8.2 KiB
This example covers
- building a problem,
- building vehicleTypes and vehicles with capacity restriction,
- building services (or customer locations),
- plotting the problem,
- reading and running a predefined algorithm,
- writing out problem and solution,
- plotting the solution,
- printing solution stats.
Add the latest release to your pom.
Assume the following problem. We can employ one vehicle(-type) located at (10,10) with one capacity dimension, e.g. weight, and a capacity value of 2 to deliver four customers located at [(5,7),(5,13),(15,7),(15,13)], each with a demand that has a weight of 1. All employed vehicles need to return to their start-locations. Setting up this problem and solving it is as simple as coding the following lines:
First, build a vehicle with its vehicle-type:
/*
* get a vehicle type-builder and build a type with the typeId "vehicleType" and a capacity of 2
* you are free to add an arbitrary number of capacity dimensions with .addCacpacityDimension(dimensionIndex,dimensionValue)
*/
final int WEIGHT_INDEX = 0;
VehicleTypeImpl.Builder vehicleTypeBuilder = VehicleTypeImpl.Builder.newInstance("vehicleType").addCapacityDimension(WEIGHT_INDEX,2);
VehicleType vehicleType = vehicleTypeBuilder.build();
/*
* get a vehicle-builder and build a vehicle located at (10,10) with type "vehicleType"
*/
VehicleImpl.Builder vehicleBuilder = VehicleImpl.Builder.newInstance("vehicle");
vehicleBuilder.setStartLocation(Location.newInstance(10, 10));
vehicleBuilder.setType(vehicleType);
VehicleImpl vehicle = vehicleBuilder.build();
Second, define the deliveries as services. Make sure their size dimensions are in line with your vehicle capacity dimensions (thus here the weight-index is made final and also used to define services).
/*
* build services with id 1...4 at the required locations, each with a capacity-demand of 1.
* Note, that the builder allows chaining which makes building quite handy
*/
Service service1 = Service.Builder.newInstance("1").addSizeDimension(WEIGHT_INDEX,1).setLocation(Location.newInstance(5, 7)).build();
Service service2 = Service.Builder.newInstance("2").addSizeDimension(WEIGHT_INDEX,1).setLocation(Location.newInstance(5, 13)).build();
Service service3 = Service.Builder.newInstance("3").addSizeDimension(WEIGHT_INDEX,1).setLocation(Location.newInstance(15, 7)).build();
Service service4 = Service.Builder.newInstance("4").addSizeDimension(WEIGHT_INDEX,1).setLocation(Location.newInstance(15, 13)).build();
and put vehicles and services together to setup the problem.
/*
* again define a builder to build the VehicleRoutingProblem
*/
VehicleRoutingProblem.Builder vrpBuilder = VehicleRoutingProblem.Builder.newInstance();
vrpBuilder.addVehicle(vehicle);
vrpBuilder.addJob(service1).addJob(service2).addJob(service3).addJob(service4);
/*
* build the problem
* by default, the problem is specified such that FleetSize is INFINITE, i.e. an infinite number of
* the defined vehicles can be used to solve the problem
* by default, transport costs are computed as Euclidean distances
*/
VehicleRoutingProblem problem = vrpBuilder.build();
Third, solve the problem by defining and running an algorithm. Here it comes out-of-the-box.
/*
* get the algorithm out-of-the-box.
*/
VehicleRoutingAlgorithm algorithm = Jsprit.createAlgorithm(problem);
/*
* and search a solution which returns a collection of solutions (here only one solution is constructed)
*/
Collection<VehicleRoutingProblemSolution> solutions = algorithm.searchSolutions();
/*
* use the static helper-method in the utility class Solutions to get the best solution (in terms of least costs)
*/
VehicleRoutingProblemSolution bestSolution = Solutions.bestOf(solutions);
Analysing the solution here, requires an output folder in your project-directory. If you do not have one, either create it manually or add the following line to your code:
File dir = new File("output");
// if the directory does not exist, create it
if (!dir.exists()){
System.out.println("creating directory ./output");
boolean result = dir.mkdir();
if(result) System.out.println("./output created");
}
Write out problem and solution (for analysis or later use in another algorithm)
new VrpXMLWriter(problem, solutions).write("output/problem-with-solution.xml");
which looks like this: problem-with-solution.xml.
Or print the results to the console concisely with
SolutionPrinter.print(problem, bestSolution, Print.CONCISE);
which results in
+--------------------------+ | problem | +---------------+----------+ | indicator | value | +---------------+----------+ | nJobs | 4 | | nServices | 4 | | nShipments | 0 | | fleetsize | INFINITE | +--------------------------+ +----------------------------------------------------------+ | solution | +---------------+------------------------------------------+ | indicator | value | +---------------+------------------------------------------+ | costs | 35.3238075793812 | | nVehicles | 2 | +----------------------------------------------------------+
or you use the Print.VERBOSE level such as
SolutionPrinter.print(problem, bestSolution, Print.VERBOSE);
and you get this addtionally:
+--------------------------------------------------------------------------------------------------------------------------------+ | detailed solution | +---------+----------------------+-----------------------+-----------------+-----------------+-----------------+-----------------+ | route | vehicle | activity | job | arrTime | endTime | costs | +---------+----------------------+-----------------------+-----------------+-----------------+-----------------+-----------------+ | 1 | vehicle | start | - | undef | 0 | 0 | | 1 | vehicle | service | 2 | 6 | 6 | 6 | | 1 | vehicle | service | 1 | 12 | 12 | 12 | | 1 | vehicle | end | - | 18 | undef | 18 | +---------+----------------------+-----------------------+-----------------+-----------------+-----------------+-----------------+ | 2 | vehicle | start | - | undef | 0 | 0 | | 2 | vehicle | service | 3 | 6 | 6 | 6 | | 2 | vehicle | service | 4 | 12 | 12 | 12 | | 2 | vehicle | end | - | 18 | undef | 18 | +--------------------------------------------------------------------------------------------------------------------------------+
or plot the results with
new Plotter(problem,bestSolution).plot("output/solution.png", "solution");
and you get solution.png
or use the very basic version of the GraphStreamViewer which dynamically renders the problem and its according solution by coding
new GraphStreamViewer(problem, bestSolution).setRenderDelay(100).display();
You can find the entire code here.