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/* 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_
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