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#!/usr/bin/env python
from nose.tools import *
import networkx as nx
class TestWeightedPath:
def setUp(self):
from networkx import convert_node_labels_to_integers as cnlti
self.grid=cnlti(nx.grid_2d_graph(4,4),first_label=1,ordering="sorted")
self.cycle=nx.cycle_graph(7)
self.directed_cycle=nx.cycle_graph(7,create_using=nx.DiGraph())
self.XG=nx.DiGraph()
self.XG.add_weighted_edges_from([('s','u',10) ,('s','x',5) ,
('u','v',1) ,('u','x',2) ,
('v','y',1) ,('x','u',3) ,
('x','v',5) ,('x','y',2) ,
('y','s',7) ,('y','v',6)])
self.MXG=nx.MultiDiGraph(self.XG)
self.MXG.add_edge('s','u',weight=15)
self.XG2=nx.DiGraph()
self.XG2.add_weighted_edges_from([[1,4,1],[4,5,1],
[5,6,1],[6,3,1],
[1,3,50],[1,2,100],[2,3,100]])
self.XG3=nx.Graph()
self.XG3.add_weighted_edges_from([ [0,1,2],[1,2,12],
[2,3,1],[3,4,5],
[4,5,1],[5,0,10] ])
self.XG4=nx.Graph()
self.XG4.add_weighted_edges_from([ [0,1,2],[1,2,2],
[2,3,1],[3,4,1],
[4,5,1],[5,6,1],
[6,7,1],[7,0,1] ])
self.MXG4=nx.MultiGraph(self.XG4)
self.MXG4.add_edge(0,1,weight=3)
self.G=nx.DiGraph() # no weights
self.G.add_edges_from([('s','u'), ('s','x'),
('u','v'), ('u','x'),
('v','y'), ('x','u'),
('x','v'), ('x','y'),
('y','s'), ('y','v')])
def test_dijkstra(self):
(D,P)= nx.single_source_dijkstra(self.XG,'s')
assert_equal(P['v'], ['s', 'x', 'u', 'v'])
assert_equal(D['v'],9)
assert_equal(nx.single_source_dijkstra_path(self.XG,'s')['v'],
['s', 'x', 'u', 'v'])
assert_equal(nx.single_source_dijkstra_path_length(self.XG,'s')['v'],9)
assert_equal(nx.single_source_dijkstra(self.XG,'s')[1]['v'],
['s', 'x', 'u', 'v'])
assert_equal(nx.single_source_dijkstra_path(self.MXG,'s')['v'],
['s', 'x', 'u', 'v'])
GG=self.XG.to_undirected()
# make sure we get lower weight
# to_undirected might choose either edge with weight 2 or weight 3
GG['u']['x']['weight']=2
(D,P)= nx.single_source_dijkstra(GG,'s')
assert_equal(P['v'] , ['s', 'x', 'u', 'v'])
assert_equal(D['v'],8) # uses lower weight of 2 on u<->x edge
assert_equal(nx.dijkstra_path(GG,'s','v'), ['s', 'x', 'u', 'v'])
assert_equal(nx.dijkstra_path_length(GG,'s','v'),8)
assert_equal(nx.dijkstra_path(self.XG2,1,3), [1, 4, 5, 6, 3])
assert_equal(nx.dijkstra_path(self.XG3,0,3), [0, 1, 2, 3])
assert_equal(nx.dijkstra_path_length(self.XG3,0,3),15)
assert_equal(nx.dijkstra_path(self.XG4,0,2), [0, 1, 2])
assert_equal(nx.dijkstra_path_length(self.XG4,0,2), 4)
assert_equal(nx.dijkstra_path(self.MXG4,0,2), [0, 1, 2])
assert_equal(nx.single_source_dijkstra(self.G,'s','v')[1]['v'],
['s', 'u', 'v'])
assert_equal(nx.single_source_dijkstra(self.G,'s')[1]['v'],
['s', 'u', 'v'])
assert_equal(nx.dijkstra_path(self.G,'s','v'), ['s', 'u', 'v'])
assert_equal(nx.dijkstra_path_length(self.G,'s','v'), 2)
# NetworkXError: node s not reachable from moon
assert_raises(nx.NetworkXNoPath,nx.dijkstra_path,self.G,'s','moon')
assert_raises(nx.NetworkXNoPath,nx.dijkstra_path_length,self.G,'s','moon')
assert_equal(nx.dijkstra_path(self.cycle,0,3),[0, 1, 2, 3])
assert_equal(nx.dijkstra_path(self.cycle,0,4), [0, 6, 5, 4])
assert_equal(nx.single_source_dijkstra(self.cycle,0,0),({0:0}, {0:[0]}) )
def test_bidirectional_dijkstra(self):
assert_equal(nx.bidirectional_dijkstra(self.XG, 's', 'v'),
(9, ['s', 'x', 'u', 'v']))
(dist,path) = nx.bidirectional_dijkstra(self.G,'s','v')
assert_equal(dist,2)
# skip this test, correct path could also be ['s','u','v']
# assert_equal(nx.bidirectional_dijkstra(self.G,'s','v'),
# (2, ['s', 'x', 'v']))
assert_equal(nx.bidirectional_dijkstra(self.cycle,0,3),
(3, [0, 1, 2, 3]))
assert_equal(nx.bidirectional_dijkstra(self.cycle,0,4),
(3, [0, 6, 5, 4]))
assert_equal(nx.bidirectional_dijkstra(self.XG3,0,3),
(15, [0, 1, 2, 3]))
assert_equal(nx.bidirectional_dijkstra(self.XG4,0,2),
(4, [0, 1, 2]))
# need more tests here
assert_equal(nx.dijkstra_path(self.XG,'s','v'),
nx.single_source_dijkstra_path(self.XG,'s')['v'])
@raises(nx.NetworkXNoPath)
def test_bidirectional_dijkstra_no_path(self):
G = nx.Graph()
G.add_path([1,2,3])
G.add_path([4,5,6])
path = nx.bidirectional_dijkstra(G,1,6)
def test_dijkstra_predecessor(self):
G=nx.path_graph(4)
assert_equal(nx.dijkstra_predecessor_and_distance(G,0),
({0: [], 1: [0], 2: [1], 3: [2]}, {0: 0, 1: 1, 2: 2, 3: 3}))
G=nx.grid_2d_graph(2,2)
pred,dist=nx.dijkstra_predecessor_and_distance(G,(0,0))
assert_equal(sorted(pred.items()),
[((0, 0), []), ((0, 1), [(0, 0)]),
((1, 0), [(0, 0)]), ((1, 1), [(0, 1), (1, 0)])])
assert_equal(sorted(dist.items()),
[((0, 0), 0), ((0, 1), 1), ((1, 0), 1), ((1, 1), 2)])
XG=nx.DiGraph()
XG.add_weighted_edges_from([('s','u',10) ,('s','x',5) ,
('u','v',1) ,('u','x',2) ,
('v','y',1) ,('x','u',3) ,
('x','v',5) ,('x','y',2) ,
('y','s',7) ,('y','v',6)])
(P,D)= nx.dijkstra_predecessor_and_distance(XG,'s')
assert_equal(P['v'],['u'])
assert_equal(D['v'],9)
(P,D)= nx.dijkstra_predecessor_and_distance(XG,'s',cutoff=8)
assert_false('v' in D)
def test_single_source_dijkstra_path_length(self):
pl = nx.single_source_dijkstra_path_length
assert_equal(pl(self.MXG4,0)[2], 4)
spl = pl(self.MXG4,0,cutoff=2)
assert_false(2 in spl)
def test_bidirectional_dijkstra_multigraph(self):
G = nx.MultiGraph()
G.add_edge('a', 'b', weight=10)
G.add_edge('a', 'b', weight=100)
dp= nx.bidirectional_dijkstra(G, 'a', 'b')
assert_equal(dp,(10, ['a', 'b']))
def test_dijkstra_pred_distance_multigraph(self):
G = nx.MultiGraph()
G.add_edge('a', 'b', key='short',foo=5, weight=100)
G.add_edge('a', 'b', key='long',bar=1, weight=110)
p,d= nx.dijkstra_predecessor_and_distance(G, 'a')
assert_equal(p,{'a': [], 'b': ['a']})
assert_equal(d,{'a': 0, 'b': 100})
def test_negative_edge_cycle(self):
G = nx.cycle_graph(5, create_using = nx.DiGraph())
assert_equal(nx.negative_edge_cycle(G), False)
G.add_edge(8, 9, weight = -7)
G.add_edge(9, 8, weight = 3)
assert_equal(nx.negative_edge_cycle(G), True)
assert_raises(ValueError,nx.single_source_dijkstra_path_length,G,8)
assert_raises(ValueError,nx.single_source_dijkstra,G,8)
assert_raises(ValueError,nx.dijkstra_predecessor_and_distance,G,8)
G.add_edge(9,10)
assert_raises(ValueError,nx.bidirectional_dijkstra,G,8,10)
def test_bellman_ford(self):
# single node graph
G = nx.DiGraph()
G.add_node(0)
assert_equal(nx.bellman_ford(G, 0), ({0: None}, {0: 0}))
assert_raises(KeyError, nx.bellman_ford, G, 1)
# negative weight cycle
G = nx.cycle_graph(5, create_using = nx.DiGraph())
G.add_edge(1, 2, weight = -7)
for i in range(5):
assert_raises(nx.NetworkXUnbounded, nx.bellman_ford, G, i)
G = nx.cycle_graph(5) # undirected Graph
G.add_edge(1, 2, weight = -3)
for i in range(5):
assert_raises(nx.NetworkXUnbounded, nx.bellman_ford, G, i)
# no negative cycle but negative weight
G = nx.cycle_graph(5, create_using = nx.DiGraph())
G.add_edge(1, 2, weight = -3)
assert_equal(nx.bellman_ford(G, 0),
({0: None, 1: 0, 2: 1, 3: 2, 4: 3},
{0: 0, 1: 1, 2: -2, 3: -1, 4: 0}))
# not connected
G = nx.complete_graph(6)
G.add_edge(10, 11)
G.add_edge(10, 12)
assert_equal(nx.bellman_ford(G, 0),
({0: None, 1: 0, 2: 0, 3: 0, 4: 0, 5: 0},
{0: 0, 1: 1, 2: 1, 3: 1, 4: 1, 5: 1}))
# not connected, with a component not containing the source that
# contains a negative cost cycle.
G = nx.complete_graph(6)
G.add_edges_from([('A', 'B', {'load': 3}),
('B', 'C', {'load': -10}),
('C', 'A', {'load': 2})])
assert_equal(nx.bellman_ford(G, 0, weight = 'load'),
({0: None, 1: 0, 2: 0, 3: 0, 4: 0, 5: 0},
{0: 0, 1: 1, 2: 1, 3: 1, 4: 1, 5: 1}))
# multigraph
P, D = nx.bellman_ford(self.MXG,'s')
assert_equal(P['v'], 'u')
assert_equal(D['v'], 9)
P, D = nx.bellman_ford(self.MXG4, 0)
assert_equal(P[2], 1)
assert_equal(D[2], 4)
# other tests
(P,D)= nx.bellman_ford(self.XG,'s')
assert_equal(P['v'], 'u')
assert_equal(D['v'], 9)
G=nx.path_graph(4)
assert_equal(nx.bellman_ford(G,0),
({0: None, 1: 0, 2: 1, 3: 2}, {0: 0, 1: 1, 2: 2, 3: 3}))
assert_equal(nx.bellman_ford(G, 3),
({0: 1, 1: 2, 2: 3, 3: None}, {0: 3, 1: 2, 2: 1, 3: 0}))
G=nx.grid_2d_graph(2,2)
pred,dist=nx.bellman_ford(G,(0,0))
assert_equal(sorted(pred.items()),
[((0, 0), None), ((0, 1), (0, 0)),
((1, 0), (0, 0)), ((1, 1), (0, 1))])
assert_equal(sorted(dist.items()),
[((0, 0), 0), ((0, 1), 1), ((1, 0), 1), ((1, 1), 2)])
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