From 80c45e3f6a8a1f823840b3ae9e924362d7e376b7 Mon Sep 17 00:00:00 2001
From: skachano <skachano@636b058d-ea47-450e-bf9e-a15bfbe3eedb>
Date: Mon, 20 Jun 2016 21:49:38 +0000
Subject: Added the forgotten files

git-svn-id: svn+ssh://scm.gforge.inria.fr/svnroot/gudhi/branches/subsampling_and_spatialsearching@1317 636b058d-ea47-450e-bf9e-a15bfbe3eedb

Former-commit-id: f5fe0bce1c55e62c87bf0da9be915f081a90e9e7
---
 src/Subsampling/include/gudhi/pick_random_points.h | 80 ++++++++++++++++++++++
 1 file changed, 80 insertions(+)
 create mode 100644 src/Subsampling/include/gudhi/pick_random_points.h

(limited to 'src/Subsampling/include/gudhi/pick_random_points.h')

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_
-- 
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