router engine is deprecated. To read about our current
vehicle routing engine documentation start reading here.
This how-to guide assumes you already completed the steps described in the 5-minute getting started experience. To test that the Nextmv CLI is correctly configured, you can optionally run the following command on your terminal. It will get some files that are necessary to work with the Nextmv Platform. You can see the expected output as well.
The Nextmv Software Development Kit (SDK) lets you automate any operational decision in a way that looks and feels like writing other code. It provides the guardrails to turn your data into automated decisions and test and deploy them into production environments.
This guide will walk you through our
unique-matrix-measure template. Apps running in our app environment are self-contained and thus, have no access to outside resources while the app is running, all needed information needs to be passed within the input data. The input data size can become quite big and in this guide we will show you a method to reduce this data size. The requirement for this method to work is that you have many stops at the same location. To get the template, simply run the following commands.
You can check that all files are available in the newly created
unique-matrix-measure folder. Running the
tree command, you should see the file structure.
README.mdgives a short introduction to the routing problem and shows you how to run the template.
go.sumdefine a Go module and are used to manage dependencies, including the Nextmv SDK.
input.jsondescribes the input data for a specific routing problem that is solved by the template.
licensecontains the Apache License 2.0 under which we distribute this template.
main.gocontains the actual code of the Nextmv routing app.
unique-matrix-measure.code-workspacefile should be used to open the template in Visual Studio Code. It is pre-configured for you so that you can run and debug the template without any further steps.
Now you can run the template with the Nextmv CLI, reading from the
input.json file and writing to an
output.json file. The following command shows you how to specify solver limits as well. You should obtain an output similar to the one shown.
Note that transient fields like timestamps, duration, versions, etc. are represented with dummy values due to their dynamic nature. I.e., every time the input is run or the version is bumped, these fields will have a different value.
Now we will show you, step by step, what the code inside the
The first part of the
main.go defines a package name, imports packages required, and defines a
main function which is the starting point for the app. In the
main function the
Run function from the Nextmv
run package is being called. This function executes a solver which is passed in the form of the
solver function further down in the file.
Before we look into the
solver function, we will examine the different structs that represent the needed data used by the app.
input struct lists the required input fields,
Ends (both optional), as well as fields for
UniquePoints is a unique set of locations that need to be visited. And
UniqueMatrix represents a matrix of costs for going from each of the unique points to another.
Stops describes the list of locations to visit. It does that by referencing the 0-based index to the set of
UniquePoints. For that reason all those stops are represented by the
stop struct which holds only an
ID and the aforementioned
Reference to the
Vehicles is an array of vehicle IDs.
solver function is where the model is defined. The function's signature adheres to the
run.Run function we saw earlier already.
When you first ran the template you passed in the parameter
-runner.input.path followed by the path to an input file. This file is automatically parsed and converted to our
input struct. Other option arguments are also interpreted automatically and passed to the solver as an
Similar to the options you passed in when you ran the template,
-diagram.expansion.limit you can also set these values directly in your
main.go if you'd prefer not to pass them from the command line.
To be able to run the routing model we first need to convert the unique matrix into a full matrix the way the solver expect it. Before we start doing this, we will do some basic validation on the data to make sure that it is complete.
checkInput function validates that the
UniqueMatrix represents size-wise the
UniquePoints and that, if given, the
Ends have the length of the
Vehicles which is a requirement of the routing engine.
Next we will create a new matrix
fullMatrix which has the size the solver requires. The solver require this size because it needs to calculate costs to each location, including the start and end location of each vehicle.
Next we create a helper variable
joinedStops which holds all stops from the input:
Ends. This will make it easier to access the required data by index. The code for joining the stops looks like this:
We first set each stop to have a reference of
-1. We do this because we need to detect if
Ends are present. Without setting the default value to
-1 all references would have a reference to
0 which is a valid reference index. Note that we are adding the
Ends alternating because the solver requires them to be in this format:
[stop-1, ..., stop-n, vehicle-1-start, vehicle-1-end, ..., vehicle-m-start, vehicle-m-end]
Now we loop over the each row and each cell in a row of the
fullMatrix to fill the matrix with the correct costs. Because the
joinedStops holds the stops in the correct order we can simply access the stops there and get the references to the
UniquePoints which at the same time are the indices for the
UniqueMatrix. If we find a reference of
-1 we know that this is value is not given and we skip over, leaving the default value of
0 in the
Before we can pass all of our data into the routing engine, we need to make it compatible with it. This means we need to pass the fullMatrix for each vehicle as an ByIndex measure, the stops may not use a reference to a location but have the location directly incorporated as its position, and the starts and ends need to be passed in as positions.
With all the data prepared we create a new routing engine:
Finally, we return a
solver for our
router passing in options that were given at the very beginning by the calling function. This solver is then executed by the
run.Run function from the beginning.