Question

我已经实现了用于路径优化的Or-Tools。它的工作正常。我只想实现每辆车的限制位置数量的一件事。例如，每辆车最多可定义两个（2）位置。

我已经尝试实现“容量约束”，但是它不起作用。我也尝试实现SetSpanUpperBoundForVehicle函数，在这种情况下，解决方案对象为null。

这是我的代码

RoutingDimension timeDimension = routing.GetMutableDimension("Time");
            timeDimension.SetSpanUpperBoundForVehicle(2, 0);
            timeDimension.SetSpanUpperBoundForVehicle(2, 1);
            timeDimension.SetSpanUpperBoundForVehicle(2, 2);

我如何限制此数量的路线？请帮忙。

Answer 1

只需创建一个计数器尺寸，在每个位置添加1，然后将每辆车的容量限制为允许的最大位置数。

例如重用vrp.py示例并添加：

   # Create counter
    def counter_callback(from_index):
        """Returns 1 for any locations except depot."""
        # Convert from routing variable Index to user NodeIndex.
        from_node = manager.IndexToNode(from_index)
        return 1 if (from_node != 0) else 0;

    counter_callback_index = routing.RegisterUnaryTransitCallback(counter_callback)

    routing.AddDimensionWithVehicleCapacity(
        counter_callback_index,
        0,  # null slack
        [4,5,4,6],  # maximum locations per vehicle
        True,  # start cumul to zero
        'Counter')

可能的输出：

%python vrp.py
Objective: 6780
Route for vehicle 0:
 0 -> 7 -> 0
Distance of the route: 388m

Route for vehicle 1:
 0 -> 14 -> 16 -> 15 -> 3 -> 4 -> 0
Distance of the route: 2716m

Route for vehicle 2:
 0 -> 13 -> 12 -> 11 -> 1 -> 0
Distance of the route: 1804m

Route for vehicle 3:
 0 -> 5 -> 8 -> 6 -> 2 -> 10 -> 9 -> 0
Distance of the route: 1872m

Total Distance of all routes: 6780m

如您所见，路由遵守4, 5, 4, 6位置限制。

注意：对于C＃语法，请参见 https://github.com/google/or-tools/blob/stable/ortools/constraint_solver/samples/VrpCapacity.cs 和https://github.com/google/or-tools/blob/stable/ortools/constraint_solver/samples/VrpCapacity.csproj

如何在Google OR工具路线优化中限制每辆车的位置数量

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