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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): Siargey Kachanovich
*
* Copyright (C) 2015 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/>.
*/
#ifndef STRONG_WITNESS_COMPLEX_H_
#define STRONG_WITNESS_COMPLEX_H_
#include <gudhi/Active_witness/Active_witness.h>
#include <utility>
#include <vector>
#include <list>
#include <limits>
namespace Gudhi {
namespace witness_complex {
/**
* \private
* \class Strong_witness_complex
* \brief Constructs strong witness complex for a given table of nearest landmarks with respect to witnesses.
* \ingroup witness_complex
*
* \tparam Nearest_landmark_table_ needs to be a range of a range of pairs of nearest landmarks and distances.
* The class Nearest_landmark_table_::value_type must be a copiable range.
* The range of pairs must admit a member type 'iterator'. The dereference type
* of the pair range iterator needs to be 'std::pair<std::size_t, double>'.
*/
template< class Nearest_landmark_table_ >
class Strong_witness_complex {
private:
typedef typename Nearest_landmark_table_::value_type Nearest_landmark_range;
typedef std::size_t Witness_id;
typedef std::size_t Landmark_id;
typedef std::pair<Landmark_id, double> Id_distance_pair;
typedef Active_witness<Id_distance_pair, Nearest_landmark_range> ActiveWitness;
typedef std::list< ActiveWitness > ActiveWitnessList;
typedef std::vector< Landmark_id > typeVectorVertex;
typedef std::vector<Nearest_landmark_range> Nearest_landmark_table_internal;
typedef Landmark_id Vertex_handle;
protected:
Nearest_landmark_table_internal nearest_landmark_table_;
public:
/////////////////////////////////////////////////////////////////////////////////////////////////////////////////////
/* @name Constructor
*/
//@{
Strong_witness_complex() {
}
/**
* \brief Initializes member variables before constructing simplicial complex.
* \details Records nearest landmark table.
* @param[in] nearest_landmark_table needs to be a range of a range of pairs of nearest landmarks and distances.
* The class Nearest_landmark_table_::value_type must be a copiable range.
* The range of pairs must admit a member type 'iterator'. The dereference type
* of the pair range iterator needs to be 'std::pair<std::size_t, double>'.
*/
Strong_witness_complex(Nearest_landmark_table_ const & nearest_landmark_table)
: nearest_landmark_table_(std::begin(nearest_landmark_table), std::end(nearest_landmark_table)) {
}
/** \brief Outputs the strong witness complex of relaxation 'max_alpha_square'
* in a simplicial complex data structure.
* \details The function returns true if the construction is successful and false otherwise.
* @param[out] complex Simplicial complex data structure, which is a model of
* SimplicialComplexForWitness concept.
* @param[in] max_alpha_square Maximal squared relaxation parameter.
* @param[in] limit_dimension Represents the maximal dimension of the simplicial complex
* (default value = no limit).
*/
template < typename SimplicialComplexForWitness >
bool create_complex(SimplicialComplexForWitness& complex,
double max_alpha_square,
Landmark_id limit_dimension = std::numeric_limits<Landmark_id>::max()) const {
Landmark_id complex_dim = 0;
if (complex.num_vertices() > 0) {
std::cerr << "Strong witness complex cannot create complex - complex is not empty.\n";
return false;
}
if (max_alpha_square < 0) {
std::cerr << "Strong witness complex cannot create complex - squared relaxation parameter must be "
<< "non-negative.\n";
return false;
}
for (auto w : nearest_landmark_table_) {
ActiveWitness aw(w);
typeVectorVertex simplex;
typename ActiveWitness::iterator aw_it = aw.begin();
float lim_dist2 = aw.begin()->second + max_alpha_square;
while ((Landmark_id)simplex.size() <= limit_dimension && aw_it != aw.end() && aw_it->second < lim_dist2) {
simplex.push_back(aw_it->first);
complex.insert_simplex_and_subfaces(simplex, aw_it->second - aw.begin()->second);
aw_it++;
}
// continue inserting limD-faces of the following simplices
typeVectorVertex& vertices = simplex; // 'simplex' now will be called vertices
while (aw_it != aw.end() && aw_it->second < lim_dist2) {
typeVectorVertex facet = {};
add_all_faces_of_dimension(limit_dimension, vertices, vertices.begin(), aw_it,
aw_it->second - aw.begin()->second, facet, complex);
vertices.push_back(aw_it->first);
aw_it++;
}
if ((Landmark_id)simplex.size() - 1 > complex_dim)
complex_dim = simplex.size() - 1;
}
return true;
}
//@}
private:
/* \brief Adds recursively all the faces of a certain dimension dim-1 witnessed by the same witness.
* Iterator is needed to know until how far we can take landmarks to form simplexes.
* simplex is the prefix of the simplexes to insert.
* The landmark pointed by aw_it is added to all formed simplices.
*/
template < typename SimplicialComplexForWitness >
void add_all_faces_of_dimension(Landmark_id dim,
typeVectorVertex& vertices,
typename typeVectorVertex::iterator curr_it,
typename ActiveWitness::iterator aw_it,
double filtration_value,
typeVectorVertex& simplex,
SimplicialComplexForWitness& sc) const {
if (dim > 0) {
while (curr_it != vertices.end()) {
simplex.push_back(*curr_it);
++curr_it;
add_all_faces_of_dimension(dim-1,
vertices,
curr_it,
aw_it,
filtration_value,
simplex,
sc);
simplex.pop_back();
add_all_faces_of_dimension(dim,
vertices,
curr_it,
aw_it,
filtration_value,
simplex,
sc);
}
} else if (dim == 0) {
simplex.push_back(aw_it->first);
sc.insert_simplex_and_subfaces(simplex, filtration_value);
simplex.pop_back();
}
}
};
} // namespace witness_complex
} // namespace Gudhi
#endif // STRONG_WITNESS_COMPLEX_H_
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