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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_LLOYD_BUILDER_H_
#define UTILS_LLOYD_BUILDER_H_
#include <vector>
#include <list>
/**
* Iteratively puts every vertex at the center of its neighbors
*/
template<typename SkBlComplex> class Lloyd_builder {
private:
SkBlComplex& complex_;
int dim;
public:
typedef typename SkBlComplex::Vertex_handle Vertex_handle;
/**
* @brief Modify complex to be the expansion of the k-nearest neighbor
* symetric graph.
*/
Lloyd_builder(SkBlComplex& complex, unsigned num_iterations) : complex_(complex), dim(-1) {
if (!complex_.empty()) {
dim = get_dimension();
while (num_iterations--) {
std::list<Point> new_points;
for (auto v : complex.vertex_range())
new_points.push_back(barycenter_neighbors(v));
auto new_points_it = new_points.begin();
for (auto v : complex.vertex_range())
complex_.point(v) = *(new_points_it++);
}
}
}
private:
int get_dimension() {
assert(!complex_.empty());
for (auto v : complex_.vertex_range())
return complex_.point(v).dimension();
return -1;
}
Point barycenter_neighbors(Vertex_handle v) const {
if (complex_.degree(v) == 0)
return complex_.point(v);
std::vector<double> res(dim, 0);
unsigned num_points = 0;
for (auto nv : complex_.vertex_range(v)) {
++num_points;
const Point& point = complex_.point(nv);
assert(point.dimension() == dim);
for (int i = 0; i < point.dimension(); ++i)
res[i] += point[i];
}
for (auto& x : res)
x /= num_points;
return Point(dim, res.begin(), res.end());
}
double squared_eucl_distance(const Point& p1, const Point& p2) const {
return Geometry_trait::Squared_distance_d()(p1, p2);
}
};
#endif // UTILS_LLOYD_BUILDER_H_
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