[Common] Add LPMProduction to mc generator map to autodetect generator from metadata in the MultModule (#18549)

Author: jesgum

Common/Core/MetadataHelper.cxx

@@ -25,6 +25,7 @@
 #include <TSystem.h>
 
 #include <array>
+#include <map>
 #include <string>
 
 using namespace o2::common::core;
@@ -153,6 +154,34 @@ std::string MetadataHelper::getO2Version() const
   return get("O2Version");
 }
 
+std::string MetadataHelper::getGenerator() const
+{
+  if (!isMC()) {
+    return {};
+  }
+
+  // MC production tag (LPMProductionTag) -> generator name, for AO2Ds without the generator in the metadata
+  static const std::map<std::string, std::string> mcGeneratorMap = {
+    {"LHC26f3", "EPOS"},
+    {"LHC26k3", "EPOS"}};
+
+  // FIXME: use the "Generator" key first once it is available in AO2Ds (it must also be added to the key list in the constructor)
+  // if (isKeyDefined("Generator")) {
+  //   return get("Generator");
+  // }
+
+  // older AO2Ds: rely on the LPMProductionTag to generator map
+  if (isKeyDefined("LPMProductionTag")) {
+    auto it = mcGeneratorMap.find(get("LPMProductionTag"));
+    if (it != mcGeneratorMap.end()) {
+      return it->second;
+    }
+  }
+
+  // no generator found in the metadata, fall back to PYTHIA
+  return "PYTHIA";
+}
+
 bool MetadataHelper::isCommitInSoftwareTag(const std::string& commitHash, const std::string& ccdbUrl) const
 {
   const std::string softwareTag = getO2Version();

Common/Core/MetadataHelper.h

@@ -55,6 +55,10 @@ struct MetadataHelper {
   /// @return the O2 version from the metadata
   std::string getO2Version() const;
 
+  /// @brief Function to get the MC generator name from the metadata
+  /// @return the generator name (e.g. "PYTHIA", "EPOS"), "PYTHIA" for MC if it cannot be determined, or an empty string for data
+  std::string getGenerator() const;
+
   /// @brief Function to get the metadata value for a given key
   /// @param key the key of the metadata
   /// @return the value of the metadata. Throws an exception if the key is not found

Common/Tools/Multiplicity/MultModule.h

@@ -346,7 +346,7 @@ struct standardConfigurables : o2::framework::ConfigurableGroup {
   o2::framework::Configurable<std::string> reconstructionPass{"reconstructionPass", "", {"Apass to use when fetching the calibration tables. Empty (default) does not check for any pass. Use `metadata` to fetch it from the AO2D metadata. Otherwise it will override the metadata."}};
 
   // centrality operation
-  o2::framework::Configurable<std::string> generatorName{"generatorName", "", {"Specify if and only if this is MC. Typical: PYTHIA"}};
+  o2::framework::Configurable<std::string> generatorName{"generatorName", "", {"MC generator name for centrality calibration (e.g. PYTHIA, EPOS). Empty: autodetect from metadata in Run 3, falling back to PYTHIA. Specify if and only if this is MC to override autodetect from metadata"}};
   o2::framework::Configurable<bool> embedINELgtZEROselection{"embedINELgtZEROselection", false, {"Option to do percentile 100.5 if not INELgtZERO"}};
 };
 
@@ -1199,16 +1199,10 @@ class MultModule
       mRunNumberCentrality = bc.runNumber(); // mark that this run has been attempted already regardless of outcome
       LOGF(info, "centrality loading procedure for timestamp=%llu, run number=%d", bc.timestamp(), bc.runNumber());
 
-      // capture the need for PYTHIA calibration in Pb-Pb runs
-      if (metadataInfo.isMC() && mRunNumber >= 544013 && mRunNumber <= 545367 && internalOpts.generatorName.value.empty()) {
-        LOGF(info, "This is MC for Pb-Pb. Setting generatorName automatically to PYTHIA");
-        internalOpts.generatorName.value = "PYTHIA";
-      }
-
-      // capture the need for PYTHIA calibration in light ion runs automatically
-      if (metadataInfo.isMC() && mRunNumber >= 564250 && mRunNumber <= 564472 && internalOpts.generatorName.value.empty()) {
-        LOGF(info, "This is MC for light ion runs. Setting generatorName automatically to PYTHIA");
-        internalOpts.generatorName.value = "PYTHIA";
+      // autodetect the generator from the metadata if not explicitly configured
+      if (metadataInfo.isMC() && internalOpts.generatorName.value.empty()) {
+        internalOpts.generatorName.value = metadataInfo.getGenerator();
+        LOGF(info, "Setting generatorName automatically from metadata to %s", internalOpts.generatorName.value);
       }
 
       LOGF(info, "centrality loading procedure for timestamp=%llu, run number=%d", bc.timestamp(), bc.runNumber());