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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
*
* 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/>.
*/
#include <gudhi/Skeleton_blocker.h>
#include <gudhi/Clock.h>
#include <stdio.h>
#include <stdlib.h>
#include <string>
#include <fstream>
#include <sstream>
typedef Gudhi::skeleton_blocker::Skeleton_blocker_simple_traits Traits;
typedef Gudhi::skeleton_blocker::Skeleton_blocker_complex<Traits> Complex;
typedef Complex::Vertex_handle Vertex_handle;
typedef Complex::Simplex Simplex;
Complex build_complete_complex(int n) {
// build a full complex with n vertices and 2^n-1 simplices
Complex complex;
for (int i = 0; i < n; i++)
complex.add_vertex();
for (int i = 0; i < n; i++)
for (int j = 0; j < i; j++)
complex.add_edge_without_blockers(Vertex_handle(i), Vertex_handle(j));
return complex;
}
int main(int argc, char *argv[]) {
Gudhi::Clock skbl_chrono("Time to build the complete complex, enumerate simplices and Euler Characteristic");
const int n = 15;
// build a full complex with n vertices and 2^n-1 simplices
Complex complex(build_complete_complex(n));
// this is just to illustrate iterators, to count number of vertices
// or edges, complex.num_vertices() and complex.num_edges() are
// more appropriated!
unsigned num_vertices = 0;
for (auto v : complex.vertex_range()) {
std::cout << "Vertex " << v << std::endl;
++num_vertices;
}
// such loop can also be done directly with distance as iterators are STL compliant
auto edges = complex.edge_range();
unsigned num_edges = std::distance(edges.begin(), edges.end());
unsigned euler = 0;
unsigned num_simplices = 0;
// we use a reference to a simplex instead of a copy
// value here because a simplex is a set of integers
// and copying it cost time
for (const Simplex & s : complex.complex_simplex_range()) {
++num_simplices;
if (s.dimension() % 2 == 0)
euler += 1;
else
euler -= 1;
}
std::cout << "Saw " << num_vertices << " vertices, " << num_edges << " edges and " << num_simplices << " simplices"
<< std::endl;
std::cout << "The Euler Characteristic is " << euler << std::endl;
std::cout << skbl_chrono;
return EXIT_SUCCESS;
}
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