diff options
author | skachano <skachano@636b058d-ea47-450e-bf9e-a15bfbe3eedb> | 2015-12-09 13:03:03 +0000 |
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committer | skachano <skachano@636b058d-ea47-450e-bf9e-a15bfbe3eedb> | 2015-12-09 13:03:03 +0000 |
commit | 8f54c437e0b895368c6151584811ce7df1575ea0 (patch) | |
tree | f7b0f1cfa2e366ca4455ebd6892451319f3fda00 /src/Witness_complex/include/gudhi/Landmark_choice_by_furthest_point.h | |
parent | 9325765e94b1bd43600fe345a033216bce55873f (diff) |
Modified Witness_complex.h + more doc
git-svn-id: svn+ssh://scm.gforge.inria.fr/svnroot/gudhi/branches/witness@936 636b058d-ea47-450e-bf9e-a15bfbe3eedb
Former-commit-id: 771e0a9cbfd0035738aee1a07b5f7c1f56bf13fc
Diffstat (limited to 'src/Witness_complex/include/gudhi/Landmark_choice_by_furthest_point.h')
-rw-r--r-- | src/Witness_complex/include/gudhi/Landmark_choice_by_furthest_point.h | 98 |
1 files changed, 98 insertions, 0 deletions
diff --git a/src/Witness_complex/include/gudhi/Landmark_choice_by_furthest_point.h b/src/Witness_complex/include/gudhi/Landmark_choice_by_furthest_point.h new file mode 100644 index 00000000..44bf9dbb --- /dev/null +++ b/src/Witness_complex/include/gudhi/Landmark_choice_by_furthest_point.h @@ -0,0 +1,98 @@ +/* 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 <http://www.gnu.org/licenses/>. + */ + +#ifndef GUDHI_LANDMARK_CHOICE_BY_FURTHEST_POINT_H_ +#define GUDHI_LANDMARK_CHOICE_BY_FURTHEST_POINT_H_ + +/** + * \class Landmark_choice_by_furthest_point + * \brief The class `Landmark_choice_by_furthest_point` allows to construct the matrix + * of closest landmarks per witness by iteratively choosing the furthest witness + * from the set of already chosen landmarks as the new landmark. + * \ingroup witness_complex + */ + +class Landmark_choice_by_random_point { + +/** + * \brief Landmark choice strategy by iteratively adding the furthest witness from the + * current landmark set as the new landmark. It takes a random access range `points` and + * writes {witness}*{closest landmarks} matrix in `knn`. + */ + + template <typename KNearestNeighbours, + typename Point_random_access_range> + Landmark_choice_by_furthest_points(Point_random_access_range &points, + KNearestNeighbours &knn) + { + int nb_points = points.end() - points.begin(); + std::vector<std::vector<double>> wit_land_dist(nb_points, std::vector<double>()); // distance matrix witness x landmarks + typeVectorVertex chosen_landmarks; // landmark list + + knn = KNearestNeighbours(nb_points, std::vector<int>()); + 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<double>::infinity(); // infinity (see next entry) + std::vector< double > dist_to_L(nb_points,infty); // vector of current distances to L from points + + //CHOICE OF THE FIRST LANDMARK + int rand_int = rand() % nb_points; + int curr_max_w = rand_int; //For testing purposes a pseudo-random number is used here + + 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 + chosen_landmarks.push_back(curr_max_w); + for (auto v: knn) + v.push_back(current_number_of_landmarks); + int i = 0; + for (const auto& p: points) + { + // used to stock the distance from the current point to L + double curr_dist = euclidean_distance(p, points.begin() + chosen_landmarks[current_number_of_landmarks]); + wit_land_dist[i].push_back(curr_dist); + knn[i].push_back(current_number_of_landmarks); + if (curr_dist < dist_to_L[i]) + dist_to_L[i] = curr_dist; + int j = current_number_of_landmarks; + while (j > 0 && wit_land_dist[i][j-1] > wit_land_dist[i][j]) + { + std::swap(knn[i][j], knn[i][j-1]); + std::swap(wit_land_dist[i][j-1], wit_land_dist[i][j-1]); + --j; + } + ++i; + } + curr_max_dist = 0; + for (auto dist: dist_to_L) { + if (dist > curr_max_dist) + { + curr_max_dist = dist; + curr_max_w = i; + } + } + } + } + +}; + +#endif |