Some changes to reduce the really long parts of tests (#2561)

* adjust some of the slowest tests. minor speedup of is_connected.

* Add adj property to AntiGraph class in kcomponents.py

* Add comment to explain why test loop only goes once

networkx/algorithms/approximation/kcomponents.py

@@ -286,6 +286,7 @@ def __getitem__(self, node):
     def adj(self):
         return self.AntiAdjacencyView(self)
 
+
     class AntiDegreeView(nx.reportviews.DegreeView):
         def __iter__(self):
             all_nodes = set(self._succ)

networkx/algorithms/components/connected.py

@@ -233,6 +233,7 @@ def node_connected_component(G, n):
 
 def _plain_bfs(G, source):
     """A fast BFS node generator"""
+    G_adj = G.adj
     seen = set()
     nextlevel = {source}
     while nextlevel:
@@ -242,4 +243,4 @@ def _plain_bfs(G, source):
             if v not in seen:
                 yield v
                 seen.add(v)
-                nextlevel.update(G[v])
+                nextlevel.update(G_adj[v])

networkx/algorithms/connectivity/tests/test_cuts.py

@@ -34,7 +34,7 @@ def _generate_no_biconnected(max_attempts=50):
 def test_articulation_points():
     Ggen = _generate_no_biconnected()
     for flow_func in flow_funcs:
-        for i in range(3):
+        for i in range(1):  # change 1 to 3 or more for more realizations.
             G = next(Ggen)
             cut = nx.minimum_node_cut(G, flow_func=flow_func)
             assert_true(len(cut) == 1, msg=msg.format(flow_func.__name__))

networkx/algorithms/connectivity/tests/test_kcutsets.py

@@ -124,8 +124,9 @@ def _check_separating_sets(G):
     for Gc in nx.connected_component_subgraphs(G):
         if len(Gc) < 3:
             continue
+        node_conn = nx.node_connectivity(Gc)
         for cut in nx.all_node_cuts(Gc):
-            assert_equal(nx.node_connectivity(Gc), len(cut))
+            assert_equal(node_conn, len(cut))
             H = Gc.copy()
             H.remove_nodes_from(cut)
             assert_false(nx.is_connected(H))
@@ -181,7 +182,7 @@ def _generate_no_biconnected(max_attempts=50):
 
 def test_articulation_points():
     Ggen = _generate_no_biconnected()
-    for i in range(2):
+    for i in range(1):  # change 1 to 3 or more for more realizations.
         G = next(Ggen)
         articulation_points = list({a} for a in nx.articulation_points(G))
         for cut in nx.all_node_cuts(G):
@@ -213,9 +214,10 @@ def test_alternative_flow_functions():
     graph_funcs = [graph_example_1, nx.davis_southern_women_graph]
     for graph_func in graph_funcs:
         G = graph_func()
+        node_conn = nx.node_connectivity(G)
         for flow_func in flow_funcs:
             for cut in nx.all_node_cuts(G, flow_func=flow_func):
-                assert_equal(nx.node_connectivity(G), len(cut))
+                assert_equal(node_conn, len(cut))
                 H = G.copy()
                 H.remove_nodes_from(cut)
                 assert_false(nx.is_connected(H))

networkx/algorithms/flow/tests/test_maxflow_large_graph.py

@@ -115,9 +115,13 @@ def test_gl1(self):
         R = build_residual_network(G, 'capacity')
         kwargs = dict(residual=R)
 
-        for flow_func in flow_funcs:
-            validate_flows(G, s, t, 156545, flow_func(G, s, t, **kwargs),
+        # do one flow_func to save time
+        flow_func = flow_funcs[0]
+        validate_flows(G, s, t, 156545, flow_func(G, s, t, **kwargs),
                            flow_func)
+#        for flow_func in flow_funcs:
+#            validate_flows(G, s, t, 156545, flow_func(G, s, t, **kwargs),
+#                           flow_func)
 
     def test_gw1(self):
         G = read_graph('gw1')
@@ -137,9 +141,13 @@ def test_wlm3(self):
         R = build_residual_network(G, 'capacity')
         kwargs = dict(residual=R)
 
-        for flow_func in flow_funcs:
-            validate_flows(G, s, t, 11875108, flow_func(G, s, t, **kwargs),
+        # do one flow_func to save time
+        flow_func = flow_funcs[0]
+        validate_flows(G, s, t, 11875108, flow_func(G, s, t, **kwargs),
                            flow_func)
+#        for flow_func in flow_funcs:
+#            validate_flows(G, s, t, 11875108, flow_func(G, s, t, **kwargs),
+#                           flow_func)
 
     def test_preflow_push_global_relabel(self):
         G = read_graph('gw1')