diff options
Diffstat (limited to 'src/Subsampling/include/gudhi/choose_n_farthest_points.h')
-rw-r--r-- | src/Subsampling/include/gudhi/choose_n_farthest_points.h | 53 |
1 files changed, 44 insertions, 9 deletions
diff --git a/src/Subsampling/include/gudhi/choose_n_farthest_points.h b/src/Subsampling/include/gudhi/choose_n_farthest_points.h index 40c7808d..5e908090 100644 --- a/src/Subsampling/include/gudhi/choose_n_farthest_points.h +++ b/src/Subsampling/include/gudhi/choose_n_farthest_points.h @@ -48,22 +48,40 @@ namespace subsampling { * \brief Subsample by a greedy strategy of iteratively adding the farthest point from the * current chosen point set to the subsampling. * The iteration starts with the landmark `starting point`. + * \tparam Kernel must provide a type Kernel::Squared_distance_d which is a model of the + * concept <a target="_blank" + * href="http://doc.cgal.org/latest/Kernel_d/classKernel__d_1_1Squared__distance__d.html">Kernel_d::Squared_distance_d</a> + * concept. + * It must also contain a public member 'squared_distance_d_object' of this type. + * \tparam Point_range Range whose value type is Kernel::Point_d. It must provide random-access + * via `operator[]` and the points should be stored contiguously in memory. + * \tparam OutputIterator Output iterator whose value type is Kernel::Point_d. * \details It chooses `final_size` points from a random access range `input_pts` and * outputs it in the output iterator `output_it`. + * @param[in] k A kernel object. + * @param[in] input_pts Const reference to the input points. + * @param[in] final_size The size of the subsample to compute. + * @param[in] starting_point The seed in the farthest point algorithm. + * @param[out] output_it The output iterator. * */ template < typename Kernel, -typename Point_container, +typename Point_range, typename OutputIterator> void choose_n_farthest_points(Kernel const &k, - Point_container const &input_pts, + Point_range const &input_pts, std::size_t final_size, std::size_t starting_point, OutputIterator output_it) { - typename Kernel::Squared_distance_d sqdist = k.squared_distance_d_object(); - std::size_t nb_points = boost::size(input_pts); - assert(nb_points >= final_size); + if (final_size > nb_points) + final_size = nb_points; + + // Tests to the limit + if (final_size < 1) + return; + + typename Kernel::Squared_distance_d sqdist = k.squared_distance_d_object(); std::size_t current_number_of_landmarks = 0; // counter for landmarks const double infty = std::numeric_limits<double>::infinity(); // infinity (see next entry) @@ -96,22 +114,39 @@ void choose_n_farthest_points(Kernel const &k, * \brief Subsample by a greedy strategy of iteratively adding the farthest point from the * current chosen point set to the subsampling. * The iteration starts with a random landmark. + * \tparam Kernel must provide a type Kernel::Squared_distance_d which is a model of the + * concept <a target="_blank" + * href="http://doc.cgal.org/latest/Kernel_d/classKernel__d_1_1Squared__distance__d.html">Kernel_d::Squared_distance_d</a> + * concept. + * It must also contain a public member 'squared_distance_d_object' of this type. + * \tparam Point_range Range whose value type is Kernel::Point_d. It must provide random-access + * via `operator[]` and the points should be stored contiguously in memory. + * \tparam OutputIterator Output iterator whose value type is Kernel::Point_d. * \details It chooses `final_size` points from a random access range `input_pts` and * outputs it in the output iterator `output_it`. + * @param[in] k A kernel object. + * @param[in] input_pts Const reference to the input points. + * @param[in] final_size The size of the subsample to compute. + * @param[out] output_it The output iterator. * */ template < typename Kernel, -typename Point_container, +typename Point_range, typename OutputIterator> void choose_n_farthest_points(Kernel const& k, - Point_container const &input_pts, + Point_range const &input_pts, unsigned final_size, OutputIterator output_it) { + // Tests to the limit + if ((final_size < 1) || (input_pts.size() == 0)) + return; + // Choose randomly the first landmark std::random_device rd; std::mt19937 gen(rd()); - std::uniform_int_distribution<> dis(1, 6); - int starting_point = dis(gen); + std::uniform_int_distribution<> dis(0, (input_pts.size() - 1)); + std::size_t starting_point = dis(gen); + choose_n_farthest_points(k, input_pts, final_size, starting_point, output_it); } |