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/* This file is part of the Gudhi Library - https://gudhi.inria.fr/ - which is released under MIT.
* See file LICENSE or go to https://gudhi.inria.fr/licensing/ for full license details.
* Author(s): Vincent Rouvreau, Hind Montassif
*
* Copyright (C) 2018 Inria
*
* Modification(s):
* - YYYY/MM Author: Description of the modification
* - 2022/02 Hind Montassif : Replace MiniBall with Sphere_circumradius
*/
#ifndef CECH_COMPLEX_H_
#define CECH_COMPLEX_H_
#include <gudhi/Sphere_circumradius.h> // for Gudhi::cech_complex::Sphere_circumradius
#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 class.
*
* \ingroup cech_complex
*
* \details
* Cech complex is a simplicial complex where the set of all simplices is filtered
* by the radius of their minimal enclosing ball and bounded by the given max_radius.
*
* \tparam Kernel CGAL kernel: either Epick_d or Epeck_d.
*
* \tparam SimplicialComplexForCechComplex furnishes `Vertex_handle` and `Filtration_value` type definition required
* by `Gudhi::Proximity_graph` and Cech blocker.
*
*/
template <typename Kernel, typename SimplicialComplexForCechComplex>
class Cech_complex {
private:
// Required by compute_proximity_graph
using Vertex_handle = typename SimplicialComplexForCechComplex::Vertex_handle;
using Filtration_value = typename SimplicialComplexForCechComplex::Filtration_value;
using Proximity_graph = Gudhi::Proximity_graph<SimplicialComplexForCechComplex>;
using cech_blocker = Cech_blocker<SimplicialComplexForCechComplex, Cech_complex, Kernel>;
using Point_d = typename cech_blocker::Point_d;
using Point_cloud = std::vector<Point_d>;
// Numeric type of coordinates in the kernel
using FT = typename cech_blocker::FT;
// Sphere is a pair of point and squared radius.
using Sphere = typename cech_blocker::Sphere;
public:
/** \brief Cech_complex constructor from a range of points.
*
* @param[in] points Range of points where each point is defined as `kernel::Point_d`.
* @param[in] max_radius Maximal radius value.
* @param[in] exact Exact filtration values computation. Not exact if `Kernel` is not <a target="_blank"
* href="https://doc.cgal.org/latest/Kernel_d/structCGAL_1_1Epeck__d.html">CGAL::Epeck_d</a>.
* Default is false.
*
*/
template<typename InputPointRange >
Cech_complex(const InputPointRange & points, Filtration_value max_radius, const bool exact = false) : max_radius_(max_radius), exact_(exact) {
point_cloud_.assign(std::begin(points), std::end(points));
cech_skeleton_graph_ = Gudhi::compute_proximity_graph<SimplicialComplexForCechComplex>(
point_cloud_, max_radius_, Sphere_circumradius<Kernel, Filtration_value>(exact));
}
/** \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.
*
*/
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(&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_d& get_point(Vertex_handle vertex) const { return point_cloud_[vertex]; }
/**
* @return Vector of cached spheres.
*/
std::vector<Sphere> & get_cache() { return cache_; }
/** \brief Check exact option
* @return Exact option.
*/
const bool is_exact() { return exact_; }
private:
Proximity_graph cech_skeleton_graph_;
Filtration_value max_radius_;
Point_cloud point_cloud_;
std::vector<Sphere> cache_;
const bool exact_;
};
} // namespace cech_complex
} // namespace Gudhi
#endif // CECH_COMPLEX_H_
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