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diff --git a/src/Bottleneck/include/gudhi/Persistence_diagrams_graph.h b/src/Bottleneck/include/gudhi/Persistence_diagrams_graph.h
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+++ b/src/Bottleneck/include/gudhi/Persistence_diagrams_graph.h
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+/*    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):       Francois Godi
+ *
+ *    Copyright (C) 2015  INRIA Saclay (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 SRC_BOTTLENECK_INCLUDE_GUDHI_PERSISTENCE_DIAGRAMS_GRAPH_H_
+#define SRC_BOTTLENECK_INCLUDE_GUDHI_PERSISTENCE_DIAGRAMS_GRAPH_H_
+
+#include <vector>
+#include <set>
+#include <cmath>
+#include <utility>  // for pair<>
+#include <algorithm>  // for max
+
+namespace Gudhi {
+
+namespace bottleneck {
+
+// Diagram_point is the type of the persistence diagram's points
+typedef typename std::pair<double, double> Diagram_point;
+
+// Return the used index for encoding none of the points
+int null_point_index();
+
+// Persistence_diagrams_graph is the interface beetwen any external representation of the two persistence diagrams and
+// the bottleneck distance computation. An interface is necessary to ensure basic functions complexity.
+
+class Persistence_diagrams_graph {
+ public:
+  // Persistence_diagram1 and 2 are the types of any externals representations of persistence diagrams.
+  // They have to have an iterator over points, which have to have fields first (for birth) and second (for death).
+  template<typename Persistence_diagram1, typename Persistence_diagram2>
+  Persistence_diagrams_graph(Persistence_diagram1& diag1, Persistence_diagram2& diag2, double e = 0.);
+  Persistence_diagrams_graph();
+  bool on_the_u_diagonal(int u_point_index) const;
+  bool on_the_v_diagonal(int v_point_index) const;
+  int corresponding_point_in_u(int v_point_index) const;
+  int corresponding_point_in_v(int u_point_index) const;
+  double distance(int u_point_index, int v_point_index) const;
+  int size() const;
+  std::vector<double>* sorted_distances();
+
+ private:
+  std::vector<Diagram_point> u;
+  std::vector<Diagram_point> v;
+  Diagram_point get_u_point(int u_point_index) const;
+  Diagram_point get_v_point(int v_point_index) const;
+};
+
+inline int null_point_index() {
+  return -1;
+}
+
+template<typename Persistence_diagram1, typename Persistence_diagram2>
+Persistence_diagrams_graph::Persistence_diagrams_graph(Persistence_diagram1& diag1, Persistence_diagram2& diag2, double e)
+    : u(), v() {
+  for (auto it = diag1.cbegin(); it != diag1.cend(); ++it)
+    if (it->second - it->first > e)
+      u.emplace_back(*it);
+  for (auto it = diag2.cbegin(); it != diag2.cend(); ++it)
+    if (it->second - it->first > e)
+      v.emplace_back(*it);
+  if (u.size() < v.size())
+    swap(u, v);
+}
+
+Persistence_diagrams_graph::Persistence_diagrams_graph::Persistence_diagrams_graph()
+    : u(), v() { }
+
+inline bool Persistence_diagrams_graph::on_the_u_diagonal(int u_point_index) const {
+  return u_point_index >= static_cast<int> (u.size());
+}
+
+inline bool Persistence_diagrams_graph::on_the_v_diagonal(int v_point_index) const {
+  return v_point_index >= static_cast<int> (v.size());
+}
+
+inline int Persistence_diagrams_graph::corresponding_point_in_u(int v_point_index) const {
+  return on_the_v_diagonal(v_point_index) ?
+      v_point_index - static_cast<int> (v.size()) : v_point_index + static_cast<int> (u.size());
+}
+
+inline int Persistence_diagrams_graph::corresponding_point_in_v(int u_point_index) const {
+  return on_the_u_diagonal(u_point_index) ?
+      u_point_index - static_cast<int> (u.size()) : u_point_index + static_cast<int> (v.size());
+}
+
+inline double Persistence_diagrams_graph::distance(int u_point_index, int v_point_index) const {
+  // could be optimized for the case where one point is the projection of the other
+  if (on_the_u_diagonal(u_point_index) && on_the_v_diagonal(v_point_index))
+    return 0;
+  Diagram_point p_u = get_u_point(u_point_index);
+  Diagram_point p_v = get_v_point(v_point_index);
+  return std::max(std::fabs(p_u.first - p_v.first), std::fabs(p_u.second - p_v.second));
+}
+
+inline int Persistence_diagrams_graph::size() const {
+  return static_cast<int> (u.size() + v.size());
+}
+
+inline std::vector<double>* Persistence_diagrams_graph::sorted_distances() {
+  // could be optimized
+  std::set<double> sorted_distances;
+  for (int u_point_index = 0; u_point_index < size(); ++u_point_index)
+    for (int v_point_index = 0; v_point_index < size(); ++v_point_index)
+      sorted_distances.emplace(distance(u_point_index, v_point_index));
+  return new std::vector<double>(sorted_distances.cbegin(), sorted_distances.cend());
+}
+
+inline Diagram_point Persistence_diagrams_graph::get_u_point(int u_point_index) const {
+  if (!on_the_u_diagonal(u_point_index))
+    return u.at(u_point_index);
+  Diagram_point projector = v.at(corresponding_point_in_v(u_point_index));
+  double x = (projector.first + projector.second) / 2;
+  return Diagram_point(x, x);
+}
+
+inline Diagram_point Persistence_diagrams_graph::get_v_point(int v_point_index) const {
+  if (!on_the_v_diagonal(v_point_index))
+    return v.at(v_point_index);
+  Diagram_point projector = u.at(corresponding_point_in_u(v_point_index));
+  double x = (projector.first + projector.second) / 2;
+  return Diagram_point(x, x);
+}
+
+}  // namespace bottleneck
+
+}  // namespace Gudhi
+
+#endif  // SRC_BOTTLENECK_INCLUDE_GUDHI_PERSISTENCE_DIAGRAMS_GRAPH_H_