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view env/lib/python3.9/site-packages/networkx/generators/tests/test_expanders.py @ 0:4f3585e2f14b draft default tip
"planemo upload commit 60cee0fc7c0cda8592644e1aad72851dec82c959"
author | shellac |
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date | Mon, 22 Mar 2021 18:12:50 +0000 |
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"""Unit tests for the :mod:`networkx.generators.expanders` module. """ import networkx as nx from networkx import adjacency_matrix from networkx import number_of_nodes from networkx.generators.expanders import chordal_cycle_graph from networkx.generators.expanders import margulis_gabber_galil_graph from networkx.generators.expanders import paley_graph import pytest def test_margulis_gabber_galil_graph(): for n in 2, 3, 5, 6, 10: g = margulis_gabber_galil_graph(n) assert number_of_nodes(g) == n * n for node in g: assert g.degree(node) == 8 assert len(node) == 2 for i in node: assert int(i) == i assert 0 <= i < n np = pytest.importorskip("numpy") scipy = pytest.importorskip("scipy") scipy.linalg = pytest.importorskip("scipy.linalg") # Eigenvalues are already sorted using the scipy eigvalsh, # but the implementation in numpy does not guarantee order. w = sorted(scipy.linalg.eigvalsh(adjacency_matrix(g).A)) assert w[-2] < 5 * np.sqrt(2) def test_chordal_cycle_graph(): """Test for the :func:`networkx.chordal_cycle_graph` function.""" primes = [3, 5, 7, 11] for p in primes: G = chordal_cycle_graph(p) assert len(G) == p # TODO The second largest eigenvalue should be smaller than a constant, # independent of the number of nodes in the graph: # # eigs = sorted(scipy.linalg.eigvalsh(adjacency_matrix(G).A)) # assert_less(eigs[-2], ...) # def test_paley_graph(): """Test for the :func:`networkx.paley_graph` function.""" primes = [3, 5, 7, 11, 13] for p in primes: G = paley_graph(p) # G has p nodes assert len(G) == p # G is (p-1)/2-regular in_degrees = {G.in_degree(node) for node in G.nodes} out_degrees = {G.out_degree(node) for node in G.nodes} assert len(in_degrees) == 1 and in_degrees.pop() == (p - 1) // 2 assert len(out_degrees) == 1 and out_degrees.pop() == (p - 1) // 2 # If p = 1 mod 4, -1 is a square mod 4 and therefore the # edge in the Paley graph are symmetric. if p % 4 == 1: for (u, v) in G.edges: assert (v, u) in G.edges def test_margulis_gabber_galil_graph_badinput(): pytest.raises(nx.NetworkXError, margulis_gabber_galil_graph, 3, nx.DiGraph()) pytest.raises(nx.NetworkXError, margulis_gabber_galil_graph, 3, nx.Graph())