diff options
Diffstat (limited to 'src/Subsampling')
5 files changed, 96 insertions, 7 deletions
diff --git a/src/Subsampling/example/CMakeLists.txt b/src/Subsampling/example/CMakeLists.txt index 54349f0c..0fd3335c 100644 --- a/src/Subsampling/example/CMakeLists.txt +++ b/src/Subsampling/example/CMakeLists.txt @@ -6,6 +6,7 @@ if(CGAL_FOUND) if (EIGEN3_FOUND) add_executable(Subsampling_example_pick_n_random_points example_pick_n_random_points.cpp) add_executable(Subsampling_example_choose_n_farthest_points example_choose_n_farthest_points.cpp) + add_executable(Subsampling_example_custom_kernel example_custom_kernel.cpp) add_executable(Subsampling_example_sparsify_point_set example_sparsify_point_set.cpp) target_link_libraries(Subsampling_example_sparsify_point_set ${CGAL_LIBRARY}) diff --git a/src/Subsampling/example/example_custom_kernel.cpp b/src/Subsampling/example/example_custom_kernel.cpp new file mode 100644 index 00000000..25b5bf6c --- /dev/null +++ b/src/Subsampling/example/example_custom_kernel.cpp @@ -0,0 +1,63 @@ +#include <gudhi/choose_n_farthest_points.h> + +#include <CGAL/Epick_d.h> +#include <CGAL/Random.h> + +#include <vector> +#include <iterator> + + +/* The class Kernel contains a distance function defined on the set of points {0, 1, 2, 3} + * and computes a distance according to the matrix: + * 0 1 2 4 + * 1 0 4 2 + * 2 4 0 1 + * 4 2 1 0 + */ +class Kernel { + public: + typedef double FT; + typedef unsigned Point_d; + + // Class Squared_distance_d + class Squared_distance_d { + private: + std::vector<std::vector<FT>> matrix_; + + public: + Squared_distance_d() { + matrix_.push_back(std::vector<FT>({0, 1, 2, 4})); + matrix_.push_back(std::vector<FT>({1, 0, 4, 2})); + matrix_.push_back(std::vector<FT>({2, 4, 0, 1})); + matrix_.push_back(std::vector<FT>({4, 2, 1, 0})); + } + + FT operator()(Point_d p1, Point_d p2) { + return matrix_[p1][p2]; + } + }; + + // Constructor + Kernel() {} + + // Object of type Squared_distance_d + Squared_distance_d squared_distance_d_object() const { + return Squared_distance_d(); + } +}; + +int main(void) { + typedef Kernel K; + typedef typename K::Point_d Point_d; + + K k; + std::vector<Point_d> points = {0, 1, 2, 3}; + std::vector<Point_d> results; + + Gudhi::subsampling::choose_n_farthest_points(k, points, 2, std::back_inserter(results)); + std::cout << "Before sparsification: " << points.size() << " points.\n"; + std::cout << "After sparsification: " << results.size() << " points.\n"; + std::cout << "Result table: {" << results[0] << "," << results[1] << "}\n"; + + return 0; +} diff --git a/src/Subsampling/include/gudhi/choose_n_farthest_points.h b/src/Subsampling/include/gudhi/choose_n_farthest_points.h index 9b45c640..5e908090 100644 --- a/src/Subsampling/include/gudhi/choose_n_farthest_points.h +++ b/src/Subsampling/include/gudhi/choose_n_farthest_points.h @@ -48,15 +48,28 @@ 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) { @@ -101,15 +114,27 @@ 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 diff --git a/src/Subsampling/include/gudhi/pick_n_random_points.h b/src/Subsampling/include/gudhi/pick_n_random_points.h index e89b2b2d..f0e3f1f1 100644 --- a/src/Subsampling/include/gudhi/pick_n_random_points.h +++ b/src/Subsampling/include/gudhi/pick_n_random_points.h @@ -57,7 +57,9 @@ void pick_n_random_points(Point_container const &points, #endif std::size_t nbP = boost::size(points); - assert(nbP >= final_size); + if (final_size > nbP) + final_size = nbP; + std::vector<int> landmarks(nbP); std::iota(landmarks.begin(), landmarks.end(), 0); diff --git a/src/Subsampling/include/gudhi/sparsify_point_set.h b/src/Subsampling/include/gudhi/sparsify_point_set.h index 7ff11b4c..507f8c79 100644 --- a/src/Subsampling/include/gudhi/sparsify_point_set.h +++ b/src/Subsampling/include/gudhi/sparsify_point_set.h @@ -64,8 +64,6 @@ sparsify_point_set( typedef typename Gudhi::spatial_searching::Kd_tree_search< Kernel, Point_range> Points_ds; - typename Kernel::Squared_distance_d sqdist = k.squared_distance_d_object(); - #ifdef GUDHI_SUBSAMPLING_PROFILING Gudhi::Clock t; #endif |