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Diffstat (limited to 'include/gudhi/Strong_witness_complex.h')
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diff --git a/include/gudhi/Strong_witness_complex.h b/include/gudhi/Strong_witness_complex.h new file mode 100644 index 00000000..a973ddb7 --- /dev/null +++ b/include/gudhi/Strong_witness_complex.h @@ -0,0 +1,185 @@ +/* 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 (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 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; + } + if (limit_dimension < 0) { + std::cerr << "Strong witness complex cannot create complex - limit dimension 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; + } + complex.set_dimension(complex_dim); + 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_ |