Mercurial > repos > shellac > sam_consensus_v3
diff env/lib/python3.9/site-packages/networkx/algorithms/approximation/ramsey.py @ 0:4f3585e2f14b draft default tip
"planemo upload commit 60cee0fc7c0cda8592644e1aad72851dec82c959"
author | shellac |
---|---|
date | Mon, 22 Mar 2021 18:12:50 +0000 |
parents | |
children |
line wrap: on
line diff
--- /dev/null Thu Jan 01 00:00:00 1970 +0000 +++ b/env/lib/python3.9/site-packages/networkx/algorithms/approximation/ramsey.py Mon Mar 22 18:12:50 2021 +0000 @@ -0,0 +1,42 @@ +""" +Ramsey numbers. +""" +import networkx as nx +from ...utils import arbitrary_element + +__all__ = ["ramsey_R2"] + + +def ramsey_R2(G): + r"""Compute the largest clique and largest independent set in `G`. + + This can be used to estimate bounds for the 2-color + Ramsey number `R(2;s,t)` for `G`. + + This is a recursive implementation which could run into trouble + for large recursions. Note that self-loop edges are ignored. + + Parameters + ---------- + G : NetworkX graph + Undirected graph + + Returns + ------- + max_pair : (set, set) tuple + Maximum clique, Maximum independent set. + """ + if not G: + return set(), set() + + node = arbitrary_element(G) + nbrs = (nbr for nbr in nx.all_neighbors(G, node) if nbr != node) + nnbrs = nx.non_neighbors(G, node) + c_1, i_1 = ramsey_R2(G.subgraph(nbrs).copy()) + c_2, i_2 = ramsey_R2(G.subgraph(nnbrs).copy()) + + c_1.add(node) + i_2.add(node) + # Choose the larger of the two cliques and the larger of the two + # independent sets, according to cardinality. + return max(c_1, c_2, key=len), max(i_1, i_2, key=len)