Add Python Simplex_tree make_filtration_non_decreasing interface and its tests

git-svn-id: svn+ssh://scm.gforge.inria.fr/svnroot/gudhi/branches/python_2.1.0_fix_vincent@3409 636b058d-ea47-450e-bf9e-a15bfbe3eedb

Former-commit-id: 6a3af66b3d90c6114886e54c5c34287a13f4b863

2 files changed, 67 insertions, 0 deletions

diff --git a/src/cython/cython/simplex_tree.pyx b/src/cython/cython/simplex_tree.pyx
index 755cdc02..38740f4f 100644
--- a/src/cython/cython/simplex_tree.pyx
+++ b/src/cython/cython/simplex_tree.pyx
@@ -55,6 +55,7 @@ cdef extern from "Simplex_tree_interface.h" namespace "Gudhi":
         void expansion(int max_dim)
         void remove_maximal_simplex(vector[int] simplex)
         bool prune_above_filtration(double filtration)
+        bool make_filtration_non_decreasing()
 
 cdef extern from "Persistent_cohomology_interface.h" namespace "Gudhi":
     cdef cppclass Simplex_tree_persistence_interface "Gudhi::Persistent_cohomology_interface<Gudhi::Simplex_tree<Gudhi::Simplex_tree_options_full_featured>>":
@@ -400,6 +401,28 @@ cdef class SimplexTree:
         """
         self.thisptr.expansion(max_dim)
 
+    def make_filtration_non_decreasing(self):
+        """Browse the simplex tree to ensure the filtration is not decreasing.
+        The simplex tree is browsed starting from the root until the leaf, and
+        the filtration values are set with their parent value (increased), in
+        case the values are decreasing.
+
+        :returns: The filtration modification information.
+        :rtype: bint
+
+
+        .. note::
+
+            Some simplex tree functions require the filtration to be valid.
+            make_filtration_non_decreasing function is not launching
+            :func:`initialize_filtration()<gudhi.SimplexTree.initialize_filtration>`
+            but returns the filtration modification
+            information. If the complex has changed , please call
+            :func:`initialize_filtration()<gudhi.SimplexTree.initialize_filtration>`
+            to recompute it.
+        """
+        return self.thisptr.make_filtration_non_decreasing()
+
     def persistence(self, homology_coeff_field=11, min_persistence=0, persistence_dim_max = False):
         """This function returns the persistence of the simplicial complex.
 
diff --git a/src/cython/test/test_simplex_tree.py b/src/cython/test/test_simplex_tree.py
index 6dec5d94..bc16183a 100755
--- a/src/cython/test/test_simplex_tree.py
+++ b/src/cython/test/test_simplex_tree.py
@@ -161,3 +161,47 @@ def test_automatic_dimension():
     assert st.upper_bound_dimension() == 2
     assert st.dimension() == 1
     assert st.upper_bound_dimension() == 1
+
+def test_make_filtration_non_decreasing():
+    st = SimplexTree()
+    assert st.__is_defined() == True
+    assert st.__is_persistence_defined() == False
+
+    # Inserted simplex:
+    #    1
+    #    o
+    #   /X\
+    #  o---o---o---o
+    #  2   0   3\X/4
+    #            o
+    #            5
+    assert st.insert([2, 1, 0], filtration=2.0) == True
+    assert st.insert([3, 0], filtration=2.0) == True
+    assert st.insert([3, 4, 5], filtration=2.0) == True
+
+    assert st.make_filtration_non_decreasing() == False
+
+    # Because of non decreasing property of simplex tree, { 0 } , { 1 } and
+    # { 0, 1 } are going to be set from value 2.0 to 1.0
+    st.insert([0, 1, 6, 7], filtration=1.0);
+
+    assert st.make_filtration_non_decreasing() == False
+
+    # Modify specific values to test make_filtration_non_decreasing
+    st.assign_filtration([0,1,6,7], 0.8);
+    st.assign_filtration([0,1,6], 0.9);
+    st.assign_filtration([0,6], 0.6);
+    st.assign_filtration([3,4,5], 1.2);
+    st.assign_filtration([3,4], 1.1);
+    st.assign_filtration([4,5], 1.99);
+
+    assert st.make_filtration_non_decreasing() == True
+
+    assert st.filtration([0,1,6,7]) == 1.
+    assert st.filtration([0,1,6]) == 1.
+    assert st.filtration([0,1]) == 1.
+    assert st.filtration([0]) == 1.
+    assert st.filtration([1]) == 1.
+    assert st.filtration([3,4,5]) == 2.
+    assert st.filtration([3,4]) == 2.
+    assert st.filtration([4,5]) == 2.