feat: Allow Core CKF to skip the start surface

Core/include/Acts/TrackFinding/CombinatorialKalmanFilter.hpp

@@ -234,6 +234,10 @@ struct CombinatorialKalmanFilterOptions {
 
   /// Whether to consider energy loss.
   bool energyLoss = true;
+
+  /// Skip the pre propagation call. This effectively skips the first surface
+  /// @note This is useful if the first surface should not be considered in a second reverse pass
+  bool skipPrePropagationUpdate = false;
 };
 
 template <typename track_container_t>
@@ -524,6 +528,9 @@ class CombinatorialKalmanFilter {
     /// Whether to consider energy loss.
     bool energyLoss = true;
 
+    /// Skip the pre propagation call. This effectively skips the first surface
+    bool skipPrePropagationUpdate = false;
+
     /// Calibration context for the finding run
     const CalibrationContext* calibrationContextPtr{nullptr};
 
@@ -547,6 +554,12 @@ class CombinatorialKalmanFilter {
         return;
       }
 
+      if (state.stage == PropagatorStage::prePropagation &&
+          skipPrePropagationUpdate) {
+        ACTS_VERBOSE("Skip first surface");
+        return;
+      }
+
       ACTS_VERBOSE("CombinatorialKalmanFilter step");
 
       assert(!result.activeBranches.empty() && "No active branches");
@@ -1263,6 +1276,8 @@ class CombinatorialKalmanFilter {
     combKalmanActor.targetReached.surface = tfOptions.targetSurface;
     combKalmanActor.multipleScattering = tfOptions.multipleScattering;
     combKalmanActor.energyLoss = tfOptions.energyLoss;
+    combKalmanActor.skipPrePropagationUpdate =
+        tfOptions.skipPrePropagationUpdate;
     combKalmanActor.actorLogger = m_actorLogger.get();
     combKalmanActor.updaterLogger = m_updaterLogger.get();
     combKalmanActor.calibrationContextPtr = &tfOptions.calibrationContext.get();

Examples/Algorithms/TrackFinding/src/TrackFindingAlgorithm.cpp

@@ -368,6 +368,7 @@ ProcessCode TrackFindingAlgorithm::execute(const AlgorithmContext& ctx) const {
                                    ctx.calibContext, slAccessorDelegate,
                                    extensions, secondPropOptions);
   secondOptions.targetSurface = m_cfg.reverseSearch ? nullptr : pSurface.get();
+  secondOptions.skipPrePropagationUpdate = true;
 
   using Extrapolator = Acts::Propagator<Acts::SympyStepper, Acts::Navigator>;
   using ExtrapolatorOptions =
@@ -542,9 +543,6 @@ ProcessCode TrackFindingAlgorithm::execute(const AlgorithmContext& ctx) const {
                 ACTS_WARNING("Second track has no reference surface.");
                 continue;
               }
-              if (secondTrack.nMeasurements() <= 1) {
-                continue;
-              }
 
               // TODO a copy of the track should not be necessary but is the
               //      safest way with the current EDM
@@ -559,8 +557,7 @@ ProcessCode TrackFindingAlgorithm::execute(const AlgorithmContext& ctx) const {
               secondTrackCopy.reverseTrackStates(true);
 
               firstState.previous() =
-                  (*std::next(secondTrackCopy.trackStatesReversed().begin()))
-                      .index();
+                  secondTrackCopy.outermostTrackState().index();
 
               // finalize the track candidate
 

Examples/Python/tests/root_file_hashes.txt

@@ -32,16 +32,16 @@ test_digitization_example_input[smeared]__particles.root: 5fe7dda2933ee6b9615b06
 test_digitization_example_input[smeared]__measurements.root: 243c2f69b7b0db9dbeaa7494d4ea0f3dd1691dc90f16e10df6c0491ff4dc7d62
 test_digitization_example_input[geometric]__particles.root: 5fe7dda2933ee6b9615b064d192322fe07831133cd998e5ed99a3b992b713a10
 test_digitization_example_input[geometric]__measurements.root: 63ec81635979058fb8976f94455bf490cf92b7b142c4a05cc39de6225f5de2fb
-test_ckf_tracks_example[generic-full_seeding]__trackstates_ckf.root: c4eb6e58fe2351f41dce134878e523f8b78b875ffd5c87bb094ebb3aa0e8e432
-test_ckf_tracks_example[generic-full_seeding]__tracksummary_ckf.root: 4fa859b395e172c613d466a2ea25cdd56ed1ab3cfd857d230f21bc184310d668
+test_ckf_tracks_example[generic-full_seeding]__trackstates_ckf.root: b61fa5d207d3d87742a8bae454eb4c97b2ef6613fe38f388f147da104ec7ff84
+test_ckf_tracks_example[generic-full_seeding]__tracksummary_ckf.root: 18580d384e3ceb126be9c5d8857e176cff6c7d549155012d87939c91dba87015
 test_ckf_tracks_example[generic-full_seeding]__performance_seeding_trees.root: 0e0676ffafdb27112fbda50d1cf627859fa745760f98073261dcf6db3f2f991e
 test_ckf_tracks_example[generic-truth_estimated]__trackstates_ckf.root: afc9984f5b1f0b9d42156a1c3917df68144f1c486dd2b9b9a199309aa958cddc
 test_ckf_tracks_example[generic-truth_estimated]__tracksummary_ckf.root: e5db2791d9d09d88705c0dbeba666b4df441ecc920b9e400510df2913766e112
 test_ckf_tracks_example[generic-truth_estimated]__performance_seeding.root: 1facb05c066221f6361b61f015cdf0918e94d9f3fce2269ec7b6a4dffeb2bc7e
 test_ckf_tracks_example[generic-truth_smeared]__trackstates_ckf.root: 47c5e18de310363fdebe79d6c82c3cf5407200f2f06879f79217924d28a67a6e
 test_ckf_tracks_example[generic-truth_smeared]__tracksummary_ckf.root: 961aa19995a8a1c64a365c6d72a90eee9809efaaee652b674db287acacfb810c
-test_ckf_tracks_example[odd-full_seeding]__trackstates_ckf.root: 4d3003d1d49a46d354301d2dc2689fc806b2a3e1f68a2e675435d4758b3f21e0
-test_ckf_tracks_example[odd-full_seeding]__tracksummary_ckf.root: 59537c52d23a77dbed9230c7b92cf653f7592c72fb882e8a24a2b33f1d27019e
+test_ckf_tracks_example[odd-full_seeding]__trackstates_ckf.root: a4e58050b9b655774a29679980a0e9b09aeda576da91c8d4220d84f2ff0bb9cb
+test_ckf_tracks_example[odd-full_seeding]__tracksummary_ckf.root: 7f27186a9678c1e36e68836a916b09c4d54d92ddd5c3fb60d1077fd74ae18bbe
 test_ckf_tracks_example[odd-full_seeding]__performance_seeding_trees.root: 43c58577aafe07645e5660c4f43904efadf91d8cda45c5c04c248bbe0f59814f
 test_ckf_tracks_example[odd-truth_estimated]__trackstates_ckf.root: 2c6feb705cdb17010d4a0d1287693c376b77b7f91cf80e595059ea43de2721e5
 test_ckf_tracks_example[odd-truth_estimated]__tracksummary_ckf.root: 3a092423e717b1fe76f78f6b95eb6df67648a196e8c4da32158061d4bc490578