Optionally refit ITS outward seeding with inward refit result

By default set to false as no effect of repeating this fit was seen so far.

Author: shahor02

Detectors/ITSMFT/ITS/tracking/GPU/ITStrackingGPU/TrackingKernels.h

@@ -219,6 +219,7 @@ void trackSeedHandler(CellSeed<nLayers>* trackSeeds,
                       const float maxChi2ClusterAttachment,
                       const float maxChi2NDF,
                       const int reseedIfShorter,
+                      const bool repeatRefitOut,
                       const bool shiftRefToCluster,
                       const o2::base::Propagator* propagator,
                       const o2::base::PropagatorF::MatCorrType matCorrType,

Detectors/ITSMFT/ITS/tracking/GPU/cuda/TrackerTraitsGPU.cxx

@@ -336,6 +336,7 @@ void TrackerTraitsGPU<nLayers>::findRoads(const int iteration)
                      startLevel,                                       // const int startLevel,
                      this->mTrkParams[0].MaxChi2ClusterAttachment,     // float maxChi2ClusterAttachment
                      this->mTrkParams[0].MaxChi2NDF,                   // float maxChi2NDF
+                     this->mTrkParams[0].RepeatRefitOut,
                      this->mTrkParams[0].ReseedIfShorter,
                      this->mTrkParams[0].ShiftRefToCluster,
                      mTimeFrameGPU->getDevicePropagator(), // const o2::base::Propagator* propagator

Detectors/ITSMFT/ITS/tracking/GPU/cuda/TrackingKernels.cu

@@ -291,6 +291,7 @@ GPUg() void __launch_bounds__(256, 1) fitTrackSeedsKernel(
   const float maxChi2ClusterAttachment,
   const float maxChi2NDF,
   const int reseedIfShorter,
+  const bool repeatRefitOut,
   const bool shifRefToCluster,
   const o2::base::Propagator* propagator,
   const o2::base::PropagatorF::MatCorrType matCorrType)
@@ -337,6 +338,34 @@ GPUg() void __launch_bounds__(256, 1) fitTrackSeedsKernel(
     if (!fitSuccess || temporaryTrack.getPt() < minPts[nLayers - temporaryTrack.getNClusters()]) {
       continue;
     }
+    if (repeatRefitOut) { // repeat outward refit seeding and linearizing with the stable inward fit result
+      o2::track::TrackParCov saveInw{temporaryTrack};
+      linRef = saveInw; // use refitted track as lin.reference
+      float saveChi2 = temporaryTrack.getChi2();
+      temporaryTrack.resetCovariance();
+      temporaryTrack.setCov(temporaryTrack.getQ2Pt() * temporaryTrack.getQ2Pt() * temporaryTrack.getCov()[o2::track::CovLabels::kSigQ2Pt2], o2::track::CovLabels::kSigQ2Pt2);
+      temporaryTrack.setChi2(0);
+      fitSuccess = fitTrack(temporaryTrack,               // TrackITSExt& track,
+                            0,                            // int lastLayer,
+                            nLayers,                      // int firstLayer,
+                            1,                            // int firstCluster,
+                            maxChi2ClusterAttachment,     // float maxChi2ClusterAttachment,
+                            maxChi2NDF,                   // float maxChi2NDF,
+                            o2::constants::math::VeryBig, // float maxQoverPt,
+                            0,                            // nCl,
+                            bz,                           // float bz,
+                            foundTrackingFrameInfo,       // TrackingFrameInfo** trackingFrameInfo,
+                            propagator,                   // const o2::base::Propagator* propagator,
+                            matCorrType,                  // o2::base::PropagatorF::MatCorrType matCorrType
+                            &linRef,
+                            shifRefToCluster);
+      if (!fitSuccess) {
+        continue;
+      }
+      temporaryTrack.getParamOut() = temporaryTrack.getParamIn();
+      temporaryTrack.getParamIn() = saveInw;
+      temporaryTrack.setChi2(saveChi2);
+    }
     tracks[iCurrentTrackSeedIndex] = temporaryTrack;
   }
 }
@@ -1174,6 +1203,7 @@ void trackSeedHandler(CellSeed<nLayers>* trackSeeds,
                       const float maxChi2ClusterAttachment,
                       const float maxChi2NDF,
                       const int reseedIfShorter,
+                      const bool repeatRefitOut,
                       const bool shiftRefToCluster,
                       const o2::base::Propagator* propagator,
                       const o2::base::PropagatorF::MatCorrType matCorrType,
@@ -1195,6 +1225,7 @@ void trackSeedHandler(CellSeed<nLayers>* trackSeeds,
     maxChi2ClusterAttachment,                 // float
     maxChi2NDF,                               // float
     reseedIfShorter,                          // int
+    repeatRefitOut,                           // bool
     shiftRefToCluster,                        // bool
     propagator,                               // const o2::base::Propagator*
     matCorrType);                             // o2::base::PropagatorF::MatCorrType
@@ -1375,6 +1406,7 @@ template void trackSeedHandler(CellSeed<7>* trackSeeds,
                                const float maxChi2ClusterAttachment,
                                const float maxChi2NDF,
                                const int reseedIfShorter,
+                               const bool repeatRefitOut,
                                const bool shiftRefToCluster,
                                const o2::base::Propagator* propagator,
                                const o2::base::PropagatorF::MatCorrType matCorrType,

Detectors/ITSMFT/ITS/tracking/include/ITStracking/Configuration.h

@@ -69,6 +69,7 @@ struct TrackingParameters {
   int ReseedIfShorter = 6; // reseed for the final fit track with the length shorter than this
   std::vector<float> MinPt = {0.f, 0.f, 0.f, 0.f};
   unsigned char StartLayerMask = 0x7F;
+  bool RepeatRefitOut = true;    // repeat outward refit using inward refit as a seed
   bool ShiftRefToCluster = true; // TrackFit: after update shift the linearization reference to cluster
   bool FindShortTracks = false;
   bool PerPrimaryVertexProcessing = false;

Detectors/ITSMFT/ITS/tracking/include/ITStracking/TrackingConfigParam.h

@@ -98,6 +98,7 @@ struct TrackerParamConfig : public o2::conf::ConfigurableParamHelper<TrackerPara
   int nIterations = MaxIter;               // overwrite the number of iterations
   int reseedIfShorter = 6;                 // for the final refit reseed the track with circle if they are shorter than this value
   bool shiftRefToCluster{true};            // TrackFit: after update shift the linearization reference to cluster
+  bool repeatRefitOut{false};              // repeat outward refit using inward refit as a seed
   bool createArtefactLabels{false}; // create on-the-fly labels for the artefacts
 
   int nThreads = 1;

Detectors/ITSMFT/ITS/tracking/src/Configuration.cxx

@@ -187,6 +187,7 @@ std::vector<TrackingParameters> TrackingMode::getTrackingParameters(TrackingMode
       p.MinPt[lslot] *= bFactor;
     }
     p.ReseedIfShorter = tc.reseedIfShorter;
+    p.RepeatRefitOut = tc.repeatRefitOut;
     p.ShiftRefToCluster = tc.shiftRefToCluster;
     p.createArtefactLabels = tc.createArtefactLabels;
 

Detectors/ITSMFT/ITS/tracking/src/TrackerTraits.cxx

@@ -778,6 +778,22 @@ void TrackerTraits<nLayers>::findRoads(const int iteration)
         if (!fitSuccess || temporaryTrack.getPt() < mTrkParams[iteration].MinPt[mTrkParams[iteration].NLayers - temporaryTrack.getNClusters()]) {
           return 0;
         }
+        if (mTrkParams[0].RepeatRefitOut) { // repeat outward refit seeding and linearizing with the stable inward fit result
+          o2::track::TrackParCov saveInw{temporaryTrack};
+          linRef = saveInw; // use refitted track as lin.reference
+          float saveChi2 = temporaryTrack.getChi2();
+          temporaryTrack.resetCovariance();
+          temporaryTrack.setCov(temporaryTrack.getQ2Pt() * temporaryTrack.getQ2Pt() * temporaryTrack.getCov()[o2::track::CovLabels::kSigQ2Pt2], o2::track::CovLabels::kSigQ2Pt2);
+          temporaryTrack.setChi2(0);
+          fitSuccess = fitTrack(temporaryTrack, 0, mTrkParams[0].NLayers, 1, mTrkParams[0].MaxChi2ClusterAttachment, mTrkParams[0].MaxChi2NDF, o2::constants::math::VeryBig, 0, &linRef);
+          if (!fitSuccess) {
+            return 0;
+          }
+          temporaryTrack.getParamOut() = temporaryTrack.getParamIn();
+          temporaryTrack.getParamIn() = saveInw;
+          temporaryTrack.setChi2(saveChi2);
+        }
+
         if constexpr (decltype(Tag)::value == PassMode::OnePass::value) {
           tracks.push_back(temporaryTrack);
         } else if constexpr (decltype(Tag)::value == PassMode::TwoPassCount::value) {