基本vrp问题模型代码
时间: 2024-01-06 11:01:32 浏览: 32
基本的VRP问题模型代码如下:
```python
from ortools.constraint_solver import routing_enums_pb2
from ortools.constraint_solver import pywrapcp
def create_data_model():
data = {}
# 客户点坐标
data['locations'] = [(4, 4), # depot
(2, 0), (8, 0), # locations to visit
(0, 1), (1, 1),
(5, 2), (7, 2),
(3, 3), (6, 3),
(5, 5), (8, 5),
(1, 6), (2, 6),
(3, 7), (6, 7),
(0, 8), (7, 8)]
# 车辆数量
data['num_vehicles'] = 4
# depot坐标
data['depot'] = 0
return data
def print_solution(data, manager, routing, assignment):
total_distance = 0
total_load = 0
for vehicle_id in range(data['num_vehicles']):
index = routing.Start(vehicle_id)
plan_output = 'Route for vehicle {}:\n'.format(vehicle_id)
route_distance = 0
route_load = 0
while not routing.IsEnd(index):
node_index = manager.IndexToNode(index)
route_load += data['demands'][node_index]
plan_output += ' {0} Load({1}) -> '.format(node_index, route_load)
previous_index = index
index = assignment.Value(routing.NextVar(index))
route_distance += routing.GetArcCostForVehicle(previous_index, index, vehicle_id)
plan_output += ' {0} Load({1})\n'.format(manager.IndexToNode(index), route_load)
plan_output += 'Distance of the route: {}m\n'.format(route_distance)
plan_output += 'Load of the route: {}\n'.format(route_load)
print(plan_output)
total_distance += route_distance
total_load += route_load
print('Total Distance of all routes: {}m'.format(total_distance))
print('Total Load of all routes: {}'.format(total_load))
def main():
data = create_data_model()
manager = pywrapcp.RoutingIndexManager(len(data['locations']), data['num_vehicles'], data['depot'])
routing = pywrapcp.RoutingModel(manager)
def distance_callback(from_index, to_index):
x1, y1 = data['locations'][from_index]
x2, y2 = data['locations'][to_index]
return int(math.hypot(x2 - x1, y2 - y1))
transit_callback_index = routing.RegisterTransitCallback(distance_callback)
routing.SetArcCostEvaluatorOfAllVehicles(transit_callback_index)
dimension_name = 'Distance'
routing.AddDimension(
transit_callback_index,
0, # no slack
3000, # vehicle maximum travel distance
True, # start cumul to zero
dimension_name
)
distance_dimension = routing.GetDimensionOrDie(dimension_name)
distance_dimension.SetGlobalSpanCostCoefficient(100)
search_parameters = pywrapcp.DefaultRoutingSearchParameters()
search_parameters.first_solution_strategy = (
routing_enums_pb2.FirstSolutionStrategy.PARALLEL_CHEAPEST_INSERTION)
solution = routing.SolveWithParameters(search_parameters)
if solution:
print_solution(data, manager, routing, solution)
if __name__ == '__main__':
main()
```
这段代码解决了基本的VRP问题,其中定义了数据模型、打印解决方案的函数和主函数。数据模型包括客户点的坐标、车辆数量和depot坐标。主函数中使用OR-Tools库中的函数来创建并求解VRP问题模型,最后打印出每个车辆的路径和距离以及总的路径长度。