Mercurial > repos > guerler > springsuite
diff planemo/lib/python3.7/site-packages/networkx/algorithms/dominating.py @ 1:56ad4e20f292 draft
"planemo upload commit 6eee67778febed82ddd413c3ca40b3183a3898f1"
author | guerler |
---|---|
date | Fri, 31 Jul 2020 00:32:28 -0400 |
parents | |
children |
line wrap: on
line diff
--- /dev/null Thu Jan 01 00:00:00 1970 +0000 +++ b/planemo/lib/python3.7/site-packages/networkx/algorithms/dominating.py Fri Jul 31 00:32:28 2020 -0400 @@ -0,0 +1,94 @@ +# -*- coding: utf-8 -*- +"""Functions for computing dominating sets in a graph.""" +from itertools import chain + +import networkx as nx +from networkx.utils import arbitrary_element + +__author__ = '\n'.join(['Jordi Torrents <jtorrents@milnou.net>']) +__all__ = ['dominating_set', 'is_dominating_set'] + + +def dominating_set(G, start_with=None): + r"""Finds a dominating set for the graph G. + + A *dominating set* for a graph with node set *V* is a subset *D* of + *V* such that every node not in *D* is adjacent to at least one + member of *D* [1]_. + + Parameters + ---------- + G : NetworkX graph + + start_with : node (default=None) + Node to use as a starting point for the algorithm. + + Returns + ------- + D : set + A dominating set for G. + + Notes + ----- + This function is an implementation of algorithm 7 in [2]_ which + finds some dominating set, not necessarily the smallest one. + + See also + -------- + is_dominating_set + + References + ---------- + .. [1] https://en.wikipedia.org/wiki/Dominating_set + + .. [2] Abdol-Hossein Esfahanian. Connectivity Algorithms. + http://www.cse.msu.edu/~cse835/Papers/Graph_connectivity_revised.pdf + + """ + all_nodes = set(G) + if start_with is None: + start_with = arbitrary_element(all_nodes) + if start_with not in G: + raise nx.NetworkXError('node {} is not in G'.format(start_with)) + dominating_set = {start_with} + dominated_nodes = set(G[start_with]) + remaining_nodes = all_nodes - dominated_nodes - dominating_set + while remaining_nodes: + # Choose an arbitrary node and determine its undominated neighbors. + v = remaining_nodes.pop() + undominated_neighbors = set(G[v]) - dominating_set + # Add the node to the dominating set and the neighbors to the + # dominated set. Finally, remove all of those nodes from the set + # of remaining nodes. + dominating_set.add(v) + dominated_nodes |= undominated_neighbors + remaining_nodes -= undominated_neighbors + return dominating_set + + +def is_dominating_set(G, nbunch): + """Checks if `nbunch` is a dominating set for `G`. + + A *dominating set* for a graph with node set *V* is a subset *D* of + *V* such that every node not in *D* is adjacent to at least one + member of *D* [1]_. + + Parameters + ---------- + G : NetworkX graph + + nbunch : iterable + An iterable of nodes in the graph `G`. + + See also + -------- + dominating_set + + References + ---------- + .. [1] https://en.wikipedia.org/wiki/Dominating_set + + """ + testset = set(n for n in nbunch if n in G) + nbrs = set(chain.from_iterable(G[n] for n in testset)) + return len(set(G) - testset - nbrs) == 0