/* 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): Siargey Kachanovich
*
* Copyright (C) 2015 INRIA Sophia Antipolis-Méditerranée (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 .
*/
#ifndef LANDMARK_CHOICE_BY_FARTHEST_POINT_H_
#define LANDMARK_CHOICE_BY_FARTHEST_POINT_H_
#include
#include
#include // for sort
#include
#include
#include
namespace Gudhi {
template < typename Point_d,
typename Heap,
typename Tree,
typename Presence_table >
void update_heap( Point_d &l,
unsigned nbL,
Heap &heap,
Tree &tree,
Presence_table &table)
{
auto search = tree.query_incremental_ANN(l);
for (auto w: search) {
if (table[w.first].first)
if (w.second < table[w.first].second->second) {
heap.update(table[w.first].second, w);
}
}
}
/**
* \ingroup witness_complex
* \brief Landmark choice strategy by iteratively adding the farthest witness from the
* current landmark set as the new landmark.
* \details It chooses nbL landmarks from a random access range `points` and
* writes {witness}*{closest landmarks} matrix in `knn`.
*
* The type KNearestNeighbors can be seen as
* Witness_range>, where
* Witness_range and Closest_landmark_range are random access ranges
*
*/
template < typename Kernel,
typename Point_container,
typename OutputIterator>
void landmark_choice_by_farthest_point( Kernel& k,
Point_container const &points,
int nbL,
OutputIterator output_it)
{
// typedef typename Kernel::FT FT;
// typedef std::pair Heap_node;
// struct R_max_compare
// {
// bool operator()(const Heap_node &rmh1, const Heap_node &rmh2) const
// {
// return rmh1.second < rmh2.second;
// }
// };
// typedef boost::heap::fibonacci_heap> Heap;
// typedef Spatial_tree_data_structure Tree;
// typedef std::vector< std::pair > Presence_table;
typename Kernel::Squared_distance_d sqdist = k.squared_distance_d_object();
// Tree tree(points);
// Heap heap;
// Presence_table table(points.size());
// for (auto p: table)
// std::cout << p.first << "\n";
// int number_landmarks = 0; // number of treated landmarks
// double curr_max_dist = 0; // used for defining the furhest point from L
// const double infty = std::numeric_limits::infinity(); // infinity (see next entry)
// std::vector< double > dist_to_L(points.size(), infty); // vector of current distances to L from points
// // Choose randomly the first landmark
// std::random_device rd;
// std::mt19937 gen(rd());
// std::uniform_int_distribution<> dis(1, 6);
// int curr_landmark = dis(gen);
// do {
// *output_landmarks++ = points[curr_landmark];
// std::cout << curr_landmark << "\n";
// number_landmarks++;
// }
// while (number_landmarks < nbL);
// }
int nb_points = boost::size(points);
assert(nb_points >= nbL);
int current_number_of_landmarks = 0; // counter for landmarks
double curr_max_dist = 0; // used for defining the furhest point from L
const double infty = std::numeric_limits::infinity(); // infinity (see next entry)
std::vector< double > dist_to_L(nb_points, infty); // vector of current distances to L from points
// Choose randomly the first landmark
std::random_device rd;
std::mt19937 gen(rd());
std::uniform_int_distribution<> dis(1, 6);
int curr_max_w = dis(gen);
for (current_number_of_landmarks = 0; current_number_of_landmarks != nbL; current_number_of_landmarks++) {
// curr_max_w at this point is the next landmark
*output_it++ = points[curr_max_w];
std::cout << curr_max_w << "\n";
unsigned i = 0;
for (auto& p : points) {
double curr_dist = sqdist(p, *(std::begin(points) + curr_max_w));
if (curr_dist < dist_to_L[i])
dist_to_L[i] = curr_dist;
++i;
}
// choose the next curr_max_w
curr_max_dist = 0;
for (i = 0; i < dist_to_L.size(); i++)
if (dist_to_L[i] > curr_max_dist) {
curr_max_dist = dist_to_L[i];
curr_max_w = i;
}
}
}
} // namespace Gudhi
#endif // LANDMARK_CHOICE_BY_FARTHEST_POINT_H_