def _add_maximum_makespan_constraints(self):
"""Defines maximum makespan"""
for route in range(1, self._n_columns):
self.makespan_constr[route] = pulp.LpConstraintVar(
"makespan_%s" % route,
pulp.LpConstraintLE,
0,
)
def _add_set_covering_constraints(self):
"""
All vertices must be visited exactly once, or periodically if
frequencies are given.
If dropping nodes is allowed, the drop variable is activated
(as well as a penalty is the cost function).
"""
for node in self.G.nodes():
if (node not in ["Source", "Sink"]
and "depot_from" not in self.G.nodes[node]
and "depot_to" not in self.G.nodes[node]):
# Set RHS
right_hand_term = (self.G.nodes[node]["frequency"]
if self.periodic else 1)
# Save set covering constraints
self.set_covering_constrs[node] = pulp.LpConstraintVar(
"visit_node_%s" % node, pulp.LpConstraintGE,
right_hand_term)
def __init__(self, *args):
super(_MasterSolvePulp, self).__init__(*args)
# create problem
self.prob = pulp.LpProblem("MasterProblem", pulp.LpMinimize)
# objective
self.objective = pulp.LpConstraintVar("objective")
# variables
self.y = {} # route selection variable
self.drop = {} # dropping variable
self.dummy = {} # dummy variable
self.dummy_bound = {} # dummy variable for vehicle bound cost
self.makespan = {} # maximum global span
# constrs
self.set_covering_constrs = {}
self.vehicle_bound_constrs = {}
self.drop_penalty_constrs = {}
self.makespan_constr = {}
# Restricted master heuristic
self.diving_heuristic = _DivingHeuristic()
# Parameter when minimizing global span
self._n_columns = 1000
self._formulate()
def _add_bound_vehicles(self):
"""Adds empty constraints and sets the right hand side"""
for k in range(len(self.num_vehicles)):
self.vehicle_bound_constrs[k] = pulp.LpConstraintVar(
"upper_bound_vehicles_%s" % k, pulp.LpConstraintLE,
self.num_vehicles[k])