view env/lib/python3.9/site-packages/networkx/linalg/tests/test_bethehessian.py @ 0:4f3585e2f14b draft default tip

"planemo upload commit 60cee0fc7c0cda8592644e1aad72851dec82c959"
author shellac
date Mon, 22 Mar 2021 18:12:50 +0000
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import pytest

np = pytest.importorskip("numpy")
npt = pytest.importorskip("numpy.testing")
sp = pytest.importorskip("scipy")

import networkx as nx
from networkx.generators.degree_seq import havel_hakimi_graph


class TestBetheHessian:
    @classmethod
    def setup_class(cls):
        deg = [3, 2, 2, 1, 0]
        cls.G = havel_hakimi_graph(deg)
        cls.P = nx.path_graph(3)

    def test_bethe_hessian(self):
        "Bethe Hessian matrix"
        # fmt: off
        H = np.array([[4, -2, 0],
                      [-2, 5, -2],
                      [0, -2, 4]])
        # fmt: on
        permutation = [2, 0, 1]
        # Bethe Hessian gives expected form
        npt.assert_equal(nx.bethe_hessian_matrix(self.P, r=2).todense(), H)
        # nodelist is correctly implemented
        npt.assert_equal(
            nx.bethe_hessian_matrix(self.P, r=2, nodelist=permutation).todense(),
            H[np.ix_(permutation, permutation)],
        )
        # Equal to Laplacian matrix when r=1
        npt.assert_equal(
            nx.bethe_hessian_matrix(self.G, r=1).todense(),
            nx.laplacian_matrix(self.G).todense(),
        )
        # Correct default for the regularizer r
        npt.assert_equal(
            nx.bethe_hessian_matrix(self.G).todense(),
            nx.bethe_hessian_matrix(self.G, r=1.25).todense(),
        )