def backtrack_color(G, coloring = None, level = 1, chro_num = None):
'''
Backtracking algorithm.
G is a NetworkX graph, coloring is an ordered dictionary, level is an integer count of the recursive depth,
and chro_num is the chromatic number of graph G.
'''
global colorings
#If this is the first call, set up the things:
if level == 1:
#Setting up results list:
colorings = []
#Setting up coloring dictionary:
coloring = OrderedDict()
#Populating coloring dictionary:
index = 0
for node in G:
#Color first node with color 0
if index == 0:
coloring[node] = 0
index += 1
#Color other nodes with nothing
else:
coloring[node] = None
#Finding chromatic number of graph G, for future recursive calls
chro_num = gp.chromatic_number(G)
#Move to node 2
level += 1
#For all nodes in the graph:
#for node in G.nodes: ###
node_list = list(G.nodes)
#For all valid colors:
for color in range(0, chro_num):
#DEBUG
#print("checking " + str(color))
#If the node has no neighbors with the color, color it and continue:
if legal_color(node_list[level-1], color, coloring):
#DEBUG
#print("coloring " + str(node_list[level-1]) + " " + str(color))
coloring[node_list[level-1]] = color
#If not all nodes have been colored, increment level and recurse:
if level < G.number_of_nodes():
backtrack_color(G, coloring, (level+1), chro_num)
#If all nodes have been colored, we have reached an optimal solution
#(optimal since we only permitted colors up to the chromatic number)
else:
#Add the solution to the list
colorings.append(coloring.copy())
import sys
sys.path.append('../')
import grinpy as gp
import numpy as np
G = gp.circular_ladder_graph(10)
chromatic_number = gp.chromatic_number(G, method='ilp')
print('Chromatic number (ILP): {}'.format(chromatic_number))
def main():
'''Driver program'''
args = parse_args()
log('Starting...')
# load graphs, or generate them if they don't exist
if not os.path.exists(str(GRAPH_DIR)):
os.mkdir(str(GRAPH_DIR))
if not os.path.exists(str(GRAPH_DIR / SML_NAME)):
record_graphs(gen_rand_graphs(SML), str(GRAPH_DIR / SML_NAME))
if not os.path.exists(str(GRAPH_DIR / MED_NAME)):
record_graphs(gen_rand_graphs(MED), str(GRAPH_DIR / MED_NAME))
if not os.path.exists(str(GRAPH_DIR / LRG_NAME)):
record_graphs(gen_rand_graphs(LRG), str(GRAPH_DIR / LRG_NAME))
if args.n < 1:
log('Must select at least one graph.')
raise SystemExit
graphs = load_graphs(args.mode, args.n)
# ground truth graphs
start = time.time()
if args.gtskip:
gt_graphs = {graph: None for graph in graphs}
else:
log('Calculating ground truth...')
gt_graphs = {graph: gp.chromatic_number(graph) for graph in graphs}
log(f'{round(time.time() - start, 3)} seconds')
# color each graph with each algorithm
# each algorithm will predict the chi of the graph and this will form new
# mappings of graph -> chi
log('Calculating greedy colorings...')
start = time.time()
gr_graphs = {graph: greedy_color(graph) for graph in graphs}
log(f'{round(time.time() - start, 3)} seconds')
log('Calculating differential evolution colorings...')
start = time.time()
de_graphs = compute_chi(de, graphs)
log(f'{round(time.time() - start, 3)} seconds')
log('Calculating particle swarm optimization colorings...')
start = time.time()
pso_graphs = compute_chi(pso, graphs)
log(f'{round(time.time() - start, 3)} seconds')
log('Calculating firefly algorithm colorings...')
start = time.time()
ff_graphs = compute_chi(ff, graphs)
log(f'{round(time.time() - start, 3)} seconds')
# print results
table_1 = tab.tabulate(
zip(list(range(len(graphs))), gt_graphs.values(), gr_graphs.values(),
de_graphs.values(), pso_graphs.values(), ff_graphs.values()),
headers=['id', 'truth', 'greedy', 'de', 'pso', 'firefly'])
log(f'\nChromatic numbers for graphs:\n{table_1}')
min_chi = min([
min(gr_graphs.values()),
min(de_graphs.values()),
min(pso_graphs.values()),
min(ff_graphs.values())
])
max_chi = max([
max(gr_graphs.values()),
max(de_graphs.values()),
max(pso_graphs.values()),
max(ff_graphs.values())
])
gr_modes = [
list(gr_graphs.values()).count(idx)
for idx in range(min_chi, max_chi + 1)
]
de_modes = [
list(de_graphs.values()).count(idx)
for idx in range(min_chi, max_chi + 1)
]
pso_modes = [
list(pso_graphs.values()).count(idx)
for idx in range(min_chi, max_chi + 1)
]
firefly_mode = [
list(ff_graphs.values()).count(idx)
for idx in range(min_chi, max_chi + 1)
]
table_2 = tab.tabulate(zip(list(range(min_chi, max_chi + 1)), gr_modes,
de_modes, pso_modes, firefly_mode),
headers=['chi', 'greedy', 'de', 'pso', 'firefly'])
log(f'\nFrequency of chromatic numbers:\n{table_2}')
log('...finished.')
return 0
def test_chromatic_number_of_complete_graph_is_order():
for i in range(1, 11):
G = gp.complete_graph(i)
assert (gp.chromatic_number(G, method='ram-rama') == G.order())
assert (gp.chromatic_number(G, method='ilp') == G.order())
def test_chromatic_number_of_petersen_graph_is_3():
G = gp.petersen_graph()
assert (gp.chromatic_number(G, method='ram-rama') == 3)
assert (gp.chromatic_number(G, method='ilp') == 3)
import sys
sys.path.append('../')
import grinpy as gp
import numpy as np
G = gp.circular_ladder_graph(10)
chromatic_number = gp.chromatic_number(G, method='ram-rama')
print('Chromatic number (Ram-Rama): {}'.format(chromatic_number))
def test_chromatic_number_of_complete_graph_is_order():
for i in range(1, 11):
G = gp.complete_graph(i)
assert gp.chromatic_number(G, method="ram-rama") == G.order()
assert gp.chromatic_number(G, method="ilp") == G.order()
def test_chromatic_number_of_petersen_graph_is_3():
G = gp.petersen_graph()
assert gp.chromatic_number(G, method="ram-rama") == 3
assert gp.chromatic_number(G, method="ilp") == 3
