def init_model(self, **kwargs):
greedy_start = kwargs.get("greedy_start", True)
verbose = kwargs.get("verbose", False)
use_cliques = kwargs.get("use_cliques", False)
if greedy_start:
if verbose:
print("Computing greedy solution")
greedy_solver = GreedyColoring(self.coloring_problem,
params_objective_function=self.params_objective_function)
result_store = greedy_solver.solve(strategy=NXGreedyColoringMethod.best, verbose=verbose)
self.start_solution = result_store.get_best_solution_fit()[0]
else:
if verbose:
print("Get dummy solution")
solution = self.coloring_problem.get_dummy_solution()
self.start_solution = solution
nb_colors = self.start_solution.nb_color
color_model = Model("color")
colors_var = {}
range_node = range(self.number_of_nodes)
range_color = range(nb_colors)
for node in self.nodes_name:
for color in range_color:
colors_var[node, color] = color_model.addVar(vtype=GRB.BINARY,
obj=0,
name="x_" + str((node, color)))
one_color_constraints = {}
for n in range_node:
one_color_constraints[n] = color_model.addConstr(quicksum([colors_var[n, c] for c in range_color]) == 1)
color_model.update()
cliques = []
g = self.graph.to_networkx()
if use_cliques:
for c in nx.algorithms.clique.find_cliques(g):
cliques += [c]
cliques = sorted(cliques, key=lambda x: len(x), reverse=True)
else:
cliques = [[e[0], e[1]] for e in g.edges()]
cliques_constraint = {}
index_c = 0
opt = color_model.addVar(vtype=GRB.INTEGER, lb=0, ub=nb_colors, obj=1)
if use_cliques:
for c in cliques[:100]:
cliques_constraint[index_c] = color_model.addConstr(quicksum([(color_i + 1) * colors_var[node, color_i]
for node in c
for color_i in range_color])
>= sum([i + 1 for i in range(len(c))]))
cliques_constraint[(index_c, 1)] = color_model.addConstr(quicksum([colors_var[node, color_i]
for node in c
for color_i in range_color])
<= opt)
index_c += 1
edges = g.edges()
constraints_neighbors = {}
for e in edges:
for c in range_color:
constraints_neighbors[(e[0], e[1], c)] = \
color_model.addConstr(colors_var[e[0], c] + colors_var[e[1], c] <= 1)
for n in range_node:
color_model.addConstr(quicksum([(color_i + 1) * colors_var[n, color_i] for color_i in range_color]) <= opt)
color_model.update()
color_model.modelSense = GRB.MINIMIZE
color_model.setParam(GRB.Param.Threads, 8)
color_model.setParam(GRB.Param.PoolSolutions, 10000)
color_model.setParam(GRB.Param.Method, -1)
color_model.setParam("MIPGapAbs", 0.001)
color_model.setParam("MIPGap", 0.001)
color_model.setParam("Heuristics", 0.01)
self.model = color_model
self.variable_decision = {"colors_var": colors_var}
self.constraints_dict = {"one_color_constraints": one_color_constraints,
"constraints_neighbors": constraints_neighbors}
self.description_variable_description = {"colors_var": {"shape": (self.number_of_nodes, nb_colors),
"type": bool,
"descr": "for each node and each color,"
" a binary indicator"}}
self.description_constraint["one_color_constraints"] = {"descr": "one and only one color "
"should be assignated to a node"}
self.description_constraint["constraints_neighbors"] = {"descr": "no neighbors can have same color"}
def init_model(self, **kwargs):
nb_facilities = self.facility_problem.facility_count
nb_customers = self.facility_problem.customer_count
use_matrix_indicator_heuristic = kwargs.get("use_matrix_indicator_heuristic", True)
if use_matrix_indicator_heuristic:
n_shortest = kwargs.get("n_shortest", 10)
n_cheapest = kwargs.get("n_cheapest", 10)
matrix_fc_indicator, matrix_length = prune_search_space(self.facility_problem,
n_cheapest=n_cheapest,
n_shortest=n_shortest)
else:
matrix_fc_indicator, matrix_length = prune_search_space(self.facility_problem,
n_cheapest=nb_facilities,
n_shortest=nb_facilities)
s = Model("facilities")
x = {}
for f in range(nb_facilities):
for c in range(nb_customers):
if matrix_fc_indicator[f, c] == 0:
x[f, c] = 0
elif matrix_fc_indicator[f, c] == 1:
x[f, c] = 1
elif matrix_fc_indicator[f, c] == 2:
x[f, c] = s.addVar(vtype=GRB.BINARY,
obj=0,
name="x_" + str((f, c)))
facilities = self.facility_problem.facilities
customers = self.facility_problem.customers
used = s.addVars(nb_facilities, vtype=GRB.BINARY, name="y")
constraints_customer = {}
for c in range(nb_customers):
constraints_customer[c] = s.addConstr(quicksum([x[f, c] for f in range(nb_facilities)]) == 1)
# one facility
constraint_capacity = {}
for f in range(nb_facilities):
s.addConstrs(used[f] >= x[f, c] for c in range(nb_customers))
constraint_capacity[f] = s.addConstr(quicksum([x[f, c] * customers[c].demand
for c in range(nb_customers)]) <= facilities[f].capacity)
s.update()
new_obj_f = LinExpr(0.)
new_obj_f += quicksum([facilities[f].setup_cost * used[f] for f in range(nb_facilities)])
new_obj_f += quicksum([matrix_length[f, c] * x[f, c]
for f in range(nb_facilities)
for c in range(nb_customers)])
s.setObjective(new_obj_f)
s.update()
s.modelSense = GRB.MINIMIZE
s.setParam(GRB.Param.Threads, 4)
s.setParam(GRB.Param.PoolSolutions, 10000)
s.setParam(GRB.Param.Method, 1)
s.setParam("MIPGapAbs", 0.00001)
s.setParam("MIPGap", 0.00000001)
self.model = s
self.variable_decision = {"x": x}
self.constraints_dict = {"constraint_customer": constraints_customer,
"constraint_capacity": constraint_capacity}
self.description_variable_description = {"x": {"shape": (nb_facilities, nb_customers),
"type": bool,
"descr": "for each facility/customer indicate"
" if the pair is active, meaning "
"that the customer c is dealt with facility f"}}
self.description_constraint = {"Im lazy."}
print("Initialized")