From 241ee99bf5d49cd125cfa712609d42fe575bc035 Mon Sep 17 00:00:00 2001
From: Marco Giacalone <mgiacalo@gmail.com>
Date: Sun, 2 Feb 2025 19:51:37 +0100
Subject: [PATCH] Fix for dpl-eventgen usage, added nEvents protection and
 executable selection

---
 .../generator/generator_pythia8_powheg.C      | 51 +++++++++++++++----
 1 file changed, 40 insertions(+), 11 deletions(-)

diff --git a/MC/config/PWGGAJE/external/generator/generator_pythia8_powheg.C b/MC/config/PWGGAJE/external/generator/generator_pythia8_powheg.C
index 989f33971..6ca884dda 100644
--- a/MC/config/PWGGAJE/external/generator/generator_pythia8_powheg.C
+++ b/MC/config/PWGGAJE/external/generator/generator_pythia8_powheg.C
@@ -1,6 +1,6 @@
 R__ADD_INCLUDE_PATH($O2DPG_MC_CONFIG_ROOT)
 ///#include "FairGenerator.h"
-//#include "Generators/GeneratorPythia8.h"
+#include "Generators/GeneratorPythia8.h"
 #include "Pythia8/Pythia.h"
 #include "Generators/GeneratorPythia8Param.h"
 #include "CommonUtils/FileSystemUtils.h"
@@ -24,13 +24,31 @@ using namespace Pythia8;
 
 // Pythia8 generator using POWHEG data that are generated during the initialization
 // of the external generator. The POWHEG configuration file is copied to the current
-// directory with the right name and the POWHEG events are generated using the pwhg_main_hvq executable.
+// directory with the right name and the POWHEG events are generated using the executable
+// specified via the type parameter, namely:
+//    0: pwhg_main_hvq
+//    1: pwhg_main_W
+//    2: pwhg_main_Z
+//    3: pwhg_main_dijet
+//    4: pwhg_main_directphoton
 class GeneratorJEPythia8POWHEG : public o2::eventgen::GeneratorPythia8
 {
 public:
   /// default constructor
-  GeneratorJEPythia8POWHEG(std::string confpath = "pwgpath")
+  GeneratorJEPythia8POWHEG(std::string confpath = "pwgpath", short int type = 0)
   {
+    // Assign events to generate with POWHEG
+    unsigned int nPowhegEvents = getTotalNEvents();
+    if (nPowhegEvents == 0) {
+      LOG(fatal) << "Number of events not set or set to 0.";
+      exit(1);
+    }
+    // Check on nEvents to generate with POWHEG
+    // due to integer limit hardcoded in the generator
+    if (nPowhegEvents > std::numeric_limits<int>::max()) {
+      LOG(fatal) << "Number of events for POWHEG exceeds the maximum allowed value";
+      exit(1);
+    }
     // Check if file exist and is not empty
     if (std::filesystem::exists(confpath) && std::filesystem::file_size(confpath) > 0) {
       // Copy the file to the current directory
@@ -51,7 +69,7 @@ public:
         if (line.find("numevts") != std::string::npos)
         {
           // Set the number of events to the number of events defined in the configuration
-          line = "numevts " + std::to_string(mSimConfig.getNEvents());
+          line = "numevts " + std::to_string(nPowhegEvents);
           // replace it in the file
           isnumevts = true;
         }
@@ -61,7 +79,7 @@ public:
         dst << "iseed " << seed << std::endl;
       }
       if (!isnumevts) {
-        dst << "numevts " << mSimConfig.getNEvents() << std::endl;
+        dst << "numevts " << nPowhegEvents << std::endl;
       }
       src.close();
       dst.close();
@@ -69,13 +87,24 @@ public:
       LOG(fatal) << "POWHEG configuration file not found or empty" << std::endl;
       exit(1);
     }
-    // Generate the POWHEG events
-    std::string cmd = "pwhg_main_hvq";
-    system(cmd.c_str());
+    // Get POWHEG executable to use
+    if (type >= mPowhegGen.size()) {
+      LOG(warn) << "Available POWHEG generators are:";
+      for (int k = 0; k < mPowhegGen.size(); k++)
+      {
+        LOG(warn) << "\t" << k << ": " << mPowhegGen[k];
+      }
+      LOG(fatal) << "POWHEG generator type " << type << " not found";
+      exit(1);
+    } else {
+      LOG(info) << "Running POWHEG using the " << mPowhegGen[type] << " executable";
+      // Generate the POWHEG events
+      system(mPowhegGen[type].c_str());
+    }
   };
 
 private:
-  o2::conf::SimConfig mSimConfig = o2::conf::SimConfig::Instance(); // local sim config object
+  const std::vector<std::string> mPowhegGen = {"pwhg_main_hvq", "pwhg_main_W", "pwhg_main_Z", "pwhg_main_dijet", "pwhg_main_directphoton"}; // POWHEG executables
 };
 
 } // namespace eventgen
@@ -83,13 +112,13 @@ private:
 
 /** generator instance and settings **/
 
-FairGenerator *getGeneratorJEPythia8POWHEG(std::string powhegconf = "pwgpath", std::string pythia8conf = "")
+FairGenerator *getGeneratorJEPythia8POWHEG(std::string powhegconf = "pwgpath", std::string pythia8conf = "", short int type = 0)
 {
   using namespace o2::eventgen;
   // Expand paths for the POWHEG configuration file
   powhegconf = o2::utils::expandShellVarsInFileName(powhegconf);
   LOG(info) << "Using POWHEG configuration file: " << powhegconf;
-  auto myGen = new GeneratorJEPythia8POWHEG(powhegconf);
+  auto myGen = new GeneratorJEPythia8POWHEG(powhegconf, type);
   if(GeneratorPythia8Param::Instance().config.empty() && pythia8conf.empty()) {
     LOG(fatal) << "No configuration provided for Pythia8";
   }