diff env/lib/python3.9/site-packages/networkx/generators/tests/test_expanders.py @ 0:4f3585e2f14b draft default tip

"planemo upload commit 60cee0fc7c0cda8592644e1aad72851dec82c959"

--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/env/lib/python3.9/site-packages/networkx/generators/tests/test_expanders.py	Mon Mar 22 18:12:50 2021 +0000
@@ -0,0 +1,71 @@
+"""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())