Simplify the multithreaded TPC digitizer after the second review

This addresses the second review of the multithreaded TPC digitizer device.

- Old lane files are found with o2::utils::listFiles, as in the chunked merger.
- Unused includes and the SpaceCharge alias are removed from the device.
- setSectorSeedingFrom fills the rings of the source digitizer, so initSectorSeeding is private.
- The seeding documentation states that the sectors share the ring contents.

https://its.cern.ch/jira/browse/O2-7309

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>

Author: sawenzel

Detectors/TPC/simulation/include/TPCSimulation/Digitizer.h

@@ -147,23 +147,24 @@ class Digitizer
   void setSCDistortionsFrom(const Digitizer& other);
 
   /// Use digitizer-owned random rings filled from seed and positioned per sector and timeframe in init(),
-  /// so that the digits of a sector do not depend on which sectors were processed before
+  /// so that the digits of a sector do not depend on which sectors were processed before.
+  /// All sectors share the ring contents and differ in the start positions, as with the singleton rings.
   /// \param seed base seed, typically DigiParams.seed
   void setUseSectorSeeding(ULong64_t seed);
 
   /// Set the timeframe identifier that enters the sector seeding
   void setSeedingTimeframe(ULong64_t timeframe) { mSeedingTimeframe = timeframe; }
 
-  /// Fill the random rings of the sector seeding, if not done yet
-  void initSectorSeeding();
-
-  /// Use copies of the sector-seeding random rings of another digitizer
-  void setSectorSeedingFrom(const Digitizer& other);
+  /// Use copies of the sector-seeding random rings of another digitizer, which fills them if needed
+  void setSectorSeedingFrom(Digitizer& other);
 
   /// Whether flush() also flushes the process-wide debug streamer
   void setFlushDebugStreamer(bool flush) { mFlushDebugStreamer = flush; }
 
  private:
+  /// Fill the random rings of the sector seeding, if not done yet
+  void initSectorSeeding();
+
   ElectronTransport& electronTransport();
   GEMAmplification& gemAmplification();
   SAMPAProcessing& sampaProcessing();

Detectors/TPC/simulation/src/Digitizer.cxx

@@ -100,8 +100,9 @@ void Digitizer::initSectorSeeding()
   }
 }
 
-void Digitizer::setSectorSeedingFrom(const Digitizer& other)
+void Digitizer::setSectorSeedingFrom(Digitizer& other)
 {
+  other.initSectorSeeding();
   mUseSectorSeeding = other.mUseSectorSeeding;
   mSeed = other.mSeed;
   if (other.mGEMAmplification) {

Steer/DigitizerWorkflow/src/TPCDigitizerMTSpec.cxx

@@ -18,7 +18,6 @@
 #include "Framework/DataProcessorSpec.h"
 #include "Framework/DataRefUtils.h"
 #include "Framework/Lifetime.h"
-#include "Framework/CCDBParamSpec.h"
 #include "Framework/Task.h"
 #include "Framework/Logger.h"
 #include "Headers/DataHeader.h"
@@ -28,13 +27,9 @@
 #include "DetectorsBase/Detector.h"
 #include "SimConfig/DigiParams.h"
 #include "SimulationDataFormat/DigitizationContext.h"
-#include "TPCBaseRecSim/CDBInterface.h"
-#include "TPCBase/ParameterGEM.h"
-#include "TPCBase/ParameterGas.h"
-#include "TPCCalibration/VDriftHelper.h"
 #include "TPCSimulation/Digitizer.h"
-#include "TPCSpaceCharge/SpaceCharge.h"
 #include "CommonUtils/DebugStreamer.h"
+#include "CommonUtils/FileSystemUtils.h"
 #include <TChain.h>
 #include <TFile.h>
 #include <TROOT.h>
@@ -53,7 +48,6 @@
 #include <vector>
 
 using namespace o2::framework;
-using SC = o2::tpc::SpaceCharge<float>;
 
 namespace o2
 {
@@ -142,11 +136,8 @@ class TPCDPLDigitizerMTTask : public o2::base::BaseDPLDigitizer
     }
 
     // the merger picks up every lane file in the directory, so files of an earlier run must not survive
-    for (const auto& entry : std::filesystem::directory_iterator(".")) {
-      const auto name = entry.path().filename().string();
-      if (name.rfind("tpc_driftime_digits_lane", 0) == 0 && entry.path().extension() == ".root") {
-        std::filesystem::remove(entry.path());
-      }
+    for (const auto& name : o2::utils::listFiles("tpc_driftime_digits_lane.*.root$")) {
+      std::filesystem::remove(name);
     }
 
     ROOT::EnableThreadSafety();
@@ -176,7 +167,6 @@ class TPCDPLDigitizerMTTask : public o2::base::BaseDPLDigitizer
     }
     if (!mSeedingShared) {
       // the rings depend only on the seed, so they are filled once and copied
-      primary.initSectorSeeding();
       for (size_t i = 1; i < mWorkers.size(); ++i) {
         mWorkers[i]->digitizer.setSectorSeedingFrom(primary);
       }