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Diffstat (limited to '.venv/lib/python3.12/site-packages/networkx/algorithms/approximation/tests/test_steinertree.py')
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diff --git a/.venv/lib/python3.12/site-packages/networkx/algorithms/approximation/tests/test_steinertree.py b/.venv/lib/python3.12/site-packages/networkx/algorithms/approximation/tests/test_steinertree.py new file mode 100644 index 00000000..1b074757 --- /dev/null +++ b/.venv/lib/python3.12/site-packages/networkx/algorithms/approximation/tests/test_steinertree.py @@ -0,0 +1,265 @@ +import pytest + +import networkx as nx +from networkx.algorithms.approximation.steinertree import ( + _remove_nonterminal_leaves, + 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) + + def test_remove_nonterminal_leaves(self): + G = nx.path_graph(10) + _remove_nonterminal_leaves(G, [4, 5, 6]) + + assert list(G) == [4, 5, 6] # only the terminal nodes are left + + +@pytest.mark.parametrize("method", ("kou", "mehlhorn")) +def test_steiner_tree_weight_attribute(method): + G = nx.star_graph(4) + # Add an edge attribute that is named something other than "weight" + nx.set_edge_attributes(G, {e: 10 for e in G.edges}, name="distance") + H = nx.approximation.steiner_tree(G, [1, 3], method=method, weight="distance") + assert nx.utils.edges_equal(H.edges, [(0, 1), (0, 3)]) + + +@pytest.mark.parametrize("method", ("kou", "mehlhorn")) +def test_steiner_tree_multigraph_weight_attribute(method): + G = nx.cycle_graph(3, create_using=nx.MultiGraph) + nx.set_edge_attributes(G, {e: 10 for e in G.edges}, name="distance") + G.add_edge(2, 0, distance=5) + H = nx.approximation.steiner_tree(G, list(G), method=method, weight="distance") + assert len(H.edges) == 2 and H.has_edge(2, 0, key=1) + assert sum(dist for *_, dist in H.edges(data="distance")) == 15 + + +@pytest.mark.parametrize("method", (None, "mehlhorn", "kou")) +def test_steiner_tree_methods(method): + G = nx.star_graph(4) + expected = nx.Graph([(0, 1), (0, 3)]) + st = nx.approximation.steiner_tree(G, [1, 3], method=method) + assert nx.utils.edges_equal(st.edges, expected.edges) + + +def test_steiner_tree_method_invalid(): + G = nx.star_graph(4) + with pytest.raises( + ValueError, match="invalid_method is not a valid choice for an algorithm." + ): + nx.approximation.steiner_tree(G, terminal_nodes=[1, 3], method="invalid_method") + + +def test_steiner_tree_remove_non_terminal_leaves_self_loop_edges(): + # To verify that the last step of the steiner tree approximation + # behaves in the case where a non-terminal leaf has a self loop edge + G = nx.path_graph(10) + + # Add self loops to the terminal nodes + G.add_edges_from([(2, 2), (3, 3), (4, 4), (7, 7), (8, 8)]) + + # Remove non-terminal leaves + _remove_nonterminal_leaves(G, [4, 5, 6, 7]) + + # The terminal nodes should be left + assert list(G) == [4, 5, 6, 7] # only the terminal nodes are left + + +def test_steiner_tree_non_terminal_leaves_multigraph_self_loop_edges(): + # To verify that the last step of the steiner tree approximation + # behaves in the case where a non-terminal leaf has a self loop edge + G = nx.MultiGraph() + G.add_edges_from([(i, i + 1) for i in range(10)]) + G.add_edges_from([(2, 2), (3, 3), (4, 4), (4, 4), (7, 7)]) + + # Remove non-terminal leaves + _remove_nonterminal_leaves(G, [4, 5, 6, 7]) + + # Only the terminal nodes should be left + assert list(G) == [4, 5, 6, 7] |