Update generator_DittoMC.C

Author: njacazio

MC/config/ALICE3/pythia8/generator_DittoMC.C

@@ -1,55 +1,57 @@
-#include "Ditto.h"
-
-#include <algorithm>
-#include <cstdint>
-#include <cstdlib>
-#include <stdexcept>
-
-#if !defined(__CLING__) || defined(__ROOTCLING__)
-
-#include <SimulationDataFormat/MCGenProperties.h>
-
+#include <Ditto/Ditto.h>
 #include <Generators/GeneratorPythia8.h>
-#include <Pythia8/Pythia.h>
 
 #include <FairGenerator.h>
-#include <FairPrimaryGenerator.h>
 
-#endif
+#include <cstdint>
+#include <cstdlib>
+#include <stdexcept>
+#include <string>
 
 // Ditto event generator
-
 class GeneratorDittoMC : public o2::eventgen::GeneratorPythia8
 {
  public:
   /// Constructor
-  GeneratorDittoMC(const TString& tuneFile) : mGenerator(makeConfig(tuneFile))
+  explicit GeneratorDittoMC(const TString& tuneFile) : mGenerator(makeConfig(tuneFile))
   {
+    // We use the Pythia8 event only as the container passed to the O2
+    // GeneratorPythia8 machinery. Particle production is handled by Ditto.
     mPythia.readString("ProcessLevel:all = off");
   }
 
+  /// Generate one Ditto event and export it to the Pythia8 event record.
   bool generateEvent() override
   {
     mGenerator.generate();
     mGenerator.loadParticles(mPythia.event, true);
     return true;
   }
 
-  ///  Destructor
-  ~GeneratorDittoMC() = default;
+  /// Destructor
+  ~GeneratorDittoMC() override = default;
 
  private:
+  /// Build the Ditto runtime configuration.
   static Ditto::Config makeConfig(const TString& tuneFile)
   {
-    Ditto::Config config;
     if (tuneFile.IsNull()) {
-      throw std::runtime_error("DITTO_TUNE_FILE must point to a Ditto tune file");
+      throw std::runtime_error("Ditto tune file must be specified");
+    }
+
+    Ditto::Config config;
+    config.mTuneFile = tuneFile.Data();
+
+    // Use the Grid process ID as the Ditto seed when available.
+    // Outside the Grid, seed 0 is used.
+    if (const char* alienProcId = std::getenv("ALIEN_PROC_ID")) {
+      config.mSeed = static_cast<std::uint64_t>(std::strtoull(alienProcId, nullptr, 10));
+    } else {
+      config.mSeed = static_cast<std::uint64_t>(std::time(nullptr));
     }
-    config.tuneFile = tuneFile;
 
-    const char* alienProcId = std::getenv("ALIEN_PROC_ID");
-    config.seed = alienProcId ? static_cast<std::uint64_t>(std::atoll(alienProcId)) : 0;
-    Printf("Using Ditto tune: %s and seed: %lu\n", config.tuneFile.c_str(), config.seed);
+    Printf("Using Ditto tune: %s and seed: %llu", config.mTuneFile.c_str(), static_cast<unsigned long long>(config.mSeed));
+
     return config;
   }