PR #35891: fix issues in the graphs module

Author: dcoudert

src/sage/graphs/base/c_graph.pyx

@@ -4819,7 +4819,7 @@ cdef class Search_iterator:
 
         Immutable graphs (see :trac:`16019`)::
 
-            sage: DiGraph([[1,2]], immutable=True).connected_components()
+            sage: DiGraph([(1, 2)], immutable=True).connected_components(sort=True)
             [[1, 2]]
 
         """

src/sage/graphs/bipartite_graph.py

@@ -1209,7 +1209,7 @@ def _check_bipartition_for_add_edges(self, edges):
             vertex_in_left[v] = False
 
         # Map each vertex to the connected component it belongs to
-        vertex_to_component = {v: comp for comp in self.connected_components()
+        vertex_to_component = {v: comp for comp in self.connected_components(sort=False)
                                    for v in comp}
 
         for e in edges:

src/sage/graphs/comparability.pyx

@@ -257,7 +257,7 @@ def greedy_is_comparability(g, no_certificate=False, equivalence_class=False):
     # Each vertex can partition its neighbors into equivalence classes
     equivalence_classes = {}
     for v in g:
-        equivalence_classes[v] = g.subgraph(vertices=g.neighbors(v)).complement().connected_components()
+        equivalence_classes[v] = g.subgraph(vertices=g.neighbors(v)).complement().connected_components(sort=False)
 
     # We build a graph h with one vertex per (vertex of g + equivalence class)
     from sage.graphs.graph import Graph
@@ -288,7 +288,7 @@ def greedy_is_comparability(g, no_certificate=False, equivalence_class=False):
         if equivalence_class:
 
             # Returning the largest equivalence class
-            cc = sorted(h.connected_components(), key=len)[-1]
+            cc = sorted(h.connected_components(sort=False), key=len)[-1]
 
             edges = []
             for v, sid in cc:

src/sage/graphs/distances_all_pairs.pyx

@@ -2572,7 +2572,7 @@ def antipodal_graph(G):
 
     if not G.is_connected():
         import itertools
-        CC = G.connected_components()
+        CC = G.connected_components(sort=False)
         for c1, c2 in itertools.combinations(CC, 2):
             A.add_edges(itertools.product(c1, c2))
         return A

src/sage/graphs/generators/world_map.py

@@ -95,7 +95,7 @@ def AfricaMap(continental=False, year=2018):
     G = Graph(common_border, format='dict_of_lists')
 
     if continental:
-        G = G.subgraph(G.connected_component_containing_vertex('Central Africa'))
+        G = G.subgraph(G.connected_component_containing_vertex('Central Africa', sort=False))
         G.name(new="Continental Africa Map")
     else:
         G.add_vertices(no_land_border)
@@ -172,7 +172,7 @@ def EuropeMap(continental=False, year=2018):
     G = Graph(common_border, format='dict_of_lists')
 
     if continental:
-        G = G.subgraph(G.connected_component_containing_vertex('Austria'))
+        G = G.subgraph(G.connected_component_containing_vertex('Austria', sort=False))
         G.name(new="Continental Europe Map")
     else:
         G.add_vertices(no_land_border)
@@ -308,7 +308,7 @@ def WorldMap():
         True
         sage: g.gps_coordinates["Bolivia"]
         [[17, 'S'], [65, 'W']]
-        sage: sorted(g.connected_component_containing_vertex('Ireland'))
+        sage: g.connected_component_containing_vertex('Ireland', sort=True)
         ['Ireland', 'United Kingdom']
 
     TESTS:

src/sage/graphs/generic_graph.py

@@ -6527,7 +6527,7 @@ def num_faces(self, embedding=None):
             else:
                 if self.is_planar():
                     # We use Euler's formula: V-E+F-C=1
-                    C = len(self.connected_components())
+                    C = self.connected_components_number()
                     return self.size() - self.order() + C + 1
                 else:
                     raise ValueError("no embedding is provided and the graph is not planar")
@@ -6734,7 +6734,7 @@ def steiner_tree(self, vertices, weighted=False, solver=None, verbose=0,
 
         # Can the problem be solved ? Are all the vertices in the same
         # connected component ?
-        cc = g.connected_component_containing_vertex(vertices[0])
+        cc = g.connected_component_containing_vertex(vertices[0], sort=False)
         if any(v not in cc for v in vertices):
             from sage.categories.sets_cat import EmptySetError
             raise EmptySetError("the given vertices do not all belong to the "
@@ -14752,7 +14752,7 @@ def is_gallai_tree(self):
         a special vertex `-1` is a ''star-shaped'' Gallai tree::
 
             sage: g = 8 * graphs.CompleteGraph(6)
-            sage: g.add_edges([(-1, c[0]) for c in g.connected_components()])
+            sage: g.add_edges([(-1, c[0]) for c in g.connected_components(sort=False)])
             sage: g.is_gallai_tree()
             True
 
@@ -19367,7 +19367,7 @@ def transitive_reduction(self):
                 return Graph(self.min_spanning_tree(weight_function=lambda e: 1))
             else:
                 G = Graph(list(self))
-                for cc in self.connected_components():
+                for cc in self.connected_components(sort=False):
                     if len(cc) > 1:
                         edges = self.subgraph(cc).min_spanning_tree(weight_function=lambda e: 1)
                         G.add_edges(edges)

src/sage/graphs/graph.py

@@ -8910,7 +8910,7 @@ def perfect_matchings(self, labels=False):
         if not self:
             yield []
             return
-        if self.order() % 2 or any(len(cc) % 2 for cc in self.connected_components()):
+        if self.order() % 2 or any(len(cc) % 2 for cc in self.connected_components(sort=False)):
             return
 
         def rec(G):
@@ -9164,7 +9164,7 @@ def effective_resistance(self, i, j, *, base_ring=None):
 
         self._scream_if_not_simple()
         if not self.is_connected():
-            connected_i = self.connected_component_containing_vertex(i)
+            connected_i = self.connected_component_containing_vertex(i, sort=False)
             if j in connected_i:
                 component = self.subgraph(connected_i)
                 return component.effective_resistance(i, j)

src/sage/graphs/graph_coloring.pyx

@@ -602,7 +602,7 @@ def vertex_coloring(g, k=None, value_only=False, hex_colors=False, solver=None,
         # by the test of degeneracy (as previously).
         if not g.is_connected():
             if value_only:
-                for component in g.connected_components():
+                for component in g.connected_components(sort=False):
                     tmp = vertex_coloring(g.subgraph(component), k=k,
                                           value_only=value_only,
                                           hex_colors=hex_colors,
@@ -612,7 +612,7 @@ def vertex_coloring(g, k=None, value_only=False, hex_colors=False, solver=None,
                         return False
                 return True
             colorings = []
-            for component in g.connected_components():
+            for component in g.connected_components(sort=False):
                 tmp = vertex_coloring(g.subgraph(component), k=k,
                                       value_only=value_only,
                                       hex_colors=False,

src/sage/graphs/graph_decompositions/clique_separators.pyx

@@ -423,7 +423,7 @@ def atoms_and_clique_separators(G, tree=False, rooted_tree=False, separators=Fal
     if not G.is_connected():
         from sage.graphs.graph import Graph
 
-        for cc in G.connected_components():
+        for cc in G.connected_components(sort=False):
             g = Graph([cc, G.edge_boundary(cc, cc, False, False)],
                       format='vertices_and_edges',
                       loops=True, multiedges=True)

src/sage/graphs/graph_decompositions/graph_products.pyx

@@ -309,7 +309,7 @@ def is_cartesian_product(g, certificate=False, relabeling=False):
 
     # Gathering the connected components, relabeling the vertices on-the-fly
     edges = [[(int_to_vertex[u], int_to_vertex[v]) for u, v in cc]
-             for cc in h.connected_components()]
+             for cc in h.connected_components(sort=False)]
 
     # Only one connected component ?
     if len(edges) == 1:
@@ -320,7 +320,7 @@ def is_cartesian_product(g, certificate=False, relabeling=False):
     for cc in edges:
         tmp = Graph()
         tmp.add_edges(cc)
-        factors.append(tmp.subgraph(vertices=tmp.connected_components()[0]))
+        factors.append(tmp.subgraph(vertices=tmp.connected_components(sort=False)[0]))
 
     # Computing the product of these graphs
     answer = factors[0]