src/TrackFitting/GsfUtils.cpp

0001 // This file is part of the ACTS project.
0002 //
0003 // Copyright (C) 2016 CERN for the benefit of the ACTS project
0004 //
0005 // This Source Code Form is subject to the terms of the Mozilla Public
0006 // License, v. 2.0. If a copy of the MPL was not distributed with this
0007 // file, You can obtain one at https://mozilla.org/MPL/2.0/.
0008
0009 #include "Acts/TrackFitting/detail/GsfUtils.hpp"
0010
0011 #include "Acts/EventData/MeasurementHelpers.hpp"
0012 #include "Acts/EventData/SubspaceHelpers.hpp"
0013 #include "Acts/EventData/Types.hpp"
0014
0015 #include <cstddef>
0016 #include <cstdint>
0017 #include <span>
0018
0019 namespace Acts::detail {
0020
0021 using TrackStateTraits =
0022     TrackStateTraits<MultiTrajectoryTraits::MeasurementSizeMax, true>;
0023
0024 double calculateDeterminant(const double* fullCalibratedCovariance,
0025                             TrackStateTraits::Covariance predictedCovariance,
0026                             BoundSubspaceIndices projector,
0027                             unsigned int calibratedSize) {
0028   return visit_measurement(calibratedSize, [&](auto N) {
0029     constexpr std::size_t kMeasurementSize = decltype(N)::value;
0030     std::span<const std::uint8_t, kMeasurementSize> validSubspaceIndices(
0031         projector.begin(), projector.begin() + kMeasurementSize);
0032     FixedBoundSubspaceHelper<kMeasurementSize> subspaceHelper(
0033         validSubspaceIndices);
0034
0035     typename Acts::TrackStateTraits<
0036         kMeasurementSize, true>::CalibratedCovariance calibratedCovariance{
0037         fullCalibratedCovariance};
0038
0039     const auto H = subspaceHelper.projector();
0040
0041     return (H * predictedCovariance * H.transpose() + calibratedCovariance)
0042         .determinant();
0043   });
0044 }
0045 }  // namespace Acts::detail