feat: Add logger to multi stepper

Core/include/Acts/Propagator/MultiEigenStepperLoop.hpp

@@ -191,6 +191,9 @@ class MultiEigenStepperLoop
   /// .curvilinearState()
   FinalReductionMethod m_finalReductionMethod = FinalReductionMethod::eMean;
 
+  /// The logger (used if no logger is provided by caller of methods)
+  std::unique_ptr<const Acts::Logger> m_logger;
+
   /// Small vector type for speeding up some computations where we need to
   /// accumulate stuff of components. We think 16 is a reasonable amount here.
   template <typename T>
@@ -218,9 +221,12 @@ class MultiEigenStepperLoop
   /// Constructor from a magnetic field and a optionally provided Logger
   MultiEigenStepperLoop(
       std::shared_ptr<const MagneticFieldProvider> bField,
-      FinalReductionMethod finalReductionMethod = FinalReductionMethod::eMean)
+      FinalReductionMethod finalReductionMethod = FinalReductionMethod::eMean,
+      std::unique_ptr<const Logger> logger = getDefaultLogger("GSF",
+                                                              Logging::INFO))
       : EigenStepper<extensionlist_t, auctioneer_t>(std::move(bField)),
-        m_finalReductionMethod(finalReductionMethod) {}
+        m_finalReductionMethod(finalReductionMethod),
+        m_logger(std::move(logger)) {}
 
   struct State {
     /// The struct that stores the individual components

Core/include/Acts/Propagator/MultiEigenStepperLoop.ipp

@@ -129,9 +129,7 @@ Result<double> MultiEigenStepperLoop<E, R, A>::step(
 
   State& stepping = state.stepping;
   auto& components = stepping.components;
-
-  // @TODO: This needs to be a real logger
-  const Logger& logger = getDummyLogger();
+  const Logger& logger = *m_logger;
 
   // Update step count
   stepping.steps++;

Examples/Algorithms/TrackFitting/src/GsfFitterFunction.cpp

@@ -118,9 +118,9 @@ ActsExamples::makeGsfFitterFunction(
     double weightCutoff, Acts::FinalReductionMethod finalReductionMethod,
     bool abortOnError, bool disableAllMaterialHandling,
     const Acts::Logger& logger) {
-  MultiStepper stepper(std::move(magneticField), finalReductionMethod);
-
   // Standard fitter
+  MultiStepper stepper(magneticField, finalReductionMethod,
+                       logger.cloneWithSuffix("Step"));
   Acts::Navigator::Config cfg{std::move(trackingGeometry)};
   cfg.resolvePassive = false;
   cfg.resolveMaterial = true;
@@ -133,9 +133,12 @@ ActsExamples::makeGsfFitterFunction(
                      logger.cloneWithSuffix("GSF"));
 
   // Direct fitter
+  MultiStepper directStepper(std::move(magneticField), finalReductionMethod,
+                             logger.cloneWithSuffix("Step"));
   Acts::DirectNavigator directNavigator{
       logger.cloneWithSuffix("DirectNavigator")};
-  DirectPropagator directPropagator(stepper, std::move(directNavigator),
+  DirectPropagator directPropagator(std::move(directStepper),
+                                    std::move(directNavigator),
                                     logger.cloneWithSuffix("DirectPropagator"));
   DirectFitter directTrackFitter(std::move(directPropagator),
                                  BetheHeitlerApprox(betheHeitlerApprox),

Tests/UnitTests/Core/Propagator/MultiStepperTests.cpp

@@ -710,7 +710,7 @@ void propagator_instatiation_test_function() {
   auto bField = std::make_shared<NullBField>();
   multi_stepper_t multi_stepper(bField);
   Propagator<multi_stepper_t, Navigator> propagator(
-      multi_stepper, Navigator{Navigator::Config{}});
+      std::move(multi_stepper), Navigator{Navigator::Config{}});
 
   auto surface = Acts::Surface::makeShared<Acts::PlaneSurface>(
       Vector3::Zero(), Vector3{1.0, 0.0, 0.0});