diff --git a/compileTimeOptions.h b/compileTimeOptions.h
index 4b32d858a5135937d2ca727bc610df329f31b17e..526e6ec2611f3897ca3c7e148c6c7109d985f1ad 100644
--- a/compileTimeOptions.h
+++ b/compileTimeOptions.h
@@ -20,3 +20,6 @@ REQUIRES(EXPLICIT_NORMAL_EDGES, USE_NEXT_FORB)
 BOOL_OPTION(USE_TWO_CUTS, 1)
 REQUIRES(USE_TWO_CUTS, USE_NEXT_FORB && EXPLICIT_NORMAL_EDGES)
 
+BOOL_OPTION(USE_DOUBLE_SUBDIVISIONS, 0)
+REQUIRES(USE_DOUBLE_SUBDIVISIONS, USE_NEXT_FORB && EXPLICIT_NORMAL_EDGES)
+
diff --git a/group-connectivity.h b/group-connectivity.h
index 1ff1eb042c156a25bb54a0c68b9b02d432df04d9..ec326fbd21bbc324ba8af34e4ff1a0209efe4993 100644
--- a/group-connectivity.h
+++ b/group-connectivity.h
@@ -11,6 +11,7 @@
 typedef int EdgeId;
 typedef int DirectedEdgeId;
 typedef std::pair<DirectedEdgeId, DirectedEdgeId> TwoCut;
+typedef std::vector<EdgeId> DoubleSubdivision;
 
 struct AbstractTester {
   bool isConnected;
@@ -25,6 +26,7 @@ struct AbstractTester {
     int edges,
     std::vector<EdgeId> spanningTree,
     std::vector<TwoCut> twoCuts,
+    std::vector<DoubleSubdivision> dSub,
     std::vector< std::vector<DirectedEdgeId> > elementaryCycles
   ) =0;
   virtual std::vector<size_t> getClasses() =0;
@@ -60,6 +62,7 @@ struct Tester : public AbstractTester {
     int edges_,
     std::vector<EdgeId> spanningTree,
     std::vector<TwoCut> twoCuts_,
+    std::vector<DoubleSubdivision> dSub,
     std::vector< std::vector<DirectedEdgeId> > elementaryCycles
   ) {
     edges = edges_;
diff --git a/groupConnectivity.pyx b/groupConnectivity.pyx
index 356f3ed1308e0c8b899fe1e5333d6a706adb25c9..b70b9ed4f2b693ea69b1324d5c7121b07ba0622b 100644
--- a/groupConnectivity.pyx
+++ b/groupConnectivity.pyx
@@ -16,9 +16,10 @@ cdef extern from "group-connectivity.h":
   ctypedef int EdgeId
   ctypedef int DirectedEdgeId
   ctypedef pair[DirectedEdgeId, DirectedEdgeId] TwoCut
+  ctypedef vector[EdgeId] DoubleSubdivision
 
   cdef cppclass AbstractTester:
-    void init(int, vector[EdgeId], vector[TwoCut], vector[vector[DirectedEdgeId]])
+    void init(int, vector[EdgeId], vector[TwoCut], vector[DoubleSubdivision], vector[vector[DirectedEdgeId]])
     vector[size_t] getClasses()
     bool run()
 
@@ -38,7 +39,8 @@ def pathToEdges(G, path):
 
 
 def testGroupConnectivity(G, group = "Z4", getClasses = False,
-                          useTwoCuts = True, debug = False):
+                          useTwoCuts = True, useDoubleSubdivisions = False,
+                          debug = False):
   cdef AbstractTester* tester = NULL
   if group == "Z4":
     tester = new Tester[Z4[int]]()
@@ -65,6 +67,8 @@ def testGroupConnectivity(G, group = "Z4", getClasses = False,
 
   spanningTreeEdges = [ l for (_, _, l) in spanningTree.edge_iterator() ]
 
+
+
   twoCuts = []
   if useTwoCuts:
     availableEdges = set(spanningTreeEdges)
@@ -95,7 +99,7 @@ def testGroupConnectivity(G, group = "Z4", getClasses = False,
     print "Elementary cycles: ", elemCycles
     print "Two cuts: ", twoCuts
 
-  tester.init(G.num_edges(), spanningTreeEdges, twoCuts, elemCycles)
+  tester.init(G.num_edges(), spanningTreeEdges, twoCuts, [], elemCycles)
   ret = tester.run()
 
   if getClasses: