def test_nan_weight(self):
invalid_graph = retworkx.PyGraph()
invalid_graph.extend_from_weighted_edge_list([(0, 1, 0.5),
(0, 2, float("nan"))])
with self.assertRaises(ValueError):
retworkx.minimum_spanning_tree(invalid_graph, lambda x: x)
def test_tree(self):
mst_graph = retworkx.minimum_spanning_tree(self.graph,
weight_fn=lambda x: x)
self.assertEqual(self.graph.nodes(), mst_graph.nodes())
self.assertEqual(
len(self.graph.nodes()) - 1, len(mst_graph.edge_list()))
self.assertEqualEdgeList(self.expected_edges,
mst_graph.weighted_edge_list())
def test_multigraph(self):
mutligraph = retworkx.PyGraph(multigraph=True)
mutligraph.extend_from_weighted_edge_list([(0, 1, 1), (0, 2, 3),
(1, 2, 2), (0, 0, -10),
(1, 2, 1)])
mst_graph = retworkx.minimum_spanning_tree(mutligraph,
weight_fn=lambda x: x)
self.assertEqualEdgeList([(0, 1, 1), (1, 2, 1)],
mst_graph.weighted_edge_list())
def test_isolated(self):
s = self.graph.add_node("S")
msf_graph = retworkx.minimum_spanning_tree(self.graph,
weight_fn=lambda x: x)
self.assertEqual("S", msf_graph.nodes()[s])
self.assertEqual(self.graph.nodes(), msf_graph.nodes())
self.assertEqual(
len(self.graph.nodes()) - 2, len(msf_graph.edge_list()))
self.assertEqualEdgeList(self.expected_edges,
msf_graph.weighted_edge_list())
def test_default_weight(self):
weightless_graph = retworkx.PyGraph()
weightless_graph.extend_from_edge_list([
(0, 1), (0, 2), (0, 3), (0, 4), (1, 5), (2, 6), (3, 7), (4, 8)
]) # MST of the graph is itself
mst_graph_default_weight = retworkx.minimum_spanning_tree(
weightless_graph)
mst_graph_weight_2 = retworkx.minimum_spanning_tree(weightless_graph,
default_weight=2.0)
self.assertTrue(
retworkx.is_isomorphic(
weightless_graph,
mst_graph_default_weight,
))
self.assertTrue(
retworkx.is_isomorphic(
weightless_graph,
mst_graph_weight_2,
))
def test_forest(self):
s = self.graph.add_node("S")
t = self.graph.add_node("T")
u = self.graph.add_node("U")
self.graph.add_edges_from([(s, t, 10), (t, u, 9), (s, u, 8)])
forest_expected_edges = self.expected_edges + [(s, u, 8), (t, u, 9)]
msf_graph = retworkx.minimum_spanning_tree(self.graph,
weight_fn=lambda x: x)
self.assertEqual(self.graph.nodes(), msf_graph.nodes())
self.assertEqual(
len(self.graph.nodes()) - 2, len(msf_graph.edge_list()))
self.assertEqualEdgeList(forest_expected_edges,
msf_graph.weighted_edge_list())