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solver.py
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solver.py
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"""Vehicles Routing Problem (VRP)."""
from __future__ import print_function
from ortools.constraint_solver import routing_enums_pb2
from ortools.constraint_solver import pywrapcp
import distance_matrix
def create_data_model(cfg):
"""Stores the data for the problem.
cfg : {
"addresses":[(x1,y1),(x2,y2),...(xn,yn)],
"num_vehicles":n,
"depot":i
}
"""
data = {}
# data['distance_matrix'] = get_distance_matrix(cfg["addresses"])
data['distance_matrix'] = distance_matrix.main(cfg['addresses'])
data['num_vehicles'] = cfg["num_vehicles"]
data['depot'] = cfg["depot"]
data['demands'] = cfg['demands']
data['vehicle_capacities'] = cfg['vehicle_capacities']
return data
def get_solution(data, manager, routing, solution):
"""Prints solution on console."""
total_distance = 0
total_load = 0
max_distance = 0
vehicle_routes = []
vehicle_distances = []
vehicle_loads = []
vehicle_load_details= []
for vehicle_id in range(data['num_vehicles']):
index = routing.Start(vehicle_id)
route_distance = 0
route_load = 0
route_load_details = []
route = []
while not routing.IsEnd(index):
node_index = manager.IndexToNode(index)
route_load += data['demands'][node_index]
route.append(node_index)
route_load_details.append(route_load)
previous_index = index
index = solution.Value(routing.NextVar(index))
route_distance += routing.GetArcCostForVehicle(
previous_index, index, vehicle_id)
route.append(manager.IndexToNode(index))
route_load_details.append(route_load)
route_load_details = [(route_load - l) for l in route_load_details]
total_distance += route_distance
total_load += route_load
if route_distance > max_distance:
max_distance = route_distance
vehicle_routes.append(route)
vehicle_distances.append(route_distance)
vehicle_loads.append(route_load)
vehicle_load_details.append(route_load_details)
result = {
"solution":True,
"routes":vehicle_routes,
"distances":vehicle_distances,
"max_distance":max_distance,
"total_distance":total_distance,
"total_load":total_load,
"loads":vehicle_loads,
"load_details":vehicle_load_details
}
return result
def main(cfg):
"""Solve the CVRP problem."""
# Instantiate the data problem.
data = create_data_model(cfg)
print(data)
if len(data['distance_matrix'])==0:
result = {
"solution":False,
"error-message":"unable to calculate distance matrix"
}
return result
# Create the routing index manager.
manager = pywrapcp.RoutingIndexManager(len(data['distance_matrix']),
data['num_vehicles'], data['depot'])
# Create Routing Model.
routing = pywrapcp.RoutingModel(manager)
# Create and register a transit callback.
def distance_callback(from_index, to_index):
"""Returns the distance between the two nodes."""
# Convert from routing variable Index to distance matrix NodeIndex.
from_node = manager.IndexToNode(from_index)
to_node = manager.IndexToNode(to_index)
return data['distance_matrix'][from_node][to_node]
transit_callback_index = routing.RegisterTransitCallback(distance_callback)
# Define cost of each arc.
routing.SetArcCostEvaluatorOfAllVehicles(transit_callback_index)
def demand_callback(from_index):
"""Returns the demand of the node."""
# Convert from routing variable Index to demands NodeIndex.
from_node = manager.IndexToNode(from_index)
return data['demands'][from_node]
# Add Distance constraint.
dimension_name = 'Distance'
routing.AddDimension(
transit_callback_index,
0, # no slack
7200, # vehicle maximum travel distance
True, # start cumul to zero
dimension_name)
demand_callback_index = routing.RegisterUnaryTransitCallback(demand_callback)
routing.AddDimensionWithVehicleCapacity(
demand_callback_index,
0, # null capacity slack
data['vehicle_capacities'], # vehicle maximum capacities
True, # start cumul to zero
'Capacity')
# Setting first solution heuristic.
search_parameters = pywrapcp.DefaultRoutingSearchParameters()
search_parameters.first_solution_strategy = (
routing_enums_pb2.FirstSolutionStrategy.PATH_CHEAPEST_ARC)
# Solve the problem.
solution = routing.SolveWithParameters(search_parameters)
# Return solution dictionary
if solution:
return get_solution(data, manager, routing, solution)
else:
result = {
"solution":False
}
return result