refactor!: (gx2f) remove zeroField option and make implicit

Core/include/Acts/TrackFitting/GlobalChiSquareFitter.hpp

@@ -108,7 +108,6 @@ struct Gx2FitterOptions {
   /// @param eLoss Whether to include energy loss
   /// @param freeToBoundCorrection_ Correction for non-linearity effect during transform from free to bound
   /// @param nUpdateMax_ Max number of iterations for updating the parameters
-  /// @param zeroField_ Disables the QoP fit in case of missing B-field
   /// @param relChi2changeCutOff_ Check for convergence (abort condition). Set to 0 to skip.
   Gx2FitterOptions(const GeometryContext& gctx,
                    const MagneticFieldContext& mctx,
@@ -120,7 +119,6 @@ struct Gx2FitterOptions {
                    const FreeToBoundCorrection& freeToBoundCorrection_ =
                        FreeToBoundCorrection(false),
                    const std::size_t nUpdateMax_ = 5,
-                   const bool zeroField_ = false,
                    double relChi2changeCutOff_ = 1e-5)
       : geoContext(gctx),
         magFieldContext(mctx),
@@ -132,7 +130,6 @@ struct Gx2FitterOptions {
         energyLoss(eLoss),
         freeToBoundCorrection(freeToBoundCorrection_),
         nUpdateMax(nUpdateMax_),
-        zeroField(zeroField_),
         relChi2changeCutOff(relChi2changeCutOff_) {}
 
   /// Contexts are required and the options must not be default-constructible.
@@ -166,9 +163,6 @@ struct Gx2FitterOptions {
   /// Max number of iterations during the fit (abort condition)
   std::size_t nUpdateMax = 5;
 
-  /// Disables the QoP fit in case of missing B-field
-  bool zeroField = false;
-
   /// Check for convergence (abort condition). Set to 0 to skip.
   double relChi2changeCutOff = 1e-7;
 };
@@ -298,7 +292,7 @@ void addToGx2fSums(BoundMatrix& aMatrix, BoundVector& bVector, double& chi2sum,
   }
 }
 
-BoundVector calculateDeltaParams(bool zeroField, const BoundMatrix& aMatrix,
+BoundVector calculateDeltaParams(const BoundMatrix& aMatrix,
                                  const BoundVector& bVector);
 
 /// Global Chi Square fitter (GX2F) implementation.
@@ -864,8 +858,7 @@ class Gx2Fitter {
       }
 
       // calculate delta params [a] * delta = b
-      deltaParams =
-          calculateDeltaParams(gx2fOptions.zeroField, aMatrix, bVector);
+      deltaParams = calculateDeltaParams(aMatrix, bVector);
 
       ACTS_VERBOSE("aMatrix:\n"
                    << aMatrix << "\n"
@@ -910,7 +903,7 @@ class Gx2Fitter {
     // Calculate covariance of the fitted parameters with inverse of [a]
     BoundMatrix fullCovariancePredicted = BoundMatrix::Identity();
     bool aMatrixIsInvertible = false;
-    if (gx2fOptions.zeroField) {
+    if (aMatrix(4, 4) == 0) {
       constexpr std::size_t reducedMatrixSize = 4;
 
       auto safeReducedCovariance = safeInverse(
@@ -921,9 +914,20 @@ class Gx2Fitter {
             .topLeftCorner<reducedMatrixSize, reducedMatrixSize>() =
             *safeReducedCovariance;
       }
-    } else {
+    } else if (aMatrix(5, 5) == 0) {
       constexpr std::size_t reducedMatrixSize = 5;
 
+      auto safeReducedCovariance = safeInverse(
+          aMatrix.topLeftCorner<reducedMatrixSize, reducedMatrixSize>().eval());
+      if (safeReducedCovariance) {
+        aMatrixIsInvertible = true;
+        fullCovariancePredicted
+            .topLeftCorner<reducedMatrixSize, reducedMatrixSize>() =
+            *safeReducedCovariance;
+      }
+    } else {
+      constexpr std::size_t reducedMatrixSize = 6;
+
       auto safeReducedCovariance = safeInverse(
           aMatrix.topLeftCorner<reducedMatrixSize, reducedMatrixSize>().eval());
       if (safeReducedCovariance) {

Core/src/TrackFitting/GlobalChiSquareFitter.cpp

@@ -12,23 +12,30 @@
 
 namespace Acts::Experimental {
 
-BoundVector calculateDeltaParams(bool zeroField, const BoundMatrix& aMatrix,
+BoundVector calculateDeltaParams(const BoundMatrix& aMatrix,
                                  const BoundVector& bVector) {
   BoundVector deltaParams = BoundVector::Zero();
-  if (zeroField) {
+  if (aMatrix(4, 4) == 0) {
     constexpr std::size_t reducedMatrixSize = 4;
     deltaParams.topLeftCorner<reducedMatrixSize, 1>() =
         aMatrix.topLeftCorner<reducedMatrixSize, reducedMatrixSize>()
             .colPivHouseholderQr()
             .solve(bVector.topLeftCorner<reducedMatrixSize, 1>());
-  } else {
+  } else if (aMatrix(5, 5) == 0) {
     constexpr std::size_t reducedMatrixSize = 5;
     deltaParams.topLeftCorner<reducedMatrixSize, 1>() =
         aMatrix.topLeftCorner<reducedMatrixSize, reducedMatrixSize>()
             .colPivHouseholderQr()
             .solve(bVector.topLeftCorner<reducedMatrixSize, 1>());
+  } else {
+    constexpr std::size_t reducedMatrixSize = 6;
+    deltaParams.topLeftCorner<reducedMatrixSize, 1>() =
+        aMatrix.topLeftCorner<reducedMatrixSize, reducedMatrixSize>()
+            .colPivHouseholderQr()
+            .solve(bVector.topLeftCorner<reducedMatrixSize, 1>());
   }
 
   return deltaParams;
 }
+
 }  // namespace Acts::Experimental

Examples/Algorithms/TrackFitting/include/ActsExamples/TrackFitting/TrackFitterFunction.hpp

@@ -105,7 +105,6 @@ std::shared_ptr<TrackFitterFunction> makeGsfFitterFunction(
 /// @param energyLoss bool
 /// @param freeToBoundCorrection bool
 /// @param nUpdateMax max number of iterations during the fit
-/// @param zerofield Disables the QoP fit in case of missing B-field.
 /// @param relChi2changeCutOff Check for convergence (abort condition). Set to 0 to skip.
 /// @param logger a logger instance
 std::shared_ptr<TrackFitterFunction> makeGlobalChiSquareFitterFunction(
@@ -114,8 +113,7 @@ std::shared_ptr<TrackFitterFunction> makeGlobalChiSquareFitterFunction(
     bool multipleScattering = true, bool energyLoss = true,
     Acts::FreeToBoundCorrection freeToBoundCorrection =
         Acts::FreeToBoundCorrection(),
-    std::size_t nUpdateMax = 5, bool zeroField = false,
-    double relChi2changeCutOff = 1e-7,
+    std::size_t nUpdateMax = 5, double relChi2changeCutOff = 1e-7,
     const Acts::Logger& logger = *Acts::getDefaultLogger("Gx2f",
                                                          Acts::Logging::INFO));
 

Examples/Algorithms/TrackFitting/src/GlobalChiSquareFitterFunction.cpp

@@ -69,7 +69,6 @@ struct GlobalChiSquareFitterFunctionImpl final : public TrackFitterFunction {
   bool energyLoss = false;
   Acts::FreeToBoundCorrection freeToBoundCorrection;
   std::size_t nUpdateMax = 5;
-  bool zeroField = false;
   double relChi2changeCutOff = 1e-7;
 
   IndexSourceLink::SurfaceAccessor m_slSurfaceAccessor;
@@ -95,7 +94,7 @@ struct GlobalChiSquareFitterFunctionImpl final : public TrackFitterFunction {
         options.geoContext, options.magFieldContext, options.calibrationContext,
         extensions, options.propOptions, &(*options.referenceSurface),
         multipleScattering, energyLoss, freeToBoundCorrection, nUpdateMax,
-        zeroField, relChi2changeCutOff);
+        relChi2changeCutOff);
 
     return gx2fOptions;
   }
@@ -132,7 +131,7 @@ ActsExamples::makeGlobalChiSquareFitterFunction(
     std::shared_ptr<const Acts::MagneticFieldProvider> magneticField,
     bool multipleScattering, bool energyLoss,
     Acts::FreeToBoundCorrection freeToBoundCorrection, std::size_t nUpdateMax,
-    bool zeroField, double relChi2changeCutOff, const Acts::Logger& logger) {
+    double relChi2changeCutOff, const Acts::Logger& logger) {
   // Stepper should be copied into the fitters
   const Stepper stepper(std::move(magneticField));
 
@@ -162,7 +161,6 @@ ActsExamples::makeGlobalChiSquareFitterFunction(
   fitterFunction->energyLoss = energyLoss;
   fitterFunction->freeToBoundCorrection = freeToBoundCorrection;
   fitterFunction->nUpdateMax = nUpdateMax;
-  fitterFunction->zeroField = zeroField;
   fitterFunction->relChi2changeCutOff = relChi2changeCutOff;
 
   return fitterFunction;

Examples/Python/python/acts/examples/reconstruction.py

@@ -1359,7 +1359,6 @@ def addGx2fTracks(
     multipleScattering: bool = False,
     energyLoss: bool = False,
     nUpdateMax: int = 5,
-    zeroField: bool = False,
     relChi2changeCutOff: float = 1e-7,
     clusters: str = None,
     calibrator: acts.examples.MeasurementCalibrator = acts.examples.makePassThroughCalibrator(),
@@ -1372,7 +1371,6 @@ def addGx2fTracks(
         "energyLoss": energyLoss,
         "freeToBoundCorrection": acts.examples.FreeToBoundCorrection(False),
         "nUpdateMax": nUpdateMax,
-        "zeroField": zeroField,
         "relChi2changeCutOff": relChi2changeCutOff,
         "level": customLogLevel(),
     }

Examples/Python/src/TrackFitting.cpp

@@ -138,17 +138,17 @@ void addTrackFitting(Context& ctx) {
            std::shared_ptr<const Acts::MagneticFieldProvider> magneticField,
            bool multipleScattering, bool energyLoss,
            Acts::FreeToBoundCorrection freeToBoundCorrection,
-           std::size_t nUpdateMax, bool zeroField, double relChi2changeCutOff,
+           std::size_t nUpdateMax, double relChi2changeCutOff,
            Logging::Level level) {
           return ActsExamples::makeGlobalChiSquareFitterFunction(
               trackingGeometry, magneticField, multipleScattering, energyLoss,
-              freeToBoundCorrection, nUpdateMax, zeroField, relChi2changeCutOff,
+              freeToBoundCorrection, nUpdateMax, relChi2changeCutOff,
               *Acts::getDefaultLogger("Gx2f", level));
         },
         py::arg("trackingGeometry"), py::arg("magneticField"),
         py::arg("multipleScattering"), py::arg("energyLoss"),
         py::arg("freeToBoundCorrection"), py::arg("nUpdateMax"),
-        py::arg("zeroField"), py::arg("relChi2changeCutOff"), py::arg("level"));
+        py::arg("relChi2changeCutOff"), py::arg("level"));
   }
 
   {

Tests/UnitTests/Core/TrackFitting/Gx2fTests.cpp

@@ -240,7 +240,7 @@ BOOST_AUTO_TEST_CASE(NoFit) {
 
   Experimental::Gx2FitterOptions gx2fOptions(
       geoCtx, magCtx, calCtx, extensions, PropagatorPlainOptions(), rSurface,
-      false, false, FreeToBoundCorrection(false), 0, true, 0);
+      false, false, FreeToBoundCorrection(false), 0, 0);
 
   Acts::TrackContainer tracks{Acts::VectorTrackContainer{},
                               Acts::VectorMultiTrajectory{}};
@@ -327,7 +327,7 @@ BOOST_AUTO_TEST_CASE(Fit5Iterations) {
 
   const Experimental::Gx2FitterOptions gx2fOptions(
       geoCtx, magCtx, calCtx, extensions, PropagatorPlainOptions(), rSurface,
-      false, false, FreeToBoundCorrection(false), 5, true, 0);
+      false, false, FreeToBoundCorrection(false), 5, 0);
 
   Acts::TrackContainer tracks{Acts::VectorTrackContainer{},
                               Acts::VectorMultiTrajectory{}};
@@ -432,7 +432,7 @@ BOOST_AUTO_TEST_CASE(MixedDetector) {
 
   const Experimental::Gx2FitterOptions gx2fOptions(
       geoCtx, magCtx, calCtx, extensions, PropagatorPlainOptions(), rSurface,
-      false, false, FreeToBoundCorrection(false), 5, true, 0);
+      false, false, FreeToBoundCorrection(false), 5, 0);
 
   Acts::TrackContainer tracks{Acts::VectorTrackContainer{},
                               Acts::VectorMultiTrajectory{}};
@@ -527,7 +527,7 @@ BOOST_AUTO_TEST_CASE(FitWithBfield) {
 
   const Experimental::Gx2FitterOptions gx2fOptions(
       geoCtx, magCtx, calCtx, extensions, PropagatorPlainOptions(), rSurface,
-      false, false, FreeToBoundCorrection(false), 5, false, 0);
+      false, false, FreeToBoundCorrection(false), 5, 0);
 
   Acts::TrackContainer tracks{Acts::VectorTrackContainer{},
                               Acts::VectorMultiTrajectory{}};
@@ -624,7 +624,7 @@ BOOST_AUTO_TEST_CASE(relChi2changeCutOff) {
 
   const Experimental::Gx2FitterOptions gx2fOptions(
       geoCtx, magCtx, calCtx, extensions, PropagatorPlainOptions(), rSurface,
-      false, false, FreeToBoundCorrection(false), 500, true, 1e-5);
+      false, false, FreeToBoundCorrection(false), 500, 1e-5);
 
   Acts::TrackContainer tracks{Acts::VectorTrackContainer{},
                               Acts::VectorMultiTrajectory{}};
@@ -724,7 +724,7 @@ BOOST_AUTO_TEST_CASE(DidNotConverge) {
   // therefore fail the fit.
   const Experimental::Gx2FitterOptions gx2fOptions(
       geoCtx, magCtx, calCtx, extensions, PropagatorPlainOptions(), rSurface,
-      false, false, FreeToBoundCorrection(false), 6, true, 0);
+      false, false, FreeToBoundCorrection(false), 6, 0);
 
   Acts::TrackContainer tracks{Acts::VectorTrackContainer{},
                               Acts::VectorMultiTrajectory{}};
@@ -792,7 +792,7 @@ BOOST_AUTO_TEST_CASE(NotEnoughMeasurements) {
 
   const Experimental::Gx2FitterOptions gx2fOptions(
       geoCtx, magCtx, calCtx, extensions, PropagatorPlainOptions(), rSurface,
-      false, false, FreeToBoundCorrection(false), 6, true, 0);
+      false, false, FreeToBoundCorrection(false), 6, 0);
 
   Acts::TrackContainer tracks{Acts::VectorTrackContainer{},
                               Acts::VectorMultiTrajectory{}};
@@ -880,7 +880,7 @@ BOOST_AUTO_TEST_CASE(FindHoles) {
 
   const Experimental::Gx2FitterOptions gx2fOptions(
       geoCtx, magCtx, calCtx, extensions, PropagatorPlainOptions(), rSurface,
-      false, false, FreeToBoundCorrection(false), 20, true, 1e-5);
+      false, false, FreeToBoundCorrection(false), 20, 1e-5);
 
   Acts::TrackContainer tracks{Acts::VectorTrackContainer{},
                               Acts::VectorMultiTrajectory{}};
@@ -985,7 +985,7 @@ BOOST_AUTO_TEST_CASE(Material) {
 
   const Experimental::Gx2FitterOptions gx2fOptions(
       geoCtx, magCtx, calCtx, extensions, PropagatorPlainOptions(), rSurface,
-      false, false, FreeToBoundCorrection(false), 5, true, 0);
+      false, false, FreeToBoundCorrection(false), 5, 0);
 
   Acts::TrackContainer tracks{Acts::VectorTrackContainer{},
                               Acts::VectorMultiTrajectory{}};

docs/core/reconstruction/track_fitting.md

@@ -344,9 +344,6 @@ Gx2FitterOptions() = delete;
 /// Max number of iterations during the fit (abort condition)
 size_t nUpdateMax = 5;
 
-/// Disables the QoP fit in case of missing B-field
-bool zeroField = false;
-
 /// Check for convergence (abort condition). Set to 0 to skip.
 double relChi2changeCutOff = 1e-7;
 };
@@ -356,11 +353,7 @@ Common options like the geometry context or toggling of the energy loss are simi
 For now there are three *GX2F* specific options:
 1. `nUpdateMax` sets an abort condition for the parameter update as a maximum number of iterations allowed.
 We do not really want to use this condition, but it stops the fit in case of poor convergence.
-2. `zeroField` toggles the q/p-fit.
-If there is no magnetic field, we get no q/p-information.
-This would crash the fitter when needing matrix inverses.
-When this option is set to `true`, most of the matrices will omit the q/p-rows and -columns.
-3. `relChi2changeCutOff` is the desired convergence criterion.
+2. `relChi2changeCutOff` is the desired convergence criterion.
 We compare at each step of the iteration the current to the previous $\chi^2$.
 If the relative change is small enough, we finish the fit.