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example_witness_complex_sphere.cpp

# Contraction

#define BOOST_PARAMETER_MAX_ARITY 12
#include <gudhi/Simplex_tree.h>
#include <gudhi/Euclidean_witness_complex.h>
#include <gudhi/pick_n_random_points.h>
#include <gudhi/choose_n_farthest_points.h>
#include <gudhi/reader_utils.h>
#include <CGAL/Epick_d.h>
#include <iostream>
#include <fstream>
#include <ctime>
#include <utility>
#include <string>
#include <vector>
#include "generators.h"
template <typename Data_range>
void write_data(Data_range& data, std::string filename) {
std::ofstream ofs(filename, std::ofstream::out);
for (auto entry : data) ofs << entry.first << ", " << entry.second << "\n";
ofs.close();
}
int main(int argc, char* const argv[]) {
using Kernel = CGAL::Epick_d<CGAL::Dynamic_dimension_tag>;
using Witness_complex = Gudhi::witness_complex::Euclidean_witness_complex<Kernel>;
if (argc != 2) {
std::cerr << "Usage: " << argv[0] << " number_of_landmarks \n";
return 0;
}
int number_of_landmarks = atoi(argv[1]);
std::vector<std::pair<int, double> > l_time;
// Generate points
for (int nbP = 500; nbP < 10000; nbP += 500) {
clock_t start, end;
// Construct the Simplex Tree
Gudhi::Simplex_tree<> simplex_tree;
Point_Vector point_vector, landmarks;
generate_points_sphere(point_vector, nbP, 4);
std::clog << "Successfully generated " << point_vector.size() << " points.\n";
std::clog << "Ambient dimension is " << point_vector[0].size() << ".\n";
// Choose landmarks
start = clock();
// Gudhi::subsampling::pick_n_random_points(point_vector, number_of_landmarks, std::back_inserter(landmarks));
Gudhi::subsampling::choose_n_farthest_points(K().squared_distance_d_object(), point_vector, number_of_landmarks,
Gudhi::subsampling::random_starting_point,
std::back_inserter(landmarks));
// Compute witness complex
Witness_complex witness_complex(landmarks, point_vector);
witness_complex.create_complex(simplex_tree, 0);
end = clock();
double time = static_cast<double>(end - start) / CLOCKS_PER_SEC;
std::clog << "Witness complex for " << number_of_landmarks << " landmarks took " << time << " s. \n";
std::clog << "Number of simplices is: " << simplex_tree.num_simplices() << "\n";
l_time.push_back(std::make_pair(nbP, time));
}
write_data(l_time, "w_time.dat");
}
Gudhi::Simplex_tree
Simplex Tree data structure for representing simplicial complexes.
Definition Simplex_tree.h:98
Gudhi::Simplex_tree::num_simplices
size_t num_simplices() const
Returns the number of simplices in the simplex_tree.
Definition Simplex_tree.h:791
Gudhi::witness_complex::Euclidean_witness_complex
Constructs (weak) witness complex for given sets of witnesses and landmarks in Euclidean space.
Definition Euclidean_witness_complex.h:53
Gudhi::subsampling::choose_n_farthest_points
void choose_n_farthest_points(Distance dist, Point_range const &input_pts, std::size_t final_size, std::size_t starting_point, PointOutputIterator output_it, DistanceOutputIterator dist_it={})
Subsample by an iterative, greedy strategy.
Definition choose_n_farthest_points.h:75
Gudhi::subsampling::random_starting_point
@ random_starting_point
Definition choose_n_farthest_points.h:43
reader_utils.h
This file includes common file reader for GUDHI.