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Diffstat (limited to 'src/Cech_complex/include/gudhi/Cech_complex.h')
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diff --git a/src/Cech_complex/include/gudhi/Cech_complex.h b/src/Cech_complex/include/gudhi/Cech_complex.h new file mode 100644 index 00000000..612c73c3 --- /dev/null +++ b/src/Cech_complex/include/gudhi/Cech_complex.h @@ -0,0 +1,124 @@ +/* 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::Radius_distance +#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 + +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::Radius_distance` distance function. + * + * \tparam SimplicialComplexForProximityGraph furnishes `Vertex_handle` and `Filtration_value` type definition required + * by `Gudhi::Proximity_graph`. + * + * \tparam ForwardPointRange furnishes `.size()`, `.begin()` and `.end()` methods, and a `const_iterator` type + * definition. + */ +template<typename SimplicialComplexForProximityGraph, typename ForwardPointRange> +class Cech_complex { + private: + using Vertex_handle = typename SimplicialComplexForProximityGraph::Vertex_handle; + using Filtration_value = typename SimplicialComplexForProximityGraph::Filtration_value; + using Proximity_graph = Gudhi::Proximity_graph<SimplicialComplexForProximityGraph>; + + 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 for which `.size()`, `.begin()` and `.end()` methods return input + * iterators on a point. `.begin()` and `.end()` methods are required for a point. + * + */ + Cech_complex(const ForwardPointRange& points, Filtration_value max_radius) + : max_radius_(max_radius), + point_cloud_(points) { + cech_skeleton_graph_ = Gudhi::compute_proximity_graph<SimplicialComplexForProximityGraph>(point_cloud_, + max_radius_, + Gudhi::Radius_distance()); + } + + /** \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, ForwardPointRange>(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 A const iterator on the point. + * @exception std::out_of_range In debug mode, if point position in the range is out. + */ + typename ForwardPointRange::const_iterator point_iterator(std::size_t vertex) const { + GUDHI_CHECK((point_cloud_.begin() + vertex) < point_cloud_.end(), + std::out_of_range("Cech_complex::point - simplicial complex is not empty")); + return (point_cloud_.begin() + vertex); + } + + private: + Proximity_graph cech_skeleton_graph_; + Filtration_value max_radius_; + ForwardPointRange point_cloud_; +}; + +} // namespace cech_complex + +} // namespace Gudhi + +#endif // CECH_COMPLEX_H_ |