fix bug in acyclic_orientations

src/sage/graphs/orientations.py

@@ -85,6 +85,29 @@ def acyclic_orientations(G):
         sage: len(list(it))
         42
 
+    Check the orientation of edges::
+
+        sage: g = Graph([(0, 1), (1, 2), (2, 3), (3, 0), (0, 2)])
+        sage: sorted(sorted(h.edges(labels=False)) for h in g.acyclic_orientations())
+        [[(0, 1), (0, 2), (0, 3), (1, 2), (2, 3)],
+         [(0, 1), (0, 2), (0, 3), (1, 2), (3, 2)],
+         [(0, 1), (0, 2), (0, 3), (2, 1), (2, 3)],
+         [(0, 1), (0, 2), (0, 3), (2, 1), (3, 2)],
+         [(0, 1), (0, 2), (1, 2), (3, 0), (3, 2)],
+         [(0, 1), (0, 2), (2, 1), (3, 0), (3, 2)],
+         [(0, 1), (0, 3), (2, 0), (2, 1), (2, 3)],
+         [(0, 1), (2, 0), (2, 1), (2, 3), (3, 0)],
+         [(0, 1), (2, 0), (2, 1), (3, 0), (3, 2)],
+         [(0, 2), (0, 3), (1, 0), (1, 2), (2, 3)],
+         [(0, 2), (0, 3), (1, 0), (1, 2), (3, 2)],
+         [(0, 2), (1, 0), (1, 2), (3, 0), (3, 2)],
+         [(0, 3), (1, 0), (1, 2), (2, 0), (2, 3)],
+         [(0, 3), (1, 0), (2, 0), (2, 1), (2, 3)],
+         [(1, 0), (1, 2), (2, 0), (2, 3), (3, 0)],
+         [(1, 0), (1, 2), (2, 0), (3, 0), (3, 2)],
+         [(1, 0), (2, 0), (2, 1), (2, 3), (3, 0)],
+         [(1, 0), (2, 0), (2, 1), (3, 0), (3, 2)]]
+
     TESTS:
 
     To count the number of acyclic orientations for a graph with 0 vertices::
@@ -291,8 +314,9 @@ def helper(G, globO, m, k):
 
     # Iterate over acyclic orientations and create relabeled graphs
     for orientation in orientations:
-        relabeled_graph = DiGraph([(reverse_vertex_labels[u], reverse_vertex_labels[v], label) for (u, v), label in orientation.items()])
-        yield relabeled_graph
+        D = DiGraph([(u, v) if label else (v, u) for (u, v), label in orientation.items()])
+        D.relabel(perm=reverse_vertex_labels, inplace=True)
+        yield D
 
 
 def strong_orientations_iterator(G):