Keep stepping state in detector members instead of statics

This moves state that is carried from step to step out of function-local statics, so that each instance has its own; with one instance per detector today, the behaviour is unchanged.

- TPC keeps the track length at the last track reference as a member, and builds the momentum vector as a local.
- FDD keeps the energy loss, photon count and entry position of the hit being built as members, and drops an unused static.
- HMPID keeps the energy loss and entry position of the charged-particle hit as members.
- MaterialBudgetMap keeps the distance to the scoring boundary as a member.
- The VMC application no longer caches the FairRootManager instance in a static.

https://its.cern.ch/jira/browse/O2-7305

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

Author: sawenzel

Detectors/FIT/FDD/simulation/include/FDDSimulation/Detector.h

@@ -20,6 +20,7 @@
 #include "DetectorsBase/Detector.h"
 #include "DataFormatsFDD/Hit.h"
 #include "FDDBase/Geometry.h"
+#include <TVector3.h>
 
 class FairModule;
 class FairVolume;
@@ -73,6 +74,11 @@ class Detector : public o2::base::DetImpl<Detector>
   std::vector<o2::fdd::Hit>* mHits = nullptr;
   int mTrackRefLastTrackID = -1; //! last track that received a TrackReference in the current event
 
+  // state of the hit being built across steps in ProcessHits
+  Float_t mElossAD = 0.; //! energy loss collected so far
+  Int_t mNPhotonsAD = 0; //! photons collected so far
+  TVector3 mHitPosAD;    //! position where the track entered
+
   Detector& operator=(const Detector&);
 
   Geometry* mGeometry = nullptr; //! Geometry

Detectors/FIT/FDD/simulation/src/Detector.cxx

@@ -151,29 +151,23 @@ Bool_t Detector::ProcessHits(FairVolume* vol)
   Int_t nPhotonsInStep_ad = Int_t(fFDDLightYield * destep_ad);
   nPhotonsInStep_ad = gRandom->Poisson(nPhotonsInStep_ad);
 
-  static Float_t eloss_ad = 0.;
-  static Float_t tlength_ad = 0.;
-  static Int_t nPhotons_ad = 0;
-
-  static TVector3 vPos;
-
-  eloss_ad += destep_ad;
+  mElossAD += destep_ad;
 
   if (fMC->IsTrackEntering()) {
-    nPhotons_ad = nPhotonsInStep_ad;
-    fMC->TrackPosition(vPos(0), vPos(1), vPos(2));
+    mNPhotonsAD = nPhotonsInStep_ad;
+    fMC->TrackPosition(mHitPosAD(0), mHitPosAD(1), mHitPosAD(2));
 
-    eloss_ad = 0.0;
+    mElossAD = 0.0;
     return kFALSE;
   }
-  nPhotons_ad += nPhotonsInStep_ad;
+  mNPhotonsAD += nPhotonsInStep_ad;
 
   if (fMC->IsTrackExiting() || fMC->IsTrackStop() || fMC->IsTrackDisappeared()) {
     Int_t trackID = fMC->GetStack()->GetCurrentTrackNumber();
 
     Float_t time = fMC->TrackTime() * 1.0e9; //time from seconds to ns
 
-    addHit(trackID, ADsector, vPos, time, eloss_ad, nPhotons_ad);
+    addHit(trackID, ADsector, mHitPosAD, time, mElossAD, mNPhotonsAD);
     return kTRUE;
   }
 

Detectors/HMPID/simulation/include/HMPIDSimulation/Detector.h

@@ -98,6 +98,10 @@ class Detector : public o2::base::DetImpl<Detector>
   int mHcel5VolID = -1;
   int mHcel6VolID = -1;
 
+  // state of a charged-particle hit being built across steps in ProcessHits
+  Float_t mMipEloss = 0;             //! energy loss collected in the amplification gap
+  Double_t mMipEntry[3] = {0, 0, 0}; //! position where the track entered the gap
+
   template <typename Det>
   friend class o2::base::DetImpl;
   ClassDefOverride(Detector, 1);

Detectors/HMPID/simulation/src/Detector.cxx

@@ -113,8 +113,6 @@ bool Detector::ProcessHits(FairVolume* v)
   } // photon hit PC
 
   // Treat charged particles
-  static Float_t eloss; // need to store mip parameters between different steps
-  static Double_t in[3];
 
   if (fMC->IsTrackEntering() && fMC->TrackCharge() && (volID == mHpad0VolID || volID == mHpad1VolID || volID == mHpad2VolID || volID == mHpad3VolID || volID == mHpad4VolID || volID == mHpad5VolID || volID == mHpad6VolID)) {
     // Trackref stored when entering in the pad volume
@@ -127,18 +125,18 @@ bool Detector::ProcessHits(FairVolume* v)
   if (fMC->TrackCharge() && (volID == mHcel0VolID || volID == mHcel1VolID || volID == mHcel2VolID || volID == mHcel3VolID || volID == mHcel4VolID || volID == mHcel5VolID || volID == mHcel6VolID)) {
     // charged particle in amplification gap (Hcel)
     if (fMC->IsTrackEntering() || fMC->IsNewTrack()) {                                     // entering or newly created
-      eloss = 0;                                                                           // reset Eloss collector
-      fMC->TrackPosition(in[0], in[1], in[2]);                                             // take position at the entrance
+      mMipEloss = 0;                                                                       // reset Eloss collector
+      fMC->TrackPosition(mMipEntry[0], mMipEntry[1], mMipEntry[2]);                        // take position at the entrance
     } else if (fMC->IsTrackExiting() || fMC->IsTrackStop() || fMC->IsTrackDisappeared()) { // exiting or disappeared
-      eloss += fMC->Edep();                                                                // take into account last step Eloss
+      mMipEloss += fMC->Edep();                                                            // take into account last step Eloss
       Int_t tid = fMC->GetStack()->GetCurrentTrackNumber();                                // take TID
       Int_t pid = fMC->TrackPid();                                                         // take PID
       Double_t out[3];
       fMC->TrackPosition(out[0], out[1], out[2]);  // take MARS position at exit
       Float_t hitTime = (Float_t)fMC->TrackTime(); // hit formation time
-      out[0] = 0.5 * (out[0] + in[0]);             //
-      out[1] = 0.5 * (out[1] + in[1]);             // take hit position at the anod plane
-      out[2] = 0.5 * (out[2] + in[2]);
+      out[0] = 0.5 * (out[0] + mMipEntry[0]);      //
+      out[1] = 0.5 * (out[1] + mMipEntry[1]);      // take hit position at the anod plane
+      out[2] = 0.5 * (out[2] + mMipEntry[2]);
       Int_t idch; // chamber number
       if (volID == mHcel0VolID) {
         idch = 0;
@@ -157,16 +155,16 @@ bool Detector::ProcessHits(FairVolume* v)
       }
       Double_t xl, yl;
       o2::hmpid::Param::instance()->mars2Lors(idch, out, xl, yl); // take LORS position
-      if (eloss > 0) {
+      if (mMipEloss > 0) {
         // HIT for MIP, position near anod plane, eloss will be set to Q
-        AddHit(out[0], out[1], out[2], hitTime, eloss, tid, idch);
-        GenFee(eloss); // generate feedback photons
+        AddHit(out[0], out[1], out[2], hitTime, mMipEloss, tid, idch);
+        GenFee(mMipEloss); // generate feedback photons
         stack->addHit(GetDetId());
-        eloss = 0;
+        mMipEloss = 0;
       }
     } else {
       // just going inside
-      eloss += fMC->Edep(); // collect this step eloss
+      mMipEloss += fMC->Edep(); // collect this step eloss
     }
     return kTRUE;
   } // MIP in GAP

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

@@ -155,7 +155,8 @@ class Detector : public o2::base::DetImpl<Detector>
   int mHitCounter = 0;
   int mElectronCounter = 0;
   int mStepCounter = 0;
-  ElementalHit mHitLast{}; ///<! buffer last processed hit to be able to fill it to mHitsPerSectorCollection
+  double mLastReferenceR = 0;        ///<! track length at the last stored track reference (cm)
+  ElementalHit mHitLast{};           ///<! buffer last processed hit to be able to fill it to mHitsPerSectorCollection
   HitGroup* mCurrentGroup = nullptr; ///<! hit group currently being filled
   int mOldTrackId = -1;              ///<! track of the current hit group
   int mOldSectorId = -1;             ///<! sector of the current hit group

Detectors/TPC/simulation/src/Detector.cxx

@@ -116,8 +116,7 @@ Bool_t Detector::ProcessHits(FairVolume* vol)
   mStepCounter++;
   auto& gasParam = ParameterGas::Instance();
   auto& detParam = ParameterDetector::Instance();
-  const Int_t kMaxDistRef = 15;       // maximal difference between 2 stored references - the parameter should be 15 cm as default
-  static Double_t lastReferenceR = 0; // keeps last reference point in radius (cm)
+  const Int_t kMaxDistRef = 15; // maximal difference between 2 stored references - the parameter should be 15 cm as default
 
   /* This method is called from the MC stepping for the sensitive volume only */
   //   LOG(info) << "tpc::ProcessHits";
@@ -166,7 +165,7 @@ Bool_t Detector::ProcessHits(FairVolume* vol)
   // if (sectorID != 0) return kFALSE;
 
   // ---| momentum and beta gamma |---
-  static TLorentzVector momentum; // static to make avoid creation/deletion of this expensive object
+  TLorentzVector momentum;
   fMC->TrackMomentum(momentum);
 
   const float time = fMC->TrackTime() * 1.0e9;
@@ -175,12 +174,12 @@ Bool_t Detector::ProcessHits(FairVolume* vol)
   if (fMC->IsTrackEntering() || fMC->IsTrackExiting()) {
     stack->addTrackReference(o2::TrackReference(position.X(), position.Y(), position.Z(), momentum.X(), momentum.Y(),
                                                 momentum.Z(), fMC->TrackLength(), time, trackID, GetDetId()));
-    lastReferenceR = fMC->TrackLength();
+    mLastReferenceR = fMC->TrackLength();
   }
-  if (TMath::Abs(lastReferenceR - fMC->TrackLength()) > kMaxDistRef) { /// we can speedup
+  if (TMath::Abs(mLastReferenceR - fMC->TrackLength()) > kMaxDistRef) { /// we can speedup
     stack->addTrackReference(o2::TrackReference(position.X(), position.Y(), position.Z(), momentum.X(), momentum.Y(),
                                                 momentum.Z(), fMC->TrackLength(), time, trackID, GetDetId()));
-    lastReferenceR = fMC->TrackLength();
+    mLastReferenceR = fMC->TrackLength();
   }
 
   // ---| remove clusters between the IFC and the FC strips |---

Steer/include/Steer/MaterialBudgetMap.h

@@ -43,21 +43,22 @@ class MaterialBudgetMap
   void FinishEvent();
 
  private:
-  Int_t mMode;      //! mode
-  Float_t mTotRadl; //! Total Radiation length
-  Float_t mTotAbso; //! Total absorption length
-  Float_t mTotGcm2; //! Total g/cm2 traversed
-  TH2F* mHistRadl;  //! Radiation length map
-  TH2F* mHistAbso;  //! Interaction length map
-  TH2F* mHistGcm2;  //! g/cm2 length map
-  TH2F* mHistReta;  //! Radiation length map as a function of eta
-  TH2F* mRZR;       //! Radiation lenghts at (R.Z)
-  TH2F* mRZA;       //! Absorbtion lengths at (R,Z)
-  TH2F* mRZG;       //! Density at (R,Z)
-  Bool_t mStopped;  //! Scoring has been stopped
-  Float_t mRmin;    //! minimum radius
-  Float_t mZmax;    //! maximum radius
-  Float_t mRmax;    //! maximum z
+  Int_t mMode;                 //! mode
+  Float_t mTotRadl;            //! Total Radiation length
+  Float_t mTotAbso;            //! Total absorption length
+  Float_t mTotGcm2;            //! Total g/cm2 traversed
+  TH2F* mHistRadl;             //! Radiation length map
+  TH2F* mHistAbso;             //! Interaction length map
+  TH2F* mHistGcm2;             //! g/cm2 length map
+  TH2F* mHistReta;             //! Radiation length map as a function of eta
+  TH2F* mRZR;                  //! Radiation lenghts at (R.Z)
+  TH2F* mRZA;                  //! Absorbtion lengths at (R,Z)
+  TH2F* mRZG;                  //! Density at (R,Z)
+  Bool_t mStopped;             //! Scoring has been stopped
+  Float_t mRmin;               //! minimum radius
+  Float_t mZmax;               //! maximum radius
+  Float_t mRmax;               //! maximum z
+  Float_t mDistToBoundary = 0; //! distance to the scoring boundary from the previous step
 };
 } // namespace steer
 } // namespace o2

Steer/src/MaterialBudgetMap.cxx

@@ -180,11 +180,10 @@ void MaterialBudgetMap::Stepping()
   // called from AliRun::Stepmanager from gustep.
   // Accumulate the 3 parameters step by step
   //
-  static Float_t t;
   Float_t a, z, dens, radl, absl;
   Int_t i, id, copy;
   const char* vol;
-  static Float_t vect[3], dir[3];
+  Float_t vect[3], dir[3];
 
   TString tmp1, tmp2;
   copy = 1;
@@ -212,12 +211,12 @@ void MaterialBudgetMap::Stepping()
       // Not the first step, add past contribution
       if (!mStopped) {
         if (absl) {
-          mTotAbso += t / absl;
+          mTotAbso += mDistToBoundary / absl;
         }
         if (radl) {
-          mTotRadl += t / radl;
+          mTotRadl += mDistToBoundary / radl;
         }
-        mTotGcm2 += t * dens;
+        mTotGcm2 += mDistToBoundary * dens;
       } // not stooped
     }   // not a new track !
     mStopped = kTRUE;
@@ -231,7 +230,7 @@ void MaterialBudgetMap::Stepping()
     dir[i] = mom[i];
   }
 
-  t = eventgen::GeneratorGeantinos::PropagateCylinder(vect, dir, mRmax, mZmax);
+  mDistToBoundary = eventgen::GeneratorGeantinos::PropagateCylinder(vect, dir, mRmax, mZmax);
 
   if (step) {
     if (absl) {

Steer/src/O2MCApplication.cxx

@@ -59,7 +59,7 @@ namespace steer
 template <typename T>
 void TypedVectorAttach(const char* name, fair::mq::Channel& channel, fair::mq::Parts& parts)
 {
-  static auto mgr = FairRootManager::Instance();
+  auto mgr = FairRootManager::Instance();
   auto vector = mgr->InitObjectAs<const std::vector<T>*>(name);
   if (vector) {
     auto buffer = (char*)&(*vector)[0];