From 6dd7403da12dff125e1dedacbc2ed0ec67e643ba Mon Sep 17 00:00:00 2001
From: fgodi <fgodi@636b058d-ea47-450e-bf9e-a15bfbe3eedb>
Date: Wed, 23 Nov 2016 14:55:25 +0000
Subject: Bottleneck.h

git-svn-id: svn+ssh://scm.gforge.inria.fr/svnroot/gudhi/branches/bottleneck_integration@1774 636b058d-ea47-450e-bf9e-a15bfbe3eedb

Former-commit-id: 3b2f26c67ceb8a61f3efe3952f0618fff98465e4
---
 src/Bottleneck_distance/include/gudhi/Bottleneck.h | 125 +++++++++++++++++++++
 1 file changed, 125 insertions(+)
 create mode 100644 src/Bottleneck_distance/include/gudhi/Bottleneck.h

(limited to 'src/Bottleneck_distance/include/gudhi/Bottleneck.h')

diff --git a/src/Bottleneck_distance/include/gudhi/Bottleneck.h b/src/Bottleneck_distance/include/gudhi/Bottleneck.h
new file mode 100644
index 00000000..6b6b1552
--- /dev/null
+++ b/src/Bottleneck_distance/include/gudhi/Bottleneck.h
@@ -0,0 +1,125 @@
+/*    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 Sophia-Antipolis (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 BOTTLENECK_H_
+#define BOTTLENECK_H_
+
+#include <gudhi/Graph_matching.h>
+
+namespace Gudhi {
+
+namespace bottleneck_distance {
+
+/** \brief Function to use in order to compute the Bottleneck distance between two persistence diagrams. You get an additive e-approximation.
+ *
+ *
+ * \ingroup bottleneck_distance
+ */
+template<typename Persistence_diagram1, typename Persistence_diagram2>
+double compute(const Persistence_diagram1& diag1, const Persistence_diagram2& diag2, double e = 0.);
+
+template<typename Persistence_diagram1, typename Persistence_diagram2>
+double compute_exactly(const Persistence_diagram1& diag1, const Persistence_diagram2& diag2);
+
+template<typename Persistence_diagram1, typename Persistence_diagram2>
+double compute_exactly(const Persistence_diagram1 &diag1, const Persistence_diagram2 &diag2) {
+    G::initialize(diag1, diag2, 0.);
+    std::shared_ptr< std::vector<double> > sd(G::sorted_distances());
+    int idmin = 0;
+    int idmax = sd->size() - 1;
+    // alpha can be modified, this will change the complexity
+    double alpha = pow(sd->size(), 0.25);
+    Graph_matching m;
+    Graph_matching biggest_unperfect;
+    while (idmin != idmax) {
+        int step = static_cast<int>((idmax - idmin) / alpha);
+        m.set_r(sd->at(idmin + step));
+        while (m.multi_augment());
+        //The above while compute a maximum matching (according to the r setted before)
+        if (m.perfect()) {
+            idmax = idmin + step;
+            m = biggest_unperfect;
+        } else {
+            biggest_unperfect = m;
+            idmin = idmin + step + 1;
+        }
+    }
+    return sd->at(idmin);
+}
+
+template<typename Persistence_diagram1, typename Persistence_diagram2>
+double compute(const Persistence_diagram1 &diag1, const Persistence_diagram2 &diag2, double e) {
+    if(e< std::numeric_limits<double>::min())
+        return compute_exactly(diag1, diag2);
+    G::initialize(diag1, diag2, e);
+    int in = G::diameter()/e;
+    int idmin = 0;
+    int idmax = in;
+    // alpha can be modified, this will change the complexity
+    double alpha = pow(in, 0.25);
+    Graph_matching m;
+    Graph_matching biggest_unperfect;
+    while (idmin != idmax) {
+        int step = static_cast<int>((idmax - idmin) / alpha);
+        m.set_r(e*(idmin + step));
+        while (m.multi_augment());
+        //The above while compute a maximum matching (according to the r setted before)
+        if (m.perfect()) {
+            idmax = idmin + step;
+            m = biggest_unperfect;
+        } else {
+            biggest_unperfect = m;
+            idmin = idmin + step + 1;
+        }
+    }
+    return e*(idmin);
+}
+
+
+
+}  // namespace bottleneck_distance
+
+}  // namespace Gudhi
+
+#endif  // BOTTLENECK_H_
+
+/* Dichotomic version
+template<typename Persistence_diagram1, typename Persistence_diagram2>
+double compute(const Persistence_diagram1 &diag1, const Persistence_diagram2 &diag2, double e) {
+    if(e< std::numeric_limits<double>::min())
+        return compute_exactly(diag1, diag2);
+    G::initialize(diag1, diag2, e);
+    double d = 0.;
+    double f = G::diameter();
+    while (f-d > e){
+        Graph_matching m;
+        m.set_r((d+f)/2.);
+        while (m.multi_augment());
+        //The above while compute a maximum matching (according to the r setted before)
+        if (m.perfect())
+            f = (d+f)/2.;
+         else
+            d= (d+f)/2.;
+    }
+    return d;
+} */
+
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