docs: Add comments grid iterator

Core/include/Acts/Seeding/BinnedSPGroup.ipp

@@ -50,7 +50,7 @@ std::tuple<boost::container::small_vector<std::size_t, 9>, std::size_t,
            boost::container::small_vector<std::size_t, 9>>
 Acts::BinnedSPGroupIterator<external_spacepoint_t>::operator*() const {
   // Global Index
-  std::array<std::size_t, 2> localPosition = m_gridItr.localPosition();
+  std::array<std::size_t, 2> localPosition = m_gridItr.localBinsIndices();
   std::size_t global_index =
       m_group->m_grid->globalBinFromLocalBins(localPosition);
 

Core/include/Acts/Utilities/GridIterator.hpp

@@ -1,6 +1,6 @@
 // This file is part of the Acts project.
 //
-// Copyright (C) 2023 CERN for the benefit of the Acts project
+// Copyright (C) 2016-2024 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
@@ -15,7 +15,11 @@
 
 namespace Acts {
 
-// Using Global iterator, including over/under flow bins
+/// @class GridGlobalIterator
+/// Grid iterator using the global position. This iterates on all
+/// the bins in the grid, including under- and over-flows
+/// @tparam T The type stored in the grid bins
+/// @tparam Axes ... The types of the axes in the grid
 template <typename T, class... Axes>
 class GridGlobalIterator {
  public:
@@ -27,46 +31,135 @@ class GridGlobalIterator {
   using pointer = value_type*;
   using reference = value_type&;
 
+  /// @brief Default constructor
   GridGlobalIterator() = default;
+  /// @brief Constructor taking ownership of the grid is not allowed
+  /// @param [in] grid The grid
+  /// @param [in] idx The global bin
   GridGlobalIterator(Acts::Grid<T, Axes...>&& grid, std::size_t idx) = delete;
+  /// @brief Constructor not taking ownership of the grid
+  /// @param [in] grid The grid
+  /// @param [in] idx The global bin
+  ///
+  /// @pre Global bin index must be a valid index for the grid
   GridGlobalIterator(const Acts::Grid<T, Axes...>& grid, std::size_t idx = 0ul);
 
+  /// @brief Copy constructor
+  /// @param [in] other The GlobalBinIterator to be copied
   GridGlobalIterator(const GridGlobalIterator<T, Axes...>& other) = default;
+  /// @brief Copy assignment
+  /// @param [in] other The GlobalBinIterator to be copied
+  /// @return The new global bin iterator
   GridGlobalIterator<T, Axes...>& operator=(
       const GridGlobalIterator<T, Axes...>& other) = default;
 
+  /// @brief Move constructor
+  /// @param [in] other The GlobalBinIterator to be moved
+  ///
+  /// This will invalidate the other GlobalBinIterator
   GridGlobalIterator(GridGlobalIterator<T, Axes...>&& other) noexcept;
+  /// @brief Move assignment
+  /// @param [in] other The GlobalBinIterator to be moved
+  /// @return The new global bin iterator
+  ///
+  /// This will invalidate the other GlobalBinIterator
   GridGlobalIterator<T, Axes...>& operator=(
       GridGlobalIterator<T, Axes...>&& other) noexcept;
 
+  /// @brief Default destructor
   ~GridGlobalIterator() = default;
 
+  /// @brief Equality operator
+  /// @param [in] other The other GridGlobalIterator to be compared against this one
+  /// @return The result of the comparison
   bool operator==(const GridGlobalIterator<T, Axes...>& other) const;
+  /// @brief (In-)Equality operator
+  /// @param [in] other The other GridGlobalIterator to be compared against this one
+  /// @return The result of the comparison
   bool operator!=(const GridGlobalIterator<T, Axes...>& other) const;
 
+  /// @brief Comparison (<) opetator
+  /// @param [in] other The other GridGlobalIterator to be compared against this one
+  /// @return The result of the comparison
   bool operator<(const GridGlobalIterator<T, Axes...>& other) const;
+  /// @brief Comparison (>) opetator
+  /// @param [in] other The other GridGlobalIterator to be compared against this one
+  /// @return The result of the comparison
   bool operator>(const GridGlobalIterator<T, Axes...>& other) const;
+  /// @brief Comparison (<=) opetator
+  /// @param [in] other The other GridGlobalIterator to be compared against this one
+  /// @return The result of the comparison
   bool operator<=(const GridGlobalIterator<T, Axes...>& other) const;
+  /// @brief Comparison (>=) opetator
+  /// @param [in] other The other GridGlobalIterator to be compared against this one
+  /// @return The result of the comparison
   bool operator>=(const GridGlobalIterator<T, Axes...>& other) const;
 
+  /// @brief Increment this iterator with an offset
+  /// @param [in] offset The increment value
+  /// @return The incremented iterator
   GridGlobalIterator<T, Axes...>& operator+=(const std::size_t offset);
+  /// @brief Decrement this iterator with an offset
+  /// @param [in] offset The decrement value
+  /// @return The decremented iterator
   GridGlobalIterator<T, Axes...>& operator-=(const std::size_t offset);
+  /// @brief Create incremented iterator
+  /// @param [in] offset The increment value
+  /// @return The incremented iterator
   GridGlobalIterator<T, Axes...> operator+(const std::size_t offset) const;
+  /// @brief Create decremented iterator
+  /// @param [in] offset The decrement value
+  /// @return The decremented iterator
   GridGlobalIterator<T, Axes...> operator-(const std::size_t offset) const;
 
+  /// @brief Distance between two GridGlobalIterators
+  /// @param [in] other The other GridGlobalIterator
+  /// @return The distance between the two iterators
+  ///
+  /// This will compute the distance by comparing the global positions in the
+  /// two iterators
+  ///
+  /// @pre The two iterators must have the same grid
   difference_type operator-(const GridGlobalIterator<T, Axes...>& other) const;
+  /// @brief Return stored value at given global position
+  /// @return The stored value in the grid from that given global position
   const value_type& operator*() const;
 
+  /// @brief Increment operator (pre)
+  /// @return The global iterator after the increment
+  ///
+  /// This will increase the global position by one
   GridGlobalIterator<T, Axes...>& operator++();
+  /// @brief Increment operator (post)
+  /// @return The global iterator before the increment
+  ///
+  /// This will increase the global position by one
   GridGlobalIterator<T, Axes...> operator++(int);
 
+  /// @brief Retrieve the global bin index
+  /// @return The current global bin index in the grid
+  std::size_t globalBinIndex() const;
+  /// @brief Retrieve the local bins indices
+  /// @return The current local bins indexed in the grid
+  std::array<std::size_t, DIM> localBinsIndices() const;
+
  private:
+  /// @brief The grid on which we are iterating
+  ///
+  /// The iterator never takes ownership of the grid. If the grid gets
+  /// invalidated (e.g. in a move operation) we can get undefined behaviours
+  /// if the iterator gets used after being invalidated
   Acts::detail::RefHolder<const Acts::Grid<T, Axes...>> m_grid{nullptr};
+  /// @brief The iteration index, corresponding to the global bin in the grid
   std::size_t m_idx{0ul};
 };
 
-// Using Local iterator, excluding over/under flow bins
-// Can also allow for custom navigation pattern along axes
+/// @class GridLocalIterator
+/// Grid iterator using the local position. This iterates on all
+/// local bins in the grid, and can exclude under- and over-flows
+/// Can also allow for custom navigation pattern along axes
+/// @tparam T The type stored in the grid bins
+/// @tparam Axes ... The types of the axes in the grid
 template <typename T, class... Axes>
 class GridLocalIterator {
  public:
@@ -78,47 +171,131 @@ class GridLocalIterator {
   using pointer = value_type*;
   using reference = value_type&;
 
+  /// @brief Default constructor
   GridLocalIterator() = default;
+  /// @brief Constructor taking ownership of the grid is not allowed
+  /// @param [in] grid The grid
+  /// @param [in] indices The local position
   GridLocalIterator(Acts::Grid<T, Axes...>&& grid,
-                    const std::array<std::size_t, DIM>& indexes) = delete;
+                    const std::array<std::size_t, DIM>& indices) = delete;
+  /// @brief Constructor taking ownership of the grid is not allowed
+  /// @param [in] grid The grid
+  /// @param [in] indices The local position
+  /// @param [in] navigation The custom navigation pattern for each axis
+  ///
+  /// @pre None of the navigation vectors is allowed to be an empty vector
   GridLocalIterator(Acts::Grid<T, Axes...>&& grid,
-                    const std::array<std::size_t, DIM>& indexes,
+                    const std::array<std::size_t, DIM>& indices,
                     std::array<std::vector<std::size_t>, DIM> navigation) =
       delete;
+  /// @brief Constructor
+  /// @param [in] grid The grid
+  /// @param [in] indices The local position
+  ///
+  /// @pre The local bins must be a valid local position in the grid
   GridLocalIterator(const Acts::Grid<T, Axes...>& grid,
-                    const std::array<std::size_t, DIM>& indexes);
+                    const std::array<std::size_t, DIM>& indices);
+  /// @brief Constructor with custom navigation pattern
+  /// @param [in] grid The grid
+  /// @param [in] indices The local position
+  /// @param [in] navigation The custom navigation pattern for each axis
+  ///
+  /// @pre The local bins must be a valid local position in the grid.
+  /// The navigation pattern must be consistent with the local bins (i.e. size
+  /// <= num bins in the axis) in the grid and have no repetitions.
+  ///
+  /// @pre None of the navigation vectors is allowed to be an empty vector
   GridLocalIterator(const Acts::Grid<T, Axes...>& grid,
-                    const std::array<std::size_t, DIM>& indexes,
+                    const std::array<std::size_t, DIM>& indices,
                     std::array<std::vector<std::size_t>, DIM> navigation);
 
+  /// @brief Copy constructor
+  /// @param [in] other The GridLocalIterator to be copied
   GridLocalIterator(const GridLocalIterator<T, Axes...>& other) = default;
+  /// @brief Copy assignment operator
+  /// @param [in] other The GridLocalIterator to be copied
+  /// @return The copied GridLocalIterator
   GridLocalIterator<T, Axes...>& operator=(
       const GridLocalIterator<T, Axes...>& other) = default;
 
+  /// @brief Move constructor
+  /// @param [in] other The GridLocalIterator to be moved
+  ///
+  /// This will invalidate the other GridLocalIterator
   GridLocalIterator(GridLocalIterator<T, Axes...>&& other) noexcept;
+  /// @brief Move assignment operator
+  /// @param [in] other The GridLocalIterator to be moved
+  /// @return The moved GridLocalIterator
+  ///
+  /// This will invalidate the other GridLocalIterator
   GridLocalIterator<T, Axes...>& operator=(
       GridLocalIterator<T, Axes...>&& other) noexcept;
 
+  /// @brief Default destructor
   ~GridLocalIterator() = default;
 
+  /// @brief Equality operator
+  /// @param [in] other The other GridLocalIterator to be compared against this one
+  /// @return The result of the comparison
   bool operator==(const Acts::GridLocalIterator<T, Axes...>& other) const;
+  /// @brief (In-)Equality operator
+  /// @param [in] other The other GridLocalIterator to be compared against this one
+  /// @return The result of the comparison
   bool operator!=(const Acts::GridLocalIterator<T, Axes...>& other) const;
 
+  /// @brief Return stored value at given local position
+  /// @return The stored value in the grid from that given local position
   const value_type& operator*() const;
 
+  /// @brief Increment operator (pre)
+  /// @return The local iterator after the increment
+  ///
+  /// This will increase the local position by one
   GridLocalIterator<T, Axes...>& operator++();
+  /// @brief Increment operator (post)
+  /// @return The local iterator before the increment
+  ///
+  /// This will increase the local position by one
   GridLocalIterator<T, Axes...> operator++(int);
 
-  std::array<std::size_t, DIM> localPosition() const;
+  /// @brief Retrieve the global bin index
+  /// @return The current global bin index in the grid
+  std::size_t globalBinIndex() const;
+  /// @brief Retrieve the local position
+  /// @return The current local position in the grid
+  std::array<std::size_t, DIM> localBinsIndices() const;
 
  private:
+  /// @brief Increment the local position
+  /// @tparam N Current dimension
   template <std::size_t N>
   void increment();
 
  private:
+  /// @brief The grid on which we are iterating
+  ///
+  /// The iterator never takes ownership of the grid. If the grid gets
+  /// invalidated (e.g. in a move operation) we can get undefined behaviours
+  /// if the iterator gets used after being invalidated
   Acts::detail::RefHolder<const Acts::Grid<T, Axes...>> m_grid{nullptr};
+  /// @brief The maximum number of local bins in the grid. This does not include
+  /// under- and over-flow bins
   std::array<std::size_t, DIM> m_numLocalBins{};
+  /// @brief The current iteration position.
+  ///
+  /// This represent the position in the navigation pattern.
+  /// For each axis, the current index goes from 0ul to the size of the
+  /// corresponding navigation
+  ///
+  /// The local position in the gris is then obtained, for each axis i,
+  /// via m_navigationIndex[m_currentIndex[i]]
   std::array<std::size_t, DIM> m_currentIndex{};
+  /// @brief The custom navigation pattern in the grid
+  ///
+  /// This allows users to define any custom iteration sequence in all the
+  /// different axes of the grid. If nothing is defined by the user, then
+  /// a std::iota is used as the default starting with the 1ul bin (0ul) is
+  /// the under-flow in the axis
   std::array<std::vector<std::size_t>, DIM> m_navigationIndex{};
 };