From 76a61bcd3279a98bd84856b011869a0be2ba99cd Mon Sep 17 00:00:00 2001
From: ROUVREAU Vincent <vincent.rouvreau@inria.fr>
Date: Thu, 30 Jul 2020 12:36:16 +0200
Subject: collapse edges for python simplex tree

---
 src/python/include/Simplex_tree_interface.h | 29 +++++++++++++++++++++++++++++
 1 file changed, 29 insertions(+)

(limited to 'src/python/include/Simplex_tree_interface.h')

diff --git a/src/python/include/Simplex_tree_interface.h b/src/python/include/Simplex_tree_interface.h
index 56d7c41d..7500098d 100644
--- a/src/python/include/Simplex_tree_interface.h
+++ b/src/python/include/Simplex_tree_interface.h
@@ -15,10 +15,12 @@
 #include <gudhi/distance_functions.h>
 #include <gudhi/Simplex_tree.h>
 #include <gudhi/Points_off_io.h>
+#include <gudhi/Flag_complex_edge_collapser.h>
 
 #include <iostream>
 #include <vector>
 #include <utility>  // std::pair
+#include <tuple>
 
 namespace Gudhi {
 
@@ -157,6 +159,33 @@ class Simplex_tree_interface : public Simplex_tree<SimplexTreeOptions> {
     return new_dgm;
   }
 
+  Simplex_tree_interface* collapse_edges(int nb_collapse_iteration) {
+    using Filtered_edge = std::tuple<Vertex_handle, Vertex_handle, Filtration_value>;
+    std::vector<Filtered_edge> edges;
+    for (Simplex_handle sh : Base::skeleton_simplex_range(1)) {
+      if (Base::dimension(sh) == 1) {
+        typename Base::Simplex_vertex_range rg = Base::simplex_vertex_range(sh);
+        std::vector<Vertex_handle> rips_edge(rg.begin(), rg.end());
+        edges.push_back(std::make_tuple(rips_edge[0], rips_edge[1], Base::filtration(sh)));
+      }
+    }
+
+    std::vector<Filtered_edge> remaining_edges;
+    for (int iteration = 0; iteration < nb_collapse_iteration; iteration++) {
+      remaining_edges = Gudhi::collapse::flag_complex_collapse_edges(edges);
+      edges = std::move(remaining_edges);
+      remaining_edges.clear();
+    }
+    Simplex_tree_interface* collapsed_stree_ptr = new Simplex_tree_interface();
+    for (auto remaining_edge : edges) {
+      collapsed_stree_ptr->insert({std::get<0>(remaining_edge)}, 0.);
+      collapsed_stree_ptr->insert({std::get<1>(remaining_edge)}, 0.);
+      collapsed_stree_ptr->insert({std::get<0>(remaining_edge), std::get<1>(remaining_edge)}, std::get<2>(remaining_edge));
+    }
+    collapsed_stree_ptr->initialize_filtration();
+    return collapsed_stree_ptr;
+  }
+
   // Iterator over the simplex tree
   Complex_simplex_iterator get_simplices_iterator_begin() {
     // this specific case works because the range is just a pair of iterators - won't work if range was a vector
-- 
cgit v1.2.3