56 lines
1.8 KiB
Python
56 lines
1.8 KiB
Python
# Copyright 2014 "cheebee7i".
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# Copyright 2014 "alexbrc".
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# Copyright 2014 Jeffrey Finkelstein <jeffrey.finkelstein@gmail.com>.
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"""Unit tests for the :mod:`networkx.generators.expanders` module.
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"""
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import networkx as nx
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from networkx import adjacency_matrix
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from networkx import number_of_nodes
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from networkx.generators.expanders import chordal_cycle_graph
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from networkx.generators.expanders import margulis_gabber_galil_graph
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import pytest
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def test_margulis_gabber_galil_graph():
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for n in 2, 3, 5, 6, 10:
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g = margulis_gabber_galil_graph(n)
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assert number_of_nodes(g) == n * n
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for node in g:
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assert g.degree(node) == 8
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assert len(node) == 2
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for i in node:
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assert int(i) == i
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assert 0 <= i < n
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np = pytest.importorskip("numpy")
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scipy = pytest.importorskip("scipy")
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scipy.linalg = pytest.importorskip("scipy.linalg")
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# Eigenvalues are already sorted using the scipy eigvalsh,
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# but the implementation in numpy does not guarantee order.
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w = sorted(scipy.linalg.eigvalsh(adjacency_matrix(g).A))
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assert w[-2] < 5 * np.sqrt(2)
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def test_chordal_cycle_graph():
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"""Test for the :func:`networkx.chordal_cycle_graph` function."""
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primes = [3, 5, 7, 11]
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for p in primes:
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G = chordal_cycle_graph(p)
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assert len(G) == p
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# TODO The second largest eigenvalue should be smaller than a constant,
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# independent of the number of nodes in the graph:
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#
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# eigs = sorted(scipy.linalg.eigvalsh(adjacency_matrix(G).A))
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# assert_less(eigs[-2], ...)
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#
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def test_margulis_gabber_galil_graph_badinput():
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pytest.raises(nx.NetworkXError, margulis_gabber_galil_graph, 3,
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nx.DiGraph())
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pytest.raises(nx.NetworkXError, margulis_gabber_galil_graph, 3,
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nx.Graph())
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