From 6279ac91dd7e2d3206e8a380d38cb2e5d503e9dc Mon Sep 17 00:00:00 2001
From: ROUVREAU Vincent <vincent.rouvreau@inria.fr>
Date: Tue, 8 Dec 2020 17:54:46 +0100
Subject: Fix #388 for the tests to pass

---
 src/cmake/modules/GUDHI_third_party_libraries.cmake | 1 +
 src/python/gudhi/simplex_tree.pyx                   | 3 +++
 src/python/include/Simplex_tree_interface.h         | 6 ++++++
 3 files changed, 10 insertions(+)

diff --git a/src/cmake/modules/GUDHI_third_party_libraries.cmake b/src/cmake/modules/GUDHI_third_party_libraries.cmake
index e1566877..e2684aa4 100644
--- a/src/cmake/modules/GUDHI_third_party_libraries.cmake
+++ b/src/cmake/modules/GUDHI_third_party_libraries.cmake
@@ -58,6 +58,7 @@ endif(WITH_GUDHI_USE_TBB)
 set(CGAL_WITH_EIGEN3_VERSION 0.0.0)
 find_package(Eigen3 3.1.0)
 if (EIGEN3_FOUND)
+  add_definitions(-DGUDHI_USE_EIGEN3)
   include( ${EIGEN3_USE_FILE} )
   set(CGAL_WITH_EIGEN3_VERSION ${CGAL_VERSION})
 endif (EIGEN3_FOUND)
diff --git a/src/python/gudhi/simplex_tree.pyx b/src/python/gudhi/simplex_tree.pyx
index cdd2e87b..7d6ab89a 100644
--- a/src/python/gudhi/simplex_tree.pyx
+++ b/src/python/gudhi/simplex_tree.pyx
@@ -627,6 +627,9 @@ cdef class SimplexTree:
 
         :param nb_iterations: The number of edge collapse iterations to perform. Default is 1.
         :type nb_iterations: int
+
+        :note: collapse_edges function requires `Eigen <installation.html#eigen>`_ >= 3.1.0, otherwise no action is
+        performed.
         """
         # Backup old pointer
         cdef Simplex_tree_interface_full_featured* ptr = self.get_ptr()
diff --git a/src/python/include/Simplex_tree_interface.h b/src/python/include/Simplex_tree_interface.h
index baff3850..2bd704b4 100644
--- a/src/python/include/Simplex_tree_interface.h
+++ b/src/python/include/Simplex_tree_interface.h
@@ -15,7 +15,9 @@
 #include <gudhi/distance_functions.h>
 #include <gudhi/Simplex_tree.h>
 #include <gudhi/Points_off_io.h>
+#ifdef GUDHI_USE_EIGEN3
 #include <gudhi/Flag_complex_edge_collapser.h>
+#endif
 
 #include <iostream>
 #include <vector>
@@ -162,6 +164,7 @@ class Simplex_tree_interface : public Simplex_tree<SimplexTreeOptions> {
   }
 
   Simplex_tree_interface* collapse_edges(int nb_collapse_iteration) {
+#ifdef GUDHI_USE_EIGEN3
     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)) {
@@ -187,6 +190,9 @@ class Simplex_tree_interface : public Simplex_tree<SimplexTreeOptions> {
       collapsed_stree_ptr->insert({std::get<0>(remaining_edge), std::get<1>(remaining_edge)}, std::get<2>(remaining_edge));
     }
     return collapsed_stree_ptr;
+#else
+    return this;
+#endif
   }
 
   // Iterator over the simplex tree
-- 
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