Propagate digitizer interaction rate via DigitizationContext

Some digitizer (EMCAL) aim to use the interaction rate for flow-control
in digitization. This is now possible from a new member in DigitizationContext
which will be filled in digitizer workflows.

DataFormats/simulation/include/SimulationDataFormat/DigitizationContext.h

@@ -81,6 +81,9 @@ class DigitizationContext
 
   void setMuPerBC(float m) { mMuBC = m; }
   float getMuPerBC() const { return mMuBC; }
+
+  /// returns the main (hadronic interaction rate) associated to this digitization context
+  float getCalculatedInteractionRate() const { return getMuPerBC() * getBunchFilling().getNBunches() * o2::constants::lhc::LHCRevFreq; }
 
   void printCollisionSummary(bool withQED = false, int truncateOutputTo = -1) const;
 
@@ -150,6 +153,9 @@ class DigitizationContext
     }
   }
 
+  void setDigitizerInteractionRate(float intRate) { mDigitizerInteractionRate = intRate; }
+  float getDigitizerInteractionRate() const  { return mDigitizerInteractionRate; }
+
   std::vector<o2::ctp::CTPDigit> const* getCTPDigits() const { return mCTPTrigger; }
   bool hasTriggerInput() const { return mHasTrigger; }
 
@@ -184,7 +190,13 @@ class DigitizationContext
   mutable std::vector<o2::ctp::CTPDigit> const* mCTPTrigger = nullptr; // CTP trigger info associated to this digitization context
   mutable bool mHasTrigger = false;                                    //
 
-  ClassDefNV(DigitizationContext, 5);
+  // The global ALICE interaction hadronic interaction rate as applied in digitization.
+  // It should be consistent with mMuPerBC but it might be easier to handle.
+  // The value will be filled/inserted by the digitization workflow so that digiters can access it.
+  // There is no guarantee that the value is available elsewhere.
+  float mDigitizerInteractionRate{-1};
+
+  ClassDefNV(DigitizationContext, 6);
 };
 
 /// function reading the hits from a chain (previously initialized with initSimChains

Detectors/EMCAL/workflow/src/EMCALDigitizerSpec.cxx

@@ -82,6 +82,9 @@ void DigitizerSpec::run(framework::ProcessingContext& ctx)
 
   // read collision context from input
   auto context = ctx.inputs().get<o2::steer::DigitizationContext*>("collisioncontext");
+
+  // get interaction rate ... so that it can be used in digitization
+  auto intRate = context->getDigitizerInteractionRate();
   context->initSimChains(o2::detectors::DetID::EMC, mSimChains);
   auto& timesview = context->getEventRecords();
   LOG(debug) << "GOT " << timesview.size() << " COLLISSION TIMES";

Steer/DigitizerWorkflow/src/SimReaderSpec.cxx

@@ -45,6 +45,7 @@ namespace steer
 {
 
 std::vector<o2::ctp::CTPDigit>* ctptrigger = nullptr;
+float gIntRate = -1.;
 
 DataProcessorSpec getSimReaderSpec(SubspecRange range, const std::vector<std::string>& simprefixes, const std::vector<int>& tpcsectors, bool withTrigger)
 {
@@ -55,7 +56,7 @@ DataProcessorSpec getSimReaderSpec(SubspecRange range, const std::vector<std::st
 
   auto doit = [range, tpcsectors, activeSectors, withTrigger](ProcessingContext& pc) {
     auto& mgr = steer::HitProcessingManager::instance();
-    const auto& context = mgr.getDigitizationContext();
+    auto& context = mgr.getDigitizationContext();
     auto eventrecords = context.getEventRecords();
 
     if (withTrigger) {
@@ -64,6 +65,9 @@ DataProcessorSpec getSimReaderSpec(SubspecRange range, const std::vector<std::st
       context.setCTPDigits(ctptrigger);
     }
 
+    // inject the global interaction rate information
+    context.setDigitizerInteractionRate(gIntRate);
+
     for (auto const& sector : tpcsectors) {
       // Note: the TPC sector header was serving the sector to lane mapping before
       // now the only remaining purpose is to propagate the mask of valid sectors
@@ -128,6 +132,10 @@ DataProcessorSpec getSimReaderSpec(SubspecRange range, const std::vector<std::st
       }
     }
 
+    gIntRate = ctx.options().get<float>("interactionRate"); // is interaction rate requested?
+    if (gIntRate < 1.f) {
+      gIntRate = 1.f;
+    }
     // do we start from an existing context
     auto incontextstring = ctx.options().get<std::string>("incontext");
     LOG(info) << "INCONTEXTSTRING " << incontextstring;
@@ -137,13 +145,8 @@ DataProcessorSpec getSimReaderSpec(SubspecRange range, const std::vector<std::st
         LOG(fatal) << "Could not read collision context from " << incontextstring;
       }
     } else {
-
-      auto intRate = ctx.options().get<float>("interactionRate"); // is interaction rate requested?
-      if (intRate < 1.f) {
-        intRate = 1.f;
-      }
-      LOG(info) << "Imposing hadronic interaction rate " << intRate << "Hz";
-      mgr.getInteractionSampler().setInteractionRate(intRate);
+      LOG(info) << "Imposing hadronic interaction rate " << gIntRate << "Hz";
+      mgr.getInteractionSampler().setInteractionRate(gIntRate);
       o2::raw::HBFUtils::Instance().print();
       o2::raw::HBFUtils::Instance().checkConsistency();
       mgr.getInteractionSampler().setFirstIR({0, o2::raw::HBFUtils::Instance().orbitFirstSampled});