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@ -39,6 +39,8 @@ Here you learn to setup the Java environment and an Integrated Development Envir
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#### If you do not want Maven
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to manage your dependencies, go to [maven central](https://search.maven.org/), search for jsprit and download the latest binaries to put them into your classpath.
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Go ahead and show me a simple example of how to setup and solve a vehicle routing problem.
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154
docs/Simple-Example.md
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154
docs/Simple-Example.md
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@ -0,0 +1,154 @@
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This example covers
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- building a problem,
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- building vehicleTypes and vehicles with capacity restriction,
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- building services (or customer locations),
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- plotting the problem,
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- reading and running a predefined algorithm,
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- writing out problem and solution,
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- plotting the solution,
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- printing solution stats.
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Add the latest release to your pom (see [Getting Started](Getting-Started.md)).
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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:
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First, build a vehicle with its vehicle-type:
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<pre><code>/*
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* get a vehicle type-builder and build a type with the typeId "vehicleType" and a capacity of 2
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* you are free to add an arbitrary number of capacity dimensions with .addCacpacityDimension(dimensionIndex,dimensionValue)
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*/
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final int WEIGHT_INDEX = 0;
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VehicleTypeImpl.Builder vehicleTypeBuilder = VehicleTypeImpl.Builder.newInstance("vehicleType").addCapacityDimension(WEIGHT_INDEX,2);
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VehicleType vehicleType = vehicleTypeBuilder.build();
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/*
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* get a vehicle-builder and build a vehicle located at (10,10) with type "vehicleType"
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*/
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VehicleImpl.Builder vehicleBuilder = VehicleImpl.Builder.newInstance("vehicle");
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vehicleBuilder.setStartLocation(Location.newInstance(10, 10));
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vehicleBuilder.setType(vehicleType);
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VehicleImpl vehicle = vehicleBuilder.build();
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</code></pre>
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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).
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<pre><code>/*
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* build services with id 1...4 at the required locations, each with a capacity-demand of 1.
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* Note, that the builder allows chaining which makes building quite handy
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*/
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Service service1 = Service.Builder.newInstance("1").addSizeDimension(WEIGHT_INDEX,1).setLocation(Location.newInstance(5, 7)).build();
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Service service2 = Service.Builder.newInstance("2").addSizeDimension(WEIGHT_INDEX,1).setLocation(Location.newInstance(5, 13)).build();
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Service service3 = Service.Builder.newInstance("3").addSizeDimension(WEIGHT_INDEX,1).setLocation(Location.newInstance(15, 7)).build();
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Service service4 = Service.Builder.newInstance("4").addSizeDimension(WEIGHT_INDEX,1).setLocation(Location.newInstance(15, 13)).build();
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</code></pre>
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and put vehicles and services together to setup the problem.
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<pre><code>/*
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* again define a builder to build the VehicleRoutingProblem
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*/
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VehicleRoutingProblem.Builder vrpBuilder = VehicleRoutingProblem.Builder.newInstance();
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vrpBuilder.addVehicle(vehicle);
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vrpBuilder.addJob(service1).addJob(service2).addJob(service3).addJob(service4);
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/*
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* build the problem
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* by default, the problem is specified such that FleetSize is INFINITE, i.e. an infinite number of
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* the defined vehicles can be used to solve the problem
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* by default, transport costs are computed as Euclidean distances
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*/
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VehicleRoutingProblem problem = vrpBuilder.build();
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</code></pre>
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Third, solve the problem by defining and running an algorithm. Here it comes out-of-the-box.
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<pre><code>/*
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* get the algorithm out-of-the-box.
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*/
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VehicleRoutingAlgorithm algorithm = Jsprit.createAlgorithm(problem);
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/*
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* and search a solution which returns a collection of solutions (here only one solution is constructed)
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*/
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Collection<VehicleRoutingProblemSolution> solutions = algorithm.searchSolutions();
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/*
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* use the static helper-method in the utility class Solutions to get the best solution (in terms of least costs)
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*/
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VehicleRoutingProblemSolution bestSolution = Solutions.bestOf(solutions);
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</code></pre>
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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:
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<pre><code>File dir = new File("output");
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// if the directory does not exist, create it
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if (!dir.exists()){
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System.out.println("creating directory ./output");
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boolean result = dir.mkdir();
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if(result) System.out.println("./output created");
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}
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</code></pre>
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Write out problem and solution (for analysis or later use in another algorithm)
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<pre><code>new VrpXMLWriter(problem, solutions).write("output/problem-with-solution.xml");
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</code></pre>
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which looks like this: [problem-with-solution.xml](https://github.com/jsprit/misc-rep/raw/master/wiki-images/problem-with-solution.xml).
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Or print the results to the console concisely with
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<code>SolutionPrinter.print(problem, bestSolution, Print.CONCISE);</code>
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which results in
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<pre><samp>+--------------------------+
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| problem |
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+---------------+----------+
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| indicator | value |
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+---------------+----------+
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| nJobs | 4 |
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| nServices | 4 |
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| nShipments | 0 |
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| fleetsize | INFINITE |
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+--------------------------+
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+----------------------------------------------------------+
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| solution |
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+---------------+------------------------------------------+
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| indicator | value |
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+---------------+------------------------------------------+
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| costs | 35.3238075793812 |
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| nVehicles | 2 |
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+----------------------------------------------------------+
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</samp></pre>
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or you use the Print.VERBOSE level such as
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<code>SolutionPrinter.print(problem, bestSolution, Print.VERBOSE);</code>
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and you get this addtionally:
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<pre><samp>+--------------------------------------------------------------------------------------------------------------------------------+
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| detailed solution |
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+---------+----------------------+-----------------------+-----------------+-----------------+-----------------+-----------------+
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| route | vehicle | activity | job | arrTime | endTime | costs |
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+---------+----------------------+-----------------------+-----------------+-----------------+-----------------+-----------------+
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| 1 | vehicle | start | - | undef | 0 | 0 |
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| 1 | vehicle | service | 2 | 6 | 6 | 6 |
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| 1 | vehicle | service | 1 | 12 | 12 | 12 |
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| 1 | vehicle | end | - | 18 | undef | 18 |
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+---------+----------------------+-----------------------+-----------------+-----------------+-----------------+-----------------+
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| 2 | vehicle | start | - | undef | 0 | 0 |
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| 2 | vehicle | service | 3 | 6 | 6 | 6 |
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| 2 | vehicle | service | 4 | 12 | 12 | 12 |
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| 2 | vehicle | end | - | 18 | undef | 18 |
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+--------------------------------------------------------------------------------------------------------------------------------+
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</samp></pre>
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or plot the results with
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<code>new Plotter(problem,bestSolution).plot("output/solution.png", "solution");</code>
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and you get [solution.png](https://github.com/jsprit/misc-rep/blob/master/wiki-images/solution.png)
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or use the <em>very basic version</em> of the GraphStreamViewer which dynamically renders the problem and its according solution by coding
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<code>new GraphStreamViewer(problem, bestSolution).setRenderDelay(100).display();</code>
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You can find the entire code [here](https://github.com/graphhopper/jsprit/blob/master/jsprit-examples/src/main/java/com/graphhopper/jsprit/examples/SimpleExample.java).
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