42 lines
1.3 KiB
Python
42 lines
1.3 KiB
Python
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import pytest
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np = pytest.importorskip("numpy")
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pytest.importorskip("scipy")
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import networkx as nx
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from networkx.generators.degree_seq import havel_hakimi_graph
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class TestBetheHessian:
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@classmethod
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def setup_class(cls):
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deg = [3, 2, 2, 1, 0]
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cls.G = havel_hakimi_graph(deg)
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cls.P = nx.path_graph(3)
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def test_bethe_hessian(self):
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"Bethe Hessian matrix"
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# fmt: off
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H = np.array([[4, -2, 0],
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[-2, 5, -2],
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[0, -2, 4]])
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# fmt: on
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permutation = [2, 0, 1]
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# Bethe Hessian gives expected form
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np.testing.assert_equal(nx.bethe_hessian_matrix(self.P, r=2).todense(), H)
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# nodelist is correctly implemented
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np.testing.assert_equal(
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nx.bethe_hessian_matrix(self.P, r=2, nodelist=permutation).todense(),
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H[np.ix_(permutation, permutation)],
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)
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# Equal to Laplacian matrix when r=1
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np.testing.assert_equal(
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nx.bethe_hessian_matrix(self.G, r=1).todense(),
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nx.laplacian_matrix(self.G).todense(),
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)
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# Correct default for the regularizer r
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np.testing.assert_equal(
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nx.bethe_hessian_matrix(self.G).todense(),
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nx.bethe_hessian_matrix(self.G, r=1.25).todense(),
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)
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