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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): David Salinas
*
* Copyright (C) 2014 INRIA Sophia Antipolis-Mediterranee (France)
*
* 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 UTILS_VERTEX_COLLAPSOR_H_
#define UTILS_VERTEX_COLLAPSOR_H_
#include <list>
#include "utils/Edge_contractor.h"
#include "utils/Furthest_point_epsilon_net.h"
#include "utils/UI_utils.h"
/**
* Iteratively puts every vertex at the center of its neighbors
*/
template<typename SkBlComplex> class Vertex_collapsor {
private:
SkBlComplex& complex_;
size_t num_collapses_;
public:
typedef typename SkBlComplex::Vertex_handle Vertex_handle;
typedef typename SkBlComplex::Edge_handle Edge_handle;
/**
* @brief Modify complex to be the expansion of the k-nearest neighbor
* symetric graph.
*/
Vertex_collapsor(SkBlComplex& complex, size_t num_collapses) :
complex_(complex), num_collapses_(num_collapses) {
// std::list<Vertex_handle> vertices;
// vertices.insert(vertices.begin(),complex_.vertex_range().begin(),complex_.vertex_range().end());
// UIDBG("Collapse vertices");
// collapse_vertices(vertices);
std::list<Vertex_handle> vertices;
UIDBG("Compute eps net");
Furthest_point_epsilon_net<Complex> eps_net(complex_);
for (auto vh : eps_net.net_filtration_)
vertices.push_back(vh.vertex_handle);
UIDBG("Collapse vertices");
collapse_vertices(vertices);
}
private:
void collapse_vertices(std::list<Vertex_handle>& vertices) {
while (!vertices.empty() && num_collapses_--) {
Vertex_handle current_vertex = vertices.front();
vertices.pop_front();
if (is_link_reducible(current_vertex))
complex_.remove_vertex(current_vertex);
}
}
bool is_link_reducible(Vertex_handle v) {
auto link = complex_.link(v);
if (link.empty()) return false;
if (link.is_cone()) return true;
if (link.num_connected_components() > 1) return false;
Edge_contractor<Complex> contractor(link, link.num_vertices() - 1);
(void)contractor;
return (link.num_vertices() == 1);
}
};
#endif // UTILS_VERTEX_COLLAPSOR_H_
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