratorFactory.cxx
+++ b/Generators/src/GeneratorFactory.cxx
@@ -284,8 +284,8 @@ void GeneratorFactory::setPrimaryGenerator(o2::conf::SimConfig const& conf, Fair
       LOG(fatal) << "Configuration file for hybrid generator does not exist";
       return;
     }
-    auto hybrid = new o2::eventgen::GeneratorHybrid(config);
-    primGen->AddGenerator(hybrid);
+    auto& hybrid = o2::eventgen::GeneratorHybrid::Instance(config);
+    primGen->AddGenerator(&hybrid);
 #endif
   } else {
     LOG(fatal) << "Invalid generator";
diff --git a/Generators/src/GeneratorHybrid.cxx b/Generators/src/GeneratorHybrid.cxx
index cfd1d7ba4e166..370671a977a5c 100644
--- a/Generators/src/GeneratorHybrid.cxx
+++ b/Generators/src/GeneratorHybrid.cxx
@@ -23,7 +23,11 @@ namespace o2
 namespace eventgen
 {
 
-std::vector<std::shared_ptr<o2::eventgen::Generator>> GeneratorHybrid::gens;
+GeneratorHybrid& GeneratorHybrid::Instance(const std::string& inputgens)
+{
+  static GeneratorHybrid instance(inputgens);
+  return instance;
+}
 
 GeneratorHybrid::GeneratorHybrid(const std::string& inputgens)
 {