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"}
class LPKnapsackGurobi(SolverDO):
def __init__(self,
knapsack_model: KnapsackModel,
params_objective_function: ParamsObjectiveFunction = None):
self.knapsack_model = knapsack_model
self.model = None
self.variable_decision = {}
self.constraints_dict = {}
self.description_variable_description = {}
self.description_constraint = {}
self.aggreg_sol, self.aggreg_dict, self.params_objective_function = \
build_aggreg_function_and_params_objective(problem=self.knapsack_model,
params_objective_function=params_objective_function)
def init_model(self, **args):
warm_start = args.get('warm_start', {})
self.model = Model("Knapsack")
self.variable_decision = {"x": {}}
self.description_variable_description = {
"x": {
"shape":
self.knapsack_model.nb_items,
"type":
bool,
"descr":
"dictionary with key the item index \
and value the boolean value corresponding \
to taking the item or not"
}
}
self.description_constraint["weight"] = {
"descr": "sum of weight of used items doesn't exceed max capacity"
}
weight = {}
list_item = self.knapsack_model.list_items
max_capacity = self.knapsack_model.max_capacity
x = {}
for item in list_item:
i = item.index
x[i] = self.model.addVar(vtype=GRB.BINARY,
obj=item.value,
name="x_" + str(i))
if i in warm_start:
x[i].start = warm_start[i]
x[i].varhinstval = warm_start[i]
weight[i] = item.weight
self.variable_decision["x"] = x
self.model.update()
self.constraints_dict["weight"] = self.model.addConstr(
quicksum([weight[i] * x[i] for i in x]) <= max_capacity)
self.model.update()
self.model.setParam("TimeLimit", 200)
self.model.modelSense = GRB.MAXIMIZE
self.model.setParam(GRB.Param.PoolSolutions, 10000)
self.model.setParam("MIPGapAbs", 0.00001)
self.model.setParam("MIPGap", 0.00000001)
def retrieve_solutions(self, range_solutions: Iterable[int]):
# nObjectives = S.NumObj
solutions = []
fits = []
# x = S.getVars()
for s in range_solutions:
weight = 0
xs = {}
self.model.params.SolutionNumber = s
obj = self.model.getAttr("ObjVal")
for e in self.variable_decision["x"]:
value = self.variable_decision["x"][e].getAttr('Xn')
if value <= 0.1:
xs[e] = 0
continue
xs[e] = 1
weight += self.knapsack_model.index_to_item[e].weight
solutions += [
KnapsackSolution(problem=self.knapsack_model,
value=obj,
weight=weight,
list_taken=[xs[e] for e in sorted(xs)])
]
fits += [self.aggreg_sol(solutions[-1])]
return ResultStorage(
list_solution_fits=[(s, f) for s, f in zip(solutions, fits)],
mode_optim=self.params_objective_function.sense_function)
def solve(self, parameter_gurobi: ParametersMilp):
self.model.setParam("TimeLimit", parameter_gurobi.TimeLimit)
self.model.modelSense = GRB.MAXIMIZE
self.model.setParam(GRB.Param.PoolSolutions,
parameter_gurobi.PoolSolutions)
self.model.setParam("MIPGapAbs", parameter_gurobi.MIPGapAbs)
self.model.setParam("MIPGap", parameter_gurobi.MIPGap)
print("optimizing...")
self.model.optimize()
nSolutions = self.model.SolCount
nObjectives = self.model.NumObj
objective = self.model.getObjective().getValue()
print('Problem has', nObjectives, 'objectives')
print('Gurobi found', nSolutions, 'solutions')
if parameter_gurobi.retrieve_all_solution:
solutions = self.retrieve_solutions(list(range(nSolutions)))
else:
solutions = self.retrieve_solutions([0])
return solutions
def solve_lns(self, parameter_gurobi: ParametersMilp,
init_solution: KnapsackSolution,
fraction_decision_fixed: float, nb_iteration_max: int):
self.model.setParam("TimeLimit", parameter_gurobi.TimeLimit)
self.model.setParam("OutputFlag", 0)
self.model.modelSense = GRB.MAXIMIZE
self.model.setParam(GRB.Param.PoolSolutions,
parameter_gurobi.PoolSolutions)
self.model.setParam("MIPGapAbs", parameter_gurobi.MIPGapAbs)
self.model.setParam("MIPGap", parameter_gurobi.MIPGap)
current_solution = init_solution
constraints = {}
list_solutions = [current_solution]
list_objective = [current_solution.value]
objective = init_solution.value
for k in trange(nb_iteration_max):
for c in constraints:
self.model.remove(constraints[c])
self.add_init_solution(current_solution)
fixed_variable = set(
random.sample(
self.variable_decision["x"].keys(),
int(fraction_decision_fixed *
len(self.variable_decision["x"]))))
constraints = self.fix_decision(current_solution, fixed_variable)
self.model.optimize()
nSolutions = self.model.SolCount
nObjectives = self.model.NumObj
objective = self.model.getObjective().getValue()
if parameter_gurobi.retrieve_all_solution:
solutions = self.retrieve_solutions(list(range(nSolutions)))
else:
solutions = self.retrieve_solutions([0])
current_solution = solutions[0]
list_solutions += [solutions[0]]
list_objective += [solutions[0].value]
print("Last obj : ", list_objective[-1])
fig, ax = plt.subplots(1)
ax.plot(list_objective)
plt.show()
def add_init_solution(self, init_solution: KnapsackSolution):
for i in self.variable_decision["x"]:
self.variable_decision["x"][i].start = init_solution.list_taken[i]
self.variable_decision["x"][
i].varhintval = init_solution.list_taken[i]
def fix_decision(self, init_solution: KnapsackSolution,
fixed_variable_keys):
constraints = {}
for i in fixed_variable_keys:
constraints[i] = self.model.addConstr(
self.variable_decision["x"][i] == init_solution.list_taken[i])
return constraints
def describe_the_model(self):
return str(self.description_variable_description) + "\n" + str(
self.description_constraint)
def generate_angle_milp(gurobi_model: grb.Model, input,
sin_cos_table: List[Tuple]):
"""MILP method
input: theta, thetadot
output: thetadotdot, xdotdot (edited)
l_{theta, i}, l_{thatdot,i}, l_{thetadotdot, i}, l_{xdotdot, i}, u_....
sum_{i=1}^k l_{x,i} - l_{x,i}*z_i <= x <= sum_{i=1}^k u_{x,i} - u_{x,i}*z_i, for each variable x
sum_{i=1}^k l_{theta,i} - l_{theta,i}*z_i <= theta <= sum_{i=1}^k u_{theta,i} - u_{theta,i}*z_i
"""
theta = input[2]
theta_dot = input[3]
k = len(sin_cos_table)
zs = []
thetaacc = gurobi_model.addMVar(shape=(1, ),
lb=float("-inf"),
name="thetaacc")
xacc = gurobi_model.addMVar(shape=(1, ), lb=float("-inf"), name="xacc")
for i in range(k):
z = gurobi_model.addMVar(lb=0,
ub=1,
shape=(1, ),
vtype=grb.GRB.INTEGER,
name=f"part_{i}")
zs.append(z)
gurobi_model.addConstr(k - 1 == sum(zs), name=f"const_milp1")
theta_lb = 0
theta_ub = 0
theta_dot_lb = 0
theta_dot_ub = 0
thetaacc_lb = 0
thetaacc_ub = 0
xacc_lb = 0
xacc_ub = 0
for i in range(k):
theta_interval, theta_dot_interval, theta_acc_interval, xacc_interval = sin_cos_table[
i]
theta_lb += theta_interval[0] - theta_interval[0] * zs[i]
theta_ub += theta_interval[1] - theta_interval[1] * zs[i]
theta_dot_lb += theta_dot_interval[
0] - theta_dot_interval[0] * zs[i]
theta_dot_ub += theta_dot_interval[
1] - theta_dot_interval[1] * zs[i]
thetaacc_lb += theta_acc_interval[0] - theta_acc_interval[0] * zs[i]
thetaacc_ub += theta_acc_interval[1] - theta_acc_interval[1] * zs[i]
xacc_lb += xacc_interval[0] - xacc_interval[0] * zs[i]
xacc_ub += xacc_interval[1] - xacc_interval[1] * zs[i]
# eps = 1e-9
gurobi_model.addConstr(theta >= theta_lb, name=f"theta_guard1")
gurobi_model.addConstr(theta <= theta_ub, name=f"theta_guard2")
gurobi_model.addConstr(theta_dot >= theta_dot_lb,
name=f"theta_dot_guard1")
gurobi_model.addConstr(theta_dot <= theta_dot_ub,
name=f"theta_dot_guard2")
gurobi_model.addConstr(thetaacc >= thetaacc_lb,
name=f"thetaacc_guard1")
gurobi_model.addConstr(thetaacc <= thetaacc_ub,
name=f"thetaacc_guard2")
gurobi_model.addConstr(xacc >= xacc_lb, name=f"xacc_guard1")
gurobi_model.addConstr(xacc <= xacc_ub, name=f"xacc_guard2")
gurobi_model.update()
gurobi_model.optimize()
if gurobi_model.status == 4:
gurobi_model.setParam("DualReductions", 0)
gurobi_model.update()
gurobi_model.optimize()
# assert gurobi_model.status == 2, f"LP wasn't optimally solved. gurobi status {gurobi_model.status}"
return thetaacc, xacc
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")