Update old comment about stable_sort.

git-svn-id: svn+ssh://scm.gforge.inria.fr/svnroot/gudhi/trunk@856 636b058d-ea47-450e-bf9e-a15bfbe3eedb

Former-commit-id: 20773a87a3a40113ad8a051be7972289144cd1d7

1 files changed, 9 insertions, 7 deletions

diff --git a/src/Simplex_tree/include/gudhi/Simplex_tree.h b/src/Simplex_tree/include/gudhi/Simplex_tree.h
index 6e51d107..4c6a95e8 100644
--- a/src/Simplex_tree/include/gudhi/Simplex_tree.h
+++ b/src/Simplex_tree/include/gudhi/Simplex_tree.h
@@ -771,12 +771,6 @@ class Simplex_tree {
    * assigned a Simplex_key corresponding to its order in the filtration (from 0 to m-1 for a
    * simplicial complex with m simplices).
    *
-   * The use of a depth-first traversal of the simplex tree, provided by
-   * complex_simplex_range(), combined with
-   * a stable sort is meant to optimize the order of simplices with same
-   * filtration value. The heuristic consists in inserting the cofaces of a
-   * simplex as soon as possible.
-   *
    * Will be automatically called when calling filtration_simplex_range()
    * if the filtration has never been initialized yet. */
   void initialize_filtration() {
@@ -785,7 +779,15 @@ class Simplex_tree {
     for (Simplex_handle sh : complex_simplex_range())
       filtration_vect_.push_back(sh);
 
-    // the stable sort ensures the ordering heuristic
+    /* We use stable_sort here because with libstdc++ it is faster than sort.
+     * is_before_in_filtration is now a total order, but we used to call
+     * stable_sort for the following heuristic:
+     * The use of a depth-first traversal of the simplex tree, provided by
+     * complex_simplex_range(), combined with a stable sort is meant to
+     * optimize the order of simplices with same filtration value. The
+     * heuristic consists in inserting the cofaces of a simplex as soon as
+     * possible.
+     */
     std::stable_sort(filtration_vect_.begin(), filtration_vect_.end(),
                      is_before_in_filtration(this));
   }