wehub-resource-sync
110 lines
2.6 KiB
Python
110 lines
2.6 KiB
Python
import easygraph as eg
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import easygraph.functions.path
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from easygraph.utils.decorators import *
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__all__ = ["diameter", "eccentricity"]
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@hybrid("cpp_eccentricity")
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def eccentricity(G, v=None, sp=None):
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"""Returns the eccentricity of nodes in G.
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The eccentricity of a node v is the maximum distance from v to
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all other nodes in G.
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Parameters
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----------
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G : EasyGraph graph
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A graph
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v : node, optional
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Return value of specified node
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sp : dict of dicts, optional
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All pairs shortest path lengths as a dictionary of dictionaries
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Returns
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-------
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ecc : dictionary
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A dictionary of eccentricity values keyed by node.
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Examples
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--------
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>>> G = eg.Graph([(1, 2), (1, 3), (1, 4), (3, 4), (3, 5), (4, 5)])
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>>> dict(eg.eccentricity(G))
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{1: 2, 2: 3, 3: 2, 4: 2, 5: 3}
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>>> dict(eg.eccentricity(G, v=[1, 5])) # This returns the eccentrity of node 1 & 5
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{1: 2, 5: 3}
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"""
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# if v is None: # none, use entire graph
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# nodes=G.nodes()
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# elif v in G: # is v a single node
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# nodes=[v]
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# else: # assume v is a container of nodes
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# nodes=v
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order = G.order()
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e = {}
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for n in G.nbunch_iter(v):
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if sp is None:
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length = eg.single_source_dijkstra(G, n)
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L = len(length)
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else:
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try:
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length = sp[n]
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L = len(length)
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except TypeError as err:
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raise eg.EasyGraphError('Format of "sp" is invalid.') from err
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if L != order:
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if G.is_directed():
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msg = (
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"Found infinite path length because the digraph is not"
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" strongly connected"
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)
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else:
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msg = "Found infinite path length because the graph is not connected"
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raise eg.EasyGraphError(msg)
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e[n] = max(length.values())
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if v in G:
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return e[v] # return single value
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else:
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return e
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def diameter(G, e=None):
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"""Returns the diameter of the graph G.
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The diameter is the maximum eccentricity.
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Parameters
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----------
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G : EasyGraph graph
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A graph
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e : eccentricity dictionary, optional
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A precomputed dictionary of eccentricities.
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Returns
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-------
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d : integer
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Diameter of graph
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Examples
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--------
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>>> G = eg.Graph([(1, 2), (1, 3), (1, 4), (3, 4), (3, 5), (4, 5)])
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>>> eg.diameter(G)
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3
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See Also
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--------
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eccentricity
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"""
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if e is None:
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e = eccentricity(G)
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return max(e.values())
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