VertexingHelpers.hpp

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// This file is part of the Acts project.
//
// Copyright (C) 2020 CERN for the benefit of the Acts project
//
// This Source Code Form is subject to the terms of the Mozilla Public
// License, v. 2.0. If a copy of the MPL was not distributed with this
// file, You can obtain one at http://mozilla.org/MPL/2.0/.

#pragma once

#include "Acts/Vertexing/Vertex.hpp"
#include "ActsExamples/EventData/ProtoVertex.hpp"
#include "ActsExamples/EventData/Track.hpp"

#include <vector>

namespace ActsExamples {

inline std::vector<const Acts::BoundTrackParameters*>
makeTrackParametersPointerContainer(
    const TrackParametersContainer& trackParameters) {
  std::vector<const Acts::BoundTrackParameters*> trackParametersPointers;
  trackParametersPointers.reserve(trackParameters.size());

  for (const auto& trackParam : trackParameters) {
    trackParametersPointers.push_back(&trackParam);
  }
  return trackParametersPointers;
}

inline ProtoVertexContainer makeProtoVertices(
    const TrackParametersContainer& trackParameters,
    const std::vector<Acts::Vertex<Acts::BoundTrackParameters>>& vertices) {
  ProtoVertexContainer protoVertices;
  protoVertices.reserve(vertices.size());

  // use pointer arithmetic to compute the position/index of the original
  // parameters in the input track parameters container.
  const Acts::BoundTrackParameters* first = trackParameters.data();
  for (const auto& vertex : vertices) {
    ProtoVertex protoVertex;
    protoVertex.reserve(vertex.tracks().size());

    for (const auto& track : vertex.tracks()) {
      protoVertex.push_back(std::distance(first, track.originalParams));
    }
    protoVertices.push_back(std::move(protoVertex));
  }

  return protoVertices;
}

}  // namespace ActsExamples