blob: 9a436ee30b13fb9661d1ab9531e759332ed762b8 (
plain)
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
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_
|
