feat: GSF backward-pass misses as outliers (#1904)

Now, the GSF does flag states as outliers that were missed at the backward pass.

Core/include/Acts/TrackFitting/GaussianSumFitter.hpp

@@ -304,7 +304,7 @@ struct GaussianSumFitter {
     }
 
     if (fwdGsfResult.measurementStates == 0) {
-      return return_error_or_abort(GsfError::NoStatesCreated);
+      return return_error_or_abort(GsfError::NoMeasurementStatesCreatedForward);
     }
 
     ACTS_VERBOSE("Finished forward propagation");
@@ -367,6 +367,7 @@ struct GaussianSumFitter {
 
       r.currentTip = fwdGsfResult.lastMeasurementTip;
       r.visitedSurfaces.push_back(&proxy.referenceSurface());
+      r.surfacesVisitedBwdAgain.push_back(&proxy.referenceSurface());
       r.measurementStates++;
       r.processedStates++;
 
@@ -388,8 +389,9 @@ struct GaussianSumFitter {
       return return_error_or_abort(bwdGsfResult.result.error());
     }
 
-    if (bwdGsfResult.processedStates == 0) {
-      return return_error_or_abort(GsfError::NoStatesCreated);
+    if (bwdGsfResult.measurementStates == 0) {
+      return return_error_or_abort(
+          GsfError::NoMeasurementStatesCreatedBackward);
     }
 
     ////////////////////////////////////
@@ -408,8 +410,29 @@ struct GaussianSumFitter {
       ACTS_DEBUG("Fwd and bwd measuerement states do not match");
     }
 
-    auto track = trackContainer.getTrack(trackContainer.addTrack());
+    // Go through the states and assign outliers / unset smoothed if surface not
+    // passed in backward pass
+    const auto& foundBwd = bwdGsfResult.surfacesVisitedBwdAgain;
+    std::size_t measurementStatesFinal = 0;
+
+    for (auto state :
+         fwdGsfResult.fittedStates->trackStateRange(fwdGsfResult.currentTip)) {
+      const bool found = std::find(foundBwd.begin(), foundBwd.end(),
+                                   &state.referenceSurface()) != foundBwd.end();
+      if (not found && state.typeFlags().test(MeasurementFlag)) {
+        state.typeFlags().set(OutlierFlag);
+        state.typeFlags().reset(MeasurementFlag);
+      }
+
+      measurementStatesFinal +=
+          static_cast<std::size_t>(state.typeFlags().test(MeasurementFlag));
+    }
 
+    if (measurementStatesFinal == 0) {
+      return return_error_or_abort(GsfError::NoMeasurementStatesCreatedFinal);
+    }
+
+    auto track = trackContainer.getTrack(trackContainer.addTrack());
     track.tipIndex() = fwdGsfResult.lastMeasurementTip;
 
     if (options.referenceSurface) {
@@ -419,7 +442,7 @@ struct GaussianSumFitter {
       track.setReferenceSurface(params.referenceSurface().getSharedPtr());
     }
 
-    track.nMeasurements() = fwdGsfResult.measurementStates;
+    track.nMeasurements() = measurementStatesFinal;
     track.nHoles() = fwdGsfResult.measurementHoles;
 
     return track;

Core/include/Acts/TrackFitting/GsfError.hpp

@@ -14,16 +14,10 @@ namespace Acts {
 namespace Experimental {
 
 enum class GsfError {
-  // ensure all values are non-zero
-  NavigationFailed = 1,
-  ComponentNumberMismatch,
-  AllComponentsSteppingError,
-  NoComponentCreated,
-  NoStatesCreated,
-  StartParametersNotOnStartSurface,
-  PropagationEndedOnWrongSurface,
-  LastStepParamsContainNan,
-  SmoothingFailed
+  NoMeasurementStatesCreatedForward = 1,
+  NoMeasurementStatesCreatedBackward,
+  NoMeasurementStatesCreatedFinal,
+  StartParametersNotOnStartSurface
 };
 
 std::error_code make_error_code(GsfError e);

Core/include/Acts/TrackFitting/detail/GsfActor.hpp

@@ -54,7 +54,7 @@ struct GsfResult {
   std::size_t processedStates = 0;
 
   std::vector<const Acts::Surface*> visitedSurfaces;
-  std::vector<const Acts::Surface*> missedActiveSurfaces;
+  std::vector<const Acts::Surface*> surfacesVisitedBwdAgain;
 
   // Propagate potential errors to the outside
   Result<void> result{Result<void>::success()};
@@ -662,7 +662,6 @@ struct GsfActor {
 
     // These things should only be done once for all components
     if (is_hole) {
-      result.missedActiveSurfaces.push_back(&surface);
       ++result.measurementHoles;
     }
 
@@ -762,6 +761,7 @@ struct GsfActor {
 
               trackState.filtered() = filtMean;
               trackState.filteredCovariance() = filtCov;
+              result.surfacesVisitedBwdAgain.push_back(&surface);
               return false;
             }
             return true;

Core/src/TrackFitting/GsfError.cpp

@@ -20,25 +20,14 @@ class GsfErrorCategory : public std::error_category {
     using Acts::Experimental::GsfError;
 
     switch (static_cast<GsfError>(c)) {
-      case GsfError::NavigationFailed:
-        return "Navigation failed, forward and backward pass incompatible";
-      case GsfError::ComponentNumberMismatch:
-        return "Component Number changed during two GSF calls";
-      case GsfError::AllComponentsSteppingError:
-        return "Stepping errors occurred in all components";
-      case GsfError::NoComponentCreated:
-        return "No component has been created in the filter step";
-      case GsfError::NoStatesCreated:
-        return "No states where created in the MultiTrajectory";
       case GsfError::StartParametersNotOnStartSurface:
         return "Start parameters don't lie in the start surface";
-      case GsfError::PropagationEndedOnWrongSurface:
-        return "The propagation did not reach the correct target surface";
-      case GsfError::LastStepParamsContainNan:
-        return "The parameters to start the last step with contain NAN values";
-      case GsfError::SmoothingFailed:
-        return "Smoothing failed because the difference between fwd and bwd "
-               "was to big";
+      case GsfError::NoMeasurementStatesCreatedForward:
+        return "No measurement states found in the forward pass";
+      case GsfError::NoMeasurementStatesCreatedBackward:
+        return "No measurement states found in the backward pass";
+      case GsfError::NoMeasurementStatesCreatedFinal:
+        return "No measurement states in the final trajectory";
       default:
         return "unknown";
     }

Examples/Python/tests/root_file_hashes.txt

@@ -34,10 +34,10 @@ test_truth_tracking_kalman[odd-0.0]__performance_track_finder.root: dacf32346bca
 test_truth_tracking_kalman[odd-1000.0]__trackstates_fitter.root: c76b77c50bd054594d0fc8dd5262a602f1c38c49611f6b975a60e77a83eb6525
 test_truth_tracking_kalman[odd-1000.0]__tracksummary_fitter.root: 0f26a2e7c67407e0c7092b2d861753d658529147ff2dc4ea968a9c9f28a19bf9
 test_truth_tracking_kalman[odd-1000.0]__performance_track_finder.root: dacf32346bca4c7010ca6a21f4868e2a9cdbc764d0918cb498cefdf322567716
-test_truth_tracking_gsf[generic]__trackstates_gsf.root: 8c26b89ca9168b6b5e84444ac1cc90cb6316b81a2c8586b8134e9d161cf05e33
-test_truth_tracking_gsf[generic]__tracksummary_gsf.root: f313dfbe29b6b3cbc4f1fb10982169424287ca170bc7807eaa36137e8761f457
-test_truth_tracking_gsf[odd]__trackstates_gsf.root: e540ca7af70fe9cc2cc41708750cd0fd420e4bf1667774a5967f91f7c5882c4f
-test_truth_tracking_gsf[odd]__tracksummary_gsf.root: 2d24d7352e8084b9bd643e8d9802dd4aecc84b73f833170a8e2cabb1887b1edc
+test_truth_tracking_gsf[generic]__trackstates_gsf.root: 34f3f0f1e0733ae63bb7bcb99028395da9e5acb3ff267c85042ed3c463e9698b
+test_truth_tracking_gsf[generic]__tracksummary_gsf.root: c183dfb54d3c37ef11544c926eb9e1f69584322f75142c0aa07a857fa389dba9
+test_truth_tracking_gsf[odd]__trackstates_gsf.root: 50ce998036bfe46a2bd5bd6d9b3802ff0f70f1486d55dbc7518aec3b2599b2e9
+test_truth_tracking_gsf[odd]__tracksummary_gsf.root: 2510705988aaea0adfaf3f0d414b0fe8fbc51dfef5ff3ca923358d76e217fa1b
 test_particle_gun__particles.root: 8549ba6e20338004ab8ba299fc65e1ee5071985b46df8f77f887cb6fef56a8ec
 test_material_mapping__material-map_tracks.root: 90a7deab073691ef431a3711e9cba40e902ce4de92a9b57162d84fbef5f97039
 test_material_mapping__propagation-material.root: c60b17ddc4921847bb3e9ebf58de10322d0d3888596ee1106f160055647d8445