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|
from collections import deque
from itertools import combinations, permutations
import pytest
import networkx as nx
from networkx.utils import edges_equal, pairwise
# Recipe from the itertools documentation.
def _consume(iterator):
"Consume the iterator entirely."
# Feed the entire iterator into a zero-length deque.
deque(iterator, maxlen=0)
class TestDagLongestPath:
"""Unit tests computing the longest path in a directed acyclic graph."""
def test_empty(self):
G = nx.DiGraph()
assert nx.dag_longest_path(G) == []
def test_unweighted1(self):
edges = [(1, 2), (2, 3), (2, 4), (3, 5), (5, 6), (3, 7)]
G = nx.DiGraph(edges)
assert nx.dag_longest_path(G) == [1, 2, 3, 5, 6]
def test_unweighted2(self):
edges = [(1, 2), (2, 3), (3, 4), (4, 5), (1, 3), (1, 5), (3, 5)]
G = nx.DiGraph(edges)
assert nx.dag_longest_path(G) == [1, 2, 3, 4, 5]
def test_weighted(self):
G = nx.DiGraph()
edges = [(1, 2, -5), (2, 3, 1), (3, 4, 1), (4, 5, 0), (3, 5, 4), (1, 6, 2)]
G.add_weighted_edges_from(edges)
assert nx.dag_longest_path(G) == [2, 3, 5]
def test_undirected_not_implemented(self):
G = nx.Graph()
pytest.raises(nx.NetworkXNotImplemented, nx.dag_longest_path, G)
def test_unorderable_nodes(self):
"""Tests that computing the longest path does not depend on
nodes being orderable.
For more information, see issue #1989.
"""
# Create the directed path graph on four nodes in a diamond shape,
# with nodes represented as (unorderable) Python objects.
nodes = [object() for n in range(4)]
G = nx.DiGraph()
G.add_edge(nodes[0], nodes[1])
G.add_edge(nodes[0], nodes[2])
G.add_edge(nodes[2], nodes[3])
G.add_edge(nodes[1], nodes[3])
# this will raise NotImplementedError when nodes need to be ordered
nx.dag_longest_path(G)
def test_multigraph_unweighted(self):
edges = [(1, 2), (2, 3), (2, 3), (3, 4), (4, 5), (1, 3), (1, 5), (3, 5)]
G = nx.MultiDiGraph(edges)
assert nx.dag_longest_path(G) == [1, 2, 3, 4, 5]
def test_multigraph_weighted(self):
G = nx.MultiDiGraph()
edges = [
(1, 2, 2),
(2, 3, 2),
(1, 3, 1),
(1, 3, 5),
(1, 3, 2),
]
G.add_weighted_edges_from(edges)
assert nx.dag_longest_path(G) == [1, 3]
def test_multigraph_weighted_default_weight(self):
G = nx.MultiDiGraph([(1, 2), (2, 3)]) # Unweighted edges
G.add_weighted_edges_from([(1, 3, 1), (1, 3, 5), (1, 3, 2)])
# Default value for default weight is 1
assert nx.dag_longest_path(G) == [1, 3]
assert nx.dag_longest_path(G, default_weight=3) == [1, 2, 3]
class TestDagLongestPathLength:
"""Unit tests for computing the length of a longest path in a
directed acyclic graph.
"""
def test_unweighted(self):
edges = [(1, 2), (2, 3), (2, 4), (3, 5), (5, 6), (5, 7)]
G = nx.DiGraph(edges)
assert nx.dag_longest_path_length(G) == 4
edges = [(1, 2), (2, 3), (3, 4), (4, 5), (1, 3), (1, 5), (3, 5)]
G = nx.DiGraph(edges)
assert nx.dag_longest_path_length(G) == 4
# test degenerate graphs
G = nx.DiGraph()
G.add_node(1)
assert nx.dag_longest_path_length(G) == 0
def test_undirected_not_implemented(self):
G = nx.Graph()
pytest.raises(nx.NetworkXNotImplemented, nx.dag_longest_path_length, G)
def test_weighted(self):
edges = [(1, 2, -5), (2, 3, 1), (3, 4, 1), (4, 5, 0), (3, 5, 4), (1, 6, 2)]
G = nx.DiGraph()
G.add_weighted_edges_from(edges)
assert nx.dag_longest_path_length(G) == 5
def test_multigraph_unweighted(self):
edges = [(1, 2), (2, 3), (2, 3), (3, 4), (4, 5), (1, 3), (1, 5), (3, 5)]
G = nx.MultiDiGraph(edges)
assert nx.dag_longest_path_length(G) == 4
def test_multigraph_weighted(self):
G = nx.MultiDiGraph()
edges = [
(1, 2, 2),
(2, 3, 2),
(1, 3, 1),
(1, 3, 5),
(1, 3, 2),
]
G.add_weighted_edges_from(edges)
assert nx.dag_longest_path_length(G) == 5
class TestDAG:
@classmethod
def setup_class(cls):
pass
def test_topological_sort1(self):
DG = nx.DiGraph([(1, 2), (1, 3), (2, 3)])
for algorithm in [nx.topological_sort, nx.lexicographical_topological_sort]:
assert tuple(algorithm(DG)) == (1, 2, 3)
DG.add_edge(3, 2)
for algorithm in [nx.topological_sort, nx.lexicographical_topological_sort]:
pytest.raises(nx.NetworkXUnfeasible, _consume, algorithm(DG))
DG.remove_edge(2, 3)
for algorithm in [nx.topological_sort, nx.lexicographical_topological_sort]:
assert tuple(algorithm(DG)) == (1, 3, 2)
DG.remove_edge(3, 2)
assert tuple(nx.topological_sort(DG)) in {(1, 2, 3), (1, 3, 2)}
assert tuple(nx.lexicographical_topological_sort(DG)) == (1, 2, 3)
def test_is_directed_acyclic_graph(self):
G = nx.generators.complete_graph(2)
assert not nx.is_directed_acyclic_graph(G)
assert not nx.is_directed_acyclic_graph(G.to_directed())
assert not nx.is_directed_acyclic_graph(nx.Graph([(3, 4), (4, 5)]))
assert nx.is_directed_acyclic_graph(nx.DiGraph([(3, 4), (4, 5)]))
def test_topological_sort2(self):
DG = nx.DiGraph(
{
1: [2],
2: [3],
3: [4],
4: [5],
5: [1],
11: [12],
12: [13],
13: [14],
14: [15],
}
)
pytest.raises(nx.NetworkXUnfeasible, _consume, nx.topological_sort(DG))
assert not nx.is_directed_acyclic_graph(DG)
DG.remove_edge(1, 2)
_consume(nx.topological_sort(DG))
assert nx.is_directed_acyclic_graph(DG)
def test_topological_sort3(self):
DG = nx.DiGraph()
DG.add_edges_from([(1, i) for i in range(2, 5)])
DG.add_edges_from([(2, i) for i in range(5, 9)])
DG.add_edges_from([(6, i) for i in range(9, 12)])
DG.add_edges_from([(4, i) for i in range(12, 15)])
def validate(order):
assert isinstance(order, list)
assert set(order) == set(DG)
for u, v in combinations(order, 2):
assert not nx.has_path(DG, v, u)
validate(list(nx.topological_sort(DG)))
DG.add_edge(14, 1)
pytest.raises(nx.NetworkXUnfeasible, _consume, nx.topological_sort(DG))
def test_topological_sort4(self):
G = nx.Graph()
G.add_edge(1, 2)
# Only directed graphs can be topologically sorted.
pytest.raises(nx.NetworkXError, _consume, nx.topological_sort(G))
def test_topological_sort5(self):
G = nx.DiGraph()
G.add_edge(0, 1)
assert list(nx.topological_sort(G)) == [0, 1]
def test_topological_sort6(self):
for algorithm in [nx.topological_sort, nx.lexicographical_topological_sort]:
def runtime_error():
DG = nx.DiGraph([(1, 2), (2, 3), (3, 4)])
first = True
for x in algorithm(DG):
if first:
first = False
DG.add_edge(5 - x, 5)
def unfeasible_error():
DG = nx.DiGraph([(1, 2), (2, 3), (3, 4)])
first = True
for x in algorithm(DG):
if first:
first = False
DG.remove_node(4)
def runtime_error2():
DG = nx.DiGraph([(1, 2), (2, 3), (3, 4)])
first = True
for x in algorithm(DG):
if first:
first = False
DG.remove_node(2)
pytest.raises(RuntimeError, runtime_error)
pytest.raises(RuntimeError, runtime_error2)
pytest.raises(nx.NetworkXUnfeasible, unfeasible_error)
def test_all_topological_sorts_1(self):
DG = nx.DiGraph([(1, 2), (2, 3), (3, 4), (4, 5)])
assert list(nx.all_topological_sorts(DG)) == [[1, 2, 3, 4, 5]]
def test_all_topological_sorts_2(self):
DG = nx.DiGraph([(1, 3), (2, 1), (2, 4), (4, 3), (4, 5)])
assert sorted(nx.all_topological_sorts(DG)) == [
[2, 1, 4, 3, 5],
[2, 1, 4, 5, 3],
[2, 4, 1, 3, 5],
[2, 4, 1, 5, 3],
[2, 4, 5, 1, 3],
]
def test_all_topological_sorts_3(self):
def unfeasible():
DG = nx.DiGraph([(1, 2), (2, 3), (3, 4), (4, 2), (4, 5)])
# convert to list to execute generator
list(nx.all_topological_sorts(DG))
def not_implemented():
G = nx.Graph([(1, 2), (2, 3)])
# convert to list to execute generator
list(nx.all_topological_sorts(G))
def not_implemented_2():
G = nx.MultiGraph([(1, 2), (1, 2), (2, 3)])
list(nx.all_topological_sorts(G))
pytest.raises(nx.NetworkXUnfeasible, unfeasible)
pytest.raises(nx.NetworkXNotImplemented, not_implemented)
pytest.raises(nx.NetworkXNotImplemented, not_implemented_2)
def test_all_topological_sorts_4(self):
DG = nx.DiGraph()
for i in range(7):
DG.add_node(i)
assert sorted(map(list, permutations(DG.nodes))) == sorted(
nx.all_topological_sorts(DG)
)
def test_all_topological_sorts_multigraph_1(self):
DG = nx.MultiDiGraph([(1, 2), (1, 2), (2, 3), (3, 4), (3, 5), (3, 5), (3, 5)])
assert sorted(nx.all_topological_sorts(DG)) == sorted(
[[1, 2, 3, 4, 5], [1, 2, 3, 5, 4]]
)
def test_all_topological_sorts_multigraph_2(self):
N = 9
edges = []
for i in range(1, N):
edges.extend([(i, i + 1)] * i)
DG = nx.MultiDiGraph(edges)
assert list(nx.all_topological_sorts(DG)) == [list(range(1, N + 1))]
def test_ancestors(self):
G = nx.DiGraph()
ancestors = nx.algorithms.dag.ancestors
G.add_edges_from([(1, 2), (1, 3), (4, 2), (4, 3), (4, 5), (2, 6), (5, 6)])
assert ancestors(G, 6) == {1, 2, 4, 5}
assert ancestors(G, 3) == {1, 4}
assert ancestors(G, 1) == set()
pytest.raises(nx.NetworkXError, ancestors, G, 8)
def test_descendants(self):
G = nx.DiGraph()
descendants = nx.algorithms.dag.descendants
G.add_edges_from([(1, 2), (1, 3), (4, 2), (4, 3), (4, 5), (2, 6), (5, 6)])
assert descendants(G, 1) == {2, 3, 6}
assert descendants(G, 4) == {2, 3, 5, 6}
assert descendants(G, 3) == set()
pytest.raises(nx.NetworkXError, descendants, G, 8)
def test_transitive_closure(self):
G = nx.DiGraph([(1, 2), (2, 3), (3, 4)])
solution = [(1, 2), (1, 3), (1, 4), (2, 3), (2, 4), (3, 4)]
assert edges_equal(nx.transitive_closure(G).edges(), solution)
G = nx.DiGraph([(1, 2), (2, 3), (2, 4)])
solution = [(1, 2), (1, 3), (1, 4), (2, 3), (2, 4)]
assert edges_equal(nx.transitive_closure(G).edges(), solution)
G = nx.DiGraph([(1, 2), (2, 3), (3, 1)])
solution = [(1, 2), (2, 1), (2, 3), (3, 2), (1, 3), (3, 1)]
soln = sorted(solution + [(n, n) for n in G])
assert edges_equal(sorted(nx.transitive_closure(G).edges()), soln)
G = nx.Graph([(1, 2), (2, 3), (3, 4)])
solution = [(1, 2), (1, 3), (1, 4), (2, 3), (2, 4), (3, 4)]
assert edges_equal(sorted(nx.transitive_closure(G).edges()), solution)
G = nx.MultiGraph([(1, 2), (2, 3), (3, 4)])
solution = [(1, 2), (1, 3), (1, 4), (2, 3), (2, 4), (3, 4)]
assert edges_equal(sorted(nx.transitive_closure(G).edges()), solution)
G = nx.MultiDiGraph([(1, 2), (2, 3), (3, 4)])
solution = [(1, 2), (1, 3), (1, 4), (2, 3), (2, 4), (3, 4)]
assert edges_equal(sorted(nx.transitive_closure(G).edges()), solution)
# test if edge data is copied
G = nx.DiGraph([(1, 2, {"a": 3}), (2, 3, {"b": 0}), (3, 4)])
H = nx.transitive_closure(G)
for u, v in G.edges():
assert G.get_edge_data(u, v) == H.get_edge_data(u, v)
k = 10
G = nx.DiGraph((i, i + 1, {"f": "b", "weight": i}) for i in range(k))
H = nx.transitive_closure(G)
for u, v in G.edges():
assert G.get_edge_data(u, v) == H.get_edge_data(u, v)
G = nx.Graph()
with pytest.raises(nx.NetworkXError):
nx.transitive_closure(G, reflexive="wrong input")
def test_reflexive_transitive_closure(self):
G = nx.DiGraph([(1, 2), (2, 3), (3, 4)])
solution = [(1, 2), (1, 3), (1, 4), (2, 3), (2, 4), (3, 4)]
soln = sorted(solution + [(n, n) for n in G])
assert edges_equal(nx.transitive_closure(G).edges(), solution)
assert edges_equal(nx.transitive_closure(G, False).edges(), solution)
assert edges_equal(nx.transitive_closure(G, True).edges(), soln)
assert edges_equal(nx.transitive_closure(G, None).edges(), solution)
G = nx.DiGraph([(1, 2), (2, 3), (2, 4)])
solution = [(1, 2), (1, 3), (1, 4), (2, 3), (2, 4)]
soln = sorted(solution + [(n, n) for n in G])
assert edges_equal(nx.transitive_closure(G).edges(), solution)
assert edges_equal(nx.transitive_closure(G, False).edges(), solution)
assert edges_equal(nx.transitive_closure(G, True).edges(), soln)
assert edges_equal(nx.transitive_closure(G, None).edges(), solution)
G = nx.DiGraph([(1, 2), (2, 3), (3, 1)])
solution = sorted([(1, 2), (2, 1), (2, 3), (3, 2), (1, 3), (3, 1)])
soln = sorted(solution + [(n, n) for n in G])
assert edges_equal(sorted(nx.transitive_closure(G).edges()), soln)
assert edges_equal(sorted(nx.transitive_closure(G, False).edges()), soln)
assert edges_equal(sorted(nx.transitive_closure(G, None).edges()), solution)
assert edges_equal(sorted(nx.transitive_closure(G, True).edges()), soln)
G = nx.Graph([(1, 2), (2, 3), (3, 4)])
solution = [(1, 2), (1, 3), (1, 4), (2, 3), (2, 4), (3, 4)]
soln = sorted(solution + [(n, n) for n in G])
assert edges_equal(nx.transitive_closure(G).edges(), solution)
assert edges_equal(nx.transitive_closure(G, False).edges(), solution)
assert edges_equal(nx.transitive_closure(G, True).edges(), soln)
assert edges_equal(nx.transitive_closure(G, None).edges(), solution)
G = nx.MultiGraph([(1, 2), (2, 3), (3, 4)])
solution = [(1, 2), (1, 3), (1, 4), (2, 3), (2, 4), (3, 4)]
soln = sorted(solution + [(n, n) for n in G])
assert edges_equal(nx.transitive_closure(G).edges(), solution)
assert edges_equal(nx.transitive_closure(G, False).edges(), solution)
assert edges_equal(nx.transitive_closure(G, True).edges(), soln)
assert edges_equal(nx.transitive_closure(G, None).edges(), solution)
G = nx.MultiDiGraph([(1, 2), (2, 3), (3, 4)])
solution = [(1, 2), (1, 3), (1, 4), (2, 3), (2, 4), (3, 4)]
soln = sorted(solution + [(n, n) for n in G])
assert edges_equal(nx.transitive_closure(G).edges(), solution)
assert edges_equal(nx.transitive_closure(G, False).edges(), solution)
assert edges_equal(nx.transitive_closure(G, True).edges(), soln)
assert edges_equal(nx.transitive_closure(G, None).edges(), solution)
def test_transitive_closure_dag(self):
G = nx.DiGraph([(1, 2), (2, 3), (3, 4)])
transitive_closure = nx.algorithms.dag.transitive_closure_dag
solution = [(1, 2), (1, 3), (1, 4), (2, 3), (2, 4), (3, 4)]
assert edges_equal(transitive_closure(G).edges(), solution)
G = nx.DiGraph([(1, 2), (2, 3), (2, 4)])
solution = [(1, 2), (1, 3), (1, 4), (2, 3), (2, 4)]
assert edges_equal(transitive_closure(G).edges(), solution)
G = nx.Graph([(1, 2), (2, 3), (3, 4)])
pytest.raises(nx.NetworkXNotImplemented, transitive_closure, G)
# test if edge data is copied
G = nx.DiGraph([(1, 2, {"a": 3}), (2, 3, {"b": 0}), (3, 4)])
H = transitive_closure(G)
for u, v in G.edges():
assert G.get_edge_data(u, v) == H.get_edge_data(u, v)
k = 10
G = nx.DiGraph((i, i + 1, {"foo": "bar", "weight": i}) for i in range(k))
H = transitive_closure(G)
for u, v in G.edges():
assert G.get_edge_data(u, v) == H.get_edge_data(u, v)
def test_transitive_reduction(self):
G = nx.DiGraph([(1, 2), (1, 3), (1, 4), (2, 3), (2, 4), (3, 4)])
transitive_reduction = nx.algorithms.dag.transitive_reduction
solution = [(1, 2), (2, 3), (3, 4)]
assert edges_equal(transitive_reduction(G).edges(), solution)
G = nx.DiGraph([(1, 2), (1, 3), (1, 4), (2, 3), (2, 4)])
transitive_reduction = nx.algorithms.dag.transitive_reduction
solution = [(1, 2), (2, 3), (2, 4)]
assert edges_equal(transitive_reduction(G).edges(), solution)
G = nx.Graph([(1, 2), (2, 3), (3, 4)])
pytest.raises(nx.NetworkXNotImplemented, transitive_reduction, G)
def _check_antichains(self, solution, result):
sol = [frozenset(a) for a in solution]
res = [frozenset(a) for a in result]
assert set(sol) == set(res)
def test_antichains(self):
antichains = nx.algorithms.dag.antichains
G = nx.DiGraph([(1, 2), (2, 3), (3, 4)])
solution = [[], [4], [3], [2], [1]]
self._check_antichains(list(antichains(G)), solution)
G = nx.DiGraph([(1, 2), (2, 3), (2, 4), (3, 5), (5, 6), (5, 7)])
solution = [
[],
[4],
[7],
[7, 4],
[6],
[6, 4],
[6, 7],
[6, 7, 4],
[5],
[5, 4],
[3],
[3, 4],
[2],
[1],
]
self._check_antichains(list(antichains(G)), solution)
G = nx.DiGraph([(1, 2), (1, 3), (3, 4), (3, 5), (5, 6)])
solution = [
[],
[6],
[5],
[4],
[4, 6],
[4, 5],
[3],
[2],
[2, 6],
[2, 5],
[2, 4],
[2, 4, 6],
[2, 4, 5],
[2, 3],
[1],
]
self._check_antichains(list(antichains(G)), solution)
G = nx.DiGraph({0: [1, 2], 1: [4], 2: [3], 3: [4]})
solution = [[], [4], [3], [2], [1], [1, 3], [1, 2], [0]]
self._check_antichains(list(antichains(G)), solution)
G = nx.DiGraph()
self._check_antichains(list(antichains(G)), [[]])
G = nx.DiGraph()
G.add_nodes_from([0, 1, 2])
solution = [[], [0], [1], [1, 0], [2], [2, 0], [2, 1], [2, 1, 0]]
self._check_antichains(list(antichains(G)), solution)
def f(x):
return list(antichains(x))
G = nx.Graph([(1, 2), (2, 3), (3, 4)])
pytest.raises(nx.NetworkXNotImplemented, f, G)
G = nx.DiGraph([(1, 2), (2, 3), (3, 1)])
pytest.raises(nx.NetworkXUnfeasible, f, G)
def test_lexicographical_topological_sort(self):
G = nx.DiGraph([(1, 2), (2, 3), (1, 4), (1, 5), (2, 6)])
assert list(nx.lexicographical_topological_sort(G)) == [1, 2, 3, 4, 5, 6]
assert list(nx.lexicographical_topological_sort(G, key=lambda x: x)) == [
1,
2,
3,
4,
5,
6,
]
assert list(nx.lexicographical_topological_sort(G, key=lambda x: -x)) == [
1,
5,
4,
2,
6,
3,
]
def test_lexicographical_topological_sort2(self):
"""
Check the case of two or more nodes with same key value.
Want to avoid exception raised due to comparing nodes directly.
See Issue #3493
"""
class Test_Node:
def __init__(self, n):
self.label = n
self.priority = 1
def __repr__(self):
return f"Node({self.label})"
def sorting_key(node):
return node.priority
test_nodes = [Test_Node(n) for n in range(4)]
G = nx.DiGraph()
edges = [(0, 1), (0, 2), (0, 3), (2, 3)]
G.add_edges_from((test_nodes[a], test_nodes[b]) for a, b in edges)
sorting = list(nx.lexicographical_topological_sort(G, key=sorting_key))
assert sorting == test_nodes
def test_topological_generations():
G = nx.DiGraph(
{1: [2, 3], 2: [4, 5], 3: [7], 4: [], 5: [6, 7], 6: [], 7: []}
).reverse()
# order within each generation is inconsequential
generations = [sorted(gen) for gen in nx.topological_generations(G)]
expected = [[4, 6, 7], [3, 5], [2], [1]]
assert generations == expected
MG = nx.MultiDiGraph(G.edges)
MG.add_edge(2, 1)
generations = [sorted(gen) for gen in nx.topological_generations(MG)]
assert generations == expected
def test_topological_generations_empty():
G = nx.DiGraph()
assert list(nx.topological_generations(G)) == []
def test_topological_generations_cycle():
G = nx.DiGraph([[2, 1], [3, 1], [1, 2]])
with pytest.raises(nx.NetworkXUnfeasible):
list(nx.topological_generations(G))
def test_is_aperiodic_cycle():
G = nx.DiGraph()
nx.add_cycle(G, [1, 2, 3, 4])
assert not nx.is_aperiodic(G)
def test_is_aperiodic_cycle2():
G = nx.DiGraph()
nx.add_cycle(G, [1, 2, 3, 4])
nx.add_cycle(G, [3, 4, 5, 6, 7])
assert nx.is_aperiodic(G)
def test_is_aperiodic_cycle3():
G = nx.DiGraph()
nx.add_cycle(G, [1, 2, 3, 4])
nx.add_cycle(G, [3, 4, 5, 6])
assert not nx.is_aperiodic(G)
def test_is_aperiodic_cycle4():
G = nx.DiGraph()
nx.add_cycle(G, [1, 2, 3, 4])
G.add_edge(1, 3)
assert nx.is_aperiodic(G)
def test_is_aperiodic_selfloop():
G = nx.DiGraph()
nx.add_cycle(G, [1, 2, 3, 4])
G.add_edge(1, 1)
assert nx.is_aperiodic(G)
def test_is_aperiodic_undirected_raises():
G = nx.Graph()
pytest.raises(nx.NetworkXError, nx.is_aperiodic, G)
def test_is_aperiodic_empty_graph():
G = nx.empty_graph(create_using=nx.DiGraph)
with pytest.raises(nx.NetworkXPointlessConcept, match="Graph has no nodes."):
nx.is_aperiodic(G)
def test_is_aperiodic_bipartite():
# Bipartite graph
G = nx.DiGraph(nx.davis_southern_women_graph())
assert not nx.is_aperiodic(G)
def test_is_aperiodic_rary_tree():
G = nx.full_rary_tree(3, 27, create_using=nx.DiGraph())
assert not nx.is_aperiodic(G)
def test_is_aperiodic_disconnected():
# disconnected graph
G = nx.DiGraph()
nx.add_cycle(G, [1, 2, 3, 4])
nx.add_cycle(G, [5, 6, 7, 8])
assert not nx.is_aperiodic(G)
G.add_edge(1, 3)
G.add_edge(5, 7)
assert nx.is_aperiodic(G)
def test_is_aperiodic_disconnected2():
G = nx.DiGraph()
nx.add_cycle(G, [0, 1, 2])
G.add_edge(3, 3)
assert not nx.is_aperiodic(G)
class TestDagToBranching:
"""Unit tests for the :func:`networkx.dag_to_branching` function."""
def test_single_root(self):
"""Tests that a directed acyclic graph with a single degree
zero node produces an arborescence.
"""
G = nx.DiGraph([(0, 1), (0, 2), (1, 3), (2, 3)])
B = nx.dag_to_branching(G)
expected = nx.DiGraph([(0, 1), (1, 3), (0, 2), (2, 4)])
assert nx.is_arborescence(B)
assert nx.is_isomorphic(B, expected)
def test_multiple_roots(self):
"""Tests that a directed acyclic graph with multiple degree zero
nodes creates an arborescence with multiple (weakly) connected
components.
"""
G = nx.DiGraph([(0, 1), (0, 2), (1, 3), (2, 3), (5, 2)])
B = nx.dag_to_branching(G)
expected = nx.DiGraph([(0, 1), (1, 3), (0, 2), (2, 4), (5, 6), (6, 7)])
assert nx.is_branching(B)
assert not nx.is_arborescence(B)
assert nx.is_isomorphic(B, expected)
# # Attributes are not copied by this function. If they were, this would
# # be a good test to uncomment.
# def test_copy_attributes(self):
# """Tests that node attributes are copied in the branching."""
# G = nx.DiGraph([(0, 1), (0, 2), (1, 3), (2, 3)])
# for v in G:
# G.node[v]['label'] = str(v)
# B = nx.dag_to_branching(G)
# # Determine the root node of the branching.
# root = next(v for v, d in B.in_degree() if d == 0)
# assert_equal(B.node[root]['label'], '0')
# children = B[root]
# # Get the left and right children, nodes 1 and 2, respectively.
# left, right = sorted(children, key=lambda v: B.node[v]['label'])
# assert_equal(B.node[left]['label'], '1')
# assert_equal(B.node[right]['label'], '2')
# # Get the left grandchild.
# children = B[left]
# assert_equal(len(children), 1)
# left_grandchild = arbitrary_element(children)
# assert_equal(B.node[left_grandchild]['label'], '3')
# # Get the right grandchild.
# children = B[right]
# assert_equal(len(children), 1)
# right_grandchild = arbitrary_element(children)
# assert_equal(B.node[right_grandchild]['label'], '3')
def test_already_arborescence(self):
"""Tests that a directed acyclic graph that is already an
arborescence produces an isomorphic arborescence as output.
"""
A = nx.balanced_tree(2, 2, create_using=nx.DiGraph())
B = nx.dag_to_branching(A)
assert nx.is_isomorphic(A, B)
def test_already_branching(self):
"""Tests that a directed acyclic graph that is already a
branching produces an isomorphic branching as output.
"""
T1 = nx.balanced_tree(2, 2, create_using=nx.DiGraph())
T2 = nx.balanced_tree(2, 2, create_using=nx.DiGraph())
G = nx.disjoint_union(T1, T2)
B = nx.dag_to_branching(G)
assert nx.is_isomorphic(G, B)
def test_not_acyclic(self):
"""Tests that a non-acyclic graph causes an exception."""
with pytest.raises(nx.HasACycle):
G = nx.DiGraph(pairwise("abc", cyclic=True))
nx.dag_to_branching(G)
def test_undirected(self):
with pytest.raises(nx.NetworkXNotImplemented):
nx.dag_to_branching(nx.Graph())
def test_multigraph(self):
with pytest.raises(nx.NetworkXNotImplemented):
nx.dag_to_branching(nx.MultiGraph())
def test_multidigraph(self):
with pytest.raises(nx.NetworkXNotImplemented):
nx.dag_to_branching(nx.MultiDiGraph())
def test_ancestors_descendants_undirected():
"""Regression test to ensure ancestors and descendants work as expected on
undirected graphs."""
G = nx.path_graph(5)
nx.ancestors(G, 2) == nx.descendants(G, 2) == {0, 1, 3, 4}
def test_compute_v_structures_raise():
G = nx.Graph()
with pytest.raises(nx.NetworkXNotImplemented, match="for undirected type"):
nx.compute_v_structures(G)
def test_compute_v_structures():
edges = [(0, 1), (0, 2), (3, 2)]
G = nx.DiGraph(edges)
v_structs = set(nx.compute_v_structures(G))
assert len(v_structs) == 1
assert (0, 2, 3) in v_structs
edges = [("A", "B"), ("C", "B"), ("B", "D"), ("D", "E"), ("G", "E")]
G = nx.DiGraph(edges)
v_structs = set(nx.compute_v_structures(G))
assert len(v_structs) == 2
def test_compute_v_structures_deprecated():
G = nx.DiGraph()
with pytest.deprecated_call():
nx.compute_v_structures(G)
def test_v_structures_raise():
G = nx.Graph()
with pytest.raises(nx.NetworkXNotImplemented, match="for undirected type"):
nx.dag.v_structures(G)
@pytest.mark.parametrize(
("edgelist", "expected"),
(
(
[(0, 1), (0, 2), (3, 2)],
{(0, 2, 3)},
),
(
[("A", "B"), ("C", "B"), ("D", "G"), ("D", "E"), ("G", "E")],
{("A", "B", "C")},
),
([(0, 1), (2, 1), (0, 2)], set()), # adjacent parents case: see gh-7385
),
)
def test_v_structures(edgelist, expected):
G = nx.DiGraph(edgelist)
v_structs = set(nx.dag.v_structures(G))
assert v_structs == expected
def test_colliders_raise():
G = nx.Graph()
with pytest.raises(nx.NetworkXNotImplemented, match="for undirected type"):
nx.dag.colliders(G)
@pytest.mark.parametrize(
("edgelist", "expected"),
(
(
[(0, 1), (0, 2), (3, 2)],
{(0, 2, 3)},
),
(
[("A", "B"), ("C", "B"), ("D", "G"), ("D", "E"), ("G", "E")],
{("A", "B", "C"), ("D", "E", "G")},
),
),
)
def test_colliders(edgelist, expected):
G = nx.DiGraph(edgelist)
colliders = set(nx.dag.colliders(G))
assert colliders == expected
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