make_filtration_non_decreasing no more called in alpha complex dD exact version and exact and safe 3d versions

4 files changed, 13 insertions, 4 deletions

diff --git a/src/Alpha_complex/doc/Intro_alpha_complex.h b/src/Alpha_complex/doc/Intro_alpha_complex.h
index f417ebb2..5ab23720 100644
--- a/src/Alpha_complex/doc/Intro_alpha_complex.h
+++ b/src/Alpha_complex/doc/Intro_alpha_complex.h
@@ -152,6 +152,8 @@ Table of Contents
  * not quite define a proper filtration (i.e. non-decreasing with respect to inclusion).
  * We fix that up by calling `SimplicialComplexForAlpha::make_filtration_non_decreasing()`.
  *
+ * \note This is not the case in `exact` version, this is the reason why it is not called in this case.
+ *
  * \subsubsection pruneabove Prune above given filtration value
  *
  * The simplex tree is pruned from the given maximum \f$ \alpha^2 \f$ value (cf.
diff --git a/src/Alpha_complex/include/gudhi/Alpha_complex.h b/src/Alpha_complex/include/gudhi/Alpha_complex.h
index b315fa99..e03bb161 100644
--- a/src/Alpha_complex/include/gudhi/Alpha_complex.h
+++ b/src/Alpha_complex/include/gudhi/Alpha_complex.h
@@ -435,8 +435,10 @@ class Alpha_complex {
       // --------------------------------------------------------------------------------------------
   
       // --------------------------------------------------------------------------------------------
-      // As Alpha value is an approximation, we have to make filtration non decreasing while increasing the dimension
-      complex.make_filtration_non_decreasing();
+      if (!exact)
+        // As Alpha value is an approximation, we have to make filtration non decreasing while increasing the dimension
+        // Only in not exact version, cf. https://github.com/GUDHI/gudhi-devel/issues/57
+        complex.make_filtration_non_decreasing();
       // Remove all simplices that have a filtration value greater than max_alpha_square
       complex.prune_above_filtration(max_alpha_square);
       // --------------------------------------------------------------------------------------------
diff --git a/src/Alpha_complex/include/gudhi/Alpha_complex_3d.h b/src/Alpha_complex/include/gudhi/Alpha_complex_3d.h
index 4e5fc933..ccc3d852 100644
--- a/src/Alpha_complex/include/gudhi/Alpha_complex_3d.h
+++ b/src/Alpha_complex/include/gudhi/Alpha_complex_3d.h
@@ -554,8 +554,10 @@ Weighted_alpha_complex_3d::Weighted_point_3 wp0(Weighted_alpha_complex_3d::Bare_
     std::clog << "cells \t\t" << count_cells << std::endl;
 #endif  // DEBUG_TRACES
     // --------------------------------------------------------------------------------------------
-    // As Alpha value is an approximation, we have to make filtration non decreasing while increasing the dimension
-    complex.make_filtration_non_decreasing();
+    if (Complexity == complexity::FAST)
+      // As Alpha value is an approximation, we have to make filtration non decreasing while increasing the dimension
+      // Only in FAST version, cf. https://github.com/GUDHI/gudhi-devel/issues/57
+      complex.make_filtration_non_decreasing();
     // Remove all simplices that have a filtration value greater than max_alpha_square
     complex.prune_above_filtration(max_alpha_square);
     // --------------------------------------------------------------------------------------------
diff --git a/src/python/doc/alpha_complex_user.rst b/src/python/doc/alpha_complex_user.rst
index fffcb3db..ef67a457 100644
--- a/src/python/doc/alpha_complex_user.rst
+++ b/src/python/doc/alpha_complex_user.rst
@@ -165,6 +165,9 @@ respect to inclusion).
 We fix that up by calling :func:`~gudhi.SimplexTree.make_filtration_non_decreasing` (cf.
 `C++ version <http://gudhi.gforge.inria.fr/doc/latest/index.html>`_).
 
+.. note::
+    This is not the case in `exact` version, this is the reason why it is not called in this case.
+
 Prune above given filtration value
 ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^