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import pytest
import networkx as nx
from networkx.algorithms.approximation.steinertree import metric_closure, steiner_tree
from networkx.utils import edges_equal
class TestSteinerTree:
@classmethod
def setup_class(cls):
G1 = nx.Graph()
G1.add_edge(1, 2, weight=10)
G1.add_edge(2, 3, weight=10)
G1.add_edge(3, 4, weight=10)
G1.add_edge(4, 5, weight=10)
G1.add_edge(5, 6, weight=10)
G1.add_edge(2, 7, weight=1)
G1.add_edge(7, 5, weight=1)
G2 = nx.Graph()
G2.add_edge(0, 5, weight=6)
G2.add_edge(1, 2, weight=2)
G2.add_edge(1, 5, weight=3)
G2.add_edge(2, 4, weight=4)
G2.add_edge(3, 5, weight=5)
G2.add_edge(4, 5, weight=1)
G3 = nx.Graph()
G3.add_edge(1, 2, weight=8)
G3.add_edge(1, 9, weight=3)
G3.add_edge(1, 8, weight=6)
G3.add_edge(1, 10, weight=2)
G3.add_edge(1, 14, weight=3)
G3.add_edge(2, 3, weight=6)
G3.add_edge(3, 4, weight=3)
G3.add_edge(3, 10, weight=2)
G3.add_edge(3, 11, weight=1)
G3.add_edge(4, 5, weight=1)
G3.add_edge(4, 11, weight=1)
G3.add_edge(5, 6, weight=4)
G3.add_edge(5, 11, weight=2)
G3.add_edge(5, 12, weight=1)
G3.add_edge(5, 13, weight=3)
G3.add_edge(6, 7, weight=2)
G3.add_edge(6, 12, weight=3)
G3.add_edge(6, 13, weight=1)
G3.add_edge(7, 8, weight=3)
G3.add_edge(7, 9, weight=3)
G3.add_edge(7, 11, weight=5)
G3.add_edge(7, 13, weight=2)
G3.add_edge(7, 14, weight=4)
G3.add_edge(8, 9, weight=2)
G3.add_edge(9, 14, weight=1)
G3.add_edge(10, 11, weight=2)
G3.add_edge(10, 14, weight=1)
G3.add_edge(11, 12, weight=1)
G3.add_edge(11, 14, weight=7)
G3.add_edge(12, 14, weight=3)
G3.add_edge(12, 15, weight=1)
G3.add_edge(13, 14, weight=4)
G3.add_edge(13, 15, weight=1)
G3.add_edge(14, 15, weight=2)
cls.G1 = G1
cls.G2 = G2
cls.G3 = G3
cls.G1_term_nodes = [1, 2, 3, 4, 5]
cls.G2_term_nodes = [0, 2, 3]
cls.G3_term_nodes = [1, 3, 5, 6, 8, 10, 11, 12, 13]
cls.methods = ["kou", "mehlhorn"]
def test_connected_metric_closure(self):
G = self.G1.copy()
G.add_node(100)
pytest.raises(nx.NetworkXError, metric_closure, G)
def test_metric_closure(self):
M = metric_closure(self.G1)
mc = [
(1, 2, {"distance": 10, "path": [1, 2]}),
(1, 3, {"distance": 20, "path": [1, 2, 3]}),
(1, 4, {"distance": 22, "path": [1, 2, 7, 5, 4]}),
(1, 5, {"distance": 12, "path": [1, 2, 7, 5]}),
(1, 6, {"distance": 22, "path": [1, 2, 7, 5, 6]}),
(1, 7, {"distance": 11, "path": [1, 2, 7]}),
(2, 3, {"distance": 10, "path": [2, 3]}),
(2, 4, {"distance": 12, "path": [2, 7, 5, 4]}),
(2, 5, {"distance": 2, "path": [2, 7, 5]}),
(2, 6, {"distance": 12, "path": [2, 7, 5, 6]}),
(2, 7, {"distance": 1, "path": [2, 7]}),
(3, 4, {"distance": 10, "path": [3, 4]}),
(3, 5, {"distance": 12, "path": [3, 2, 7, 5]}),
(3, 6, {"distance": 22, "path": [3, 2, 7, 5, 6]}),
(3, 7, {"distance": 11, "path": [3, 2, 7]}),
(4, 5, {"distance": 10, "path": [4, 5]}),
(4, 6, {"distance": 20, "path": [4, 5, 6]}),
(4, 7, {"distance": 11, "path": [4, 5, 7]}),
(5, 6, {"distance": 10, "path": [5, 6]}),
(5, 7, {"distance": 1, "path": [5, 7]}),
(6, 7, {"distance": 11, "path": [6, 5, 7]}),
]
assert edges_equal(list(M.edges(data=True)), mc)
def test_steiner_tree(self):
valid_steiner_trees = [
[
[
(1, 2, {"weight": 10}),
(2, 3, {"weight": 10}),
(2, 7, {"weight": 1}),
(3, 4, {"weight": 10}),
(5, 7, {"weight": 1}),
],
[
(1, 2, {"weight": 10}),
(2, 7, {"weight": 1}),
(3, 4, {"weight": 10}),
(4, 5, {"weight": 10}),
(5, 7, {"weight": 1}),
],
[
(1, 2, {"weight": 10}),
(2, 3, {"weight": 10}),
(2, 7, {"weight": 1}),
(4, 5, {"weight": 10}),
(5, 7, {"weight": 1}),
],
],
[
[
(0, 5, {"weight": 6}),
(1, 2, {"weight": 2}),
(1, 5, {"weight": 3}),
(3, 5, {"weight": 5}),
],
[
(0, 5, {"weight": 6}),
(4, 2, {"weight": 4}),
(4, 5, {"weight": 1}),
(3, 5, {"weight": 5}),
],
],
[
[
(1, 10, {"weight": 2}),
(3, 10, {"weight": 2}),
(3, 11, {"weight": 1}),
(5, 12, {"weight": 1}),
(6, 13, {"weight": 1}),
(8, 9, {"weight": 2}),
(9, 14, {"weight": 1}),
(10, 14, {"weight": 1}),
(11, 12, {"weight": 1}),
(12, 15, {"weight": 1}),
(13, 15, {"weight": 1}),
]
],
]
for method in self.methods:
for G, term_nodes, valid_trees in zip(
[self.G1, self.G2, self.G3],
[self.G1_term_nodes, self.G2_term_nodes, self.G3_term_nodes],
valid_steiner_trees,
):
S = steiner_tree(G, term_nodes, method=method)
assert any(
edges_equal(list(S.edges(data=True)), valid_tree)
for valid_tree in valid_trees
)
def test_multigraph_steiner_tree(self):
G = nx.MultiGraph()
G.add_edges_from(
[
(1, 2, 0, {"weight": 1}),
(2, 3, 0, {"weight": 999}),
(2, 3, 1, {"weight": 1}),
(3, 4, 0, {"weight": 1}),
(3, 5, 0, {"weight": 1}),
]
)
terminal_nodes = [2, 4, 5]
expected_edges = [
(2, 3, 1, {"weight": 1}), # edge with key 1 has lower weight
(3, 4, 0, {"weight": 1}),
(3, 5, 0, {"weight": 1}),
]
for method in self.methods:
S = steiner_tree(G, terminal_nodes, method=method)
assert edges_equal(S.edges(data=True, keys=True), expected_edges)
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