102 lines
3.0 KiB
Python
102 lines
3.0 KiB
Python
from itertools import chain
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import networkx as nx
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import pytest
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def _check_partition(G, cut_value, partition, weight):
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assert isinstance(partition, tuple)
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assert len(partition) == 2
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assert isinstance(partition[0], list)
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assert isinstance(partition[1], list)
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assert len(partition[0]) > 0
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assert len(partition[1]) > 0
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assert sum(map(len, partition)) == len(G)
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assert set(chain.from_iterable(partition)) == set(G)
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partition = tuple(map(set, partition))
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w = 0
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for u, v, e in G.edges(data=True):
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if (u in partition[0]) == (v in partition[1]):
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w += e.get(weight, 1)
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assert w == cut_value
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def _test_stoer_wagner(G, answer, weight='weight'):
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cut_value, partition = nx.stoer_wagner(G, weight,
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heap=nx.utils.PairingHeap)
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assert cut_value == answer
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_check_partition(G, cut_value, partition, weight)
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cut_value, partition = nx.stoer_wagner(G, weight,
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heap=nx.utils.BinaryHeap)
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assert cut_value == answer
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_check_partition(G, cut_value, partition, weight)
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def test_graph1():
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G = nx.Graph()
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G.add_edge('x', 'a', weight=3)
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G.add_edge('x', 'b', weight=1)
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G.add_edge('a', 'c', weight=3)
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G.add_edge('b', 'c', weight=5)
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G.add_edge('b', 'd', weight=4)
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G.add_edge('d', 'e', weight=2)
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G.add_edge('c', 'y', weight=2)
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G.add_edge('e', 'y', weight=3)
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_test_stoer_wagner(G, 4)
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def test_graph2():
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G = nx.Graph()
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G.add_edge('x', 'a')
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G.add_edge('x', 'b')
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G.add_edge('a', 'c')
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G.add_edge('b', 'c')
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G.add_edge('b', 'd')
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G.add_edge('d', 'e')
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G.add_edge('c', 'y')
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G.add_edge('e', 'y')
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_test_stoer_wagner(G, 2)
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def test_graph3():
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# Source:
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# Stoer, M. and Wagner, F. (1997). "A simple min-cut algorithm". Journal of
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# the ACM 44 (4), 585-591.
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G = nx.Graph()
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G.add_edge(1, 2, weight=2)
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G.add_edge(1, 5, weight=3)
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G.add_edge(2, 3, weight=3)
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G.add_edge(2, 5, weight=2)
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G.add_edge(2, 6, weight=2)
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G.add_edge(3, 4, weight=4)
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G.add_edge(3, 7, weight=2)
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G.add_edge(4, 7, weight=2)
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G.add_edge(4, 8, weight=2)
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G.add_edge(5, 6, weight=3)
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G.add_edge(6, 7, weight=1)
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G.add_edge(7, 8, weight=3)
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_test_stoer_wagner(G, 4)
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def test_weight_name():
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G = nx.Graph()
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G.add_edge(1, 2, weight=1, cost=8)
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G.add_edge(1, 3, cost=2)
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G.add_edge(2, 3, cost=4)
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_test_stoer_wagner(G, 6, weight='cost')
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def test_exceptions():
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G = nx.Graph()
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pytest.raises(nx.NetworkXError, nx.stoer_wagner, G)
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G.add_node(1)
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pytest.raises(nx.NetworkXError, nx.stoer_wagner, G)
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G.add_node(2)
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pytest.raises(nx.NetworkXError, nx.stoer_wagner, G)
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G.add_edge(1, 2, weight=-2)
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pytest.raises(nx.NetworkXError, nx.stoer_wagner, G)
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G = nx.DiGraph()
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pytest.raises(nx.NetworkXNotImplemented, nx.stoer_wagner, G)
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G = nx.MultiGraph()
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pytest.raises(nx.NetworkXNotImplemented, nx.stoer_wagner, G)
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G = nx.MultiDiGraph()
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pytest.raises(nx.NetworkXNotImplemented, nx.stoer_wagner, G)
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