## Mercurial > repos > shellac > sam_consensus_v3

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

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"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.algorithms.wiener` module.""" from networkx import complete_graph from networkx import DiGraph from networkx import empty_graph from networkx import path_graph from networkx import wiener_index class TestWienerIndex: """Unit tests for computing the Wiener index of a graph.""" def test_disconnected_graph(self): """Tests that the Wiener index of a disconnected graph is positive infinity. """ assert wiener_index(empty_graph(2)) == float("inf") def test_directed(self): """Tests that each pair of nodes in the directed graph is counted once when computing the Wiener index. """ G = complete_graph(3) H = DiGraph(G) assert (2 * wiener_index(G)) == wiener_index(H) def test_complete_graph(self): """Tests that the Wiener index of the complete graph is simply the number of edges. """ n = 10 G = complete_graph(n) assert wiener_index(G) == (n * (n - 1) / 2) def test_path_graph(self): """Tests that the Wiener index of the path graph is correctly computed. """ # In P_n, there are n - 1 pairs of vertices at distance one, n - # 2 pairs at distance two, n - 3 at distance three, ..., 1 at # distance n - 1, so the Wiener index should be # # 1 * (n - 1) + 2 * (n - 2) + ... + (n - 2) * 2 + (n - 1) * 1 # # For example, in P_5, # # 1 * 4 + 2 * 3 + 3 * 2 + 4 * 1 = 2 (1 * 4 + 2 * 3) # # and in P_6, # # 1 * 5 + 2 * 4 + 3 * 3 + 4 * 2 + 5 * 1 = 2 (1 * 5 + 2 * 4) + 3 * 3 # # assuming n is *odd*, this gives the formula # # 2 \sum_{i = 1}^{(n - 1) / 2} [i * (n - i)] # # assuming n is *even*, this gives the formula # # 2 \sum_{i = 1}^{n / 2} [i * (n - i)] - (n / 2) ** 2 # n = 9 G = path_graph(n) expected = 2 * sum(i * (n - i) for i in range(1, (n // 2) + 1)) actual = wiener_index(G) assert expected == actual