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Diffstat (limited to 'src/Subsampling/include/gudhi/Pick_random_points.h')
-rw-r--r-- | src/Subsampling/include/gudhi/Pick_random_points.h | 80 |
1 files changed, 80 insertions, 0 deletions
diff --git a/src/Subsampling/include/gudhi/Pick_random_points.h b/src/Subsampling/include/gudhi/Pick_random_points.h new file mode 100644 index 00000000..9a436ee3 --- /dev/null +++ b/src/Subsampling/include/gudhi/Pick_random_points.h @@ -0,0 +1,80 @@ +/* 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) 2016 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 PICK_RANDOM_POINTS_H_ +#define PICK_RANDOM_POINTS_H_ + +#include <boost/range/size.hpp> + +#include <random> // random_device, mt19937 +#include <algorithm> // shuffle +#include <numeric> // iota +#include <iterator> +#include <gudhi/Clock.h> + + +namespace Gudhi { + + /** + * \ingroup witness_complex + * \brief Landmark choice strategy by taking random vertices for landmarks. + * + * \details It chooses nbL distinct landmarks from a random access range `points` + * and outputs them to an output iterator. + * Point_container::iterator should be ValueSwappable and RandomAccessIterator. + */ + + template <typename Point_container, + typename OutputIterator> + void pick_random_points(Point_container const &points, + unsigned nbL, + OutputIterator output_it) { +#ifdef GUDHI_LM_PROFILING + Gudhi::Clock t; +#endif + + unsigned nbP = boost::size(points); + assert(nbP >= nbL); + std::vector<int> landmarks(nbP); + std::iota(landmarks.begin(), landmarks.end(), 0); + + std::random_device rd; + std::mt19937 g(rd()); + + std::shuffle(landmarks.begin(), landmarks.end(), g); + landmarks.resize(nbL); + + for (int l: landmarks) + *output_it++ = points[l]; + +#ifdef GUDHI_LM_PROFILING + t.end(); + std::cerr << "Random landmark choice took " << t.num_seconds() + << " seconds." << std::endl; +#endif + + + } + +} // namespace Gudhi + +#endif // LANDMARK_CHOICE_BY_RANDOM_POINT_H_ |