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Diffstat (limited to 'include/gudhi/Cech_complex.h')
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diff --git a/include/gudhi/Cech_complex.h b/include/gudhi/Cech_complex.h new file mode 100644 index 00000000..f9b8a269 --- /dev/null +++ b/include/gudhi/Cech_complex.h @@ -0,0 +1,130 @@ +/* This file is part of the Gudhi Library. The Gudhi library + * (Geometric Understanding in Higher Dimensions) is a generic C++ + * library for computational topology. + * + * Author(s): Vincent Rouvreau + * + * Copyright (C) 2018 Inria + * + * This program is free software: you can redistribute it and/or modify + * it under the terms of the GNU General Public License as published by + * the Free Software Foundation, either version 3 of the License, or + * (at your option) any later version. + * + * This program is distributed in the hope that it will be useful, + * but WITHOUT ANY WARRANTY; without even the implied warranty of + * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the + * GNU General Public License for more details. + * + * You should have received a copy of the GNU General Public License + * along with this program. If not, see <http://www.gnu.org/licenses/>. + */ + +#ifndef CECH_COMPLEX_H_ +#define CECH_COMPLEX_H_ + +#include <gudhi/distance_functions.h> // for Gudhi::Minimal_enclosing_ball_radius +#include <gudhi/graph_simplicial_complex.h> // for Gudhi::Proximity_graph +#include <gudhi/Debug_utils.h> // for GUDHI_CHECK +#include <gudhi/Cech_complex_blocker.h> // for Gudhi::cech_complex::Cech_blocker + +#include <iostream> +#include <stdexcept> // for exception management +#include <vector> + +namespace Gudhi { + +namespace cech_complex { + +/** + * \class Cech_complex + * \brief Cech complex data structure. + * + * \ingroup cech_complex + * + * \details + * The data structure is a proximity graph, containing edges when the edge length is less or equal + * to a given max_radius. Edge length is computed from `Gudhi::Minimal_enclosing_ball_radius` distance function. + * + * \tparam SimplicialComplexForProximityGraph furnishes `Vertex_handle` and `Filtration_value` type definition required + * by `Gudhi::Proximity_graph`. + * + * \tparam ForwardPointRange must be a range for which `std::begin()` and `std::end()` methods return input + * iterators on a point. `std::begin()` and `std::end()` methods are also required for a point. + */ +template <typename SimplicialComplexForProximityGraph, typename ForwardPointRange> +class Cech_complex { + private: + // Required by compute_proximity_graph + using Vertex_handle = typename SimplicialComplexForProximityGraph::Vertex_handle; + using Filtration_value = typename SimplicialComplexForProximityGraph::Filtration_value; + using Proximity_graph = Gudhi::Proximity_graph<SimplicialComplexForProximityGraph>; + + // Retrieve Coordinate type from ForwardPointRange + using Point_from_range_iterator = typename boost::range_const_iterator<ForwardPointRange>::type; + using Point_from_range = typename std::iterator_traits<Point_from_range_iterator>::value_type; + using Coordinate_iterator = typename boost::range_const_iterator<Point_from_range>::type; + using Coordinate = typename std::iterator_traits<Coordinate_iterator>::value_type; + + public: + // Point and Point_cloud type definition + using Point = std::vector<Coordinate>; + using Point_cloud = std::vector<Point>; + + public: + /** \brief Cech_complex constructor from a list of points. + * + * @param[in] points Range of points. + * @param[in] max_radius Maximal radius value. + * + * \tparam ForwardPointRange must be a range of Point. Point must be a range of <b>copyable</b> Cartesian coordinates. + * + */ + Cech_complex(const ForwardPointRange& points, Filtration_value max_radius) : max_radius_(max_radius) { + // Point cloud deep copy + point_cloud_.reserve(boost::size(points)); + for (auto&& point : points) point_cloud_.emplace_back(std::begin(point), std::end(point)); + + cech_skeleton_graph_ = Gudhi::compute_proximity_graph<SimplicialComplexForProximityGraph>( + point_cloud_, max_radius_, Gudhi::Minimal_enclosing_ball_radius()); + } + + /** \brief Initializes the simplicial complex from the proximity graph and expands it until a given maximal + * dimension, using the Cech blocker oracle. + * + * @param[in] complex SimplicialComplexForCech to be created. + * @param[in] dim_max graph expansion until this given maximal dimension. + * @exception std::invalid_argument In debug mode, if `complex.num_vertices()` does not return 0. + * + */ + template <typename SimplicialComplexForCechComplex> + void create_complex(SimplicialComplexForCechComplex& complex, int dim_max) { + GUDHI_CHECK(complex.num_vertices() == 0, + std::invalid_argument("Cech_complex::create_complex - simplicial complex is not empty")); + + // insert the proximity graph in the simplicial complex + complex.insert_graph(cech_skeleton_graph_); + // expand the graph until dimension dim_max + complex.expansion_with_blockers(dim_max, + Cech_blocker<SimplicialComplexForCechComplex, Cech_complex>(&complex, this)); + } + + /** @return max_radius value given at construction. */ + Filtration_value max_radius() const { return max_radius_; } + + /** @param[in] vertex Point position in the range. + * @return The point. + */ + const Point& get_point(Vertex_handle vertex) const { return point_cloud_[vertex]; } + + private: + Proximity_graph cech_skeleton_graph_; + Filtration_value max_radius_; + Point_cloud point_cloud_; +}; + +} // namespace cech_complex + +} // namespace Gudhi + +#endif // CECH_COMPLEX_H_ |